The role of water in the degradation of Pt3Co/C nanoparticles: An Identical Location Transmission Electron Microscopy study in polymer electrolyte environment

Abstract

The degradation mechanisms of nanostructured Pt3Co/C electrocatalysts aged in dry electrochemical environment using a Nafion® 115 membrane as polymer electrolyte were characterized by Identical Location Transmission Electron Microscopy, in conditions that perfectly mimic real PEMFC operation. The structural, morphological and compositional changes of the Pt3Co/C nanoparticles occurring during an accelerated stress test were bridged to changes of their intrinsic kinetics toward the oxygen reduction reaction in Nafion® 115 electrolyte, thanks to an ultramicroelectrode with cavity loaded with the catalyst. The unique setup used herein further enabled to compare the Nafion® environment with conventional liquid electrolyte in which accelerated stress tests are usually performed. Although the Pt3Co/C nanoparticles are modified upon aging at Nafion® interface, the degradation processes are milder and different than those observed in liquid electrolyte, mostly following the absence of liquid water and the lack of ion mobility within the Nafion® membrane.