Abstract
Summary PtNi-based nanomaterials represent an emerging class of highly active catalysts for the oxygen reduction reaction (ORR) in fuel cells. However, they suffer from poor stability in operating conditions, which is the key challenge in maintaining their activity advantage over Pt in practice. We report significantly enhanced stability and activity of octahedral PtNi nanoparticles by tuning their surface elemental distribution through the introduction of a third element (Cu) during synthesis. To uncover the mechanism behind this observation, we performed kinetic Monte Carlo (KMC) simulations initialized using growth-tracking experiments and demonstrated that PtNiCu has improved Ni and Cu retention compared with PtNi, in agreement with experiments. The tracked movement of individual atoms in KMC reveals that the enhanced stability can be attributed to increased surface Pt composition in as-synthesized catalysts, which reduces the generation of surface vacancies and suppresses the surface migration and subsequent dissolution of subsurface Cu and Ni atoms.
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