High Temperature PEM Fuel Cell Stacks with Advent TPS Meas

High power/high energy applications are expected to greatly benefit from high temperature Polymer Electrolyte Membrane Fuel Cells (PEMFCs). In this work, a combinatorial approach is presented, in which separately developed and evaluated MEAs, design and engineering are employed to result in reliable and effective stacks operating above 180°C and having the characteristics well matched to applications including auxiliary power, micro combined heat and power, and telecommunication satellites

Synergistic effect of Yttrium and pyridine-functionalized carbon nanotube on platinum nanoparticles toward the oxygen reduction reaction in acid medium

International audienc

High Temperature PEM Fuel Cell Stacks with Advent TPS Meas

High power/high energy applications are expected to greatly benefit from high temperature Polymer Electrolyte Membrane Fuel Cells (PEMFCs). In this work, a combinatorial approach is presented, in which separately developed and evaluated MEAs, design and engineering are employed to result in reliable and effective stacks operating above 180°C and having the characteristics well matched to applications including auxiliary power, micro combined heat and power, and telecommunication satellites

A Highly Efficient and Stable Oxygen Reduction Reaction on Pt/CeOx/C Electrocatalyst Obtained via a Sacrificial Precursor Based on a Metal-Organic Framework

International audienceAdvanced Pt/CeOx/C nanocomposite, where C = porous carbon and multi-walled carbon nanotube (MWCNT), was synthesized using a precursor based on Ce-containing metal organic framework (MOF), via carbonyl chemical route, followed by heat-treatment at 900 °C under argon atmosphere. Based on the analyses of powder X-ray diffraction (pXRD) data, and via the Williamson-Hall method, the lattice parameter, stacking fault and micro-strain values on Pt/CeOx/C was found to decrease, whereas the crystallite size increased with respect to the as-prepared sample. Combined with the results of transmission electron microscopy (TEM), these changes were related to the in-situ formation of intimately contacted Pt/CeOx nanoparticles (NPs), well-dispersed onto MWCNT support. However, both the pXRD and TEM results showed that the Pt NPs were agglomerated upon heating and finally detached from the support in the MOF-free samples. Thus, MOF could protect Pt nanoparticles (NPs) from agglomeration at high temperature. The X-ray photoelectron spectroscopy (XPS) showed that the Pt surface was less oxidized in Pt/CeOx/C nanocomposite in comparison to as-prepared and MOF-free samples. Moreover, only the Ce3+ was detected in the nanocomposite. These facts together with Raman spectroscopy and surface electrochemistry experiments assessed the stabilization of the electronic state of Pt° and Ce3+ via the interaction between Pt and CeOx. In addition, enhanced catalytic activity towards the oxygen reduction reaction (ORR) was observed in acid medium. The specific and mass activity at 0.9 V/RHE on Pt/CeOx/C were ca. 1279 μA cm−2Pt and 870 mA mg−1Pt, respectively, ca. 10–11 fold higher than commercial Pt/C (Johnson Matthey, JM) in half-cell. Accelerating durability tests (ADT), after 16,000 potential cycles, demonstrated higher stability of Pt/CeOx/C in contrast to oxide-free and Pt/C (JM) catalyst. Compared with other homemade or commercial Pt/C (JM) cathodes, the innovative cathode catalyst showed enhanced cell performance in a H2/O2 micro-laminar flow fuel cell syste

<i>Operando</i> Near Ambient Pressure XPS (NAP-XPS) Study of the Pt Electrochemical Oxidation in H₂O and H₂O/O₂ Ambients

Oxides on the surface of Pt electrodes are largely responsible for the loss of their electrocatalytic activity in the oxygen reduction and oxygen evolution reactions. In this work we apply near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) to study <i>in operando</i> the electrooxidation of a nanoparticulated Pt electrode integrated in a membrane-electrode assembly of a high temperature proton-exchange membrane under water and water/oxygen ambient. Three types of surface oxides/hydroxides gradually develop on the Pt surface depending on the applied potential at +0.9, + 2.5, and +3.7 eV relative to the 4f peak of metal Pt and were attributed to the formation of adsorbed O/OH, PtO, and PtO₂, respectively. The presence of O₂ in the gas-phase results in the increase of the extent of surface oxidation, and in the growth of the contribution of the PtO₂ oxide. Depth profiling studies, in conjunction with quantitative simulations, allowed us to propose a tentative mechanism of the Pt oxidation at high anodic polarization, consisting of adsorption of O/OH followed by nucleation of PtO/PtO₂ oxides and their subsequent three-dimensional growth