Controlling platinum loading in PEMFC membrane electrodes by sputtering time: a systematic study from ultra-low to high loading for optimal performance

Abstract

Magnetron sputtering technology holds significant application value in preparing low-platinum catalysts for proton exchange membrane fuel cells (PEMFCs) due to its atomic-level deposition precision and controllable thin-film structure. In this work, the effects of sputtering time (10–360 s) on platinum (Pt) loading, film morphology, and catalytic performance in PEMFC membrane electrodes were systematically investigated using magnetron sputtering technology. The correlations between the sputtering time, platinum loading, film structure, and oxygen reduction reaction (ORR) activity are revealed through combined SEM, XRD, XPS and electrochemical analyses (CV/LSV). The results demonstrate that dispersed Pt nanoparticles formed at short sputtering time (10 s) exhibit high electrochemical surface area (ECSA, 94.3 m² g⁻¹) but insufficient loading, which compromises ORR performance (22.4 A g⁻¹). In contrast, prolonged sputtering (>180 s) produces continuous dense films with increased loading (0.251 mg cm⁻²) but significantly degraded ORR activity (2.5 A g⁻¹). Among the sputtering times tested, the 30 s-sputtered sample exhibits optimal ORR mass activity (108.9 A g⁻¹), attributable to its balanced Pt dispersion and metallic Pt⁰-dominated surface structure. This work not only elucidates the mechanism of sputtering time effects on Pt catalyst performance, but also provides valuable guidelines for optimizing low-Pt-loading catalyst designs in fuel cell applications.