Kinetically controlled synthesis of Co3O4 nanoparticles on Ni(OH)2 nanosheet arrays for efficient oxygen evolution reaction

Co3O4 is a promising electrocatalyst for oxygen evolution reaction (OER), yet its controllable synthesis has been challenging. Herein, a versatile approach is developed to fabricate Co3O4 nanoparticles (NPs) on diverse supports through the hydrothermal treatment of Co(NH3)63+ with an ammonia mediator. The ammonia is critical as it determines the dissociation kinetics of Co(NH3)63+, which in turn affects the nucleation and growth processes for kinetically controlling the size and dispersion of Co3O4 NPs. The Co3O4 NPs grown on 3D architectured Ni(OH)2 nanosheet arrays (Co3O4@Ni(OH)2) are applied as the catalysts for OER. Promoting by electron migration from Ni(OH)2 to Co3O4 to improve the intrinsic activity and the structural merits, the optimal Co3O4@Ni(OH)2 exhibits excellent OER performance, showing a competitive eta 100 of 399 mV and a small Tafel slope of 60 mV dec- 1. This research presents a simple and efficient ammonia-mediated strategy to controllably synthesize Co3O4 on various supports for OER and beyond.