Design of Pd‐Based Bimetallic Catalysts for ORR: A DFT Calculation Study

Abstract

Developing Pd‐lean catalysts for oxygen reduction reaction (ORR) is the key for large‐scale application of proton exchange membrane fuel cells (PEMFCs). In the present paper, we have proposed a multiple‐descriptor strategy for designing efficient and durable ORR Pd‐based alloy catalysts. We demonstrated that an ideal Pd‐based bimetallic alloy catalyst for ORR should possess simultaneously negative alloy formation energy, negative surface segregation energy of Pd, and a lower oxygen binding ability than pure Pt. By performing detailed DFT calculations on the thermodynamics, surface chemistry and electronic properties of Pd‐M alloys, Pd‐V, Pd‐Fe, Pd‐Zn, Pd‐Nb, and Pd‐Ta, are identified theoretically to have stable Pd segregated surface and improved ORR activity. Factors affecting these properties are analyzed. The alloy formation energy of Pd with transition metals M can be mainly determined by their electron interaction. This may be the origin of the negative alloy formation energy for Pd‐M alloys. The surface segregation energy of Pd is primarily determined by the surface energy and the atomic radius of M. The metals M which have smaller atomic radius and higher surface energy would tend to favor the surface segregation of Pd in corresponding Pd‐M alloys.