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

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 ([email protected] 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 [email protected] NSs–1, [email protected] NSs–2 and [email protected] NSs–3 catalysts were investigated using commercial Pt/C catalyst for comparison reasons. It is found that the [email protected] NSs–2 catalyst with moderate shell thickness showed excellent ORR performance. Under 0.9 V (vs. reversible hydrogen electrode (RHE)), [email protected] NSs–2 (1.038 A mg-1Pt+Pd) achieved mass activity (MA) 6.25 times of commercial Pt/C catalyst. Superior performance of [email protected] 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.