High activity and durability of carbon-supported core-shell PtPx@Pt/C catalyst for oxygen reduction reaction

Abstract

Alloying Pt with transition metals can significantly improve the catalytic properties for the oxygen reduction reaction (ORR). However, the application of Pt-transition metal alloys in fuel cells is largely limited by poor long-term durability because transition metals can easily leach. In this study, we developed a nonmetallic doping approach and prepared a P-doped Pt catalyst with excellent durability for the ORR. Carbon-supported core-shell nanoparticles with a P-doped Pt core and Pt shell (denoted as PtPx@Pt/C) were synthesized via heat-treatment phosphorization of commercial Pt/C, followed by acid etching. Compositional analysis using electron energy loss spectroscopy and X-ray photoelectron spectroscopy clearly demonstrated that Pt was enriched in the near-surface region (approximately 1 nm) of the carbon-supported core-shell nanoparticles. Owning to P doping, the ORR specific activity and mass activity of the PtP1.4@Pt/C catalyst were as high as 0.62 mA cm−2 and 0.31 mA μgPt−1, respectively, at 0.90 V, and they were enhanced by 2.8 and 2.1 times, respectively, in comparison with the Pt/C catalyst. More importantly, PtP1.4@Pt/C exhibited superior stability with negligible mass activity loss (6% after 30000 potential cycles and 25% after 90000 potential cycles), while Pt/C lost 46% mass activity after 30000 potential cycles. The high ORR activity and durability were mainly attributed to the core-shell nanostructure, the electronic structure effect, and the resistance of Pt nanoparticles against aggregation, which originated from the enhanced ability of the PtP1.4@Pt to anchor to the carbon support. This study provides a new approach for constructing nonmetal-doped Pt-based catalysts with excellent activity and durability for the ORR.