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 Co 3 O 4 nanoparticles on Ni(OH) 2 nanosheet arrays, in which the sample prepared with 2 M NH 3(aq) exhibits superior catalytic performance toward oxygen evolution reaction. [Display omitted] • Ammonia mediated hydrothermal decomposition of Co(NH 3) 6 3+ produces Co 3 O 4 NPs. • Ammonia decides the dissociation of Co(NH 3) 6 3+ to control the growth of Co 3 O 4 NPs. • Moderate dispersion of Co 3 O 4 NPs on Ni(OH) 2 increases active site number for OER. • Electron transfer from Ni(OH) 2 to the Co 3 O 4 phase boosts OER activity of Co 3 O 4 NPs. Co 3 O 4 is a promising electrocatalyst for oxygen evolution reaction (OER), yet its controllable synthesis has been challenging. Herein, a versatile approach is developed to fabricate Co 3 O 4 nanoparticles (NPs) on diverse supports through the hydrothermal treatment of Co(NH 3) 6 3+ with an ammonia mediator. The ammonia is critical as it determines the dissociation kinetics of Co(NH 3) 6 3+, which in turn affects the nucleation and growth processes for kinetically controlling the size and dispersion of Co 3 O 4 NPs. The Co 3 O 4 NPs grown on 3D architectured Ni(OH) 2 nanosheet arrays (Co 3 O 4 @Ni(OH) 2) are applied as the catalysts for OER. Promoting by electron migration from Ni(OH) 2 to Co 3 O 4 to improve the intrinsic activity and the structural merits, the optimal Co 3 O 4 @Ni(OH) 2 exhibits excellent OER performance, showing a competitive η 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 Co 3 O 4 on various supports for OER and beyond. [ABSTRACT FROM AUTHOR]