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9 figures, 5 tables.-- Supplementary information available, Active and durable electrocatalysts for the oxygen evolution reaction (OER), capable of replacing noble metal catalysts, are required to develop efficient and competitive devices within the frame of the water electrolysis technology for hydrogen production. In this work, we have investigated tantalum based catalysts supported on carbon nanofibers (CNF) for the first time. The effect of CNF characteristics and the catalyst annealing temperature on the electrochemical response for the OER have been analyzed in alkaline environment using a rotating ring disc electrode (RRDE). The best OER activity and oxygen efficiency were found with a highly graphitic CNF, despite its lower surface area, synthesized at 700 °C, and upon a catalyst annealing temperature of 800 °C. The ordering degree of carbon nanofibers favors the production of oxygen in combination with a low oxygen content in tantalum oxides. The most active catalyst exhibited also an excellent durability., The authors want to thank the Ministerio de Economía, Industria y Competitividad (MICINN) and FEDER for the received funding in the project of reference ENE2017-83976-C2-1-R, and to the Gobierno de Aragón (DGA) for the funding to Grupo de Investigación Conversión de Combustibles (T06_17R). J.C. Ruiz-Cornejo acknowledges DGA for his PhD grant. D. Sebastián acknowledges the MICINN for the Ramón y Cajal research contract (RyC-2016-20944).

11 figures, 4 tables.-- Información suplementaria., Biomass from agricultural by-products is gaining increasing interest as cheap and abundant precursor in the development of active materials for efficient and environmentally friendly devices like fuel cells. Herein, we investigated iron and nitrogen co-doped nanoporous carbons derived from aronia, peach stones and coal tar pitch/furfural as electrocatalysts for the electrochemical oxygen reduction reaction (ORR) in alkaline media. Urea was used as nitrogen precursor and two annealing steps with intermediate acid leaching served to activate the catalysts. Within the series, the peach stone-derived catalyst exhibited a catalytic activity for the ORR close to the benchmark Pt/C, with a 60 mV dec−1 Tafel slope upon the incorporation of 0.57 wt% Fe and proper combination of N-Fe species (20%) with pyridinic/pyridonic moieties (49%). We concluded that the microporosity and a certain content of meso/macro-pores of the activated carbon, together with the creation of graphitic domains result in a high relative amount of Fe-N4 and nitrogen functionalities, which determine the electrocatalytic performance., The authors gratefully acknowledge financial support given by the project BLOW UP "Balkans Waste to Products: transfer of NoI model to Balkan area: de-siloing new waste-derived raw materials and developing new applications" from EIT RAW MATERIAL EIT16320, Horizon 2020. D. Sebastián and C. Alegre acknowledge the Ministry of Economy, Industry and Competitiveness for their Ramón y Cajal (RyC-2016-20944) and Juan de la Cierva Incorporación (IJCI-2017-32354) research contracts, respectively.

12 figures, 4 tables.--This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.jpcc.0c11346, In the pursuit of good performing, low cost, and scalable anion-exchange membranes (AEM), a series of blended electrolytes based on cross-linked quaternized poly epichlorohydrin (qPECH) and polyvinylidene fluoride (PvDF) were prepared to evaluate their suitability for AEM fuel cell application. The thermo-mechanical and swelling analyses revealed that the blending of these two macromolecules produces robust and heat-resistant microphase-segregated membranes with good dimensional stability. By varying the blend ratio, the ion-exchange capacity (IEC) and transport properties of the resulting membrane can be easily adjusted and optimized with clear impact on its electrochemical performance. At 67:33 wt % blend ratio, high hydroxide conductivity (i.e., 56.3 mS cm–1 at 80 °C) and quite reasonable alkaline stability were achieved. The single H2–O2 fuel cell using the qP-67 membrane yielded a beginning-of-life maximum power density of 32 mW cm–2 and an open circuit voltage (OCV) of 1.03 V at 50 °C without optimization. These preliminary results demonstrate that qPECH/PvDF blended membranes can be potentially applied in AEMFCs., We gratefully appreciate thefinancial support from the Italian Ministry of Education, Universities and Research (MIUR) by the AIM Project: “Attraction and International Mobility”(PON R&I 2014−2020; AIM1899391-2). CSIC authors acknowledge Gobierno de Aragón (DGA) for the financial support of Grupo de Investigación Conversión de Combustibles (T06_17R).

7 figures, 2 tables., The development of active and low-cost electrocatalysts for the oxygen reduction reaction (ORR) is crucial for the sustainable commercialization of fuel cell technologies. In this study, we have synthetized Me/Mo2C (Me = Fe, Co, Cu)-based composites embedded in N- and P-dual doped carbon by means of inexpensive industrial materials, such as melamine and chitosan, as C and N sources, and the heteropolyacid H3PMo12O40 as P and Mo precursor. The effect of the transition metal (Fe, Co, and Cu) on the ORR in alkaline medium has been investigated. The physicochemical properties of the electrocatalysts were performed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM). Activity towards ORR was carried out in a three-electrode cell using a ring-disk electrode in 0.1M NaOH. The results obtained clearly show the important role played by each transition metal (Fe, Co, and Cu) in the electrochemical activity. Among them, Fe gives rise to the best performing composite in carrying out the oxygen reduction reaction. The formation Fe3C/Mo2C species embedded in N- and P-dual doped carbon seems to be the determining role in the increase of the ORR performance., The authors acknowledge the Ministerio de Ciencia, Innovación y Universidades (MCIU), and FEDER for the funding received for the project, with references ENE2017-83976-C2-1-R, Spanish National Research Council COOPB20202, and MERC project 721399002.

8 figures, Polymer electrolyte fuel cells with alkaline anion exchange membranes (AAEMs) have gained increasing attention because of the faster reaction kinetics associated with the alkaline environment compared to acidic media. While the development of anion exchange polymer membranes is increasing, the catalytic layer structure and composition of electrodes is of paramount importance to maximize fuel cell performance. In this work, we examine the preparation procedures for electrodes by catalyst-coated substrate to be used with a well-known commercial AAEM, Fumasep® FAA-3, and a commercial ionomer of the same nature (Fumion), both from Fumatech GmbH. The anion exchange procedure, the ionomer concentration in the catalytic layer and also the effect of membrane thickness, are investigated as they are very relevant parameters conditioning the cell behavior. The best power density was achieved upon ion exchange of the ionomer by submerging the electrodes in KCl (isopropyl alcohol/water solution) for at least one hour, two exchange steps, followed by treatment in KOH for 30 min. The optimum ionomer (Fumion) concentration was found to be close to 50 wt%, with a relatively narrow interval of functioning ionomer percentages. These results provide a practical guide for electrode preparation in AAEM-based fuel cell research., This research was funded by the Ministry of Economy, Industry and Innovation (MICINN) and FEDER, grant number ENE2017-83976-C2-1-R and by the Government of Aragón and FEDER for supporting ‘Grupo de Conversión de Combustibles’, grant number T06_17R. D.S. and J.M.L.-C. acknowledge also MICINN for their Ramón y Cajal research contract (RyC-2016-20944) and Ph.D. grant, respectively. G.L. acknowledges as well Aragón Government for his Ph.D. grant.

8 Figuras.- 4 Tablas, Pd and PdM (M = Fe or Co) nanostructured electrocatalysts were synthesized by the impregnation method and supported on carbon black Vulcan XC-72R for the formic acid oxidation reaction, FAOR, in acid medium. Nitrates or chlorides were used as Fe and Co precursors to study the counter ion role on the physicochemical features and electrochemical performance of the electrocatalysts. TEM analysis showed that PdM was deposited on the carbon material with a particle size around 2–3 nm. From XRD, peaks associated with the fcc palladium planes were observed along with evidence of PdM alloy formation, particularly when the nitrate salts were used as metal precursors. Furthermore, XPS analyses indicated that nitrates promote the metal oxide formation to a greater extent than chlorides, mainly for Pd. PdCo electrocatalyst obtained from nitrates exhibited the highest performance for FAOR with a steady state current density of 451 and 313 μA cm−2 at 200 and 400 mV respectively, which is in both cases, 3 times larger than that developed for a commercial Pd/C catalyst., LJM is grateful to CONACYT for the grant awarded for this research, as well as to the UAM-A and the ICB for the support provided. MGMY, MRR, MPP and AEM thank the SNI for the distinction of their membership and the stipend provided. MGMY is indebted to L'oreál-UNESCO-CONACyT-AMC for the grant Women in Science 2016. MJL and SPR gratefully acknowledge financial support given by Spanish MINECO (ENE2014-52158-C2-1-R).

2 Figuras. 1 Tabla., Differential electrochemical mass spectrometry (DEMS) was used to establish the difference in surface acidity in sulfuric acid solution between commercially available carbon black (Vulcan) and Vulcan which had been chemically modified with concentrated nitric acid (VulcanO). The mass signal for the m/z = 2 associated with H2 formation was observed to be influenced by functional groups at the carbon surfaces. Analysis of the mass spectra with the help of the Nernst equation allowed us to quantitatively find the difference in surface pH between the two carbon-based materials in acid media. The elevated concentration of functional groups at the VulcanO surface results in a decrease in the local acidity of the surface under these conditions (0.5 M H2SO4), and consequently the hydrogen evolution reaction (HER) is delayed., The authors gratefully acknowledge financial support given by Spanish MINECO (ENE2014-52158-C2-2-R and 1-R). GG acknowledges the Viera y Clavijo program (ACIISI & ULL) for financial support.

Iron and cobalt materials have attracted enormous interest as low-cost alternatives to noble-metal catalysts able to catalyse oxygen reduction reaction. Here, the effect of the heteropolyacid H3PMo12O40 (HPMo) into the structure of new composites formed by Fe, Co and reduced-graphene oxide/chitosan (rGOCS) has been investigated. Chitosan was used as a nitrogen precursor for nanocarbon, while reduced graphene oxide was introduced to tune the electrical conductivity. The physicochemical properties of electrocatalysts were performed by Raman, XRD, XPS and TEM. Activity toward ORR was carried out in a three-electrode electrochemical cell using a rotating disk electrode (RDE). The molybdophosphoric acid incorporation into the structure of Fe/rGOCS composites resulted in an increase of the activity of the oxygen reduction reaction in alkaline medium. Furthermore, the replacement of iron by cobalt yielded in a great improvement of the activity and stability, which may open new avenues for the design of nanomaterials utilizing HPMo/reduced-graphene oxide/chitosan composites., This work was supported by the Spanish Government under the MINECO projectENE2014-52158-C2-1R (co-funded by FEDER), Spanish National Research CouncilCOOPB20202 and MERC project721394002. M.R.A acknowledges the FPU-2012 program for financial support.

Low temperature fuel cells technologies are currently shifting very fast from fundamental research to real growth. The development of electrocatalysts plays a vital role in the electrocatalytic reactions involved in these devices, because the catalyst determines the overall reaction efficiency, durability and cost. This article review progress in the research and development of electrocatalysts for low temperature fuel cells technologies, with especial attention in the contribution of our research teams over the last 15 years or so. The intensive research efforts in reducing or replacing Pt-based electrodes in fuel cells have been focus in the use of carbon nanomaterials as electrocatalytic supports, including carbon nanostructures tailored by surface modification or building in particular dopants/defects. Recent research effort has also led to the use of electronic conductivity noncarbon support materials. In addition, carbon-composite materials are proving to be a robust, inexpensive and active electrocatalysts, where the synergetic effect between the carbon nanomaterials and the ceramic or polymer nanostructures can lead to a superior electrocatalytic performance and durability for low temperature fuel cells. Perspectives on these catalysts and possible pathways to address current remaining challenges are also discussed., Authors thank the Ministry of Economy and Competitiveness (MINECO) and FEDER through the Project ENE2014-52158-C2-1-R for financial support.

10 figuras, 2 tablas. Datos asociados suplementarios están disponibles en la versión en línea del editor., In the present work, a wide variety of electrocatalysts, involving different metals, synthesis routes and oxidation states, have been prepared and the response towards the CO2 reduction on carbon-supported established. In particular, catalysts based on non-noble metals (Cu, Co, Fe and Ni) supported on carbon black (Vulcan XC-72R) were tested in the electrochemical reduction of CO2. Amorphous oxides of magnetite/maghemite and crystalline CuO and Cu2O oxides obtained by different methodologies were also studied. Previously, the efficiency of the catalysts for the hydrogen formation was evaluated in 0.1 M NaHCO3 since it takes place as a competitive reaction during CO2 reduction in aqueous electrolytes. By comparison of the voltammograms in the absence and presence of CO2, an inhibition of the hydrogen evolution was showed for all (metal and oxide-based) catalysts due to the adsorption of species from CO2 reduction (CO2,red). Interestingly, the CO2,red formation on Co and Fe-surfaces operating under these conditions has not been stated before. A strong current decrease, and consequently, a higher adsorbate amount, was observed on copper-oxides (75–85%) vs. the metal catalyst (45%)., The authors gratefully acknowledge financial support given by Spanish MINECO (CTQ2011-28913-C02-01 and 02) and Gobierno de Aragon (T07). S. Pérez-Rodríguez acknowledges also Gobierno de Aragón for the DGA grant. Authors thank Advanced Microscopy Laboratory at Instituto de Nanociencia de Aragón and Electronic Microscopic Service at Universidad de Zaragoza for offering access to STEM and TEM facilities, respectively.

4 figures, It has recently been established that 1-octanethiol in the electrolyte can allow iron electrodes to be discharged at higher rates. However, the effect of thiol additives on the air electrode has not yet been studied. The effect of solvated thiols on the surface positive electrode reaction is of prime importance if these are to be used in an iron-air battery. This work shows that the air-electrode catalyst is poisoned by the presence of octanethiol, with the oxygen reduction overpotential at the air electrode increasing with time of exposure to the solution and increased 1-octanethiol concentration in the range 0–0.1 mol dm−3. Post-mortem XPS analyses were performed over the used air electrodes suggesting the adsorption of sulphur species over the catalyst surface, reducing its performance. Therefore, although sulphur-based additives may be suitable for nickel-iron batteries, they are not recommended for iron-air batteries except in concentrations well below 10 × 10−3 mol dm−3., This work was enabled by an EU grant FP7 (NECOBAUT grant agreement no. 314159). H.A.F-R. acknowledges financial support from CONACYT, Mexico. CNR-ITAE authors acknowledge funding from the “Accordo di Programma CNR-MiSE, Gruppo tematico Sistema Elettrico Nazionale – Progetto: Sistemi elettrochimici per l’accumulo di energia”. C.A. thanks the Short-Term Mobility project of CNR and for her Juan de la Cierva contract (FJCI-2015-25560). The authors also acknowledge financial support given by Aragon Government to the Fuel Conversion Group (T06_17R).

8 Figures, 3 Tables.-- Supplementary material.-- © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/, We report the electrochemical properties of a novel nanocarbon material obtained by chemical oxidation and ultrasound-assisted exfoliation of fishbone carbon nanofibers (CNF). The resulting material maintains its tubular morphology and presents a characteristic interlayer spacing of graphene oxide (above 0.75 nm). Thus, this is called graphene oxide nanofibers (GONF). The new rearrangement of the accessible sp2-carbon domains makes the GONF a potential alternative for electrochemical energy conversion/storage applications, showing a developed porosity and tuneable surface chemistry. The influence of the oxidation degree of GONF on its electrochemical behaviour in 0.5 M H2SO4 is reported. Cyclic voltammetry and electrochemical impedance spectroscopy evidenced a significant increase of the capacitance for GONF, being 4–27 times higher than that obtained for pristine CNF. An optimum in the capacitance (49.2 F g−1) was obtained using an oxidation ratio (OR = KMnO4/Sample) of 6 and 60 min of sonication. The latter is ascribed to the unique structure of this material containing both graphitic and graphene oxide domains. Higher OR or longer sonication times led to a partial loss of graphitic domains and higher contribution of micropores, which worsen the fast ion/electrolyte transport. Additionally, the optimized material exhibited an improved activity for the hydrogen evolution reaction., This work was funded by FEDER, the Spanish Ministry of Science, Innovation and Universities MICINN (ENE2017-83976-C2-1-R & ENE2017-83854-R) and by the Aragón Government to the Fuel Conversion Group (T06_17R). DS thanks MICINN for his Ramon y Cajal research contract (RyC-2016-20944).

9 Figures, 3 Tables.-- Informacion suplementaria disponible en línea en la página web del editor.-- © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/, Nitrogen doped reduced graphene oxide (NrGO) catalysts and composites of these with carbon nitride (CN) with nitrogen content as high as 19.8 wt% and 35.8 wt%, respectively, have been synthesized by thermal annealing of multilayer graphene oxide and urea at different temperatures. Nitrogen has been effectively introduced as a mix of pyridinic, pyrrolic, pyridonic and quaternary bonding configurations into the carbon lattice of graphene upon removal of CN phase over 650 °C. The electrocatalytic activity towards oxygen reduction reaction (ORR) in 0.1 M NaOH has been investigated. NrGO catalysts with less nitrogen content show better performance than composites. NrGO produced at 800 °C presents the best activity with half-wave potential of 0.76 V vs. RHE and a mean number of electrons of 3.7, which are close to a commercial Pt/C catalyst. This study concludes that a high concentration of nitrogen atoms in multilayer reduced graphene oxide does not necessarily produce a highly active electrocatalyst, suggesting that carbon in the neighbourhood of nitrogen atoms are the active sites for ORR in alkaline medium., Authors acknowledge the financial support given by the Spanish Ministry of Science, Innovation and Universities (MICINN) through projects ENE2014-52158-C2-1-R and 2-R and ENE2017-83976-C2-1-R and 2-R (co-founded by FEDER) and Aragón Government to support “Grupo de Conversion de Combustibles” (T06_17R). G. Lemes and D. Sebastián thank the Aragón Government and MICINN for their Ph.D. grant and Ramón y Cajal research contract (RyC-2016-20944), respectively.

6 Figuras.- 4 Tablas.- Datos suplementarios disponibles en línea en la página web del editor., Ordered mesoporous carbon materials (OMC), obtained by the template carbonization pathway from silica templates (sacrificial method), exhibit promising features for many applications mainly due to their large surface area. Graphitization is a common approach to improve the electrical conductivity and degradation resistance. We have investigated the graphitization of two different OMC at 1500 °C and the electrochemical oxidation by potential holding at 1.4 V vs. reversible hydrogen electrode (RHE) in acidic electrolyte. Graphitization conducts to a significant reduction of the electrooxidation associated charge, between 50 and 90% depending on the carbon properties, together with a decrease of surface area of 35–48%. The materials still exhibit a large electrochemical surface area, according to electrochemical impedance and cyclic voltammetry experiments. Upon electrooxidation, the relative amount of oxygen increases according to a comparative analysis of X-ray photoelectron spectroscopy test of the electrodes before and after potential holding. The results are of interest to define strategies towards the amelioration of carbon degradation by electrooxidation in electrochemical devices., The authors gratefully acknowledge financial support given by Spanish Ministry of Science, Innovation and Universities MICINN (ENE2017-83976-C2-1-R) and to the Aragón Government to the Fuel Conversion Group (T06_17R). DS acknowledges also MICINN for his Ramón y Cajal contract (RyC-2016-20944).

1 figure.-- Abstract of the poster presented at the VII International Symposium SRUK/CERU (2019), organized by the Society of Spanish Researchers in the United Kingdom. 28th-30th June 2019, Liverpool (United Kingdom)., Graphene oxide nanomaterials, specifically reduced few-layer graphene oxide (rFLGO) sheets and reduced graphene oxide quantum dots (rGOQD), were explored as active and cost-effective counter electrodes for dye-sensitized solar cells (DSSCs). The synthesis strategy adopted in this work for these materials is based on an economic and easily scalable route of exfoliation of multi-wall carbon nanotubes (Top-Down approach). This allows the easy tailoring of rFLGO/rGOQD size and oxidation degree for their use as bulk material in counter electrodes, having a significant influence on the photovoltaic performance and stability. Despite the slower kinetics of carbon for the reduction of triiodide compared to platinum, they are characterized by low cost and promising stability. The electrochemical performance of DSSC assembled with either rFLGO or rGOQD at the counter electrode is correlated to their most important physico-chemical features. The domain size of graphene sheets had an important effect on the performance at the counter electrode, with quantum dots performing 13% higher efficiency than rFLGO, correlated with a higher density of active sites. Both graphene nanostructures exhibited a better stability behavior upon electrochemical cycling and seasoning of the cells as compared to Pt counter electrode., ICB-CSIC authors acknowledge the Raw Materials Network of Infrastructure ITO substitution in opto-electronic devices (European Union), and the funding of the FEDER and the Spanish Economy and Competitiveness Ministry (MINECO) (ENE2011-28318-C03-01 and ENE2014-52189-C02-01-R). JLP and DS thank MINECO for their Ramon y Cajal research contracts (RyC-2013-12494 and RyC-2016-20944). CNR-ITAE authors acknowledge the financial support from the FotoH2 project. This project has received funding from the European Union s Horizon 2020 research and innovation programme under Grant Agreement n° 760930.

The effect of chemical surface oxidation of the carbon black Vulcan XC-72R on the capacitance, tolerance to corrosion and electrochemical activity toward the hydrogen evolution reaction (HER) has been studied in 0.1 M NaHCO3. Acid treatments with HNO3 or a HNO3H2SO4 mixture resulted in a progressive introduction of oxygen-containing groups which led to a strong increase of the capacitance and a higher tendency to carbon corrosion. In contrast, an inhibition of the hydrogen evolution current (at potentials more negative than −1.0 V) was observed for oxidized samples in comparison to the un-treated material. HER was also tested in the presence of dissolved CO2 to study the influence of the surface chemistry on the CO2 electroreduction. An inhibition of the H2 evolution current was evidenced in the CO2 saturated electrolyte due to the adsorption of species from CO2 reduction. A strong hydrogen current decrease (65–78%), and thus a higher tendency to adsorb (CO2)red species, was obtained on the original Vulcan and the HNO3-treated samples, in comparison to the carbon oxidized with HNO3H2SO4 (15%), which could be related to the highest content of basic groups of the last carbon., The authors gratefully acknowledge financial support given by Spanish MINECO (ENE2014-52158-C2-1-R and 2-R). S. Pérez-Rodríguez thanks Gobierno de Aragón for the DGA grant. Furthermore, the authors wish to acknowledge Dra. Ana Beatriz García for the TPD measurements.

6 Figuras. 4 Tablas.-- Datos suplementarios sobre el artículo disponibles en la versión en línea del editor.-- © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/, This work reports a study of the electrical conductivity under compression of nanostructured carbon powders with different physicochemical properties (texture, chemical-surface and morphology): a commercial carbon black (Vulcan XC-72R) and synthesized ordered mesoporous carbon (OMC), carbon nanocoils (CNC) and carbon nanofibers (CNF). The electrical conductivity was determined from the sample resistance under compaction (from 0.5 to 140 MPa) using the four-probe technique. A comparison of intrinsic and grain electrical conductivities (calculated according to the percolation theory and the general effective media approximation) was performed. Additionally, samples were subjected to chemical oxidation or graphitization treatments to evaluate the effect of oxygen content and structural properties on the electrical conductivity. In spite of the physicochemical differences of carbon materials, an exponential decrease of the electrical conductivity with the oxygen amount was stated. Finally, thermal treatment of OMC at 1500 °C led to a surprising increase in its conductivity due to the graphitization of the amorphous carbon structure of the original material and the oxygen removal., The authors gratefully acknowledge financial support given by Spanish MINECO (ENE2014-52158-C2-1-R). Furthermore, the authors wish to thank Dra. Ana Beatriz García (INCAR-CSIC) for the graphitization treatment of OMC and the TPD measurements.

10 Figuras, 8 Tablas.-- Material suplementario disponible en línea en la página web del editor., The electrochemical oxidation of carbon represents a relevant limitation for the application of carbon-based materials at the electrodes of several electrochemical devices, like fuel cells, metal-air batteries, water electrolyzers or supercapacitors. Understanding the key influencing parameters is thus of paramount importance to prevent and avoid the degradation of carbon materials. In the present investigation, carbon xerogels (CXGs) as a model of synthetic amorphous carbon, were studied on the basis of different surface chemistry and structure. Electro-oxidation experiments consisted of potential holding (1.2 V vs. RHE) on electrodes prepared with CXGs. The results indicate that the presence of oxygen groups (-C-O) and a higher ordering degree hinder the carbon oxidation reaction. A sub-structural parameter considering both the amount of oxygen-free carbon atoms (C-C + C*-C-O) from X-ray photoelectron spectroscopy, and the disordering degree from Raman spectra (in terms of ID/IG) is here proposed as a new factor to evaluate the tendency of an amorphous carbon material, like xerogels, to be electrochemically oxidized., Authors acknowledge financial support given by Spanish Ministry of Science, Innovation and University (MICINN) through project ENE2017-83976-C2-1-R (co-founded by FEDER) and from Aragón Government to the Fuel Conversion Group. C. Alegre and D. Sebastián acknowledge also MICINN for their Juan de la Cierva (FJCI-2015-25560) and Ramón y Cajal (RyC-2016-20944) research contracts, respectively.

Developing efficient, durable, and low cost catalysts based on earth-abundant elements for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for renewable energy conversion and energy storage devices. We report herein a simple one-pot procedure for the synthesis of non-precious metals N-doped graphene composites employing urea as nitrogen source, and their application as bifunctional catalysts for both the ORR and OER in alkaline environment. In this study, the effects of the addition of Ti and Co on the structure and performance of the N-doped graphene composites are investigated. The incorporation of Ti leads to a composite with both anatase and rutile TiO2 crystalline phases as well as Ti3+ species stabilized upon hybridization with N-doped reduced graphene oxide. The ORR onset potential for the Ti-based composite is 0.85 V (vs. RHE) and the number of electrons transferred is 3.5, showing superior stability than Pt/C after accelerated potential cycling in alkaline solution. However, this composite shows low activity and stability for the OER. On the other hand, the composite consisting of metallic Co and Co3O4 nanocrystals grown on N-doped reduced graphene oxide exhibits the best performance as bifunctional catalyst, with ORR and OER onset potentials of 0.95 V and 1.51 V (vs. RHE), respectively, and a number of electrons transferred of 3.6 (ORR). The results reveal the presence of important structural features such as metallic Co as the predominant crystalline component, amorphous Co3O4 phase and the coordination of Co-N-doped graphene. All of them seem to be fundamental for the high activity and stability towards ORR and OER., Authors acknowledge financial support given by Spanish Ministry of Economy and Competitiveness (MINECO) through projects ENE2014-52158-C2-1-R and 2-R (co-founded by FEDER). J. M. Luque and G. Lemes also thank MINECO and Aragon Government, respectively, for their Ph.D. grants.

Nanocatalyst performance towards the ethanol oxidation reaction (EOR) for fuel cell applications can be enhanced by exploiting the benefits of structural and compositional sensitivity and control. We describe the synthesis and characterization of cubic Pt-Sn alloyed nanoparticles consisting of (100) faceted Pt-Sn nanoparticles with a core-shell structure, with a Pt-rich core and a Sn-rich shell. Stability tests indicated that this catalyst preserves its morphology and remains well-dispersed on the carbon support after 5,000 potential cycles, while a cubic (pure) Pt catalyst exhibited severe agglomeration of the nanoparticles after the same stability testing protocol. Analysis of the elemental distribution in the nanoparticles by STEM-EELS indicated that Sn dissolves from the outer part of the shell after potential cycling, forming a ~0.5 nm Pt skin. Finally, the activity of this bimetallic core-shell nanostructured electrocatalyst towards the EOR was investigated, exhibiting currents about three times higher than those of unshaped Pt-Sn nanoparticles and six times higher than Pt nanocubes., This work has been supported by Fundación Cajacanarias (project BIOGRAF), the Ministry of Economy and Competitiveness (MINECO) through the projects CTQ2011-28913-C02-02 and ENE2014-52158-C2-2-R (co-funded by FEDER) and the. The authors acknowledge the SEGAI services of Universidad de La Laguna for important technical assistance and R.R also thanks the funding received from MINECO (EEBB-I-16-11762) to carry out a predoctoral stay in a foreign R&D center. E.P. acknowledges support from an electron microscopy facilities supported by the NSF MRSEC program (DMR 1120296) and an NSF MRI grant (DMR 1429155).J.S.G. acknowledges financial support from VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante.

9 Figuras. 4 Tablas. Datos suplementarios pueden encontrarse en la versión en línea del editor., This work reports a study of the electrocatalytic properties and stability of nanostructured carbon electrodes by on-line differential electrochemical mass spectrometry (DEMS). A wide electrochemical characterization in 0.1 M NaHCO3 involving anodic (carbon corrosion and oxygen evolution reaction, OER) and cathodic (CO2 reduction and hydrogen evolution reaction, HER) key reactions in energy-conversion devices was performed. DEMS studies showed that the faradaic current from 1.3 to 1.6 V vs. RHE of carbons was only associated to CO2 formation by corrosion and not to OER, the stability being improved by the graphitic character of carbon. H2 evolution was also enhanced with graphitic carbon nanofilaments, even though metal traces might positively influence their catalytic activity. By comparison of the faradaic currents and the H2 formation signals, in the absence and presence of CO2, a high inhibition of the HER was established for all carbon electrodes due to the species adsorption from CO2 reduction., The authors gratefully acknowledge financial support given by Spanish MINECO (CTQ2011‐28913‐C02‐01 and 02). S. Pérez-Rodríguez acknowledges Gobierno de Aragón for the DGA grant.

8 Figuras, 1 Tabla, 2 Esquemas, The mechanism of CO and HCOOH electrooxidation in an acidic solution on carbon-supported Au–Pd core–shell nanoparticles was investigated by differential electrochemical mass spectrometry and in situ Fourier transform infrared (FTIR) spectroscopy. Analysis performed in nanostructures with 1.3 ± 0.1 nm (CS1) and 9.9 ± 1.1 nm (CS10) Pd shells provides compelling evidence that the mechanism of adsorbed CO (COads) oxidation is affected by structural and electronic effects introduced by the Au cores. In the case of CS10, a band associated with adsorbed OH species (OHads) is observed in the potential range of CO oxidation. This feature is not detected in the case of CS1, suggesting that the reaction follows an alternative mechanism involving COOHads species. The faradaic charge associated with COads oxidation as well as the Stark slope measured from FTIR indicates that the overall affinity and orbital coupling of CO to Pd are weaker for CS1 shells. FTIR spectroscopy also revealed the presence of HCOOads intermediate species only in the case of CS1. This observation allowed us to conclude that the higher activity of CS10 toward this reaction is due to a fast HCOOads oxidation step, probably involving OHads, to generate CO2. Density functional theory calculations are used to estimate the contributions of the so-called ligand and strain effects on the local density of states of the Pd d-band. The calculations strongly suggest that the key parameter contributing to the change in mechanism is the effective lattice strain., V.C. gratefully acknowledges the UK National Academy for their support through the International Newton Fellowship program (NF120002). D.P. and D.J.F. gratefully acknowledge funding from EPSRC (EP/K007025/1). J.J.L.H. is grateful for the Ph.D. scholarship partly funded by Sasol UK and NERC. E.P. acknowledges financial support from the Ministry of Economy and Competitiveness through Project ENE2014-52158-C2-2-R. D.J.F. is also grateful for the Research Fellowship from the Institute of Advanced Studies of the University of Bristol. TEM studies were performed at the University of Bristol Chemistry Imaging Facility with equipment funded by UoB and EPSRC (EP/K035746/1 and EP/M028216/1). We are grateful to Prof. Jeremy Sloan (University of Warwick, Coventry, U.K.) and Dr. Christoph Mitterbauer (FEI Co.) for the high-resolution TEM images of the CS1 nanoparticles. This work is part of the research network of the Deutsche Forschungsgemeinschaft FOR1376. E.S. acknowledges PIP-CONICET 112-201001-00411 and PICT 2012-2324; whereas P.M.Q. acknowledges PICT-2014-1084 (Agencia Nacional de Promoción Científica y Tecnológica, FONCYT, préstamo BID). A grant of computing time from the Baden-Württemberg grid is gratefully acknowledged. All the data presented in this paper can be freely accessed from the Bristol’s Research Data Repository (http://data/bris.ac.uk/10.5523/bris.1om4r04s216tn164tab9nfjyfg).

11 Figuras, 3 Tablas.-- Material suplementario disponible en línea en la página web del editor., Oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts play an important role in energy conversion and storage devices, but highly active and robust nonprecious metal catalysts are required to address the cost and durability issues. In this work, a modified gel methodology has been used to obtain nanocomposites of perovskite CoTiO3 and N-doped reduced graphene oxide (NrGO). Moreover, the influence of the annealing extent in the synthesis has been studied. The composites show higher activity in oxygen evolution and reduction reactions in alkaline environment compared to sole ilmenite, which is related to a strong interaction between cobalt titanate and NrGO carbon matrix. The annealing duration appears as a key variable to modulate the physicochemical properties and the electrochemical behavior. The composite prepared at the largest duration (3 h) exhibit enhanced bifunctional properties for ORR and OER, with onset potentials of 0.93 V and 1.53 V vs. RHE respectively, which is mainly attributed to higher concentration of nitrogen, larger extent of defects and/or the presence of more oxidized Co species in the nanocomposite., The authors wish to acknowledge the Ministerio de Ciencia, Innovación y Universidades (MICINN) and FEDER for the received funding in the project of reference ENE2017-83976-C2-1-R. Thanks also to the Gobierno de Aragón (DGA) the funding for the Grupo de Investigación Conversión de Combustibles (T06_17R). J. M. Luque also thanks MICINN for its Ph.D. grant. D. Sebastián acknowledges the MICINN for the contract Ramón y Cajal (RyC-2016-20944).

The electrooxidation of ethanol and carbon monoxide on Pt nanoparticles (NPs) supported on carbon nanofibers (CNFs) and carbon blacks (oxidized and non-oxidized) is studied. Quite similar characteristics are found for Pt NPs, including particle size and crystal phases, regardless of the nature of carbon support. Cyclic voltammetries and current-transient curves show higher ethanol oxidation current density for Pt/CNF than for Pt/Vulcan. In situ spectroelectrochemical techniques including Fourier transform infrared spectroscopy (FTIR) and differential electrochemical mass spectrometry (DEMS), are employed in order to identify adsorbed reaction intermediates and products. Pt/CNF results in a lower CO poisoning of the NP surface compared to Pt/Vulcan, allowing higher amount of free Pt active sites for the oxidation of ethanol which leads to the formation of acetic acid during the reaction., This work has been supported by Fundación Cajacanarias (project BIOGRAF) and the Ministry of Economy and Competitiveness (MINECO) through the project ENE2014-52158-C2-2-R and -1-R (co-funded by FEDER). The authors acknowledge the SEGAI services of Universidad de La Laguna for technical assistance and R.R also thanks the MINECO for the pre-doctoral grant.

Pt-Sn catalysts supported on carbon, with different Pt-Sn atomic ratios (3:1, 1:1, 1:3), were prepared through the formic acid method (FAM) and supported on different carbon supports (nanofibers and carbon blacks) to study their behavior toward CO stripping and ethanol oxidation reaction (EOR). PtSn/C catalysts and supports were physicochemically characterized by XRD, EDX, XPS, TEM and TPD. Good particle dispersion onto the carbon support, similar particle sizes (around 4-5 nm) and the presence of tin oxides were observed in all cases. Sn insertion favored the development of the Pt3Sn1 phase and the presence of higher oxidation states of both metals in the catalyst. Ethanol and adsorbed CO oxidation was studied at these materials both in acid and alkaline media, by linear sweep voltammetry and chronoamperometry. Higher EOR current densities were obtained with the increase in the amount of Sn in the samples, been those materials supported on CNF the ones with the best CO tolerance and catalytic activity toward this reaction. As expected, a great improvement of the EOR activity was found in alkaline media compare with sulfuric acid media, providing good expectative for these materials as catalysts for alkaline direct ethanol fuel cells., This work has been supported by Fundación Cajacanarias (project BIOGRAF) and the Ministry of Economy and Competitiveness (MINECO) through the projects CTQ2011-28913- C02-02 and ENE2014-52158-C2-2-R. R.R. is also indebted with the MINECO for the pre-doctoral grant.

6 Figures, 4 Tables.-- Work presented at the 5th Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries (HYCELTEC 2015), 5-8 July 2015, Tenerife, Spain, The graphitisation of ordered mesoporous carbons (CMK-3) was carried out by thermal treatments under different conditions of temperature and heating rate. The electrochemical characterization in acidic medium of the graphitised CMK-3 showed that such a thermal treatment is effective to decrease the carbon oxidation rate (corrosion) while preserving a good porosity in terms of capacitance. Besides, the graphitisation degree and, in consequence the electrochemical corrosion resistance, can be modulated by an appropriate choice of thermal treatment conditions, where the heating rate and temperature appear as critical parameters. Under certain graphitisation conditions, the carbon corrosion of CMK-3 can be minimized showing lower rates compared to a commercial carbon black (Vulcan XC-72R). Palladium nanoparticles were supported on the most promising graphitised CMK-3 and Vulcan using a method based on impregnation and reduction with borohydride, resulting in suitable metal crystallite sizes. The electrocatalytic activity towards the oxidation of carbon monoxide and formic acid were assessed in aqueous sulphuric acid electrolyte for application at the anode of direct formic acid fuel cells (DFAFCs). The best activity results were obtained for the Pd catalyst supported on a graphitised CMK-3., The authors want to thank the Spanish Ministry of Economy and Competitiveness and FEDER for financial support under the project ENE2014-52158-C2-1-R. V. Celorrio also acknowledges the Royal Society and the UK National Academy by the support through the Newton International Fellows program.

5 figures, 3 tables.-- Supplementary material.-- © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/, In this work, Pd–Ni catalysts supported on carbon nanofibers were synthesized, with metal contents and Pd:Ni atomic ratios close to 25 wt.% and 1:2, respectively. Previously, the carbon nanofibers were chemically treated, in order to create surface oxygen and/or nitrogen groups. The synthesized catalysts displayed low crystallinity degree and high dispersion on carbon supports, especially in those with surface functional groups. Oxygen reduction reaction (ORR) was studied by rotating ring-disk electrode (RRDE) techniques. When the kinetic current is normalized by the mass of Pd present in the electrode, higher activities were obtained for the synthesized materials in comparison with the activity observed for a commercial Pd/C E-TEK catalyst. Some differences are reported for the different materials under study, mainly dependent on the presence of oxygen surface groups on the carbon support. In light of the results, we can propose the synthesized catalysts as possible candidates for cathodes in alkaline direct methanol fuel cells., The authors gratefully acknowledge financial support given by Spanish MINECO (ENE2014-52518-C2-1-R). UK Catalysis Hub is kindly thanked by VC and DJF for resources and support provided via our membership of the UK Catalysis Hub Consortium and funded by EPSRC (grants EP/K014706/1, EP/K014668/1, EP/K014854/1, EP/K014714/1 and EP/M013219/1).

10 figures, 4 tables, supplementary information.-- Work presented at the 5th Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries (HYCELTEC 2015), 5-8 July 2015, Tenerife, Spain, Graphitized ordered mesoporous carbon CMK-3-R8 supported PtCrCo electrocatalysts were synthetized by the borohydride reduction method (BM) and then submitted to a reductive thermal treatment (TT) at 300, 500 and 700 °C with the aim to improve their catalytic activity toward the oxygen reduction reaction (ORR) and the methanol tolerance. Atomic composition and total metal loading were determined by energy dispersive X-ray (EDX) analysis and the values obtained were close to the nominal ones, i.e. 20 wt.% PtCrCO/CMK-3. Electrochemical measurements were carried out using rotating disk electrode (RDE) technique in oxygen-saturated sulfuric acid solution in absence and presence of dissolved methanol. Besides other species and parameters, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis revealed the formation of an ordered PtCr alloy phase and the surface enrichment by CrO species with the rise of the annealing temperature. The last, in conjunction with the absence of Pt sites with (110) orientation, enhances the catalytic activity toward the ORR and the methanol tolerance. Kinetic parameters are reported and analyzed in terms of the physicochemical properties of the catalysts obtained by the X-ray techniques., This research was funded by the Spanish Ministry of Economy and Competitiveness under projects CTQ2011-28913-C02 and ENE2014-52158-C2 (co-funded by FEDER). L.M. Rivera acknowledges the Canary Government (ACIISI) for its PhD scholarship. V.C. kindly thanks for resources and support provided via membership of the UK Catalysis Hub Consortium and funded by EPSRC (grants EP/K014706/1, EP/K014668/1, EP/K014854/1EP/K014714/1 and EP/M013219/1).