Shell-thickness-dependent Pd@PtNi core–shell nanosheets for efficient oxygen reduction reaction

Abstract

Platinum-based ultrathin core–shell nanosheets catalyst with moderate shell thickness have great potential to solve the problems of highly active catalyst for oxygen reduction reaction (ORR) within proton exchange membrane fuel cells (PEMFCs). Herein, three kinds of Pd/PtNi core–shell nanosheets (Pd@PtNi NSs) catalyst under different shell thickness were developed by a synthetic strategy of depositing platinum-nickel (Pt-Ni) precursors on palladium nanosheets (Pd NSs). The ORR electrocatalytic performance of Pd@PtNi NSs–1, Pd@PtNi NSs–2 and Pd@PtNi NSs–3 catalysts were investigated using commercial Pt/C catalyst for comparison reasons. It is found that the Pd@PtNi NSs–2 catalyst with moderate shell thickness showed excellent ORR performance. Under 0.9 V (vs. reversible hydrogen electrode (RHE)), Pd@PtNi NSs–2 (1.038 A mg-1Pt+Pd) achieved mass activity (MA) 6.25 times of commercial Pt/C catalyst. Superior performance of Pd@PtNi NSs–2 was mainly attributed to: i) the ultrathin layer structure, ii) the core–shell structure, iii) the maximum coverage of Pd core, and iv) the maximum surface alloying by surface atomic diffusion.