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[EN] To make SOFC high efficiency energy generation devices, thin ceramic films are proposed as their main components. The rate of the oxygen reduction reaction is relevant for the overall performance of the SOFC, hence a lot of attention is given to the cathodes and their interfaces. The airbrushed solution combustion (ASC) method was used to fabricate an LSM thin film on a dense YSZ substrate. A single phase LSM perovskite was obtained with very thin and interconnected porosity, and a small average grain size (55 nm). The nanostructured LSM thin film electrode showed a low total activation energy (1.27 eV) at high temperatures, but a high area specific resistance at 850°C (55 Ω.cm²). The activation energy for the dissociative adsorption and diffusion of oxygen was significantly low (1.27eV), while the charge transfer and oxygen ion migration activation energy at the LSM/YSZ interface (1.28 eV) was closer to those usually reported., The authors would like to thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNpQ) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) in Brazil and Instituto de Cerámica y Vidrio (ICV) and Consejo Superior de Investigaciones Científicas (CSIC) in Spain.

An appropriate evaluation of oxide-based compound powders as non-platinum cathodes for polymer electrolyte fuel cells is required to investigate the active sites of oxide-based cathodes for the oxygen reduction reaction. A mixture of carbon black powder as an electro-conductive material with oxide catalysts that had low electrical conductivity was attempted to evaluate the oxygen reduction reaction (ORR) activity. An appropriate mixture of carbon black and the oxide catalysts let to the electrochemical activation of the oxide surface by the formation of electron conduction networks. Using the carbon black mixture, the niobium-added titanium oxides heat-treated at 700 °C for 10 min under Ar containing 4% hydrogen without carbon materials were focused on to reveal the dependence of ORR activity on the added amount of niobium. The ORR activity of the niobium-added titanium oxides increased the Nb mole percentage from 0 to 20. This was due to the increase in the ratio of the Ti3+/(Ti4++Ti3+), and suggests that the active sites were Ti3+ and/or oxygen vacancies in the anatase phase. On the other hand, although the ratio of the Ti3+/(Ti4++Ti3+) of the oxide with an Nb mole percentage of 30 was almost twice as that with an Nb mole percentage of 20, the ORR activities were almost the same. This might be responsible for the deposition of the amorphous phase composed of Nb2O5, which consisted of a thin layer on the surface of the oxide particles and had low ORR activity.

Solution combustion synthesis was used to prepare cobalt oxide nanoparticles at different fuel ratio (φ = 0.5, 1, and 1.75). The synthesized particles were characterized using XRD, SEM, TEM, FTIR and XPS to study the morphological and structural features. The fuel rich condition provides a reducing atmosphere limiting further oxidation of synthesized nanoparticles but produces more carbon residue on the catalyst surface compared to fuel lean conditions. Increasing the fuel ratio (φ value) from 0.5 to 1.75 increases the crystallite size and lowers the surface area. The electrocatalytic performance studies conducted by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) indicate significant changes in catalytic activities due to variation in synthesis conditions. The LSV results obtained between potential of −1.2 V and 0.75 V shows all the three cobalt oxide catalysts to have bifunctional properties of being active for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), with Co synthesized at lower fuel ratio (φ = 0.5) displaying the highest current density. The onset potential for Co (φ = 0.5) is more positive than Co (φ = 1) and Co (φ = 1.75). The kinetic current density for Co (φ = 0.5) is 6.45 mA cm−2 and decreases with increase in fuel ratio. The OER current starts at ∼0.45 V for all the catalysts showing maximum density for Co (φ = 0.5) and gradually decreasing for catalysts synthesized at higher fuel ratio. Qatar Foundation;Qatar National Research Fund;Qatar University Scopus

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.

We report novel method for synthesis of carbon aerogel as platinum support for PEM fuel cells applications. The sol gel polymerization has been carried out using resorcinol and furfuraldehyde in non-aqueous medium followed by gelation at high pressure. This resulted in highly conducting and mesoporous carbon aerogel under ambient drying conditions. Platinum nano-particles are impregnated in the mesoporous carbon aerogel using microwave assisted polyol process. The support material and the catalyst are characterized by different analytical techniques like surface area analyzer, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Cyclic voltammetry and linear sweep voltammetry are used to evaluate the electro catalytic activity of the Pt/carbon aerogel catalyst using rotating disk electrode technique. Well dispersed Pt nano-particles of size similar to 3 nm on carbon aerogel showed good catalytic activity with onset potential of 964 mV and half wave potential of 814 mV towards oxygen reduction reaction kinetics. A membrane electrode assembly fabricated with the prepared Pt/carbon aerogel catalyst as a cathode and anode is tested in PEMFCs (H-2-O-2) single cell, the power density of 536 mW cm(-2) at 0.6 V is obtained at 60 degrees C under atmospheric pressure. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Iron phthalocyanine (FePc) was used as iron/nitrogen/carbon source and templated with an ordered mesoporous silica (SBA-15), followed by heat treatment and leaching of SiO2 with hydrofluoric acid (sacrificial method). The Fe–N–C catalyst was tested for the oxygen reduction reaction using a rotating disk electrode (three electrode configuration) in the presence of methanol at different concentrations. Furthermore, the catalyst was investigated in a single cell configuration of a direct methanol fuel cell (DMFC) under different methanol concentrations and temperatures. The optimal operating condition was found to be 1 M at 110 °C, reaching 11.2 mW cm−2 using a commercial Pt-Ru black at the anode and the Fe–N–C at the cathode side. Interestingly, the cathodic catalyst was not dramatically affected by the presence of crossovered methanol, showing only a 12% drop in maximum power density with the highest methanol concentration of 10 M at the anode. A 3D multiphysics model was implemented to further explain the experimental DMFC performance data using a commercial platform (Comsol® Multiphysics v4.4a). The model agreed with the experimental data, showing a direct relationship between water saturation, and oxygen consumption, consequently oxygen starvation at the cathodic catalytic layer. The model considered two phases on the cathode side computed by extended Darcy law within the catalytic layer and the gas diffusion layer domains.

Various Pt/TiOx-C catalysts are synthesized by changing the temperature of synthesis of TiOx from 500 to 1000 °C. The carbon support is a commercial multi-wall carbon nanotubes. The synthesis temperature of the TiOx affects the structure and morphology of the support generating different types of suboxides, ranging from TiO2 anatase, TiO2 rutile, Ti3O, and Ti3O5. The catalysts are characterized by means of BET, EDX, XRD, and ICP-MS analyses. The obtained catalysts display a Pt loading of 13.6–19.2 wt.%, with a Pt/Ti atomic ratio of 0.177–0.194. The catalysts are electrochemically characterized by CV, CO stripping, and LSV. The presence of Ti3O5 suboxide positively improves the performance of the catalyst with respect to the oxygen reduction reaction, and enhances the catalyst stability under potential cycling, with an increase of the electrochemical active surface area (ECSA) compared to the commercial Pt/Vulcan catalyst. After stability test for 4000 cycles in range of 0.06–1.26 V vs RHE the ECSA that resulted was equal to 22.73 m2 gPt−1. Moreover, the catalyst is highly methanol tolerant.

We report a significant increase in the performance of a hybrid carbon structure of one dimensional (1D) multi-walled carbon nanotubes (MWNTs) and 2D graphene sheets as the catalyst support material for proton exchange membrane fuel cells. A few upper layers of multiwalled carbon nanotubes were cut open in the longitudinal direction to achieve a hybrid structure of opened up MWNTs as graphene "wings" attached to the unaffected inner tubes by modifying the chemical oxidation method followed by hydrogen induced reduction technique. These partially exfoliated nanotubes (PENTs) were used as the support material for Pt deposition using chemical reduction with ethylene glycol. These PENTs supported Pt catalysts were used for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). An enhanced performance of 1000 mW/cm2 compared to a cell with a commercial Pt/C (418 mW/cm2) was achieved which was attributed to the specific structure of the support material giving an improved effectual surface area as well as higher conductivity. � 2015 Hydrogen Energy Publications, LLC.

A novel carbon nanostructure grown by catalytic chemical vapour deposition technique has been applied as an electrocatalyst support for oxygen reduction reaction in proton exchange membrane fuel cell. The growth of carbon nanostructure (CNS) is carried over a low cost bi-metal oxide catalyst (Fe-Sn-O) synthesized by sol-gel technique. Platinum nanoparticle decoration on Fe-Sn-O incorporated CNS (CNS-FSO) is performed by ethylene glycol reduction method. The structural as well as morphological analysis confirms the formation of CNS-FSO and platinum decoration on CNS-FSO. The electrochemically active surface area (ECSA) of platinum decorated CNS-FSO (Pt/CNS-FSO) is 68 m2 g -1, as revealed from cyclic voltammetry. Polarization studies are carried out at different temperatures (40 �C, 50 �C and 60 �C) to exploit the oxygen reduction reaction activity of Pt/CNS-FSO. A maximum power density of 449 mW cm-2 (without back pressure) at 60 �C shows the potential of this novel CNS-FSO as an electrocatalyst support in proton exchange membrane fuel cell. Copyright � 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

The role of functionalized multiwalled carbon nanotubes (MWNTs) decorated with platinum nanoparticles (Pt/f-MWNTs) and platinum-cobalt alloy nanoparticles (Pt 3Co/f-MWNTs) has been investigated for oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell. The electrocatalysts are synthesized by a conventional sodium borohydride reduction method and modified polyol reduction method. The modified polyol reduction method yields better uniform dispersion, higher loading and optimum particle size of Pt and Pt 3Co alloy nanoparticles over the MWNTs compared to the conventional sodium borohydride reduction method. The electrochemical surface area of the electrocatalysts is calculated using cyclic voltammetry. Pt 3Co/f- MWNTs synthesized via modified polyol reduction method yield the highest performance with a maximum power density of 798 mW cm -2 at 60 �C without any back pressure. The enhanced catalytic activity of Pt 3Co/f-MWNTs toward ORR is attributed to uniform dispersion and optimum particle size of Pt 3Co alloy nanoparticles over the surface of f-MWNTs. � 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Oxygen Reduction Reaction (ORR) kinetics is known to be one of the major bottle necks in PEM Fuel Cell performance. Several attempts are being made to enhance the ORR. Inspite of several attempts Pt in the vicinity of high surface area oxide catalysts seems to be the best choice although some alloy catalyst have shown good performance in half cell studies and single cell studies. We are investigating methods to improve the performance of PEM fuel cell especially in low air flow conditions which is the condition that will arise in surge power requirements. We have found that oxygen reduction reaction (ORR) performance of Pt/C can be increased in the presence of cerium-zirconium oxides especially Ce0.8Zr0.2O2 (CZO) in the cathode catalyst layer. Ce0.8Zr0.2O2 was prepared by co-precipitation method and the formation is confirmed by the XRD results. An XPS study of Ce 3d emission spectra dominated by atomic multiplet effects in core level spectroscopy of Ce0.8Zr0.2O2-Pt/C are studied from which the possible oxidation states of Ce on Ce 0.8Zr0.2O2-Pt/C surface are examined. The ORR improvement in the CZO added electrodes have been studied using chronoammperometry and fuel cell testing. � 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.