Simultaneous immobilization of physically vaporized platinum alloy atoms for oxygen reduction electrocatalysis

Abstract

In this work, we employ physical vapor deposition (PVD) to synthesize PtCu nanoparticles on carbon supports (PtCu/C) with varied Cu contents, followed by acid-leaching to induce porosity and optimize catalyst structure. Characterization by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy reveals that despite initial differences in Pt:Cu ratios, all post-leaching catalysts converge to an approximately 1:1 composition. Notably, catalysts initially containing higher Cu levels present a greater fraction of metallic Pt (Pt0) after leaching, strongly enhancing the oxygen reduction reaction (ORR) activity. The best-performing PtCu/C achieves mass and specific activities approximately four and nine times higher, respectively, than commercial Pt/C. These findings highlight the importance of controlling initial Cu content and acid leaching conditions to optimize surface chemistry, porosity, and Pt oxidation states, ultimately maximizing ORR kinetics. By reducing noble metal usage while boosting performance, PVD-synthesized PtCu catalysts offer a promising route toward cost-effective, high-performance cathodes for next-generation PEMFCs. This work underscores the potential of PVD as a scalable, environmentally benign alternative to wet-chemical methods for producing advanced alloy catalysts and provides critical insights into the relationship between acid-leaching, Pt degrees fraction, and enhanced ORR activity. The approach can be extended to other alloy systems for fuel cell applications.