Oxygen reduction activity and stability trends of bimetallic Pt_0.5M_0.5 nanoparticle in acid

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 Pt_0.5M_0.5 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 V_dissolve transition metals despite their strong alloy-formation energy, where V_dissolve 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 V_dissolve 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.