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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.-- Supplementary information available., Bifunctional oxygen electrocatalysts are essential in the development of low-temperature unitized regenerative fuel cells (URFCs), as a promising alternative for storing energy via hydrogen. TiO2, as a semiconductor material, is commonly not established as an active electrocatalyst for oxygen reduction and oxygen evolution due to its poor electrical conductivity and low reactivity. Here, we demonstrated that composites composed of TiO2 and N-doped graphene can be active in oxygen reduction and evolution reactions in an alkaline environment. Combination factors such anatase/rutile interaction, N-doping graphene, and the presence of Ti3+/Ti–N species raise the active sites and improve the electrochemical activity. Our results may afford an opportunity to develop a non-noble and promising electrocatalyst in energy storage technology., This research was funded by the Ministry of Science, Innovation and Universities and FEDER, grant number ENE2017-83976-C2-1-R

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.

5 figures., Carbonaceous materials have always played an important role in history of electrochemical processes, from the fabrication of solid electrodes to the development of porous matrixes in the conversion and storage of energy and chemicals. This book chapter provides a general overview of emerging carbon nanostructures potentially used in electrochemistry. One-dimensional carbon nanofilaments, such as carbon nanotubes and carbon nanofibers, two-dimensional graphene, and three-dimensional materials, such as carbon gels and ordered mesoporous carbons, are reviewed. The chapter focuses on the physicochemical properties and synthesis methodologies of these carbon nanostructures together with their application to cutting-edge technologies for electrochemical energy conversion and storage, such as fuel cells, electrolyzers, supercapacitors, or batteries. The major challenges and directions for future research are also discussed to guide the design of efficient carbon-based electrodes and catalysts for electrochemical devices., Authors acknowledge financial support given by Spanish Ministry of Science, Innovation and University (MICINN) through project ENE2017-83976-C2-1-R (cofounded by FEDER). C. Alegre and D. Sebastián acknowledge also MICINN for their Juan de la Cierva (IJCI-2017-32354) and Ramón y Cajal (RyC-2016-20944) research contracts, respectively.

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.

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, 1 table., In order to decrease the cost of direct methanol fuel cells (DMFCs), allowing the market penetration of these devices, it is necessary to reduce the costs of the components, in particular the cathode catalysts based on platinum. Another issue of these fuel cells is related to methanol crossover through the polymeric membrane, which creates a mixed potential at the cathode and decreases the overall efficiency. For this reason the development of methanol-tolerant cathode catalysts that are cheaper than Pt are of great importance in this field. In this chapter a short review analysis on Pt-free catalysts, mainly based on Pd and platinum group metal-free compounds with the general formula M–N–C (M being a transition metal such as Fe or Co) for the cathode, with good methanol-tolerance characteristics, has been carried out. Preparation procedures for the catalysts and physicochemical characteristics are reported and discussed in correlation with the DMFC performance., Introduction.-- Palladium as oxygen reduction reaction catalyst in direct methanol fuel cells.-- Non platinum-group-metal electrocatalysts based on M–N–C.-- Conclusion

8 figures, 1 table.-- Supporting information available, Alkaline unitized regenerative fuel cells (URFCs) could well be one of the energy sources in the next future. This technology has the potential to provide power to portable devices, transportation and stationary sectors. The bifunctional oxygen electrode plays a central role in catalytic activity and stability due to its slow kinetics under extremely oxidizing or reducing environments. With the aim to solve the principal catalytic problems at the bifunctional electrocatalysts, carbonaceous materials including carbon nanofibers (CNFs), graphitized mesoporous carbon (gCMK-3) and hydrazine-reduced graphene oxide (H-rGO) were synthesized, characterized and tested toward the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) and compared to commercial carbon black (Vulcan), graphite, and glassy carbon (GC). Physicochemical characterization was conducted by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), elemental analysis and Raman spectroscopy, meanwhile rotating ring-disk electrode (RRDE) was employed to determine the electrochemical activity and stability. Main results indicate that CNFs can act as a feasible catalyst for URFC applications., The Spanish Ministry of Economy and Competitiveness (MINECO) has supported this work under project ENE2017-83976-C2-2-R (co-funded by FEDER). L.M.R. thanks the ACIISI for his PhD fellowships and G.G. acknowledges the Viera y Clavijo program (ACIISI and ULL) for financial support.

5 figures, 2 tables., In the present work, Pd and PdFe nanoparticles supported on CNT with and without functionalization (CNT and CNTox) were used for Formic Acid Oxidation Reaction (FAOR) in acid media. Electrocatalysts were synthesized by the borohydride reduction method with 20 wt.% metal loading. The CNTs were synthesized by the methane catalytic decomposition, and subjected to an oxidation treatment with nitric acid, named as CNTox. Themorphology, composition and structural properties were studied by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX) and X-Ray Diffraction (XRD). The FAOR was evaluated in acid media in a conventional three-electrode cell by means of cyclic voltammetry and chronoamperometry. From the steady state current density, it was found that Pd and PdFe supported at CNTox allowed improving the catalytic activity in comparison with the nonoxidized support., The authors thank the organizers of the meeting. LJM is grateful to CONACYT for the scholarship granted for the completion of the PhD studies and the ECS for the support given to attend the meeting. MGMOY, MARR, MEPP and EMAE thank the SNI for the distinction of their membership and the stipend received.

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.

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).

Carbon nanocoils (CNCs) synthesized via the catalytic graphitization of resorcinol formaldehyde gel were investigated as an electrocatalyst support in PEMFC anodes.Their textural and physical properties make them a highly efficient catalyst support for anodic hydrogen oxidation in low temperature PEMFC. When the oxidation of adsorbed CO was studied, a shift of 140 mV is observed compared with the commercial catalysts (Pt/C E-TEK) which is expected to be a key parameter in the fuel cell (PEM) performance. Furthermore, the behaviour of the electrocatalysts prepared was compared with that of a Pt/C E-TEK in a 5 cm2 PEM fuel cell. At room temperature, results showed a 4% increase in current density at 0.6 V in comparison with the Pt/C E-TEK electrocatalysts., The authors gratefully acknowledge financial support given by the Ministry of Economy and Competitiveness through the Projects CTQ2011-28913-C02-01 and -02. V. Celorrio also acknowledges CSIC and FSE for their JAE Grant; and the UK National Academy by the support though the Newton International Fellow program.

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).

Pd nanoparticles have been supported onto different novel carbon materials to be used in the electroreduction of CO2 to high-added value products. Carbon nanocoils (CNCs), carbon nanofibers (CNFs) and ordered mesoporous carbon materials (OMCs) have been studied as support of the catalysts. In addition, Pd catalyst supported onto Vulcan XC-72R has been synthesized in order to establish a comparison with the commercial support. In this way, the influence of the carbon material on the physicochemical and electrochemical properties of the catalysts for the CO2 electroreduction process can be analyzed. Supports presented different morphologies and structures. CNFs and CNCs exhibited a crystalline structure with well-aligned graphitic layers and OMCs a hexagonal ordered structure composed of not crystalline carbon. Finally, Vulcan presented an intermediate structure between amorphous and graphitic. These differences do not affect significantly the average Pd crystallite size,although a different metal dispersion was found depending on the carbon material. On the other hand, cyclic voltammetry studies showed that CO2 was effectively reduced to other species at the surface of Pd/C catalysts. Additionally, it was proved that these species were adsorbed onto Pd at -1.0 V vs Ag/AgCl. Finally, a different catalytic activity towards the CO2 reduction reaction was observed for the different electrocatalysts, indicating an influence of the carbon support., 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.

11 pag., 15 figures, 4 tables., Cordierite monolith-supported and powder Fe-K/Al2O3 catalysts were prepared and thoroughly characterized by bulk (XRD, Raman spectroscopy, XRF, ICP-OES, TPR) and surface (XPS, IR, N2-BET, NOx-TPD, K-TPD) sensitive methods. The catalytic activity was tested in TPO (temperature programmed oxidation) of model soot. The influence of the calcination temperature, i.e. 450 and 650°C, on the catalysts physicochemical properties and reactivity, type of surface states of K promoter and their role in the soot oxidation mechanism in the presence of NOx was evaluated. In the catalysts calcined at 450°C potassium was found to be mostly as free KNO3 whereas calcination at 650°C successfully transformed KNO3 into K2O, which during the soot oxidation yielded K2CO3 species. Such carbonates underwent decomposition in the presence of the oxygen surface groups of the support, leading to the formation of active basic O2- groups. NOx species were found to adsorb strongly on these O2- sites. The increased stability of thus formed NOx-species resulted in lower soot oxidation activity. In the same time, the catalysts calcined at 650°C evidenced higher ability towards the reduction of NOx, occurring simultaneously with the soot oxidation process. Additionally, the higher calcination temperature led to significantly higher stability of K promoter species as evidenced by potassium thermodesorption experiments. An overall schematic model of the catalyst morphology and relative distribution of the active components (K, Fe) over the Al2O3 support is proposed. © 2014 Elsevier B.V., Polish part would like to acknowledge the Polish National Science Center for funding awarded by the decision number DEC-2011/01/B/ST4/00574. On the Polish part the research was partially carried out with the equipment purchased thanks to the financial support of the European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no. POIG.02.01.00-12- 023/08). S. Ascaso thanks CSIC for her JAE doctoral grant. S. Ascaso thanks CSIC for her JAE doctoral grant. M.E. Gálvez is indebted to the Spanish Ministry of Economy and Competitiveness (Secretaría de Estado de I+D+I, previously MICINN) for her Ramón y Cajal contract.

A novel differential electrochemical mass spectrometry (DEMS) cell has been developed to study gas diffusion electrodes (GDEs) used in fuel cells under operating conditions. In this way, catalytic and diffusion properties of the electrodes can be evaluated at the same time. Moreover, DEMS, allows the detection of volatile and gaseous products and intermediates generated in the electrochemical reactions with good sensitivity. In this way, CO2 conversion efficiencies are evaluated during alcohol oxidation reaction. In the present communication, the electrochemical behaviour towards hydrogen evolution and CO and alcohol electrooxidation at different platinum-based catalysts has been studied using the new DEMS cell configuration. The relative yields of CO2 and by-side products during methanol oxidation have been evaluated to determine the CO2 conversion efficiency. In addition, the diffusional properties of diverse GDEs have been considered., This work has been supported by the Gobierno de Aragón and Obra Social LaCaixa under project GA-LC-008/2009 and by the Gobierno de Canarias under project PI2007/023. S. Pérez-Rodríguez also acknowledges Gobierno de Aragón for their DGA grant. G. García acknowledges to the JAE program (CSIC) for financial support.