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This report describes a general method to correlate the features determining the performance of an electrocatalyst (EC), including the accessibility of O2 to the active sites and the kinetic activation barrier, with the outcome of conventional electrochemical experiments. The method has been implemented for oxygen reduction reaction ECs by cyclic voltammetry with the thin-film rotating ring-disk electrode (CV-TF-RRDE) setup. The method: (i) does not rely on the simplifications associated with the Butler-Volmer kinetic description of electrochemical processes and (ii) does not make assumptions on the specific features of the EC, allowing to compare accurately the kinetic performance of oxygen reduction reaction ECs with completely different chemistry. Finally, with respect to other widespread figures of merit (e.g., the half-wave potential E1/2), the figure of merit here proposed, E(jPt(5%)), allows for much more accurate comparisons of the kinetic performance of ECs.

Electrochemical energy conversion and storage (EECS) devices are a family of systems that are playing a major role in today’s efforts worldwide to decarbonize the energy infrastructure, with the ultimate goal to mitigate the greenhouse effect and reduce global warming [1]. Though EECS devices include very diverse systems such as secondary batteries, fuel cells, redox flow batteries and supercapacitors, among many others, all EECS devices share the same basic components i.e., two electrodes (where redox process take place) sandwiching a separator that allows for the selective transport of ions. In particular, the separator plays a crucial role to set some of the most relevant features of every EECS device, including the maximum power density that it can express and the durability/cyclability. Ionic liquids (ILs) have demonstrated a huge potential to enable the realization of EECS devices exhibiting an improved performance and durability. This feat is possible by leveraging on the unique features of ILs, with a particular reference to their highly customizable chemistry [2]. Suitable synthetic approaches allow to obtain systems specifically tailored to a certain application. In some instances, the best electrolytes are achieved by: (i) using the IL to soak a suitable matrix (e.g., a perfluorosulfonic acid derivative); (ii) dissolving a suitable dissociable compound (e.g., LiTFSI or δ-MgCl2) into the IL; and/or (iii) dispersing a suitable inorganic filler into the IL. The resulting IL-based electrolytes exhibit the desired features in terms of: (i) chemistry of the mobile species (e.g., the proton, lithium complexes, magnesium species); (ii) facile and selective transport of such mobile species; (iii) good compatibility with the electrodes, allowing an efficient plating/stripping of the desired metal species and minimizing undesired parasitic reactions; (iv) broad electrochemical stability window (ESW); and (v) well-controlled hydrophilicity/hydrophobicity features. The present contribution overviews our activities in the synthesis, characterization and implementation into various EECS device prototypes of IL-based electrolytes. The latter include: (i) electrolytes for proton-exchange membrane fuel cells (PEMFCs) obtained by swelling a perfluorosulfonic acid derivative with proton-conducing ionic liquids (PCILs) [3]; (ii) hybrid electrolytes for lithium batteries obtained by dispersing suitable inorganic fillers into ILs [4]; (iii) catenated ILs for multivalent batteries obtained by dissolving magnesium/aluminum/titanium halides into suitable ILs [5]; and (iv) highly hydrophobic ILs for special applications [6]. Particular efforts are dedicated to elucidate the complex interplay between: (i) the synthetic parameters; (ii) the physicochemical properties; (iii) the electric response; (iv) the long-range charge transport mechanism; and (v) the performance and durability of the IL-based electrolyte upon implementation into an EECS device prototype. Acknowledgments This work received funding from the U.S. Army Research Office under the grant W911NF-21-1-0347, from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 829145 (FETOPEN-VIDICAT) and from the University of Padova under the grant BIRD2121_01. References [1] P. Poizot et al., Energy Environ. Sci. 4, 2003-2019 (2011). [2] M. Armand et al., Nature Materials 8, 621-629 (2009). [3] V. Di Noto et al., J. Am. Chem. Soc., 132, 2183-2195 (2010). [4] F. Bertasi et al., Electrochim. Acta 307, 51-63 (2019). [5] G. Pagot et al., J. Power Sources, 524, 231084 (2022). [6] F. Bertasi et al., Phys. Chem. Chem. Phys., 19, 26230–26239 (2017).

Redox flow batteries are of potential importance to both large scale energy storage and powering the electrical vehicle. Among critical challenges are low volumetric energy density of redox electrolytes, high cost and the maintenance limitations that greatly impede the wide application of conventional flow batteries. In this respect, the redox-active charge-storage material has a significant impact on the performance of a flow battery. The concentration of redox centers and their reaction kinetics have an influence on the available current densities and, thus, the power of the device. Many inorganic and organic electroactive systems have been proposed as alternatives to vanadium species in redox flow batteries. In the study, we explore the concept of highly concentrated solutions of such redox systems as iodine/iodide and poloxometallates of molybdenum and tungsten, and the possibility of optimizing their performance to exhibit high rates of charge propagation. While the iodine/iodide system can be prepared at high concentrations, the polyoxometallates of molybdenum and tungsten can serve as model examples of multi-electron systems for all-liquid redox flow batteries and related fundamental investigations. Reactions in the zinc/iodine (polyiodide) redox flow battery are as follows: Zn → Zn2+ + 2e- (E = −0.76 V vs SHE) at the negative electrode (anode), and 3I- → I3 − + 2e− (E = 0.54 V vs SHE) at the positive electrode (cathode) thus yielding a total theoretical potential output as high as ∼1.3 V. The increase of current density could be achieved not only by reducing the viscosity of the electrolyte, thus accelerating charge-carrier transport, but also – by referencing to our experience with the iodine/iodide couple as charge relay for dye-sensitized solar cells – through improvement of the dynamics of charge propagation in highly concentrated iodine/iodide solution via the catalyzed enhancement of rates of electron self-exchange (hopping) between iodine/iodide (polyiodide) redox species as well as by accelerating the interfacial kinetics at electrodes. This can be realized by choosing appropriate electrode materials and through their activation or modification. The electrochemical activities of the redox couples are usually significantly increased through application of nanostructured functionalized carbons. While dispersed in solutions they can improve electron transfers to the redox sites. The proposed chemistry has been first tested using the microelectrode methodology to determine mass-transport (effectively diffusional) coefficients for charge propagation, heterogeneous and homogeneous (electron self-exchange) rates of electron transfers. Unless catalyzed, both interfacial and bulk (self-exchange) electron transfers involving the iodine/iodide redox system are somewhat complicated; there is a need to break the I-I bond in the I3 -or I2 molecule; it has also been well-established that platinum (e.g. when deposited on the counter electrode) induces electron transfers within the iodine/iodide redox system. As far as heteropolyacids are concerned, they exhibit very strong Brønsted acidity, act as proton conductors, and undergo fast, reversible, multi-electron electron transfers leading to the formation of highly conducting, mixed-valence (e.g. tungsten(VI,V) or molybdenum(VI,V) heteropoly blue) compounds. The polyoxometallate-based redox electrolytes have different chemical identities, and they could be considered as anolytes or catholytes, depending on their redox potentials but, typically, their use would require formation of an asymmetric system with different-type redox species. While dynamics of electrochemical processes has an influence on the systems’ current densities, the viscosity of the electrolyte and the mass transport dynamics are also affected by the choice of the redox-active material and its concentration. Trying to develop useful electroanalytical diagnostic criteria, we are going to extend the historical concepts of charge propagation in semi-solid or semi-liquid systems developed for mixed-valence redox polymers and polynuclear materials to the development of redox electrolytes. Fundamental electroanalytical approaches utilizing ultramicrodisk electrodes and interdigitated arrays will be adapted to characterization of redox electrolytes.

Several families of electrochemical energy conversion and storage devices (e.g., fuel cells and metal-air batteries) exploit the oxygen reduction reaction (ORR) in their operation. Very often, the ORR is the slowest electrochemical process in these systems and plays the most relevant role to degrade their energy conversion efficiency. Thus, to devise high-performing ORR electrocatalysts (ECs) is of crucial importance for practical applications. Unfortunately, to understand in detail the operating mechanism of an ORR EC is typically complex and time-consuming, requiring the implementation of a broad spectrum of advanced techniques and extensive data analysis. Consequently, there is a strong need to design simple methods capable to yield information on the most critical features of an ORR EC for screening purposes. In this regard, cyclic voltammetry with the thin-film rotating ring-disk electrode (CV-TF-RRDE) is a very popular approach. The latter allows for the facile study of the kinetics of an electrochemical process as promoted by an EC and minimizes the influence of complex spurious phenomena (e.g., charge and mass transport). In this contribution a general method is discussed allowing for the correlation of the outcome of conventional electrochemical experiments with the critical features determining the performance of an ORR EC. Such features include prominently: (i) the kinetic activation barrier of the ORR; and (ii) the accessibility of O2 to the active sites. The proposed method: (i) adopts the CV-TF-RRDE setup; (ii) does not lean on the simplifications associated with the conventional Butler-Volmer kinetic description of electrochemical processes; and (iii) does not make assumptions on the specific features of the EC. As a result, the proposed method allows to compare accurately the kinetic performance of ORR ECs exhibiting a completely different chemistry. Finally, it is shown that the figure of merit considered in this method, E(j Pt(5%)), is much more accurate than other popular figures of merit to gauge the ORR such as the half-wave potential E1/2. Acknowledgements This research has received funding from (a) the European Union’s Horizon 2020 research and innovation program under grant agreement 881603 (b) the project ‘Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells’ funded by EIT Raw Materials, (c) Alkaline membranes and (platinum group metals)-free catalysts enabling innovative, open electrochemical devices for energy storage and conversion d AMPERE, FISR 2019 project funded by the Italian Ministry of University and Research, and (d) the project ‘Hierarchical electrocatalysts with a low platinum loading for low-temperature fuel cells d HELPER’ funded by the University of Padova. PJK and IAR (University of Warsaw) were supported in part by the National Science Center (NCN, Poland) under Opus Project 2018/29/B/ ST5/02627.

The technology of Redox Flow Batteries is an important option to store energy from the operating irregularly renewable energy sources. The perspectives concern stationary energy storage, including grid-scale energy storage, thanks to their high power performance, flexible design, and ease of scaling-up. The flow-based electrochemical energy storage systems utilize the appropriate electroactive species dissolved in externally flowing electrolytes which are ready to accumulate all (or part) of the charge. Among important issues is the search for highly efficient (i.e., capable of fast electron transfers) electroactive systems that would yield high power and energy densities during the systems’ operation. In the present work, we concentrate on utilization of highly concentrated iodine/iodide redox systems and their possibility to exhibit high rates of charge propagation. In practical terms, it can be combined with ZnI2, or other zinc salt, containing electrolyte. Reactions in the zinc/iodine (polyiodide) redox flow battery are as follows: Zn → Zn2+ + 2e- (E = −0.76 V vs SHE) at the negative electrode (anode), and 3I- → I3 − + 2e− (E = 0.54 V vs SHE) at the positive electrode (cathode) thus yielding a total theoretical potential output as high as ∼1.3 V. The increase of current density could be achieved not only by reducing the viscosity of the electrolyte, thus accelerating charge-carrier transport, but also – by referencing to my experience with the iodine/iodide couple as charge relay for dye-sensitized solar cells – through improvement of the dynamics of charge propagation in highly concentrated iodine/iodide solution via the catalyzed enhancement of rates of electron self-exchange (hopping) between iodine/iodide (polyiodide) redox species as well as by accelerating the interfacial kinetics at electrodes. This can be realized by choosing appropriate electrode materials and through their activation or modification. The electrochemical activities of the redox couples are usually significantly increased through application of nanostructured functionalized carbons. While dispersed in solutions they can improve electron transfers to the redox sites. The proposed chemistry has been first tested using the microelectrode methodology to determine mass-transport (effectively diffusional) coefficients for charge propagation, heterogeneous and homogeneous (electron self-exchange) rates of electron transfers. Unless catalyzed, both interfacial and bulk (self-exchange) electron transfers involving the iodine/iodide redox system are somewhat complicated; there is a need to break the I-I bond in the I3 -or I2 molecule; it has also been well-established that platinum (e.g. when deposited on the counter electrode) induces electron transfers within the iodine/iodide redox system [1]. In the presentation, we are going to explore the respective interfacial (electrocatalytic) phenomena on nanostructured metal oxides (e.g. zirconia), in addition to traces of expensive platinum or palladium nanoparticles (provided that catalytic centers are three-dimensionally distributed in the electrolyte phase), and we will utilize them to enhance iodine/iodide electron transfers to develop a new generation of redox mediators or ultra-fast components of redox electrolytes. Our results show that the catalyzed iodine/iodide system can reach extremely high electron self-exchange rates, namely on the level of 109 – 1010 mol-1 dm3 s-1 . [1] I.A. Rutkowska I.A., M. Marszalek, J. Orlowska, W. Ozimek, S.M. Zakeeruddin, P.J. Kulesza, M. Grätzel, ChemSusChem 8 (2015) 2560-2568.

Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, under such condition, O2-reduction reaction (ORR) often proceeds at a less positive potential, and produces higher amounts of undesirable H2O2-intermediate. Recent studies have demonstrated that the rational design of a catalytic system is based on nanostructures of platinum, or carbon-supported platinum (Pt/C), and metal oxide (MOx). By combining the catalytic properties of both components, such hybrid Pt-MOx catalysts are capable of tuning of the activity and durability of Pt. Due to strong interactions of MOx with Pt catalytic nanoparticles leading to the improved activity and durability during ORR, certain nanostructured metal oxides are considered as co-catalysts or active components of supports. The existence of specific interactions between MOx and noble metal (Pt) nanoparticles should improve the stability and activity of the metal catalytic sites due to modification of the Pt electronic structure and diminishing of the oxo (OH) species adsorption on Pt surface, thus promoting centers for the adsorption of oxygen and the cleavage of O=O bonds. The interactions mentioned above would also facilitate dispersion of Pt, inhibit their detachment and further aggregation, and, consequently, prevent or decrease their degradation during the fuel cell operation [1]. The catalytic activity of substoichiometric ceria, CeOx (where x < 2) additive results from its unique structure, presence of oxygen vacancies, and other features resulting from the 4f-electronic configuration of cerium. While the oxygen defects are likely to serve as active oxygen adsorption sites, the mixed-valent CeIII/CeIV redox sites should permit the electron shuffling within the lattice of oxygen vacancies and enhancing the ORR activity. The formation of oxygen-defects is accompanied by the localization of electrons left behind in Ce 4f states, thus leading to the formation of CeIII species capable of elongating and reducing the O–O bond strength of the adsorbed O2 molecule; consequently, by increasing the relative ratio of CeIII-to-CeIV, the ORR electrocatalytic activity can be improved [1]. Therefore, in the present study, we consider the intentionally reduced CeOx nanostructured components through subjecting them to high-temperature pretreatment in the presence of argon gas admixed with hydrogen. It is reasonable to expect that, the increased population of CeIII sites on the surfaces of the pretreated ceria particles would stabilize the neighboring active Pt-metal centers, exhibit reductive interactions toward Pt-oxo species, and to improve durability of the catalytic materials. Thus the boundary formed between the Pt-metal and CeOx-metal oxide should facilitate inhibition of the Pt oxide formation by the CeOx layer. Furthermore, our recent studies clearly show that, in the presence of ceria, the oxidative degradation of carbon carriers is also largely decreased. Finally, cerium oxide is known to act as the oxidative scavenger for free radicals such as hydroxyl (HO•) and hydroperoxyl (HOO•), which, once generated, would otherwise lead to the formation of undesirable hydrogen peroxide. Sub-stoichiometric CeOx is capable of rapidly switching between CeIII and CeIV oxidation states, thus inducing the decomposition of both radicals and peroxides. The above observation seems to be very helpful when it comes to designing highly active and durable ORR catalysts containing low platinum loadings. [1] A.Kostuch, I.A. Rutkowska, B. Dembinska, A. Wadas, E. Negro, K. Vezzù, V. Di Noto, P.J. Kulesza, Molecules 26 (2021) 5147. Acknowledgements: This work was supported by the National Science Center (Poland) under Opus Project (2018/29/B/ST5/02627) and under auspices of the European Union EIT Raw Materials ALPE 19247 Project (Specific Grant Agreement No. EIT/RAW MATERIALS/SGA2020/1).

Redox flow batteries are of potential importance to both large scale energy storage and powering the electrical vehicle. It is now accepted that flow batteries are the battery technology with the greatest potential to be one of the key elements in the energy transition to a sustainable electricity supply. Among critical challenges are low volumetric energy density of redox electrolytes, high cost and the maintenance limitations that greatly impede the wide application of conventional flow batteries. In this respect, the redox-active charge-storage material has a significant impact on the performance of a flow battery. The concentration of redox centers and their reaction kinetics have an influence on the available current densities and, thus, the power of the device. Many inorganic and organic electroactive systems have been proposed as alternatives to vanadium species in redox flow batteries. In the study, we explore the concept that highly concentrated solutions of the polyoxometallates of molybdenum and tungsten can serve as model examples of multi-electron systems for all-liquid redox flow batteries and related fundamental investigations. Polyoxometallates are polynuclear inorganic materials with well-defined multi-electron reversible electrochemistry and electrocatalytic properties [1]. Among other important characteristics of heteropolyacids are that they exhibit very strong Brønsted acidity, act as proton conductors, and undergo fast, reversible, multi-electron electron transfers leading to the formation of highly conducting, mixed-valence (e.g. tungsten(VI,V) or molybdenum(VI,V) heteropoly blue) compounds. The polyoxometallate-based redox electrolytes have different chemical identities, and they could be considered as anolytes or catholytes, depending on their redox potentials but, typically, their use would require formation of an asymmetric system with different-type redox species. The scope of existing inorganic and organic electroactive materials can be expanded due the possibility of their functionalization and structural modification. Recent developments in the area of the transition-metal-derivatized polyoxometallates are also promising [2] because they imply the feasibility of formation of the bi-redox polyoxmetallate-based electrolytes. In particular, the systems containing such metals as copper, iron, ruthenium, nickel or tin could of interest. Such features as the feasibility of reversible multi-electron redox processes, the improved potential output and cycling performance, sufficiently high solubility and reasonable stability will be examined here. An alternative approach can be based on the preparation of robust zeolite-type cesium salts of polyoxometallates, Cs2.5H0.5PMo12O40, Cs2.5H1.5SiMo12O40, Cs2.5H0.5PW12O40, and Cs2.5H1.5SiW12O40. It is noteworthy that, at certain contents of cesium (or rubidium), these porous salts are characterized by fast charge propagation. They can be considered for application in a form of colloidal suspensions. While kinetics of electrochemical processes has an influence on the systems’ current densities, the viscosity of the electrolyte and the mass transport dynamics are also affected by the choice of the redox-active material and its concentration. Trying to develop useful electroanalytical diagnostic criteria, we are going to extend the historical concepts of charge propagation in semi-solid or semi-liquid systems developed for mixed-valence redox polymers and polynuclear materials to the development of redox electrolytes. Fundamental electroanalytical approaches utilizing ultramicrodisk electrodes and interdigitated arrays will be adapted to characterization of solid suspensions synthesized in a form of stable colloidal solutions utilizing redox active centers capable of exhibiting fast electron transfers according to electron hopping mechanism. Of additional interest is the dynamics of electron transfer at the electrolyte/electrode interface, considered at the molecular and monolayer scales. [1] I.A. Rutkowska, P.J. Kulesza, “Metal Oxide Cluster and Polyoxometallate Supports for Noble Metal Nanoparticles in Efficient Electrocatalysis” in Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Elsevier, vol. 5, pp 207–216, 2018. [2] J. Goura, B.S. Bassil, J.K. Bindra, I.A. Rutkowska, P.J. Kulesza, N.S. Dalal, U. Kortz, Chemistry - A European Journal 26 (2020) 15821 – 15824.

In the recent years, the global energy economy is experiencing a transition towards its production from more sustainable and “green” sources. The intrinsic characteristics of these methods, such as the intermittency and misalignment between disposability and demand, require the use of energy storage systems, such as secondary batteries. Despite the high performance of Li-ion batteries, the high cost, low abundance and toxicity of their components (e.g., the Co-based cathodes) request the development of new devices based on novel chemistries. In this regard, the holy grail is the production of battery systems based on abundant multivalent metals. It has been recently demonstrated that ionic liquids (ILs) are suitable solvents in order to obtain stable and high performing electrolytes able to conduct and deposit/strip multivalent metals [1-5]. The outstanding electrochemical properties of these materials are ensured by the presence of a high-reactive magnesium salt (i.e., the “delta” form of MgCl2) and of a suitable metal halide (e.g., AlCl3, TiCl4, etc.). In this project we have developed a family of IL-based electrolytes for the Mg2+ ion conduction doped with an alkyl tin halide compound. In this way, the hybrid chemico-physical properties of Sn-based species can be exploited to improve the coordination existing between the inorganic magnesium salt and the organic IL. An advanced study on the thermal and structural properties of the proposed material will be presented, with a particular focus on the interactions established between the different chemical species and complexes composing the materials. Insights on the conductivity mechanism occurring in a wide range of temperature will be gauged and thoroughly described by means of the broadband electrical spectroscopy studies. Acknowledgments The project “Interplay between structure, properties, relaxations and conductivity mechanism in new electrolytes for secondary Magnesium batteries” (Grant Agreement W911NF-21-1-0347-(78622-CH-INT)) of the U.S. Army Research Office. The project “ACHILLES” (prot. BIRD219831) of the University of Padua. The project “VIDICAT” (Grant Agreement 829145) of the FET-Open call of Horizion 2020. References [1] G. Pagot, K. Vezzù, S. Greenbaum and V. Di Noto, Journal of Power Sources 492 (2021) 229681. [2] R. Dominko, J. Bitenc, R. Berthelot, M. Gauthier, G. Pagot and V. Di Noto, Journal of Power Sources 478 (2020) 229027. [3] G. Pagot, F. Bertasi, K. Vezzù, F. Sepehr, X. Luo, G. Nawn, E. Negro, S.J. Paddison and V. Di Noto, Electrochimica Acta 246 (2017) 914-923. [4] F. Bertasi, F. Sepehr, G. Pagot, S.J. Paddison and V. Di Noto, Advanced Functional Materials 26 (2016) 4860-4865. [5] F. Bertasi, C. Hettige, F. Sepehr, X. Bogle, G. Pagot, K. Vezzù, E. Negro, S.J. Paddison, S.G. Greenbaum, M. Vittadello and V. Di Noto, ChemSusChem 8 (2015) 3069-3076.

The proton-exchange membrane fuel cell (PEMFC) technology is one of the most promising approaches for energy conversion in automotive applications. Despite the use of expensive noble metal electrocatalysts, the sluggish kinetics of the oxygen reduction reaction (ORR) in acid media, and formation of the undesirable hydrogen peroxide intermediate are still the main drawbacks, on top of the stability problems, when it comes to the widespread commercialization of PEMFC devices. The progress in this subject is greatly hindered by the high cost and scarcity of the state-of-the-art platinum-based materials which are regarded as the most effective cathode catalysts. Therefore, most of the current research studies have been devoted to the optimization of active centers and maximization of their utilization, which should allow the lowering of the cathode Pt loadings without loss of performance and durability. Unfortunately, the problem of electrochemical stability and the danger of generation of higher quantities of the undesirable hydrogen peroxide intermediate may become even more serious in the case of systems utilizing lower amounts of the Pt catalyst Among important strategies is hybridization, activation, and stabilization of carbon-supported Pt catalysts by functionalization through admixing with certain nanostructured and typically substoichiometric metal oxides. Special attention is paid to application of the bi- or multi-metallic Pt-based alloys in their various forms and structures. Additionally, doping of carbon carriers with heteroatoms would produce surface functional groups and active centers capable of not only improving the catalysts’ performance, but also affecting their stability. Among other important issues are such features as porosity, hydrophilicity, and degree of graphitization of carbon components, in addition to the existence of metal–support interactions, high electrochemical active surface area, electronic structure of interfacial Pt, and the feasibility of adsorptive or activating interactions with oxygen molecules. Voltammetric approaches, particularly the rotating ring-disk electrode (RRDE) methodology, are typically applied to diagnose mechanisms and dynamics of ORR. A tempting alternative for recording the electrochemical responses is to integrate the current and to report charge passed as a function of time. Chronocoulometry offers important advantages including good signal-to-noise ratio because the act of integration smooths random noise on the current transients. Furthermore, by integrating the responses, it is possible to separate surface phenomena (e.g. interfacial oxidation of carbon or platinum) more readily from bulk electrochemical responses (ORR). The double-potential-step chronocoulometry permits, in principle, estimation of the number of electrons (n) involved in the oxygen reduction and the percent of formation of the H2O2 intermediate. The problem lies in understanding the reaction kinetics and mechanisms in order to define properly experimental parameters (potential steps and pulse times). Comparative measurements are performed using RRDE voltammetry. Hybrid supports, which utilize metal oxides (e.g., CeO2, WO3, or ZrO2) have been demonstrated to stabilize Pt and carbon nanostructures and diminish their corrosion while exhibiting high activity toward the four-electron (most efficient) reduction of oxygen. Acknowledgements: This work was supported by the National Science Center (Poland) under Opus Project (2018/29/B/ST5/02627) and under auspices of the European Union EIT Raw Materials ALPE 19247 Project (Specific Grant Agreement No. EIT/RAW MATERIALS/SGA2020/1).

The widespread commercialization of proton-exchange membrane fuel cells (PEMFCs) is still bottlenecked by the high loading of platinum-group elements (PGMs), typically platinum, in the cathodic electrocatalytic layer. One strategy to overcome the sluggish kinetics of the oxygen reduction reaction (ORR) taking place at the PEMFC cathode is to increase the mass activity of Pt by implementing Pt-alloy electrocatalysts (ECs) [1]. This strategy allows to decrease the overall Pt loading in the membrane electrode assembly (MEA), the crucial functional component at the heart of the PEMFC. This contribution discusses “core-shell” hierarchical ECs (H-ECs) consisting of: (i) a hierarchical “core” comprising a blend of nanostructured carbons, that are covered by (ii) a carbon nitride (CN) “shell” wherein Pt-alloy active sites are stabilized by C- and N- ligands in “coordination nests” [2]. The active sites are based on Pt together with Ni and Cu as “co-catalysts” to enhance the ORR kinetics [3]. The bulk of the support of the H-ECs is minimized to promote mass transport phenomena. The morphology of the H-ECs is probed by ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM), and is discussed in relation to the synthetic parameters and chemical composition. In a second step, nitrogen physisorption techniques are used to evaluate the porosimetric features of the H-ECs, including the specific surface area and the size distribution of the pores. The porosimetric and morphological features are correlated with the electrochemical performance of the H-ECs as measured: (i) “ex-situ”, via cyclic voltammetry with the thin-film rotating ring-disk electrode method (CV-TF-RRDE); and (ii) in single PEMFC under operating conditions as a function of the partial pressure of oxygen in the cathodic feed. A new framework is finally proposed to rationalize and quantify the porosity-morphology-performance correlation for the H-ECs. References [1] Y. Sun, S. Polani, F. Luo, S. Ott, P. Strasser, F. Dionigi. Nature Commun. 12, 5984 (2021). [2] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn. Electrochem. Soc. Interface, 24, Summer 2015, 59-64 (2015). [3] V. Di Noto, E. Negro, A. Bach Delpeuch, F. Bertasi, G. Pagot, K. Vezzù, Patent application PCT/EP2017/084801 (2017). Acknowledgements The described research has received funding from: (a) the European Union's Horizon 2020 research and innovation programme under grant agreement 881603; (b) the project "Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells" funded by EIT Raw Materials; and (c) the project "Hierarchical electrocatalysts with a low platinum loading for low-temperature fuel cells e HELPER" funded by the University of Padova.

A family of hybrid inorganic-organic ion-exchange membranes (IEMs) is prepared, indicated as [Nafion/(WO3)x]. The IEMs consist of Nafion® dispersing different loadings (x) of tungsten oxide nanofiller. Morphology studies carried out by scanning electron microscopy (SEM) and micro-Raman investigations reveal that one side of each hybrid IEM exhibits a high concentration of the WO3 nanofiller. In the remaining part of each IEM the concentration of the filler is much lower and constant. The correlation between the asymmetrical nature and the performance of the hybrid IEMs is studied in a single-cell vanadium redox flow battery (VRFB). In comparison with the Nafion 212 reference, at the same current density of 50 mA∙cm−2, [Nafion/(WO3)0.587] demonstrates: (i) a higher Coulombic efficiency (93% vs. 88%), a higher energy efficiency (75% vs. 65%) and a higher capacity retention (62% vs. 42%).

The electrical relaxation and polarization phenomena of electrospun PVDF (P)/Nafion (N) blended fiber mats ([P/N0.9]M and β–[P]M) and membranes ([P/N0.9]MM) are compared with those of the solvent-c...

Platinum nanoparticles have been deposited onto hybrid carriers composed of iron hexacyanoferrate (Prussian Blue) pretreated or functionalized reduced graphene oxide (rGO), and the resulting system’s electrocatalytic activity has been investigated during oxygen reduction reaction in acid solution. Physicochemical properties of the Pt nanoparticle-containing materials have been obtained using transmission electron microscopy, X-ray diffraction and various electrochemical diagnostic techniques including cyclic voltammetry and rotating ring-disk electrode (RRDE) voltammetry. Although functionalization of rGO carriers with Prussian Blue, followed by the system’s thermal treatment at 300°C, does not change activity of Pt catalytic centers in terms of the electroreduction potential of oxygen in 0.5 mol dm−3 H2SO4 (under rotating disk voltammetric conditions), the presence of cyanide-bridged iron ionic sites tends to decrease formation of the undesirable hydrogen peroxide intermediate, as demonstrated by monitoring ring currents during RRDE measurements. The results imply usefulness of PB-modified rGO supports for dispersed Pt nanoparticles at the low loading of 10 μg cm−2 in the oxygen reduction electrocatalysis. In addition to the possible metal-support activating interactions, the mechanism, in which oxygen reduction is initiated at Pt centers and the hydrogen peroxide intermediate is reductively decomposed at reactive PB-modified rGO supports, is feasible.

Mixed-metal olivine cathode materials are one of the most promising systems in the field of lithium batteries. Their main drawback is their low electronic conductivity, which limits the current rate at which they can be cycled. Herein, the effect on electrochemical properties of vicariant high-valence transition metals (HVTMs) inserted in the olivine crystal structure has been studied. The strategy adopted herein consists of doping a LiFe1/3Ni1/15Co3/5PO4 cathode by substituting part of the cobalt(II) ions with vanadium(IV), niobium(V), or tantalum(V) HVTMs. The WAXD studies reveal that small HVTMs in molar quantities (HVTM/P = 0.04) are vicariant into the olivine crystal lattice. Single-cell tests show that the Nb-doped cathode has a high-voltage (ca. 4.5 V) and a specific capacity of 149 mA h g−1 (656 mW h g−1). Thus, the insertion of HVTMs in the cathode structure exceptionally improved the electric conductivity of the material and yielded an improved cyclability and rate capability owing to its electro-compensation effect.

Hybrid systems composed of the reduced graphene oxide-supported platinum and multiwalled carbon nanotube-supported iridium (both noble metals utilized at low loadings on the level of 15 and &le, 2 &micro, g cm&minus, 2, respectively) were considered as catalytic materials for the reduction of oxygen in acid media (0.5-mol dm&minus, 3 H2SO4). The electrocatalytic activity toward reduction of oxygen and formation of hydrogen peroxide intermediate are tested using rotating ring&ndash, disk electrode (RRDE) voltammetric experiments. The efficiency of the proposed catalytic systems was also addressed by performing galvanodynamic measurements with gas diffusion electrode (GDE) half-cell at 80 &deg, C. The role of carbon nanotubes is to improve charge distribution at the electrocatalytic interface and facilitate the transport of oxygen and electrolyte in the catalytic systems by lowering the extent of reduced graphene oxide restacking during solvent evaporation. The diagnostic electrochemical experiments revealed that&mdash, in iridium-containing systems&mdash, not only higher disk currents, but also somehow smaller ring currents are produced (when compared to the Ir-free reduced graphene oxide-supported platinum), clearly implying formation of lower amounts of the undesirable hydrogen peroxide intermediate. The enhancement effect originating from the addition of traces of iridium (supported onto carbon nanotubes) to platinum, utilized at low loading, may originate from high ability of iridium to induce decomposition of the undesirable hydrogen peroxide intermediate.

The electrical response of zirconia composite polybenzimidazole membranes [PBI4N(ZrO2)x](H3PO4)y is studied by Broadband Electrical Spectroscopy (BES), and correlated with our previous Dynamic Mechanical Analysis (DMA) and Modulated Differential Scanning Calorimetry (MDSC) measurements. The presence of nanofiller in the PBI4N polymer matrix is shown to plasticize the membrane, with a maximum effect observed at a nanofiller loading level of x ≈ 0.13. The disrupting effect of the nanofiller on the interchain dipole interactions modulates the overall electrical response of the materials. Following acid doping, a marked increase in conductivity is observed as new chemistry is installed at the interfaces between polymer and nanofiller that facilitates dipolar fluctuations and segmental motions of the polymer chains. In these composite membranes, two mechanisms of conductivity are postulated based on BES analysis; i) proton hopping between binding sites, and ii) proton hopping at the interfaces between HnPBI4Nn+/HnPBI4Nn+ and HnPBI4Nn+/HmZrO2m+. The results here presented demonstrate the effect of zirconia nanofiller and subsequent acid doping on the conductivity properties of composite PBI4N membranes. Of note, at 100 °C for [PBI4N(ZrO2)0.132](H3PO4)11, conductivity as high as 0.035 S/cm is achieved.

Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, then O2-reduction often proceeds at a less positive potential, and produces higher amounts of undesirable H2O2-intermediate. Hybrid supports, which utilize metal oxides (e.g., CeO2, WO3, Ta2O5, Nb2O5, and ZrO2), stabilize Pt and carbon nanostructures and diminish their corrosion while exhibiting high activity toward the four-electron (most efficient) reduction in oxygen. Porosity of carbon supports facilitates dispersion and stability of Pt nanoparticles. Alternatively, the Pt-based bi- and multi-metallic catalysts, including PtM alloys or M-core/Pt-shell nanostructures, where M stands for certain transition metals (e.g., Au, Co, Cu, Ni, and Fe), can be considered. The catalytic efficiency depends on geometric (decrease in Pt–Pt bond distances) and electronic (increase in d-electron vacancy in Pt) factors, in addition to possible metal–support interactions and interfacial structural changes affecting adsorption and activation of O2-molecules. Despite the stabilization of carbons, doping with heteroatoms, such as sulfur, nitrogen, phosphorus, and boron results in the formation of catalytically active centers. Thus, the useful catalysts are likely to be multi-component and multi-functional.

A critical bottleneck of PEMFC operation is the performance of the cathode electrode, where the oxygen reduction reaction (ORR) takes place. Two of the most important phenomena that conspire to curtail the cathode performance are: (i) the sluggish kinetics of the oxygen reduction reaction (ORR) [1]; and (ii) the mass transport issues. In particular, the latter become progressively more evident as the current density of the PEMFC is increased upon approaching operating conditions that are relevant for practical applications [2]. Both of these shortcomings are addressed by developing new ORR electrocatalysts (ECs). The ECs described here exhibit a “core-shell” morphology: a hierarchical graphene-based support (H-GR) “core” is covered by a carbon nitride “shell” stabilizing the active sites in “coordination nests” [3]. The “core” comprises highly defected graphene nanoplatelets [4] and carbon black nanoparticles; the latter act as spacers and facilitate the charge and mass transport phenomena occurring during the EC operation. The ECs proposed here are characterized by a significant loading of platinum (on the order of ca. 20-40 wt%), that is the “active metal”. Ni and Cu are introduced as the “co-catalysts” to further boost the ORR kinetics of the ECs [3]. The high loading of “active metal” and “co-catalyst” in the ECs is meant to minimize the bulk of the support, facilitating mass transport phenomena. The innovative support of the proposed ECs is very different from that typically adopted in the state of the art in terms of morphology and especially porosity. Thus, this latter feature is to be studied in detail to fully exploit the potential of such support and guide the synthesis of new ECs beyond today’s state of the art. This information is achieved by a comprehensive characterization of the proposed ECs by a variety of porosimetric methods involving the adsorption of suitable probe molecules. Physisorption of N2 is carried out to evaluate the specific surface area of the ECs, together with their micro- and mesoporosity. Water adsorption is executed as well, being a crucial tool to elucidate the hydrophobicity of the ECs. Indeed, the latter feature is critical to prevent electrode flooding during PEMFC operation. Furthermore, through the study of the real ECs’ density a new parameter is proposed, namely the surface area per volume “Σ” (expressed as m2/cc). This latter is of paramount importance to design efficient membrane electrode assemblies (MEAs). As a final step, the results of morphologic/porosimetric studies are correlated with: (i) the outcome of both bulk and surface chemical characterizations carried out by CHNS microanalysis, energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS); and (ii) the “ex-situ” intrinsic ORR performance and selectivity in the 4-electron mechanism determined by cyclic voltammetry with the thin-film rotating ring-disk method (CV-TF-RRDE). Acknowledgements The research leading to the results reported in this work has received funding from: (a) the European Union’s Horizon 2020 research and innovation programme under grant agreement 881603; (b) the project “Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells” funded by EIT Raw Materials; and (c) the project “Hierarchical electrocatalysts with a low platinum loading for low-temperature fuel cells e HELPER” funded by the University of Padova. References [1] I. Katsounaros, S. Cherevko, A. R. Zeradjanin, K. J. J. Mayrhofer, Angew. Chem. Int. Ed., 53, 102 (2014). [2] R. O'Hayre, S.-W. Cha, W. Colella, F. B. Prinz, Fuel Cell Fundamentals, Wiley (2016). [3] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn, The Electrochemical Society Interface, Summer 2015, (2015) 59-64. [4] V. Di Noto, E. Negro, A. Bach Delpeuch, F. Bertasi, G. Pagot, K. Vezzù, Patent application PCT/EP2017/084801 (2017).

New and novel systems for the reversible electrochemical storage of energy are required to sustain the increasing global energy demands. Indeed the high cost, the intrinsic energy limits and the strategic aspects of lithium and lithium technology-related metals (e.g., Co) are prompting the research towards the development of battery systems based on novel chemistries. In this regard, light multivalent metals are considered the holy grail. Magnesium and aluminum, for example, can be considered one of the best choices due to their low reduction potential (-1.66 and -2.37 V vs. SHE for Al3+/Al and Mg2+/Mg, respectively), high volumetric and gravimetric theoretical capacities (2980 Ah∙kg-1 and 8046 Ah∙dm-3 for Al, and 2205 Ah∙kg-1 and 3832 Ah∙dm-3 for Mg), high abundance in the Earth’s crust and low cost (1’925 and 2’700 $∙ton-1 for Al and Mg, respectively) [1, 2]. The main roadblock to the development of these technologies is the discovery of efficient, stable and high-performing electrolytes. Ionic liquids have been demonstrated to be a good choice to be used as solvents in multivalent metal electrolytes, thanks to the low volatility and high solvating powers [3, 4]. Despite large efforts, there are no examples in the literature that demonstrate the advantage of the synergic effect of the coupling of Mg2+/Al3+ in the deposition and stripping processes. Moreover, the fundamental understanding of ion coordination in this novel class of electrolytes would be a cornerstone information necessary to reveal the conduction mechanism. In this work we study the properties of a family of hybrid Al/Mg electrolytes with formula [Pyr14Cl/(AlCl3)1.5]/(δ-MgCl2)x (x = 0, 0.056, 0.091 and 0.146), to foster the synergic effect of these two metals for application in multivalent metal secondary batteries. In this study we combine thermal analyses, vibrational, electric and nuclear magnetic spectroscopies to achieve a clear picture of the ionic coordination occurring in the proposed electrolytes and how ions are able to rearrange and form ionic coordination nanodomains. It is demonstrated that AlCl4 - and Al2Cl7 - species are formed, which act as ligands for δ-MgCl2 units. Thus, the Mg2+/Al3+ conduction occurs through the exchange of anionic species between the different ionic clusters. These phenomena are significantly correlated to the host medium dynamics of the IL matrix. The rise of the temperature results in an increased degree of disorder in the nanodomains, which modifies the long-range charge migration process. Finally, the electrochemical activity in the synergic Al/Mg alloy deposition and stripping is demonstrated. Acknowledgements This project has received funding from the program “Budget Integrato per la Ricerca Interdipartimentale - BIRD 2018” of the University of Padova (protocol BIRD187913). References [1] R. Dominko, J. Bitenc, R. Berthelot, M. Gauthier, G. Pagot, V. Di Noto, Magnesium batteries: Current picture and missing pieces of the puzzle, Journal of Power Sources, 478 (2020) 229027. [2] D.J. Kim, D.-J. Yoo, M.T. Otley, A. Prokofjevs, C. Pezzato, M. Owczarek, S.J. Lee, J.W. Choi, J.F. Stoddart, Rechargeable aluminium organic batteries, Nature Energy, 4 (2019) 51-59. [3] F. Bertasi, C. Hettige, F. Sepehr, X. Bogle, G. Pagot, K. Vezzù, E. Negro, S.J. Paddison, S.G. Greenbaum, M. Vittadello, V. Di Noto, A Key concept in Magnesium Secondary Battery Electrolytes, ChemSusChem, 8 (2015) 3069-3076. [4] F. Bertasi, F. Sepehr, G. Pagot, S.J. Paddison, V. Di Noto, Toward a Magnesium-Iodine Battery, Adv. Funct. Mater., 26 (2016) 4860-4865.

Lithium batteries (LiBs) are among the most promising systems that could address today’s strongly increasing needs for an efficient, compact and reversible electrochemical storage of energy [1]. Indeed, LiBs are characterized by a high specific capacity, a high efficiency, and a long lifespan [2]. Unfortunately, improvements in the working potential, in the specific energy, and in the rate capability properties of the cathodes are still needed to comply with the specifications required by practical applications. This work describes the synthesis and the characterization of a new family of high-voltage and high-rate cathodes for LiBs. A high-performing olivine material of the type LiMPO4 (M = Fe, Ni, and Co) [3] has been modified by inserting into the structure high-valence transition metal ions (e.g., V(V), Nb(IV), and Ta(IV)) [4]. The effects of the insertion of the different ions on the structural, morphological, electrical and electrochemical properties of the materials have been thoroughly studied. The stoichiometry is evaluated by means of Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES); the morphology and size distribution of the grains are characterized by Scanning Electron Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM); the structure is examined by powder X-Ray Diffraction (XRD) as well as a variety of IR spectroscopy techniques. The electrochemical characterization is carried out by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and charge/discharge tests at different current rates. Finally, the conductivity mechanism is studied by Broadband Electrical Spectroscopy (BES). The cathode materials described in this report exhibit a high performance in terms of working potential (4.0 ÷ 5.0 V vs. Li/Li+), specific capacity (149 mAh∙g-1), and specific energy (656 mWh∙g-1). Moreover, the insertion of high-valence transition metals results in an improvement of the rate capability of the cathodes, allowing for fast charge and discharge processes. References [1] V. Di Noto, T. A. Zawodzinski, A. M. Herring, G. A. Giffin, E. Negro, S. Lavina, Int. J. Hydrogen Energy 37 (2012) 6120-6131. [2] B. Scrosati, J. Garche, J. Power Sources 195 (2010) 2419-2430. [3] G. Pagot, F. Bertasi, G. Nawn, E. Negro, G. Carraro, D. Barreca, C. Maccato, S. Polizzi, V. Di Noto, Adv. Funct. Mater. 25 (2015) 4032-4037. [4] G. Pagot, M. Bandiera, K. Vezzù, A. Migliori, R. Bertoncello, E. Negro, V. Morandi, V. Di Noto, Journal of Materials Chemistry A, doi: 10.1039/D0TA06865A

Electrochemical energy conversion and storage (EECS) systems are of major interest for both industry and scientific community due to their high energy conversion efficiency and easy scalability [1]. Two families of EECS systems are attracting particular attention: ion-exchange membrane fuel cells and redox flow batteries (RFBs). On one hand, ion-exchange membrane fuel cells are particularly suited for light-duty vehicles and small-scale stationary systems (e.g., auxiliary power units) owing to their high energy and power densities. On the other hand, RFBs (with a particular reference to all-vanadium redox flow batteries, VRFBs) are ideally suited to the large-scale storage of energy for the power grid as they are characterized by a very high turnover efficiency and an outstanding cyclability. Electrolyte membranes (EMs) are found at the core of both ion-exchange membrane fuel cells and VRFBs. The role of such EMs is to: (i) keep separated the electroactive species involved in the redox reactions taking place at the electrodes and, at the same time, (ii) ensure a facile and selective migration of ions to prevent the polarization of the device and allow for the establishment of large current densities. As of today, the most widely adopted EMs for both ion-exchange membrane fuel cells and VRFBs are based on perfluorinated ionomers such as Nafion™ and other similar macromolecules [2]. These systems exhibit an outstanding proton conductivity and a very high chemical and electrochemical stability; however, they also suffer from important drawbacks such as: (i) a dramatic drop in conductivity at T > 80°C and in dry conditions; (ii) poor mechanical properties; and (iii) a large permeability to vanadium species [3, 4]. Consequently, it is often necessary to: (i) add humidification modules to ion-exchange membrane fuel cells, thus raising the bulk and cost of the device; or (ii) especially in the case of VRFBs, use thick EMs that curtail the current density. These drawbacks can be addressed by implementing several different strategies, that include: (i) the introduction of a filler in the EM, giving so rise to a hybrid inorganic-organic membrane [5]; (ii) the fabrication of the EM with a different macromolecule (e.g., a sulfonated polyaromatic system such as sulfonated polyether ether ketone, SPEEK [6]) and (iii) the doping of the EM with an ion-conducting medium (e.g., phosphoric acid [7], or a proton-conducting ionic liquid [8]). All of these strategies operate by modulating the physicochemical properties of the EMs, with a particular reference to the details of the phase segregation at the nano/mesoscale. This work overviews the study of the interplay between the physicochemical properties of hybrid ion-exchange membranes (with a particular reference to the chemical composition, thermoanalytical properties, morphology and structure), and the electrical response as determined by means of advanced investigation techniques such as Broadband Electrical Spectroscopy (BES). Results allow to: (i) elucidate the interactions between the different phases and components within each EM; and (ii) clarify the conductivity mechanism. On these bases, it is possible to identify the most promising avenues of research to devise EMs for application in ion-exchange membrane fuel cells and RFBs exhibiting a performance and a cyclability beyond the state of the art. Acknowledgement We acknowledge the support from: (a) the European Union’s Horizon 2020 research and innovation programme under grant agreement 881603; (b) the project “Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells” funded by EIT Raw Materials; and (c) the project “HELPER” funded by the University of Padova; and (d) the BIRD 2020 program of UNIPD. References [1] B. Dunn, H. Kamath, J.M. Tarascon, Science, 334, 928 (2011). [2] V. Di Noto, T. A. Zawodzinski, A. M. Herring, G. A. Giffin, E. Negro, S. Lavina, Int. J. Hydrog. Energy, 37, 6120 (2012). [3] C. Sun, A. Zlotorowicz, G. Nawn, E. Negro, F. Bertasi, G. Pagot, K. Vezzù, G. Pace, M. Guarnieri, V. Di Noto, Solid State Ionics, 319, 110 (2018). [4] C. Sun, K. Vezzù, G. Pagot, A. Nale, Y. Herve Bang, G. Pace, E. Negro, C. Gambaro, L. Meda, T. A. Zawodzinski, V. Di Noto, Electrochim. Acta 318, 913-921 (2019). [5] V. Di Noto, M. Piga, G. A. Giffin, K. Vezzù, T. A. Zawodzinski, J. Am. Chem. Soc., 134, 19099 (2012). [6] V. Di Noto, M. Piga, G. A. Giffin, G. Pace, J. Membr. Sci., 390-391, 58 (2012). [7] G. Nawn, K. Vezzù, F. Bertasi, G. Pagot, G. Pace, F. Conti, E. Negro, V. Di Noto, Electrochim. Acta, 228, 562 (2017). [8] V. Di Noto, E. Negro, J. Y. Sanchez, C. Iojoiu, J. Am. Chem. Soc., 132, 2183 (2010).

The performance of electrochemical energy conversion and storage (EECS) devices is modulated by a cascade of phenomena that include: (i) the redox processes taking place at the electrodes; (ii) the transport of charge, with a particular reference to the migration of ions through the electrolyte; and (iii) the transport of mass involved in the provision of reactants/removal of products to/from the electrodes. These phenomena are intimately correlated with one another and with all the different features of the functional materials adopted in the fabrication of the specific EECS device. Thus, it is often very complex to unravel the different contributions to overall system performance. In addition, it is not practical to pursue a purely “trial-and-error” approach where all the possible combinations of functional materials are used to fabricate and test full-fledged EECS prototypes, as this would entail too massive an investment in terms of both resources and time. For this reason, there is a great need to implement experimental approaches able to elucidate the details of specific electrochemical features (e.g., reaction kinetics) of the various functional materials used in EECS devices, at the same time minimizing the cloaking effects due to: (i) the formation of complex interfaces with other components of the device; and (ii) spatial and temporal inhomogeneity in the motion of both charged and neutral species through the system. The resulting information is critical in the development of advanced functional materials bestowing to the EECS device a performance and durability beyond the state of the art. Perhaps the most successful and widely adopted of such approaches is cyclic voltammetry conducted with a thin-film rotating disk electrode or ring-disk electrode (CV-TF-R(R)DE) [1]. CV-TF-R(R)DE is typically used to screen quickly the performance and the details of the reaction mechanism of electrocatalysts (ECs) for the oxygen reduction reaction (ORR). The latter process is widely exploited in a broad variety of EECS devices including fuel cells (FCs) and metal-air batteries. The ORR is particularly critical since it often bottlenecks the operation of the entire system. Even though the CV-TF-R(R)DE method is very popular and broadly used in the scientific community, most researchers do not use all its remarkable capabilities. Here it is shown how to implement both innovative and more traditional (but no longer widespread) approaches to exploit CV-TF-R(R)DE to its full potential, with the purpose to study the most relevant electrochemical features of ORR ECs and quickly identify the most promising candidates for application in FCs or other electrochemical devices [2]. Particular emphasis is devoted to analysis techniques meant to study in detail the ORR kinetic features of vastly different ECs, allowing for quantitative performance comparisons at the same high level of accuracy without risking serious distortions due to an excessive impact of corrections during data analysis. It is also shown how to adopt the CV-TF-R(R)DE approach to understand quantitatively whether an ORR EC exhibits improved morphology/mass transport features in comparison with a Pt/C benchmark. In summary, it is elucidated how to expand significantly the scope of CV-TF-R(R)DE studies with respect to the level typically achieved in the state of the art, taking into consideration both kinetic and morphology/mass transport features by means of a simple morphokinetic (MK) correlation map. Acknowledgements The research leading to the results reported in this work has received funding from: (a) the European Union’s Horizon 2020 research and innovation programme under grant agreement 881603; (b) the project “Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells” funded by EIT Raw Materials; and (c) the project “Hierarchical electrocatalysts with a low platinum loading for low-temperature fuel cells e HELPER” funded by the University of Padova. References [1] Y. Garsany, O.A. Baturina, K.E. Swider-Lyons, S.S. Kocha, Anal. Chem. 82(15) (2010) 6321-6328. [2] V. Di Noto, E. Negro, A. Nale, G. Pagot, K. Vezzù, P. Atanassov, Curr. Opinion Electrochem. 25 (2021) 100626.

A new family of ionic liquid based electrolytes ([EMImCl/(TiCl 4 ) 1.4 ]/(δ-MgCl 2 ) x ) for electrochemical applications is proposed. These materials are obtained by direct reaction of 1-ethyl-3-methylimidazolium chloride (EMImCl) with titanium(IV) chloride (TiCl 4 ), and doped with increasing amounts of δ-MgCl 2 . Modulated differential scanning calorimetry (MDSC) measurements show that in these electrolytes the glass transition temperature, T g , occurs at −36 °C, and that the crystallization and melting transitions are inhibited by the presence of large and highly amorphous charge delocalized anionic domains. Vibrational studies indicate that in the electrolyte the anionic domains consist of large monomeric and dimeric 3D-catenated halotitanate clusters, in which magnesium chloride units are coordinated to Ti species, and whose equilibrium concentration is modulated by the concentration of δ-MgCl 2 . Density functional theory (DFT) based electronic structure calculations were undertaken to understand the structural features of these materials and to confirm the vibrational frequency assignments. Broadband electrical spectroscopy (BES) studies reveal that the electric response of these materials is modulated by polarization and dielectric relaxation events. These measurements revealed the correlations existent between conductivity mechanisms and the dielectric relaxations of the host matrix of the electrolytes. At 40 °C, the conductivity is found to depend on the δ-MgCl 2 concentration and approximately on the order of 10 −4 S cm −1 . Preliminary electrochemical measurements reveal a reversible deposition and stripping process of a Mg-Ti alloy, with an average columbic efficiency of 99.3% and a deposition overvoltage of only 10 mV.

Five bimetallic electrocatalysts (ECs) including a carbon nitride (CN) support are synthesised through the pyrolysis of a solid precursor obtained through sol-gel and gel-plastic processes. The resulting ECs are characterised through ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy) and XPS (X-ray Photoelectron spectroscopy); their performance and reaction mechanism in the oxygen reduction reaction (ORR) are evaluated with the CV-TF-RRDE method (Cyclic Voltammetry Thin-Film Rotating Ring-Disk Electrode). Special attention is given to XPS results with the aim to carry out a thorough investigation of the surface concentration and the chemical environments of the different elements, as well as providing information on the structure of the metal components of the ECs and their interactions with the carbon nitride support. The correlation of the results obtained from the chemical analyses, XPS and the electrochemical studies allows to improve the fundamental understanding of: (i) the interplay between the preparation parameters and the surface and bulk chemical composition of the CN-supported ECs; and (ii) the factors controlling the ORR kinetics and reaction pathway in bimetallic CN-supported ECs, identifying the roles played by the various metal species. In this regard, the VI-period metal included in each EC has the highest impact on the ORR performance. Indeed, the ORR onset potential rises from ca. 300 to ca. 780 to ca. 900 mV vs. RHE for ECs based on Au, Ir and Pt, respectively. On the other hand, the second metal (i.e., Ni, Rh, and also Ir in the case of an EC including both Pt and Ir) plays a secondary role. With respect to the Pt/C ref., the CN-supported EC including Pt and Ni exhibits a higher onset potential (900 and 911 mV vs. RHE, respectively); finally, it is shown that Ir and Rh promote the selectivity of the ORR in the 4-electron mechanism.

A new type of polymer blend, prepared by electrospinning nanofibers containing the immiscible polymers polyvinylidene fluoride (PVDF, 10 wt%) and Nafion® perfluorosulfonic acid (90 wt%), has been characterized experimentally. The internal nanofiber morphology is unique and unlike a normal blend, with individual phase-separated and randomly distributed fibrils of Nafion and PVDF (∼2-7 nm in diameter) that are bundled together and aligned in the fiber axis direction (where the fiber diameter is ∼500 nm). This morphology is retained when fiber mats are hot-pressed into dense films. The physicochemical properties of the electrospun blended fibers are also highly unusual and unanticipated. As shown in this study, each polymer component influences the thermal and structural behavior of the other, especially in the dry state. Thus, dry composite polymer mats and membranes exhibit properties and attributes that are not observed for either pure PVDF or pure Nafion. Experimental results indicate that: (i) PVDF imparts conformational constraints on the polytetrafluoroethylene (PTFE) backbone chains of Nafion, resulting in an increased 21 helical conformation that effects Nafion's water uptake and thermal properties; and (ii) dipole-dipole interactions between PVDF polymer chains and Nafion make the β-phase polymorph of PVDF much more stable at elevated temperatures. Such "reciprocal templating" in electrospun fibers may not be unique to Nafion and PVDF, thus the procedure represents a new method of creating nanostructured multi-component polymer materials with innovative features.

The development of innovative proton-conducting membranes exhibiting an improved [H+/VO2+] ion selectivity in comparison with baseline perfluorinated ionomers (e.g., Nafion) is critical to prompt the large-scale implementation of vanadium redox flow batteries (VRFBs) characterized by a performance and cyclability compatible with the applications. This paper pursues this objective by reporting the preparation and characterization of a new family of hybrid inorganic-organic membranes, that are labeled “[SPEEK/(WO3)x]”, consisting of a sulfonated poly (ether ether ketone) (SPEEK) matrix hosting between 0 and 23.6 wt% of WO3 nanoparticles (NPs). The physicochemical characterization of the [SPEEK/(WO3)x] membranes elucidates the impact of the introduction of WO3 NPs on the thermal, structural and transport properties of the SPEEK host. It is found that the [SPEEK/(WO3)0.20] membrane presents the highest [H+/VO2+] ion selectivity (2.1 × 104 S min cm−3), that is more than three times higher than that of recast Nafion (6.5 × 103 S min cm−3). [SPEEK/(WO3)0.20] is then mounted in a single cell VRFB, that is tested extensively under realistic operating conditions and demonstrates a coulombic efficiency and cyclabilty that are improved with respect to the corresponding figures of a VRFB incorporating a Nafion 212 membrane to provide the basis for a comparison. This outcome is in compliance with the result of the “ex-situ” investigations, and allows for the proposal of a structural model correlating the physicochemical properties of the [SPEEK/(WO3)x] membranes with the transport properties and the proton conductivity.

A polyketone-b-poly[N-(4 methyl-methylpyridium)-ethylenepyrrole+][X−], with X− = I− or OH−, is investigated as an example of anion-exchange membrane with potential applications in fuel cells. The polyketone starting material PK and the functionalized polyketones Pyr-FPKmI and Pyr-FPKmOH are investigated via Broadband Electrical Spectroscopy (BES) to understand the conductivity mechanism. BES signals are collected in the frequency range of 10−2 – 107 Hz and from −100° to 120 °C. BES measurements reveal the presence of up to three interdomain polarizations phenomena, one electrode polarization event and two β dielectric relaxation modes for both wet Pyr-FPKmI and Pyr-FPKmOH. Ion conductivity for Pyr-FPKmI and Pyr-FPKmOH is found to be 0.0086 and 0.0105 S cm−1 at 80 °C, respectively. The overall conductivity mechanism is attributed to the superposition of two conduction pathways, via delocalization bodies and via interdomain percolation pathways, which are associated with two different physical phenomena.

This work reports two quasi-solid composite electrolytes based on LiFT (Lithiated Fluorinated Titania) nanopowder and either 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) or 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) ionic liquid (IL). In details, LiFT nanopowder is doped with ca. 30 wt% of IL, giving rise to materials with formula LiFT/(EMImBF(4))(0.)(183) and LiFT/(EMImTESI)(0.)(087). The resulting composite electrolytes appear as powder-like solids as the IL is completely absorbed by LiFT. The correlation between structure, thermal properties and long-range charge migration processes of the here proposed electrolytes is investigated by several characterization techniques, as follows: i) differential scanning calorimetry (DSC) and high-resolution thermog-ravimetry (HR-TGA); ii) Fourier-transform infrared spectroscopy in both the medium and the far infrared (FT-MIR and FT-FIR); and iii) broadband electrical spectroscopy (BES). The conductivity of the here proposed composite electrolytes is promising. Indeed, at 30 and 100 degrees C it corresponds respectively to 1.75 x 10(-3) S cm(-1) and 1.05 x 10(-2) S cm(-1) for LiFT/(EMImBF(4))(0.183), and 1.36 x 10(-2) S cm(-1) and 4.42 x 10(-2) S cm(-1) for LiFT/(EMIMITSI)(0.087). Finally, LiFT/(EMImTESI)(0.087) is used to fabricate a coin cell prototype, that is tested by galvanostatic cycling for performance and durability. (C) 2019 Elsevier Ltd. All rights reserved.

The sluggishness of the oxygen reduction reaction (ORR) is a major bottleneck in the operation of low-temperature fuel cells (FCs), with a particular reference to proton-exchange membrane fuel cells (PEMFCs) [1]. Hence, it is necessary to devise efficient and affordable electrocatalysts (ECs) able to minimize the overpotentials associated with the ORR. This issue is further exacerbated considering that the single chemical element affording the lowest ORR overpotentials in the highly acidic environment found at the PEMFC cathode is Pt, whose abundance in Earth’s crust is very limited [2]. This raises serious concerns towards the incipient large-scale rollout of PEMFCs, that may face serious supply bottlenecks. On these bases, massive research efforts are currently devoted to develop new ORR ECs. A serious issue faced by the researchers is that it is often very difficult to transfer the intrinsic ORR performance of an EC into a single FC. The performance of a single FC is limited by transport phenomena, that are not easy to gauge by means of the well-assessed “ex-situ” techniques routinely adopted to determine the physicochemical properties and the “pure” ORR kinetics of an EC taken on its own. Thus, the optimization of the cathodic electrocatalytic layer of the FC (that hosts the ORR EC) is a crucial step to transfer effectively the ORR performance and ultimately to maximize the current and power outputs of the FC as a whole. In order to address this issue, this work describes a characterization approach that, by combining the information derived from single fuel cell measurements collected in different current density regimes, and upon modulating the partial pressure of oxygen at the cathode, allows for the identification and quantification a few simple figures of merit. The latter: (i) picture the extent with which the intrinsic ORR performance of the cathodic EC is transferred to the single FC; and (ii) gauge the contribution of different transport phenomena in the determination of single FC performance. The results are studied with an innovative analysis framework, yielding information that is then correlated to the physicochemical properties of the cathodic EC and to its electrochemical performance as determined by “ex-situ” measurements. Important insights are thus achieved, that play a crucial role in the optimization of the cathodic electrocatalytic layer with the final purpose to maximize the performance of the FC. The proposed characterization approach and subsequent analysis framework are straightforward, and suitable for a broad variety of FCs. The latter may also include cathodic ECs (e.g., low-Pt materials exhibiting a “core-shell” morphology [3], or completely “Pt-free” systems) that are very different from the conventional Pt/C of the state of the art. In conclusion this work describes a tool, simple and of broad applicability, able to provide important contributions to facilitate the implementation of developmental cathodic ECs in single FCs in the ongoing quest to realize efficient and low-carbon energy conversion systems. Acknowledgements This work has received funding from: (a) the European Union's Horizon 2020 research and innovation programme under grant agreement 881603; (b) the project “Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells” funded by EIT Raw Materials; (c) the program “Budget Integrato per la Ricerca Interdipartimentale - BIRD 2018” of the University of Padova (protocol BIRD187913); and (d) the project “Hierarchical electrocatalysts with a low platinum loading for low-temperature fuel cells – HELPER” funded by the University of Padova.

The unique feature of Keggin-type dodecatungstosilicate (SiW12O404−) to undergo adsorption on silver surfaces is explored here to fabricate, modify and stabilize silver nanoparticles in acid medium, as well as to link them to different reduced graphene oxide (rGO) substrates: SiO2-doted rGO, carboxylate-derivatized rGO, and conventional rGO (obtained through the chemical reduction method). Upon medium transfer to alkaline electrolyte, the inorganic polyoxometalate-capping-ligand disappears but silver nanostructures remain on rGO supports. The electrocatalytic activity of the resulting systems are probed during the oxygen reduction reaction (ORR). It is apparent from XRD data that silver is crystalline in nature and, particularly in a case of SiO2-doted rGO supports, metallic silver nanocrystals have face-centered-cubic structures enriched with high-index Ag(111) facets known to facilitate ORR. Functionalization of graphene with SiO2 seems to provide an efficient way to keep the nanosheets of graphene exfoliated thus facilitating unimpeded flux of reactants and making the system easily accessible for intercalation with catalytic Ag. Silver nanoparticles supported onto SiO2-doted rGO are relatively the most active toward ORR when examined under rotating ring disk conditions in terms of the observed highest catalytic current density, the most positive ORR onset potential, and the lowest percent formation of the H2O2 reaction intermediate.

Electrochemical energy conversion and storage systems are very important in today’s worldwide efforts to decarbonize the energy sector. Indeed, these systems exhibit a very high energy conversion efficiency, are easy to scale-up and are not affected by geographical constrains [1]. Two important examples of these systems are ion-exchange membrane fuel cells (IEMFCs) and redox flow batteries (RFBs). On one hand, ion-exchange membrane fuel cells are particularly suited for light-duty vehicles and small-scale stationary systems (e.g., auxiliary power units) owing to their high energy and power densities. On the other hand, redox flow batteries are ideally suited to the large-scale storage of energy for the power grid as they are characterized by a very high turnover efficiency and an outstanding cyclability [2]. Electrolyte membranes (EMs) are present at the core of both IEMFCs and RFBs. The role of such EMs is to: (i) keep separated the electroactive species involved in the redox reactions taking place at the electrodes and, at the same time, (ii) ensure a facile and selective migration of ions to prevent the polarization of the device and allow for the establishment of large current densities. As of today, the most widely adopted EMs are based on perfluorinated ionomers such as Nafion™, SPEEK and other similar macromolecules [3, 4]. These systems exhibit a high conductivity, chemical and electrochemical stability; however, they also suffer from important drawbacks such as: (i) a dramatic drop in conductivity at T > 80°C and in dry conditions; (ii) poor mechanical properties; and (iii) a high permeability to active species (e.g., vanadium) [5]. Consequently, it is often necessary to: (i) add humidification modules to ion-exchange membrane fuel cells, thus raising the bulk and cost of the device; or (ii) especially in the case of vanadium redox flow batteries (VRFBs), use thick EMs that curtail the current density. These drawbacks can be addressed by implementing several different strategies, that include: (i) the introduction of a filler in the EM, giving rise to a hybrid inorganic-organic membrane [6]; (ii) the fabrication of EMs with different macromolecules (e.g., polybenzimidazole, PBI) [6-11]. All of these strategies operate by modulating the physicochemical properties of the EMs, with a particular reference to the phase segregation at the nano/mesoscale [3]. This work overviews the study of the interplay between the physicochemical properties (i.e., the chemical composition, thermoanalytical properties, morphology and structure) and the electrical response of hybrid ion-exchange membranes by means of advanced investigation techniques such as Broadband Electrical Spectroscopy (BES). The results allow to elucidate the interplay among chemical and physical properties of the different phases within each EM and their conductivity mechanism. Indeed, the understanding of the relationship taking place between structure and ion conduction mechanisms is crucial in order to trigger the development of new high-performing proton and anion conducting membranes for applications in fuel cells and redox flow batteries. References [1] B. Dunn, H. Kamath, J.M. Tarascon, Science, 334, 928 (2011) [2] C. Zhang, L. Zhang, Y. Ding, S. Peng, X. Guo, Y. Zhao, G. He, G. Yu, Energy Storage Materials, 15, 324 (2018) [3] V. Di Noto, T.A. Zawodzinski, A.M. Herring, G.A. Giffin, E. Negro, S. Lavina. Int. J. Hydrogen Energy, 37, 6120-6131 (2012). [4] V. Di Noto, M. Piga, G.A. Giffin, G. Pace. J. Membrane Sci., 390-391, 58-67 (2012). [5] C. Sun, A. Zlotorowicz, G. Nawn, E. Negro, F. Bertasi, G. Pagot, K. Vezzù, G. Pace, M. Guarnieri, V. Di Noto. Solid State Ionics, 319, 110-116 (2018) [6] V. Di Noto, M. Piga, G.A. Giffin, K. Vezzù, T.A. Zawodzinski. J. Am. Chem. Soc., 134, 19099-19107 (2012). [7] K. Vezzù, A.M. Maes, F. Bertasi, A.R. Motz, T-H Tsai, E.B. Coughlin, A.M. Herring, V. Di Noto. JACS, 140, 1372-1384 (2018) [8] G. Nawn, K. Vezzu', F. Bertasi, G. Pagot, G. Pace; F. Conti, E. Negro, V. Di Noto. Electrochimica Acta, 228, 562–574 (2017). [9] G. Nawn, K. Vezzù, F. Bertasi, G. Pagot, E. Negro, G. Pace, F. Conti, V. Di Noto. Solid State Ionics, 320, 172-176 (2018) [10] V. Di Noto, M. Piga, G.A. Giffin, S. Lavina, E.S. Smotkin, J.-Y. Sanchez, C. Iojoiu J. Phys. Chem. C, 116, 1370-1379 (2012). [11] G. Nawn, K. Vezzù, G. Cavinato, G. Pace, F., Bertasi, G. Pagot, E. Negro, V. Di Noto. Advanced Functional Materials, 28(29) 1706522 (2018).

The study of the interplay between structure and conductivity in lithium-conducting electrolytes is a pivotal point for the development of future secondary batteries [1]. The use of Glycerol as a low molecular weight component in electrolytes is particularly interesting due to its glass-forming behavior and low glass transition temperature (-78.5°C). In addition, a high flexibility of the alkyl backbone chain and the well-known capability of oxygen functionalities to coordinate lithium cations make Glycerol very appealing as ion-conducting media as well as building block to obtain hybrid polymer electrolytes [2]. On this basis a family of eleven electrolytes based on Lithium Glycerolate with general formula C3H8-xO3Lix, where 0 ≤ x ≤ 1, is prepared and investigated [3]. In these electrolytes the Glycerolate (C3H8-xO3 x-) component acts as a large and flexible macro-anion which is able to provide a high single-ion conductivity to the material (8.36∙10-5 S∙cm-1 at 20°C and 1.55∙10-2 S∙cm-1 at 150°C for x = 0.25). Finally, the Glycerol∙∙∙Li+ interactions in these electrolytes are studied on T and x, with a particular reference to the detection of: a) macro-anion coordination sites; and b) the secondary structure of Glycerol chains. Insights on the long-range charge transfer mechanism and Glycerol relaxation events are also discussed. These studies are carried out by Inductively-Coupled Plasma Atomic Emission Spectroscopy, IR and Raman spectroscopies, DSC, TGA, and Broadband Electrical Spectroscopy. References [1] V. Di Noto, S. Lavina, G. A. Giffin, E. Negro, B. Scrosati, Electrochim. Acta 57 (2011) 4-13. [2] V. Di Noto, M. Vittadello, S. G. Greenbaum, S. Suarez, K. Kano, T. Furukawa, The Journal of Physical Chemistry B 108 (2004) 18832-18844. [3] G. Pagot, S. Tonello, K. Vezzù, V. Di Noto, Batteries 4 (2018) 41.

Rechargeable batteries based on magnesium virtually provide high volumetric capacity, safety, and cost savings thanks to the abundance, dendrite-free electrodeposition, and environmentally green properties of Mg metal anode. The lack of cathodes that can deliver high currents at high potential is one of the principal bottlenecks that limit the entrance of Mg batteries into the market. Here we report the synthesis and characterization of a novel cathode for magnesium secondary batteries based on graphene oxide (GO) and vanadium (V) active species. Thermogravimetric analysis, structural and vibrational analyses, and high-resolution electron microscopies elucidate the complex architecture that characterizes the proposed material and that bestows exceptional electrochemical properties to the cathode. The proposed synthesis is able to give rise to V-based nanoparticles with a very porous surface and wrapped inside a chrysalis-like GO ordered superstructure. Finally, a coin cell device is assembled using a Mg metal anode and the proposed material as cathode. This prototype is able to deliver good capacities when cycled at high current rates (1000 mA g−1) in a higher potential range with respect to classical cathodes for Mg batteries. Thus, a sufficient power (1.70 W g−1) is obtained, making this battery promising towards the substitution of lithium batteries.

We report on the development of two new Pt-free electrocatalysts (ECs) for the oxygen reduction reaction (ORR) process based on graphene nanoplatelets (GNPs). We designed the ECs with a core-shell morphology, where a GNP core support is covered by a carbon nitride (CN) shell. The proposed ECs present ORR active sites that are not associated with nanoparticles of metal/alloy/oxide but are instead based on Fe and Sn subnanometric clusters bound in coordination nests formed by carbon and nitrogen ligands of the CN shell. The performance and reaction mechanism of the ECs in the ORR are evaluated in an alkaline medium by cyclic voltammetry with the thin-film rotating ring-disk approach and confirmed by measurements on gas-diffusion electrodes. The proposed GNP-supported ECs present an ORR overpotential of only ca. 70 mV higher with respect to a conventional Pt/C reference EC including a XC-72R carbon black support. These results make the reported ECs very promising for application in anion-exchange membrane fuel cells. Moreover, our methodology provides an example of a general synthesis protocol for the development of new Pt-free ECs for the ORR having ample room for further performance improvement beyond the state of the art.

This study reports the preparation and characterization of a new family of electrocatalysts (ECs) for the oxygen reduction reaction (ORR) exhibiting a “core-shell” morphology. The “core” consists of graphene sheets, which are covered by a carbon nitride (CN) “shell” embedding Au and Ni active sites. The investigated ECs are labeled AuNi10-CNl 600/Gr and AuNi10-CNl 900/Gr. The chemical composition and thermal stability are studied by inductively-coupled plasma atomic emission spectroscopy (ICP-AES), elemental analysis and by high-resolution thermogravimetric analysis (HR-TGA). The morphology of the ECs is probed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction (XRD). The ORR performance of the ECs is studied both in acid (0.1 M HClO4) and in alkaline medium (0.1 M KOH) by Cyclic Voltammetry with the Thin-Film Rotating Ring-Disk Electrode (CV-TF-RRDE) method. Both ECs exhibit a promising performance in the ORR in the alkaline medium.

Graphene is, in principle, a promising material for consideration as component (support, active site) of electrocatalytic materials, particularly with respect to the reduction of oxygen, an electrode reaction of importance to low-temperature fuel cell technology. Different concepts of utilization, including nanostructuring, doping, admixing, preconditioning, modification or functionalization of various graphene-based systems for catalytic electroreduction of oxygen are elucidated, as well as important strategies to enhance the systems’ overall activity and stability are discussed.

The centre piece at the heart of numerous energy storage and conversion devices, such as fuel cells and redox flow batteries, is the ion-exchange membrane (IEM). This typically polymeric material is responsible for the migration of ionic species, separation of fuel stocks and for providing additional support to the electrode assemblies. As a result, IEMs are required to possess excellent stability (both thermal and chemical), long lifetimes, electrical insulation, and high ionic conductivity and specificity. Current state-of-the-art polymer electrolytes possessing the more desirable properties tend to come with a price tag that can render their use in energy storage/conversion technologies somewhat cost prohibitive [1]. This has created a strong driving force aimed towards new, cheaper but still high performing materials, for use in energy storage/exchange systems. The copolymerization of carbon monoxide and ethylene (two readily available and cheap feedstocks) leads to the formation of polyketone, a high performance thermoplastic that has found many applications resulting in its global production of thousands of tonnes per annum. The alternating 1,4-dicarbonyl functionality of aliphatic polyketone enables access, via classic Paal-Knorr chemistry, to a variety of new functionalized polymers [2]. Here we present a new ion conducting polymeric material derived from polyketone, that possess N-functionalized pyrrole units in the backbone (FPK) [3]. Ion-conductivities on the order of 10.6 and 8.6 mScm-1 for the hydroxide and iodide forms of methylated FPKs have been achieved at 80 oC, with the hydroxide FPK demonstrating high resistance towards alkaline conditions for over 20 hours at 80 oC. The flexibility in the choice of the N-substituent renders these new materials higher tailorable and potentially useful in a range of energy storage/conversion technologies as either proton or anion exchange membranes. Acknowledgements The authors wish to thank the Strategic Project of the University of Padova “Materials for Membrane-Electrode Assemblies to Electric Energy Conversion and Storage Devices (MAESTRA)” for funding. V.D.N. thanks the University Carlo III of Madrid for granting him the “Catedra de Excelentia” (Chair of Excellence). References [1] S. Eckroad in Handbook of Energy Storage for Transmission or Distribution Applictions, Electric Power Research Institute Report 1007189, California, USA (2002) [2] A. Sen et al., Macromolecules, 22, (1989), 2012, A.A. Broekhuis et al., J. Apply. Polm. Sci., (2016), 42924, A.A. Broekhuis et al., J. Appl. Polym. Sci., 107, (2008), 107, 262, A.A. Broekhuis, Dyes and Pigments, 98, (2013), 51 [3] N. Ataollahi, K. Vezzù, G. Nawn, G. Pace, G. Cavinato, F. Girardi, P. Scardi, V. Di Noto, R. Di Maggio, Electrochimica Acta., 226 (2017) 148-157.