Low-Surface-Energy Copper Promotes Atomic Diffusion and Ordering in PtFeCu Intermetallic Compounds for Oxygen Reduction Catalysis

Abstract

Carbon-supported platinum intermetallic compound nanoparticles are seen as the next-generation cathodic catalysts for hydrogen fuel cells due to their high activity and stability. However, their synthesis faces challenges from a large diffusion barrier for atom ordering, leading to limited oxygen reduction performance. Understanding the formation mechanisms during synthesis is crucial for material design and device-level validation, which remains a challenge. Herein, copper-induced atom ordering is reported for the reconstruction of commercial Pt/C into ordered PtFeCu intermetallic compounds. Low-surface-energy copper is the key to the boosted atom ordering. Due to its lower surface energy than those of platinum and iron, Cu atoms are prone to diffuse to the surface, thereby leaving more vacancies behind vacant sites and facilitating atom diffusion into intermetallic structures. Copper-induction alters the electronic structure of PtFeCu and therefore enhances its mass activity to 1.0 A mg⁻¹ in liquid half-cells. H₂─O₂ powered fuel cells demonstrate remarkable stability, retaining over 75% of initial performance, thereby exceeding the US Department of Energy target, with a minimal platinum loading of merely 0.1 mg cm⁻². The study offers insights into the rational design of intermetallic compound catalysts and validation of their application for hydrogen fuel cells.