Composition-Graded PdxNi1-x Nanospheres with Pt Monolayer Shells as High-Performance Electrocatalysts for Oxygen Reduction Reaction

摘要

It is undoubtedly desirable, albeit very challenging, to appropriately balance the catalytic activity, electrochemical durability, and noble-metal (NM) utilization when developing Pt-based catalysts for oxygen reduction reaction (ORR). Accordingly, in this work, a versatile and effective strategy that promises the nanostructure of both composition-graded core and mono- or multilayer shell is proposed to synthesize highly uniform, sub-10 nm PdxNi1-x@Pt nanospheres (NSs) as high-performance ORR electrocatalysts. Highly uniform and composition-graded PdxNi1-x NSs are previously obtained via a facile one-pot Ni-substitution-based process, and then Pt mono- or multilayer shells are coated onto them through Cu underpotential deposition coupled with Pt2+ galvanic displacement. Results show that carbon supported PdxNi1-x@Pt electrocatalysts possess both high catalytic activity and highly efficient NM utilization toward ORR The optimized Pd0.42Ni0.58@Pt/C exhibits 0.61 mA cm(-2), 0.42 A mg(Pd+pt)(-1), and 1.45 A mg(Pt)(-1) @ 0.9 V (vs RHE) in the area-specific, NM-mass specific, and Pt-mass-specific activity, respectively, reaching 2.8, 3.3, and 11.2 times relative to those of the commercial Pt/C. Moreover, Pd0.42Ni0.58@Pt/C also has a satisfactory electrochemical durability, preserving its high ORR catalytic activity even after 12 000 potential cycles of the accelerated degradation test. The synthetic mechanism of PdxNi1-x NS core, Pt monolayer shell and their combined effects on the catalytic activity, electrochemical durability, and NM utilization of PdxNi1-x@Pt/C toward ORR are comprehensively investigated.