Platinum redispersion on metal oxides in low temperature fuel cells

Abstract

We have analyzed the aptitude of several metal oxide supports (TiO₂, SnO₂, NbO₂, ZrO₂, SiO₂, Ta₂O₅ and Nb₂O₅) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied in detail; however, due to different operating conditions it is not straightforward to link the chemical and the electrochemical environment. The largest differences reflect in (1) the oxidation state of the surface (the oxygen species coverage), (2) temperature and (3) the possibility of platinum dissolution at high potentials and the interference of redispersion with normal working potential of the PEMFC cathode. We have calculated the PtO_x (x = 0, 1, 2) adsorption energies on different metal oxides' surface terminations as well as inside the metal oxides' bulk, and we have concluded that NbO₂ might be a good support for platinum redispersion at PEMFC cathodes.