Primacy of lattice distortion over strain in platinum fuel cell nanoalloy catalysts

Abstract

Alloying platinum with early or late transition metals enhances its intrinsic activity toward the oxygen reduction reaction for proton exchange membrane fuel cells (PEMFCs), according to strain and ligand effects. However, these alloying effects disappear following the dissolution of non-noble metal component(s) during operation, leading to PEMFC performance degradation. In this study, we investigate PtNi nanoalloys across critical stages of their development (viz. as-synthesized, post-electrochemical activation, after membrane electrode assembly fabrication, and following accelerated stress testing) using a comprehensive set of ex situ, in situ, operando, and post mortem characterization techniques, which allows assessing the contributions from alloying and structural effects. Our results reveal that local lattice distortion, rather than global strain and ligand effects, is an important factor effectively contributing to both catalytic activity and durability in PEMFC. These finding challenges conventional electrocatalyst design strategies and validates the defect-engineering strategy for advanced fuel cell applications, independently from transition metal(s) retention.