Dataset of "Operando and ex situ comparison of Pt and Pt3Co catalyst degradation under ORR in PEMFC"

In this work we investigate the early-stage evolution of bare Pt and Pt₃Co catalysts for the oxygen reduction reaction in low-temperature PEM fuel cells. While Pt₃Co alloys offer higher performance than Pt, their stability is compromised by Co dealloying, forming a Pt-rich skin. Using in operando and ex situ electrochemistry, Small-Angle X-ray Scattering, X-ray Absorption Spectroscopy, X-ray Photoelectron Spectroscopy, and SEM-EDX, we monitored changes during break-in and catalyst-specific accelerated stress tests (ASTs). Bare Pt showed minimal morphological and oxidation changes after break-in, but particle size increased from 2.28 to 6.21 nm—mostly within the first 3000 AST cycles. In Pt₃Co, Co leaching was evident after break-in, accompanied by particle size shrinkage and reduced metallic Co content. During ASTs, Co oxidation increased within the first 1250 cycles, while Pt-rich skin formation mitigated electrochemically active surface area loss, with particle size growing from 2.59 to 6.14 nm between 3000 and 6000 cycles.