Dissolution of Ru from PtRu Electrocatalysts and its Consequences in DMFCs

Abstract

Rapid and irreversible performance loss could be observed for a single cell DMFC using a PtRu anode electrocatalyst when it was operated under non-optimized conditions. Post-mortem cyclic voltammetry and EDAX data reveal that the anode electrode became depleted in Ru, and the dissolved Ru crossed through the PE membrane and then deposited onto the Pt cathode electrode. Comparative elemental compositional as well as CO and MeOH electrooxidation performance analysis was performed with commercial PtRu black samples having the same 50:50 atomic ratio but different degree of alloying. The data suggests that the latter physical property is crucial in maintaining the anodic activity for prolonged time. On the other hand, dissolved Ru species present in the micromolar concentration range in liquid electrolyte are shown to have severe detrimental impacts on ORR kinetics on a Pt thin-film RDE (having a surface roughness factor of ca. 6).