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

A facile ammonia-mediated strategy is developed for the kinetically controlled synthesis of Co3O4 nanoparticles on Ni(OH)2 nanosheet arrays, in which the sample prepared with 2 M NH3(aq) exhibits superior catalytic performance toward oxygen evolution reaction. [Display omitted] •Ammonia mediated hydrothermal decomposition of Co(NH3)63+ produces Co3O4 NPs.•Ammonia decides the dissociation of Co(NH3)63+ to control the growth of Co3O4 NPs.•Moderate dispersion of Co3O4 NPs on Ni(OH)2 increases active site number for OER.•Electron transfer from Ni(OH)2 to the Co3O4 phase boosts OER activity of Co3O4 NPs. 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 η100 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.