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 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.