Oxygen Reduction Activity and Stability Trends of Bimetallic Pt0.5M0.5 Nanoparticle in Acid

Abstract

Pt-transition-metal (PtM) alloy catalysts are widely used to catalyze oxygen reduction reaction (ORR) and CO oxidation. Here we report a systematic investigation of compositional, particle size, and catalytic activity changes of seven Pt0.5M0.5 having similar initial sizes and transition-metal content. We found that the extent of transition-metal dissolution from PtM nanoparticles increases when Pt is alloyed with more negative Vdissolve transition metals despite their strong alloy-formation energy, where Vdissolve or dissolution potential is the thermodynamic potential for transition-metal dissolution (M ⇔ Mn+ + n e–) at pH 0. Decreased transition-metal dissolution from PtM nanoparticles is accompanied by decreased positive shifts in the onset voltage of CO oxidation from surface-chemistry-sensitive CO stripping after voltage cycling. Moreover, increasing the extent of transition-metal dissolution and decreasing Vdissolve was correlated with the ORR activity of PtM nanoparticles. Our work suggests that the dissolution potential of the transition-metal solute in PtM alloying catalysts might be used to design catalysts with enhanced ORR activity and stability.