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This research focuses on the rational design of porous enzymatic electrodes, using horseradish peroxidase (HRP) as a model biocatalyst. Our goal was to identify the main obstacles to maximizing biocatalyst utilization within complex porous structures and to assess the impact of various carbon nanomaterials on electrode performance. We evaluated as-synthesized carbon nanomaterials, such as Carbon Aerogel, Coral Carbon, and Carbon Hollow Spheres, against the commercially available Vulcan XC72 carbon nanomaterial. The 3D electrodes were constructed using gelatin as a binder, which was cross-linked with glutaraldehyde. The bioelectrodes were characterized electrochemically in the absence and presence of 3 mM of hydrogen peroxide. The capacitive behavior observed was in accordance with the BET surface area of the materials under study. The catalytic activity towards hydrogen peroxide reduction was partially linked to the capacitive behavior trend in the absence of hydrogen peroxide. Notably, the Coral Carbon electrode demonstrated large capacitive currents but low catalytic currents, an exception to the observed trend. Microscopic analysis of the electrodes indicated suboptimal gelatin distribution in the Coral Carbon electrode. This study also highlighted the challenges in transferring the preparation procedure from one carbon nanomaterial to another, emphasizing the importance of binder quantity, which appears to depend on particle size and quantity and warrants further studies. Under conditions of the present study, Vulcan XC72 with a catalytic current of ca. 300 µA cm−2 in the presence of 3 mM of hydrogen peroxide was found to be the most optimal biocatalyst support. [ABSTRACT FROM AUTHOR]

Over the past 20 years, a revolution has been seen in battery research culminating with a much‐awaited Nobel Prize in Chemistry in 2019 for the development of Li‐ion batteries. New Li‐ion battery materials have been developed recently with improvements in performance. New Li battery chemistries have also emerged, exhibiting high energy density such as Li‐S, Li‐O2, Li‐metal with solid state electrolytes as well as zero‐excess Li anode metal batteries. This is tremendous progress and batteries are becoming more efficient and cheaper each year. Yet, most research in batteries is entirely focused on performance while the sustainability of all battery components making up the cell, as well as the battery chemistry itself are much overlooked. In this essay some perspectives are discussed and opinion is provided on the advancement of sustainability in battery research. [ABSTRACT FROM AUTHOR]

The aqueous oxygen reduction reaction (ORR) has recently received increased attention due to its critical role in clean and sustainable energy‐generation technologies, such as proton exchange membranes (PEM) fuel cells, alkaline fuel cells and Zn–air batteries. The sluggish kinetics associated with ORR result from multistep electron‐transfer process. The slow kinetics are partially related to the O2 adsorption process onto the catalyst, which happens at the triple‐phase boundary (TPB) of the electrocatalyst–electrolyte–oxygen interface. Hence, tremendous efforts have been devoted to improving the intrinsic properties of electrocatalysts such as active sites, electrical conductivity and porosity. Engineering the electrocatalyst's interfacial properties is another critical issue in ORR, however less described in the literature. The surface of the catalyst provides the microenvironment for the triple boundary interface reaction, which directly influences its electrocatalytic activity and the kinetics. This Minireview is a summary of the existing literature on manipulating the interfacial surface of non‐precious metal catalysts at the triple point between the solid catalyst, the aqueous electrolyte and the O2 gas with the aim of improving the ORR efficiency. Various approaches towards improving the wettability and nanostructuring the catalyst surface to boost the activity of the surface‐active sites and provide improved stability are discussed. Promoting adsorption: The sluggish kinetics resulting from multistep electron transfer processes is the main concern in ORR. Promoting O2 adsorption, which happens on the triple‐phase boundary (TPB) of electrocatalyst–electrolyte–oxygen interface can overcome the slow kinetics. In this paper we review some of the existing surface engineering strategies in the literature aiming to manipulate the triple point boundary (TPB) to promote the aqueous ORR. [ABSTRACT FROM AUTHOR]

Electrochemical Double Layer Capacitors (EDLCs) with ionic liquid electrolytes outperform conventional ones using aqueous and organic electrolytes in energy density and safety. However, understanding the electrochemical behaviors of ionic liquid electrolytes under compressive/tensile strain is essential for the design of flexible EDLCs as well as normal EDLCs, which are subject to external forces during assembly. Despite many experimental studies, the compression/stretching effects on the performance of ionic liquid EDLCs remain inconclusive and controversial. In addition, there is hardly any evidence of prior theoretical work done in this area, which makes the literature on this topic scarce. Herein, for the first time, we developed an atomistic model to study the processes underlying the electrochemical behaviors of ionic liquids in an EDLC under strain. Constant potential non-equilibrium molecular dynamics simulations are conducted for EMIM BF4 placed between two graphene walls as electrodes. Compared to zero strain, low compression of the EDLC resulted in compromised performance as the electrode charge density dropped by 29%, and the performance reduction deteriorated significantly with a further increase in compression. In contrast, stretching is found to enhance the performance by increasing the charge storage in the electrodes by 7%. The performance changes with compression and stretching are due to changes in the double-layer structure. In addition, an increase in the value of the applied potential during the application of strain leads to capacity retention with compression revealed by the newly performed simulations. [ABSTRACT FROM AUTHOR]

Carbon-based structures are the most versatile materials used in the modern field of renewable energy (i.e., in both generation and storage) and environmental science (e.g., purification/remediation). However, there is a need and indeed a desire to develop increasingly more sustainable variants of classical carbon materials (e.g., activated carbons, carbon nanotubes, carbon aerogels, etc.), particularly when the whole life cycle is considered (i.e., from precursor ''cradle'' to ''green'' manufacturing and the product end-of-life ''grave''). In this regard, and perhaps mimicking in some respects the natural carbon cycles/production, utilization of natural, abundant and more renewable precursors, coupled with simpler, lower energy synthetic processes which can contribute in part to the reduction in greenhouse gas emissions or the use of toxic elements, can be considered as crucial parameters in the development of sustainable materials manufacturing. Therefore, the synthesis and application of sustainable carbon materials are receiving increasing levels of interest, particularly as application benefits in the context of future energy/chemical industry are becoming recognized. This review will introduce to the reader the most recent and important progress regarding the production of sustainable carbon materials, whilst also highlighting their application in important environmental and energy related fields. [ABSTRACT FROM AUTHOR]

Abstract: The production of porous materials together with their associated applications using cheap precursors demonstrates the potential of a “chimie douce” based on carbohydrates and their hydrothermal decomposition products to replace same of the standard organic monomers, fulfilling the today''s requirements towards greener chemistry processes and the sustainability of the starting products. [Copyright &y& Elsevier]

The production of functional nanostructured materials starting from cheap natural precursors using environmentally friendly processes is a highly attractive subject in material chemistry today. Recently, much attention has been focused on the use of plant biomass to produce functional carbonaceous materials, encompassing economic, environmental and social issues. Besides the classical route to produce activated carbons from agricultural side products, the hydrothermal carbonization (HTC) process shows clear advantages in that it can generate a variety of cheap and sustainable carbonaceous materials with attractive nanostructure and functionalization patterns for a wide range of applications. In this tutorial reviewwe present the latest developments in this traditional but recently invigorated technique. It will be shown that HTC does not only access carbonaceous materials under comparatively mild hydrothermal conditions, but also replaces the more technical and structurally well-defined charring by a controlled chemical process. It will be shown that this makes it possible to tailor the final structure with the tools of colloid and polymer science, leading to very different morphologies with miscellaneous applications, including modern carbon nanocomposites and hybrids. [ABSTRACT FROM AUTHOR]

Silica particles containing immobilised peptidic templates have been used for the generation of hierarchically imprinted polymers. The pores of the silica mould were filled with a mixture of monomers/initiator and polymerised, followed by dissolution of the silica template. This method leaves behind imprinted polymers with binding sites located at the surface, which are capable of recognising larger molecules with the same immobilised epitope. All the products resulting from solid-phase synthesis of peptides were characterised by elemental analysis, FT-IR spectroscopy and fluorescence microscopy. The hierarchically imprinted polymers generated from these products were characterised by elemental analysis, FT-IR spectroscopy, fluorescence microscopy, scanning electron microscopy (SEM) and nitrogen adsorption, providing evidence concerning the reproducibility of each step. The chromatographic properties of the materials have been investigated and the advantages of the immobilisation method have been proven. The materials exhibit selectivity for their templates and other structurally related dipeptides. Furthermore, the polymers proved to be capable of recognising larger peptides containing the immobilised sequence. [ABSTRACT FROM AUTHOR]

Nature has vast experience in optimising systems to perform adaptively to their environment. Bio-organisms are intrinsically dynamic: as they react to stimuli, their components work synergistically to achieve the appropriate response to the range of conditions of the environment they are in. Due to this singular specificity, achieved with exquisite tailoring of function and structure from the nanoscopic to the macroscopic level, biological systems have been an inspiration not only for materials design but for many engineering-related applications, including energy storage devices, in particular batteries, which are covered in this review. Bioinspiration is explored as a tool to unlock new materials, hierarchical architectures, and chemistries to achieve specific functions that will be key to addressing the complex range of performance and sustainability requirements for future batteries. Many excellent examples of biomimicry and bioinspiration can be found in the literature, yet the conceptualization of fully biomimetic batteries has not been accomplished. In this review we analyse the possibilities by which batteries could expand beyond structure replication of individual materials, components or chemistries found in nature and provide a broader perspective on their integration. We place battery systems at the interface between green chemistry, nanotechnology, and bioengineering to analyse their basic requirements and contrast how nature has achieved these needs in biological systems. [ABSTRACT FROM AUTHOR]

Accelerating waste management requires the conversion of polymer waste to value-added materials through sustainable approaches. While depolymerised PET has been used as feedstock to produce metal–organic frameworks, this is the first report of the successful one-pot hydrothermal synthesis of the desirable UiO-66 topology through the judicious choice of reactants, modulators and reaction conditions. [ABSTRACT FROM AUTHOR]

Commercial polymer electrolyte membrane fuel cells have relied on scares Platinum to catalyse the kinetically sluggish oxygen reduction reaction occurring at their anodes. Over the last decade organic materials, frequently based on graphitic structures have been demonstrated as promising alternative electrocatalysts to the noble metals. Researchers typically utilize ultrasonic treatment as part of the synthesis procedure to achieve homogeneous dispersion of graphitic carbon prior to. Herein we investigate the implications of the structural and compositional changes induced by the ultrasonication treatment on boron-doped reduced graphene oxide for oxygen reduction reaction. It is shown that ultrasonication pre-treatment prior to the boron doping and reduction of graphene oxide via hydrothermal process step leads to the increase of both substitutional B and electrocatalytic surface area, with associated reduction of average pore size diameter, leading to a significant improvement in the oxygen reduction reaction performance, with respect to the non-ultrasonicated material. It is proposed that the higher degree of substitutional doping of boron is a result of formation of the additional epoxy functionalities on graphitic planes, which act as a doping site for boric acid. • Ultrasonication enables higher doping of boron into Graphene oxide. • Longer ultrasonication times leads to higher substitutional boron. • Longer ultrasonication times leads to higher ORR activity. [ABSTRACT FROM AUTHOR]

Atomically dispersed iron–nitrogen–carbon catalysts are promised, low‐cost, and high‐performance electrocatalysts for the Oxygen Reduction Reaction (ORR) in fuel cells. However, most Fe–N–C materials are produced via pyrolysis at a high temperature and it is difficult to characterise the precise Fe–N configurations. This can lead to confusion surrounding the best chemical and coordination environment for Fe and understanding the subsequent ORR mechanisms. In this work, Fe porphyrin is used to produce a specific Fe–N environment, therefore allowing the role and activity of this environment to be studied. Carbon nanotubes (CNTs) are covalently functionalized with iron 5,10,15,20‐triphenylporphyrin (FeTPP) motifs via aryl diazonium methodology, enabling the exact role of only the Fe‐Pyrrolic N4 configuration of FeTPP in ORR to be studied and better understood. Upon covalent functionalization, a high electrochemical active site density of 1.12 × 1015 sites cm−2, approximately six‐fold more than that of noncovalently functionalized samples with 12.7% electrochemical active site. The heightened active site density and superior electrochemical active site utilization (12.7%) lead to the more favorable 4‐electron pathway for the ORR. Furthermore, a preliminary discussion regarding the selectivity of the ORR pathway is initiated. [ABSTRACT FROM AUTHOR]

Sluggish kinetics in the oxygen reduction reaction (ORR) require significant quantities of expensive Pt-based nanoparticles on carbon (Pt/C) at the cathode of proton exchange membrane fuel cells (PEMFCs). This catalyst requirement hinders their large-scale implementation. Single atom Fe in N-doped C (Fe–N–C) electrocatalysts offer the best non-Pt-based ORR activities to date, but their environmental impacts have not been studied and their production costs are rarely quantified. Herein, we report a comparative life-cycle assessment and techno-economic analysis of replacing Pt/C with Fe–N–C at the cathode of an 80 kW PEMFC stack. In the baseline scenario (20 gPt/Cvs. 690 gFe–N–C), we estimate that Fe–N–C could reduce damages on ecosystems and human health by 88–90% and 30–44%, respectively, while still increasing global warming potential by 53–92% and causing a comparable impact on resource depletion. The environmental impacts of Pt/C predominantly arise from the Pt precursor while those of Fe–N–C are presently dominated by the electricity consumption. The monetized costs of environmental externalities for both Fe–N–C and Pt/C catalysts exceed their respective direct production costs. Based on catalyst performance with learning curve analysis at 500 000 PEMFC stacks per annum, we estimate replacing Pt/C with Fe–N–C would increase PEMFC stack cost from 13.8 to 41.6 USD per kW. The cost increases despite a reduction in cathode catalyst production cost from 3.41 to 0.79 USD per kW (excluding environmental externalities). To be cost-competitive with a Pt-based PEMFC stack delivering 2020 US Department of Energy target of 1160 mW cm−2 (at 0.657 V), the same stack with an Fe–N–C cathode would need to reach 874 mW cm−2, equivalent to a 200% performance improvement. These findings demonstrate the need for continued Fe–N–C activity development with sustainable synthesis routes in mind to replace Pt-based cathode catalyst in PEMFCs. Based on forecasting scenarios of fuel cell vehicle deployment targets, we find that Pt consumption would be constrained by Pt supply. [ABSTRACT FROM AUTHOR]

We report the influence of structural features on the properties of porous carbonaceous materials obtained using soft-templating coupled with hydrothermal carbonisation. Our results demonstrate that using d - glucose with Pluronic P123 results in a more homogeneous particle size distribution of carbon spheres compared with d - fructose. The textural properties of the carbon materials, both surface area and pore volume, have improved when the carbonisation temperature was increased from 550 °C to 900 °C, while the amount of C C bonds was also increased. Physical activation with CO 2 was found to open the pores and thereby improve textural properties, including total pore volume, micropore volume, and surface area. Concomitantly, the CO 2 and H 2 S uptake also underwent significant enhancement, achieving a maximum CO 2 adsorption capacity of 8.37 mmol/g at 0 °C and 1 bar, and ca. 6 mmol/g at room temperature and 1 bar. The same samples showed about 25.7 mmol/g adsorption capacity for H 2 S at room temperature and atmospheric pressure, with approximately 32% process efficiency. Image 1 • Soft templating strategy coupled with hydrothermal carbonisation (HTC) resulted in improved porosity. • The highest CO 2 uptake has been obtained after physical activation. • H 2 S adsorption efficiency was boosted after physical activation step. [ABSTRACT FROM AUTHOR]

The electrochemical CO2 reduction reaction (CO2RR) to value‐added chemicals with renewable electricity is a promising method to decarbonize parts of the chemical industry. Recently, single metal atoms in nitrogen‐doped carbon (MNC) have emerged as potential electrocatalysts for CO2RR to CO with high activity and faradaic efficiency, although the reaction limitation for CO2RR to CO is unclear. To understand the comparison of intrinsic activity of different MNCs, two catalysts are synthesized through a decoupled two‐step synthesis approach of high temperature pyrolysis and low temperature metalation (Fe or Ni). The highly meso‐porous structure results in the highest reported electrochemical active site utilization based on in situ nitrite stripping; up to 59±6% for NiNC. Ex situ X‐ray absorption spectroscopy (XAS) confirms the penta‐coordinated nature of the active sites. The catalysts are amongst the most active in the literature for CO2 reduction to CO. The density functional theory calculations (DFT) show that their binding to the reaction intermediates approximates to that of Au surfaces. However, it is found that the turnover frequencies (TOFs) of the most active catalysts for CO evolution converge, suggesting a fundamental ceiling to the catalytic rates. [ABSTRACT FROM AUTHOR]

Review: 199 refs. [ABSTRACT FROM AUTHOR]

After being undervalued for a long-time, the potential use of lignins have gained interest as a source of wealth from waste. Despite the complexity of lignins chemical structure, its high carbon content compared to cellulose and sugars makes lignin a very promising precursor for the development of nanocarbons for broad range applications, including supercapacitors for energy storage. High performing supercapacitors have been made using dimensionally different nanocarbon entities (zero-to three), such as carbon nanoparticles, carbon nanodots, carbon fibers, and carbon nanosheets with modular and interconnected pore structures, which are prepared from lignins of various types with and without use of templates, porogens and chemical agents. Control of physicochemical and electrochemical properties in such nanocarbons remains the key for their high energy density, flexibility, and long-term stability. To this end, nanocarbons conductivity, porosity and surface areas are controlled by various synthesis approaches while detailed adjustment of pore structure, pore width and pore distribution have been made to improve electrolyte access, ions confinement, and transportation. To compare performances of nanocarbons made from different lignin types, we must do meaningful investigations on the lignin's structure, composition, and purity to understand how their structure-property relationships are influenced by pyrolysis, carbonization and activation methods/conditions used. In this review, a clear overview of the lignins structure, classification, and properties is presented, wherein we compared the structure-property-performance relationships of nanostructured carbons from lignins for improvement of supercapacitor device performances with recent advances. Separation processes of lignin from wood, steps involved in preparing dimensionally different nanocarbon entities (zero -to three), and electrolytes for the fabrication of sustainable and flexible supercapacitor devices. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of efficient and sustainable electrochemical systems able to provide clean-energy fuels and chemicals is one of the main current challenges of materials science and engineering. Over the last decades, significant advances have been made in the development of robust electrocatalysts for different reactions, with fundamental insights from both computational and experimental work. Some of the most promising systems in the literature are based on expensive and scarce platinum-group metals; however, natural enzymes show the highest per-site catalytic activities, while their active sites are based exclusively on earth-abundant metals. Additionally, natural biomass provides a valuable feedstock for producing advanced carbonaceous materials with porous hierarchical structures. Utilizing resources and design inspiration from nature can help create more sustainable and cost-effective strategies for manufacturing cost-effective, sustainable, and robust electrochemical materials and devices. This review spans from materials to device engineering; we initially discuss the design of carbon-based materials with bioinspired features (such as enzyme active sites), the utilization of biomass resources to construct tailored carbon materials, and their activity in aqueous electrocatalysis for water splitting, oxygen reduction, and CO2 reduction. We then delve in the applicability of bioinspired features in electrochemical devices, such as the engineering of bioinspired mass transport and electrode interfaces. Finally, we address remaining challenges, such as the stability of bioinspired active sites or the activity of metal-free carbon materials, and discuss new potential research directions that can open the gates to the implementation of bioinspired sustainable materials in electrochemical devices. [ABSTRACT FROM AUTHOR]

Climate change, global warming, urban air pollution, energy supply uncertainty and depletion, and rising costs of conventional energy sources are, among others, potential socioeconomic threats that our community faces today. Transportation is one of the primary sectors contributing to oil consumption and global warming, and natural gas (NG) is considered to be a relatively clean transportation fuel that can significantly improve local air quality, reduce greenhouse-gas emissions, and decrease the energy dependency on oil sources. Internal combustion engines (ignited or compression) require only slight modifications for use with natural gas; rather, the main problem is the relatively short driving distance of natural-gas-powered vehicles due to the lack of an appropriate storage method for the gas, which has a low energy density. The U.S. Department of Energy (DOE) has set some targets for NG storage capacity to obtain a reasonable driving range in automotive applications, ruling out the option of storing methane at cryogenic temperatures. In recent years, both academia and industry have foreseen the storage of natural gas by adsorption (ANG) in porous materials, at relatively low pressures and ambient temperatures, as a solution to this difficult problem. This review presents recent developments in the search for novel porous materials with high methane storage capacities. Within this scenario, both carbon-based materials and metal-organic frameworks are considered to be the most promising materials for natural gas storage, as they exhibit properties such as large surface areas and micropore volumes, that favor a high adsorption capacity for natural gas. Recent advancements, technological issues, advantages, and drawbacks involved in natural gas storage in these two classes of materials are also summarized. Further, an overview of the recent developments and technical challenges in storing natural gas as hydrates in wetted porous carbon materials is also included. Finally, an analysis of design factors and technical issues that need to be considered before adapting vehicles to ANG technology is also presented. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) have attracted more and more attention for scalable electrical energy storage due to the abundance and wide distribution of Na resources. However, the anode still remains a great challenge for the application of SIBs. Here the production of uniform hard carbon microtubes (HCTs) made from natural cotton through one simple carbonization process and their application as an anode are reported. The study shows that the electrochemical performance of the HCTs is seriously affected by the carbonization temperature due to the difference in their microstructure and heteroatomic content. The HCTs carbonized at 1300 °C deliver the highest reversible capacity of 315 mAh g−1 and good rate capability due to their unique tubular structure. This contribution not only provides a new approach for the preparation of hard carbon materials with unique tubular microstructure using natural inspiration, but it also deepens the fundamental understanding of the sodium storage mechanism. [ABSTRACT FROM AUTHOR]

Lignin is produced in large quantities as a by-product of the papermaking and biofuel industries. Lignin is the most abundant aromatic biopolymer on the planet with its chemical structure rendering it ideal for carbon materials production and finely tailored architectures of these sustainable carbon materials are beginning to find use in high value energy applications. This review focuses on lignin chemistry, various lignin extraction and fractionation techniques, and their impact on lignin structure/property relationships for energy applications are discussed. Chemistries behind important and emerging energy applications from recent research on this increasingly valuable sustainable polymer are described. [ABSTRACT FROM AUTHOR]

Iron-based single-site catalysts hold immense potential for achieving highly selective chemical processes, with the added advantage of iron being an earth-abundant metal. They are widely explored in electrocatalysis for oxygen reduction and display promising catalytic activity for organic transformations. In particular, FeNx@C catalysts are active for the reduction of nitroarene into aromatic amines. Yet, they are difficult to mass-produce, and most preparation methods fail to avoid single site aggregation. Here we prepared FeNx@C catalysts from bio-derived compounds, xylose and haemoglobin, in a simple two-step process. Since haemoglobin naturally contains FeNx single-sites, we successfully repurposed them into hydrogenation catalytic centers and avoided their aggregation during the preparation of the material. Their single-site nature was demonstrated by aberration-corrected transmission electron microscopy and X-ray absorption techniques. They were shown to be active for transfer hydrogenation of nitroarenes into anilines, with excellent substrate selectivity and recyclability, as demonstrated by the preserved yield across seven catalytic cycles. We also showed that FeNx@C could be used to prepare 2-phenylbenzimidazole through a reduction/condensation tandem. Our work shows for the first time the viability of biomass precursors to prepare Fe single-site hydrogenation catalysts. [ABSTRACT FROM AUTHOR]

Materials that combine the functionalities of both of proteins and graphene are of great interest for the engineering of biosensing, drug delivery, and regenerative devices. Graphene oxide (GO) offers an opportunity to design GO‐protein interactions but the need for harsh reduction processes to enable GO photoexcitation remains a limitation. A disinfector‐assisted low temperature method to reduce GO‐protein materials and fabricate surgical dressings with tuneable photothermal efficiency and bioactive properties for the postoperative treatment of melanoma is reported. The approach harnesses the capacity of 70% ethanol to penetrate the protein shell of microorganisms to infiltrate GO‐protein complexes and reduce GO at low temperature (85 °C) while maintaining the material structure and bioactivity. Both experiments and coarse‐grained simulations are used to describe the reduction process and assess the material properties. In vitro and in vivo validation revealed the capacity of the dressings to prevent tumor recurrence and promote healing after tumor resection. [ABSTRACT FROM AUTHOR]

The next generation of proton exchange membrane fuel cells (PEMFCs) require a substantial reduction or elimination of Pt-based electrocatalyst from the cathode, where O 2 reduction takes place. The most promising alternative to Pt is atomic Fe embedded in N-doped C (Fe–N–C). Successful incorporation of Fe–N–C in PEMFCs relies on a thorough understanding of the catalyst layer properties, both ex situ and in situ , with tailored electrode interface engineering. To help resolve this conundrum, we provide a quantitative protocol on the optimisation of I/C for Fe–N–Cs. It is demonstrated that a high pore volume (3.33 cm3 g−1 FeNC) Fe–N–C catalyst requires a sufficiently high ionomer to catalyst mass ratio (I/C, 2.8≤I/C ≤ 4.2) for optimum PEMFC activity under H 2 /O 2. Emerging electrochemical techniques (distribution of relaxation times and Fourier transformed alternating current voltammetry) were used to deconvolute for the first time the trade-off between proton and electron resistance and accessible FeN x active site density with increasing ionomer loading. These findings highlight the significant impact of tuning the I/C ratio based on the catalyst layer properties and feature the power of evolving electrochemical tools for optimising performance in PEMFCs and other electrochemical devices. [Display omitted] • In situ FTacV quantified Fe–N–C electrochemical active site density in fuel cell. • Fe–N–C active site density and current density correlated with ionomer loading. • DRT quantified resistance to proton transport and oxygen diffusion in fuel cell. • Fe–N–C to ionomer ratio optimised based on quantitative protocol. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries as a prospective alternative to lithium‐ion batteries are facing the challenge of developing high‐performance, low‐cost and sustainable anode materials. Hard carbons are appropriate to store sodium ions, but major energy and environmental concerns during their fabrication process (i.e., high‐temperature carbonization) have not been properly assessed. Furthermore, the rational design of high‐performing hard carbon anodes is usually limited by the conventional direct carbonization of organic precursors. Here, the hydrothermal carbonization process is employed as a versatile pre‐treatment method of renewable precursors, followed by high‐temperature carbonization, for producing advanced hard carbon anodes. The critical role of hydrothermal pre‐treatment in regulating the structure for an optimized performance of hard carbon anodes is elucidated, while revealing the sodium‐ion storage mechanism using electrochemical kinetic calculations, advanced characterization and multi‐scale modeling. Furthermore, the environmental impacts of hydrothermal pre‐treatment and subsequent carbonization are evaluated using life cycle assessment compared to direct carbonization. By comparing hard carbon anodes with and without the hydrothermal pre‐treatment, it is verified that the additional hydrothermal process is responsible for enhanced electrochemical performance, increased carbon yields and reduced carbon emissions. The work provides a systematic understanding of functions and energy consumptions of hydrothermal systems to achieve next‐generation sustainable sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

The role of 13C solid state nuclear magnetic resonance (ssNMR) in the elucidation of the structure of biomass and carbonaceous solids derived from biomass has been crucial since the mid-70s, which gives it a more than 30-year history. As soon as magic angle spinning was coupled to cross-polarization, ssNMR suddenly became of high use to approach structural resolution in cellulose, lignin, coals and various types of carbonaceous materials, up to the more recent hydrothermal carbons (HTC). This review focuses on the specific contribution that ssNMR has made to this field and in particular, the technical advances in the field of ssNMR (advanced pulse sequences for spectral editing, more advanced Magic Angle Spinning probes, high-field spectrometers) will be outlined in terms of their usefulness for the specific purpose of studying the structure of complex biomass (lignin, cellulose) and their char obtained either via a pyrolytic or hydrothermal approach. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs) are prospective candidates for large‐scale energy storage systems cause of their abundant resources. However, unsatisfactory rate and cycling performance of carbon‐based anodes present a bottleneck for the applications of SIBs/PIBs due to the large sizes of sodium/potassium ions. Herein, oxygen‐doped vertically aligned carbon aerogels (VCAs) with hierarchically tailored channels are synthesized as anodes in SIBs/PIBs via a controllable unidirectional ice‐templating technique. VCA‐3 (cooling rate of 3 K min−1) delivers the highest reversible capacity of ≈298 mAh g−1 at 0.1 C with an excellent cycling performance over 2000 cycles at 0.5 C for SIBs, while VCA‐5 manifests a superior capacity of ≈258 mAh g−1 at 0.1 C with an 82.7% retention over 1000 cycles at 0.5 C for PIBs. Moreover, their full cells demonstrate the promising potential of VCAs in applications. This novel controllable ice‐templating strategy opens unique avenues to tune the construction of hollow aligned channels for shortening ion‐transport pathways and ensuring structural integrity. New insights into structure‐performance correlations regulated by the cooling rates of an ice‐templating strategy and design guidelines for electrodes applicable in multiple energy storage technologies are reported. [ABSTRACT FROM AUTHOR]

Heteroatom doping has been proved to effectively enhance the sloping capacity, nevertheless, the high sloping capacity almost encounters a conflict with the disappointing initial Coulombic efficiency (ICE). Herein, we propose a heteroatom configuration screening strategy by introducing a secondary carbonization process for the phosphate‐treated carbons to remove the irreversible heteroatom configurations but with the reversible ones and free radicals remaining, achieving a simultaneity between the high sloping capacity and ICE (≈250 mAh g−1 and 80 %). The Na storage mechanism was also studied based on this "slope‐dominated" carbon to reveal the reason for the absence of the plateau. This work could inspire to distinguish and filter the irreversible heteroatom configurations and facilitate the future design of practical "slope‐dominated" carbon anodes towards high‐power Na‐ion batteries. [ABSTRACT FROM AUTHOR]

Heteroatom doping has been proved to effectively enhance the sloping capacity, nevertheless, the high sloping capacity almost encounters a conflict with the disappointing initial Coulombic efficiency (ICE). Herein, we propose a heteroatom configuration screening strategy by introducing a secondary carbonization process for the phosphate‐treated carbons to remove the irreversible heteroatom configurations but with the reversible ones and free radicals remaining, achieving a simultaneity between the high sloping capacity and ICE (≈250 mAh g−1 and 80 %). The Na storage mechanism was also studied based on this "slope‐dominated" carbon to reveal the reason for the absence of the plateau. This work could inspire to distinguish and filter the irreversible heteroatom configurations and facilitate the future design of practical "slope‐dominated" carbon anodes towards high‐power Na‐ion batteries. [ABSTRACT FROM AUTHOR]

Summary: The thermal treatment of an activated carbon/chars with a nitrogen precursor is not a sustainable nor an efficient method for the incorporation of N into the carbon structure. This study proposes the use of hydrothermal carbonization (HTC) as an environmentally friendly method for the incorporation of N into the bulk of carbon materials. The authors propose the following sequence for the synthesis of N‐enriched carbon materials (NCM) for energy storage applications: HTC of the N precursor and biomass → activation of N‐hydrochar (N‐HC). To investigate the proposed method, HTCs of spent coffee grounds (SCG) with N precursors (urea and alanine) were conducted at 220°C for 5 hours. The resulted N‐HCs were subjected to a mild thermal activation via pyrolysis at 600°C for 2 hours. The results showed that HTC enhances the incorporation of N into the carbon matrix via many reactions, for example, the Maillard reaction (MR) or the Mannich reaction, which may accompany the formation of HC via the solved‐intermediate pathway or the solid‐to‐solid pathway, respectively. However, adjusting some parameters before HTC, for example, the concentration of the N precursor and the pH value of the slurry is important to avoid a significant reduction in the N‐HC yield. The proposed method led to the synthesis of NCM with a N content of 10.3wt% The X‐ray photoelectron spectroscopy (XPS) confirmed the incorporation of N into the bulk of NCM and showed a significant increase in the content of heterocyclic N compounds (pyridinic N, pyrrolic N, and graphitic N) in the NCM. The incorporation of N via the proposed method significantly improved the electrochemical properties of NCM as the values of the specific capacitance and the electrical conductivity in the NCM increased by five times and four times, respectively. [ABSTRACT FROM AUTHOR]

Electrochemical clean energy conversion and the production of sustainable chemicals are critical in the journey to realizing a truly sustainable society. To progress electrochemical storage and conversion devices to commercialization, improving the electrocatalyst performance and cost are of utmost importance. Research into dual‐metal atom catalysts (DACs) is rising in prominence due to the advantages of these sites over single‐metal atom catalysts (SACs), such as breaking scaling relationships for the adsorption energy of reaction intermediates and synergistic effects. This review provides an examination of the fundamental theoretical principles and experimental electrochemical performance of DACs in idealized half cells, as well as fuel cells, before proceeding to analyze the methods used for producing and identifying DACs. Current challenges and potential future research directions of DACs are also discussed. [ABSTRACT FROM AUTHOR]

Biomass is recognized as an ideal CO2 neutral, abundant, and renewable resource substitute to fossil fuels. The rich proton content in most biomass derived materials, such as ethanol, 5‐hydroxymethylfurfural (HMF) and glycerol allows it to be an effective hydrogen carrier. The oxidation derivatives, such as 2,5‐difurandicarboxylic acid from HMF, glyceric acid from glycerol are valuable products to be used in biodegradable polymers and pharmaceuticals. Therefore, combining biomass‐derived compound oxidation at the anode and hydrogen evolution reaction at the cathode in a biomass electrolysis or photo‐reforming reactor would present a promising strategy for coproducing high value chemicals and hydrogen with low energy consumption and CO2 emissions. This review aims to combine fundamental knowledge on photo and electro‐assisted catalysis to provide a comprehensive understanding of the general reaction mechanisms of different biomass‐derived molecule oxidation. At the same time, catalyst requirements and recent advances for various feedstock compounds are also reviewed in detail. Technoeconomic assessment and life cycle analysis are performed on various feedstocks to assess the relative benefits of various processes, and finally critical prospects are given on the challenges and opportunities for technology development to meet the sustainability requirement of the future global energy economy. [ABSTRACT FROM AUTHOR]

Atomically dispersed transition metal‐nitrogen‐carbon catalysts are emerging as low‐cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost‐effective and scalable synthesis strategy for these catalysts is still required, as well as a greater understanding of their mechanisms. Herein, iron, nitrogen co‐doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization and high‐temperature post carbonization. It is determined that FeN4 is the main form of iron existing in the obtained Fe@NCS. Two different precursors containing Fe2+ and Fe3+ are compared. Both chemical and structural differences have been observed in catalysts starting from Fe2+ and Fe3+ precursors. Fe2+@NCS‐A (starting with Fe2+ precursor) shows better catalytic activity for the oxygen reduction reaction. This catalyst is studied in an anion exchange membrane fuel cell. The high open‐circuit voltage demonstrates the potential approach for developing high‐performance, low‐cost fuel cell catalysts. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hydrothermal processes avoid the energy intensive step of biomass drying. [•] Hydrogen or methane can be formed throughout hydrothermal biomass gasification. [•] Hydrothermal liquefaction produces oils with a high heating value. [•] Lignin can be hydrothermally liquefied to valuable chemicals. [•] Hydrothermal carbonization produces biochars and other interesting materials. [ABSTRACT FROM AUTHOR]

In terms of broadening the potential application range of carbon based materials, heteroatom doping provides a useful tool to moderate their physical and chemical properties. While nitrogen doped carbons have been extensively researched, the reports for sulfur, and especially nitrogen/sulfur dual-doped materials is far less exhaustive. We present a one-pot synthesis of dual nitrogen/sulfur doped materials which is based on sustainable carbohydrate and amino acid precursors and enables tailoring of the final material's physicochemical properties. The addition of cysteine gives rise to pending sulfur functionalities, while addition of thienyl-cysteine results in structurally bound sulfur within the carbonaceous framework. Post pyrolysis offers an additional tool for controlling the material stability and results in microporosity as well as superior conductivity relative to undoped carbon microspheres from glucose. Nitrogen doping levels of about 4 wt% and sulfur doping levels of 3 wt% to 12 wt% could be achieved. The samples were, amongst other methods, characterized by XPS, 13C MAS solid state NMR and both N2 and CO2 sorption isotherms. Since this is the first report on heteroatom doped, sulfur containing carbon materials obtained via hydrothermal carbonization, we anticipate our work to be a starting point for more sophisticated studies concerning the role of sulfur (and nitrogen) on the physicochemical properties of hydrothermal carbon. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) has demonstrated that it is an effective technique for the production of functionalized carbon materials from simple carbohydrates, such as monosaccharides and disaccharides. The chemical structure of the HTC carbon has been identified in detail by means of solid-state MAS 13C NMR investigations. However, it has not yet been clearly shown what the effects are of the processing temperature and time on the chemical structure and morphology of the generated HTC carbon. This study shows, with the help of SEM, elemental and yield analysis and solid-state MAS 13C NMR, the effects of these two key variables on the final nature of the produced material, allowing the development of a mechanistic model. According to the chosen set of processing parameters, the chemical structure of the HTC carbon can be tuned from polyfuran rich in oxygen containing functional groups to a carbon network of extensive aromatic domains. The same kind of investigation using lignocellulosic biomass as a carbon precursor shows a striking difference between the HTC mechanism of glucose and cellulose. The biopolymer, when it is treated under mild hydrothermal conditions (180–280 °C), tends to react according to a reaction scheme which leads to its direct transformation into an aromatic carbon network and which has strong similarities with classical pyrolysis. [ABSTRACT FROM AUTHOR]

Abstract: One of the recent major improvements of HPLC was the introduction of monolithic silica columns, which have the advantage of faster separation and lower back pressure as compared to common silica beads. Here, we present an interesting alternative to such reversed-phase monolithic columns by a convenient coupling route of a thermo-responsive polymer to hydrophilic silica monoliths. Poly(N-isopropylacrylamide) (PNIPAM) was polymerized in solution via a reversible addition fragmentation chain transfer (RAFT) polymerization technique and coupled then in situ onto an amino-modified silica monolithic column. These columns were compared with RP-18 monolithic columns in the separation of steroids under isocratic condition in aqueous mobile phase. Separation is optimized just by changing the temperature, instead of changing the mobile phase composition. [Copyright &y& Elsevier]

Hard carbons (HCs) are a significantly promising anode material for alkali metal-ion batteries. However, long calcination time and much energy consumption are required for the traditional fabrication way, resulting in an obstacle for high-throughput synthesis and structure regulation of HCs. Herein, we report an emerging sintering method to rapidly fabricate HCs from different carbon precursors at an ultrafast heating rate (300 to 500 °C min-1) under one minute by a multifield-regulated spark plasma sintering (SPS) technology. HCs prepared via the SPS possess significantly fewer defects, lower porosity, and less oxygen content than those pyrolyzed in traditional sintering ways. The molecular dynamics simulations are employed to elucidate the mechanism of the remarkably accelerated pyrolysis from the quickly increased carbon sp² content under the multifield effect. As a proof of concept, the SPSderived HC exhibits an improved initial Coulombic efficiency (88.9%), a larger reversible capacity (299.4 mAh⋅g-1), and remarkably enhanced rate capacities (136.6 mAh⋅g-1 at 5 A⋅g-1) than anode materials derived from a traditional route for Na-ion batteries. [ABSTRACT FROM AUTHOR]

Alkali metal ion batteries are instrumental in the widespread implementation of electric vehicles, portable electronics, and grid energy storage. From experimental characterisation of hard carbons, these carbon anodes were shown to contain a variety of functional groups. Through density functional theory simulations, the effect of functional groups (O, OH, NH 2 , and COOH) on edges and basal plane surfaces of carbonaceous materials on the adsorption of lithium, sodium, and potassium are investigated. These simulations show that the functionalisation of H-terminated edges and curved surfaces rather than basal planes is more energetically favourable and thus more likely to be present. Comparison of experimental FTIR and computational vibrational frequency analysis confirmed the occurrence of the investigated functional groups (O, OH, NH 2 , and COOH) in the synthesised hard carbon materials. Metal adsorption on the functionalised models showed that adsorption energies were stronger on the functionalised basal plane in comparison to the functionalised edge sites and contribute to the metal ion immobilization and consequent irreversible capacity loss. The metal adsorption on the curved surface was further improved by the addition of functional groups, benefitting the initial lithiation/sodiation/potassiation of the carbon anode. Hence, the morphology of the functionalised carbon systems plays an important role in the charge/discharge performance of carbonaceous anodes. [Display omitted] • XPS and FTIR identify functional groups in hard carbon. • Functional groups can adsorb at different carbon motifs. • DFT simulations show that functional groups bind strongly to edge sites. • Li, Na, and K bind strongly to hydroxyl groups. • Functional group type and site play important roles in the charge/discharge process. [ABSTRACT FROM AUTHOR]

Accurate modelling of particle shrinkage during biomass pyrolysis is key to the production of biochars with specific morphologies. Such biochars represent sustainable solutions to a variety of adsorption-dependent environmental remediation challenges. Modelling of particle shrinkage during biomass pyrolysis has heretofore been based solely on theory and ex-situ experimental data. Here we present the first in-situ phase-contrast X-ray imaging study of biomass pyrolysis. A novel reactor was developed to enable operando synchrotron radiography of fixed beds of pyrolysing biomass. Almond shell particles experienced more bulk shrinkage and less change in porosity than did walnut shell particles during pyrolysis, despite their similar composition. Alkaline pretreatment was found to reduce this difference in feedstock behaviour. Ex-situ synchrotron X-ray microtomography was performed to study the effects of pyrolysis on pore morphology. Pyrolysis led to a redistribution of pores away from particle surfaces, meaning newly formed surface area may be less accessible to adsorbates. [ABSTRACT FROM AUTHOR]

Insufficient light absorption and low carrier separation/transfer efficiency constitute two key issues that hinder the development of efficient photocatalytic hydrogen production. Here, multishell ZnS/CoS2 bisulfide microspheres with gradient distribution of Zn based on the heat diffusion theory are designed. The Zn distribution can be adjusted by regulating the heating rate and manipulating the diffusion coefficients of the different elements conforming the multishell photocatalyst. Because of the unique structure, a gradient energy level is created from the core to the exterior of the multishell microspheres, which effectively facilitates the exciton separation and electron transfer. In addition, stronger light absorption and larger specific surface area have been achieved in the multishell ZnS/CoS2 photocatalysts. As a result, the multishell ZnS/CoS2 microspheres with gradient distribution of Zn exhibit a remarkable hydrogen production rate of 8001 µmol g−1 h−1, which is 3.5 times higher than that of the normal multishell ZnS/CoS2 particles with well‐distributed Zn and 11.3 times higher than that of the mixed nonshell ZnS and CoS2 particles. This work demonstrates for the first time that controlling the diffusion rate of the different elements in the semiconductor is an effective route to simultaneously regulate morphology and structure to design highly efficient photocatalysts. [ABSTRACT FROM AUTHOR]

A deeper understanding of the water‐splitting hydrogen evolution reaction (HER) mechanism during photocatalytic processes is crucial for the rational design of efficient photocatalysts. In particular, the HER mechanism promoted by multielement hybrid structures remains extremely challenging and elusive. Herein, an in situ photoelectrochemical/Raman measurement system is employed to monitor the HER mechanism of hybrid nanostructures under realistic working conditions via operando Raman spectra and linear‐sweep voltammetry curves. As a proof of concept, tunable composition transition metal dichalcogenides MoS2xSe2(1−x) nanosheets are used as a model photocatalyst to unveil the corresponding photocatalytic mechanism. The spectroscopic studies reveal that hydrogen atoms can be adsorbed to active sulfur and selenium atoms via intermediate species formed during the photocatalytic process. More importantly, the studies demonstrate that an exponential relationship exists between the number of reactive electrons and the Raman intensity of intermediate species, which can serve as a guideline to directly evaluate the HER performance in photocatalysts by comparing the Raman intensities of the intermediate species. As a simple, intuitive, and general analytical method, the designed operando Raman measurement approach provides a new tool for elucidating catalytic reaction mechanisms in a realistic and complex environment; and strategically improving H2 production performance of multielement photocatalysts. [ABSTRACT FROM AUTHOR]

Introduced in the literature in 1913 by Bergius, who at the time was studying biomass coalification, hydrothermal carbonisation, as many other technologies based on renewables, was forgotten during the "industrial revolution". It was rediscovered back in 2005, on the one hand, to follow the trend set by Bergius of biomass to coal conversion for decentralised energy generation, and on the other hand as a novel green method to prepare advanced carbon materials and chemicals from biomass in water, at mild temperature, for energy storage and conversion and environmental protection. In this review, we will present an overview on the latest trends in hydrothermal carbonisation including biomass to bioenergy conversion, upgrading of hydrothermal carbons to fuels over heterogeneous catalysts, advanced carbon materials and their applications in batteries, electrocatalysis and heterogeneous catalysis and finally an analysis of the chemicals in the liquid phase as well as a new family of fluorescent nanomaterials formed at the interface between the liquid and solid phases, known as hydrothermal carbon nanodots. [ABSTRACT FROM AUTHOR]

Hard carbons are among the most promising materials for alkali‐ion metal anodes. These materials have a highly complex structure and understanding the metal storage and migration within these structures is of utmost importance for the development of next‐generation battery technologies. The effect of different carbon structural motifs on Li, Na, and K storage and diffusion are probed using density functional theory based on experimental characterizations of hard carbon samples. Two carbon structural models—the planar graphitic layer model and the cylindrical pore model—are constructed guided by small‐angle X‐ray scattering and transmission electron microscopy characterization. The planar graphitic layers with interlayer distance <6.5 Å are beneficial for metal storage, but do not have significant contribution to rapid metal diffusion. Fast diffusion is shown to take place in planar graphitic layers with interlayer distance >6.5 Å, when the graphitic layer separation becomes so wide that there is negligible interaction between the two graphitic layers. The cylindrical pore model, reflecting the curved morphology, does not increase metal storage, but significantly lowers the metal migration barriers. Hence, the curved carbon morphologies are shown to have great importance for battery cycling. These findings provide an atomic‐scale picture of the metal storage and diffusion in these materials. [ABSTRACT FROM AUTHOR]

Sustainable energy production at an acceptable cost is key for its widespread application. At present, noble metals and metal oxides are the most widely used for electrocatalysis, but they suffer from low selectivity, poor durability, and scarcity. Because of this, metal‐free carbons have become the subject of great interest as promising alternative electrocatalysts for energy conversion and storage devices, and remarkable progress has been accomplished in the advance of metal‐free carbons as electrocatalysts for renewable energy technologies. Particularly interesting are 3D porous carbon architectures, which exhibit outstanding features for electrocatalysis applications, including broad range of active sites, interconnected porosity, high conductivity, and mechanical stability. This review summarizes the latest advances in 3D porous carbon structures for oxygen and hydrogen electrocatalysis. The structure–performance relationship of these materials is consequently rationalized and perspectives on creating more efficient 3D carbon electrocatalysts are suggested. [ABSTRACT FROM AUTHOR]

Pyridinic-N configurations and intrinsic defects on nanocarbons have been regarded as potentially active-sites for the oxygen reduction reaction (ORR). In this work, a facile strategy is demonstrated to achieve pyridinic-N dominated porous carbon nanosheets with edge-enriched defective nature through the selection of the bio-precursor guanine as C/N sources. It is able to achieve high contents of pyridinic-N dominated (48.1% from gross N) species and the few-layers carbon architectures with hierarchical porosity by a template-free carbonization method. These 2D carbon structures are of low cost, scalable and economically attractive while based on renewable and highly abundant resources. As a result, the optimized catalyst delivers a significantly enhanced electrocatalytic performance for ORR under wide range of pH from alkaline to acid, i. e. possessing a 30 mV more positive half-wave potential (0.885 V) than Pt/C (0.855 V) catalyst in 0.1 M KOH, and very close activities to Pt/C in 0.1 M PBS and 0.1 M HClO 4 solution. This ORR performance is attributed to the synergistic effects of unique graphene-like architecture, high porosity, and coexistences of high contents of pyridinic-N species and abundant edge/defect sites. Image 1 A facile strategy is demonstrated to achieve pyridinic-N dominated porous carbon nanosheets with edge-enriched defective nature through the selection of the biological nucleobase precursor as C/N sources. [ABSTRACT FROM AUTHOR]

The regenerative hydrogen/vanadium fuel cell (RHVFC) is investigated with Freudenberg carbon paper electrodes (CPs). Along with thermal treatment, the Freudenberg CPs are also treated with reduced graphene oxide (rGO) using electrophoretic deposition at 300 V. The rGO modified CP results in 25% higher power density than its untreated counterpart under the same operating conditions. In comparison to the first preliminary study, the power density reported herein is more than four times higher. Additionally, the Freudenberg CPs modified with heat treatment followed by rGO deposition facing the membrane (rGOHTFM) provide the best electrolyte discharge utilization (UE) of 99%, followed by untreated (98%) and heat treated samples (97%) at 50 mA cm−2. The rGOHTFM also record high charge and discharge energy efficiencies (η E) of 93% at the same current density, which is slightly higher than untreated CPs (η E = 91%). Cycling the system 10 times also results in higher η E and UE for rGOHTFM CP (η E = 92% and UE = 99% on average) in comparison to untreated electrodes (η E = 86% and UE = 97% on average). In comparison the widely investigated SGL 10AA CP has lower efficiencies and utilization as expected (η E = 74% and UE = 83% on average). Image 1 • Freudenberg carbon paper electrodes are studied in hydrogen/vanadium fuel cell. • Freudenberg electrodes give much better charge/discharge response to SGL 10AA. • Untreated samples have similar performance to rGO modified ones at 50 mA cm−2. • Reduced graphene oxide modification of heat treated samples gave best results. • High cycling efficiencies (92%) and electrolyte utilization (99%) are reported. [ABSTRACT FROM AUTHOR]

Reversibly intercalating ions into host materials for electrochemical energy storage is the essence of the working principle of rocking-chair type batteries. The most relevant example is the graphite anode for rechargeable Li-ion batteries which has been commercialized in 1991 and still represents the benchmark anode in Li-ion batteries 30 years later. Learning from past lessons on alkali metal intercalation in graphite, recent breakthroughs in sodium and potassium intercalation in graphite have been demonstrated for Na-ion batteries and K-ion batteries. Interestingly, some significant differences proved to exist for the intercalation of Na+ and K+ into graphite compared with the Li+ case. Such different host–guest interactions are unique depending on the host materials and electrolytes, which greatly contribute to a deeper understanding of intercalation-type electrode materials for next generation alkali metal ion batteries. This review summarizes significant advances from both experimental and theoretical calculations with a focus on comparing the intercalation of three alkali metal ions (Li+, Na+, K+) into graphite and aims to clarify the intimate host–guest relationships and the underlying mechanisms. New approaches developed to achieve favorable intercalation coupled with the challenges in this field are also discussed. We also extrapolate alkali metal ion intercalation in graphite to mono-/multi-valent ions in layered electrode materials, which will deepen the understanding of intercalation chemistry and provide guidance to explore new guests and hosts. [ABSTRACT FROM AUTHOR]

High activity, selectivity and recyclability are crucial parameters in the design of performant catalysts. Furthermore, depletion of platinum‐group metals (PGM) drives further research towards highly available metal‐based catalysts. In this framework, iron‐based active sites supported on nitrogen‐doped carbon materials (Fe/N@C) have been explored to tackle important applications in organic chemistry, for both oxidation and reduction of C−O/C−N bonds, as well as in electrocatalysis for energy applications. This versatile reactivity makes them ideal substitutes to PGM‐based catalysts, being based on abundant elements. Despite important advances in material science and characterisation techniques allowing the analysis of heterogeneous/electro‐ catalysts at the atomic scale, the nature of the catalytically active sites in Fe/N@C remains elusive. Most recent theoretical studies point at individual FeNx single sites as the origin of the catalytic activity. Although their identification is still challenging with current technology, establishing their real nature will foster further research on these PGM‐free and redox‐polyvalent catalysts. In this review, we provide an overview of their applications in both thermal and electrochemical processes. Throughout the review, we highlight the different characterisation techniques employed to gain insight into the catalyst's active sites. [ABSTRACT FROM AUTHOR]

A hard templating method, using SBA‐15 in combination with glucose solution and different heteroatom precursors, has been employed to investigate the influence of the different heteroatom dopants nitrogen, boron, sulfur, and phosphorus on carbon electrocatalysts for the oxygen reduction reaction. Samples were synthesized under the same conditions and resulted in a similar morphology and surface areas around 1000 m2/g. Incorporating nitrogen into the carbon matrix was found to be easier than for boron or phosphorus, while sulfur doping proved problematic and only yielded 2 at% of sulfur or less. Different dopant concentrations as well as a combination of dopants suggested that nitrogen was the only heteroatom exerting an actual influence on the catalytic activity, resulting in higher electron transfer numbers. The other dopants exhibited a similar performance regardless of the dopant content, though slightly improved when compared to an undoped control sample. These findings indicate that incorporated nitrogen can act as catalytic sites, while boron, sulfur and phosphorus can enhance the catalytic activity by possibly creating defects in the carbon matrix. [ABSTRACT FROM AUTHOR]