Abstract
Developing cost-effective and durable electrocatalysts with high hydrogen evolution efficiency remains a critical challenge for sustainable energy conversion. Herein, spinel-type Co(2)CuO(4) and Co(3)O(4) nanosheet electrodes were fabricated directly on Ni foam via a simple electrodeposition route and evaluated for the alkaline hydrogen evolution reaction (HER) in 1.0 M KOH. Structural and surface analyses confirmed the formation of phase-pure, porous, and highly interconnected nanosheet architectures, where the substitution of Cu(2+) into the Co(3)O(4) lattice induced charge-redistribution and optimized the electronic configuration. The Co(2)CuO(4) catalyst exhibited superior activity, requiring an overpotential of 127 mV to achieve 10 mA cm(-2) with a corresponding Tafel slope of 61 mV dec(-1), outperforming the Co(3)O(4) catalyst (176 mV and 95 mV dec(-1)). This enhancement arises from improved intrinsic kinetics, higher turnover frequency, and reduced charge-transfer resistance, reflecting an increased density of active sites and enhanced interfacial conductivity. Furthermore, the Co(2)CuO(4) catalyst maintained excellent stability for 100 h at both 10 and 500 mA cm(-2), attributed to its strong adhesion and open nanosheet framework, which facilitates efficient gas release and electrolyte diffusion. These findings establish Co(2)CuO(4) as a promising and durable HER electrocatalyst for alkaline water electrolysis.