Controlled Hydrolysis of a Nickel–Ammonia Complex on Pt Nanoparticles for the Preparation of Highly Active and Stable PtNi/C Catalysts

Abstract

Thermal annealing at high temperatures is usually employed to alloy Pt with transitional metals to produce Pt-based electrocatalysts in an oxygen reduction reaction for polymer exchange membrane fuel cells. How to curb thermal annealing induced aggregation and sintering has been a major concern in post-treatment. Here we developed an optimized impregnation method by controlled hydrolysis of a nickel–ammonia complex on Pt/C via dropwise addition of NaOH to form homogeneously dispersed catalyst precursors. These precursor powders are then subjected to thermal annealing and subsequent acidic leaching to produce alloyed A-PtNi/C catalysts. A-PtNi/C displayed a high mass activity (MA) and specific activity (SA) of 0.903 A mgPt–1@0.9 V and 2.36 mA cm–2, respectively. In addition, the electrochemical surface area (ECSA) and MA only suffered losses of 3 and 33%, respectively, after an accelerated durability test. Both activity and stability of A-PtNi/C far exceed the 2020 Department of Energy target set for ORR catalysts.