Local Structural Disorder Enhances the Oxygen Reduction Reaction Activity of Carbon-Supported Low Pt Loading CoPt Nanocatalysts

A facile strategy for preparing carbon-supported Co₉₅Pt₅ nanocatalysts (NCs) with low platinum (Pt) loading and high Pt utilization via thermal reduction treatment in a carbon monoxide (CO) atmosphere is reported. By cross-referencing results of microscopy, X-ray spectroscopy, and electrochemical analysis, we demonstrate that the Pt atoms tend to form disordered atomic clusters capping on the Co nanoparticle surface. The values of unfilled d-states (h_Ts) extracted from X-ray absorption near-edge spectroscopy were used to calculate the d-band vacancies of Pt. Accordingly, CoPt-CO570 (reduced in CO at 570 K) possesses the lowest h_Ts value (0.302) (i.e., the lowest Pt d-band vacancies) among experimental samples, indicating a strong electron relocation from Co atoms. Such electron relocations are attributed to the high extent of the heteroatomic intermix between Pt and Co atoms and thus improves the oxygen reduction reaction activity of CoPt-CO570. For providing further evidence, structural and electrochemical properties for H₂ and NaBH₄ reduction-prepared CoPt NCs are compared as the control. This work may represent an appealing step toward the structural design of low Pt and high activity catalysts for fuel cell cathode catalysts.