Atomic Rearrangement in Core–Shell Catalysts Induced by Electrochemical Activation for Favorable Oxygen Reduction in Acid Electrolytes

In Pt-based alloy structures, selective leaching out of the non-Pt metal component (known as “dealloying)” improves catalytic activity during operation due to an increase in the electrochemically active surface area. This indicates that in Pt-based alloy structures, an electrochemical stimulus induces structural change, and the non-Pt component plays an important role in determining the catalytic performance. In this study, we prepared highly active and durable Pd@Cu@Pt core–shell catalysts for an acidic oxygen reduction reaction by a facile method and elucidated the correlation between performance improvement and repetitive potential cycling beyond a simple dealloying effect. Electrochemical activation induces the formation of a localized PtCu alloy, which is strongly correlated with excellent catalytic activity and durability (mass activity after durability test: 2.6 A mg–1Pt), on the surface and subsurface via atomic rearrangement. The origin of such catalytic activity and durability is determined by synchrotron X-ray spectroscopy, electrochemical analysis, and density functional theory calculations

Role of Electronic Perturbation in Stability and Activity of Pt-Based Alloy Nanocatalysts for Oxygen Reduction

The design of electrocatalysts for polymer electrolyte membrane fuel cells must satsify two equally important fundamental principles: optimization of electrocatalytic activity and long-term stability in acid media (pH <1) at high potential (0.8 V). We report here a solution-based approach to the preparation of Pt-based alloy with early transition metals and realistic parameters for the stability and activity of Pt₃M (M = Y, Zr, Ti, Ni, and Co) nanocatalysts for oxygen reduction reaction (ORR). The enhanced stability and activity of Pt-based alloy nanocatalysts in ORR and the relationship between electronic structure modification and stability were studied by experiment and DFT calculations. Stability correlates with the d-band fillings and the heat of alloy formation of Pt₃M alloys, which in turn depends on the degree of the electronic perturbation due to alloying. This concept provides realistic parameters for rational catalyst design in Pt-based alloy systems