Ultra-thin nanohoneycomb porous CoMoO₄ with excellent catalytic performance for water splitting at large current densities

Electrocatalytic water splitting for hydrogen production is considered the most effective and cleanest strategy to make full use of renewable energy. It still lacks the highly efficient and stable bifunctional catalyst to deliver high current density for large scale application of water splitting. Here, we innovatively developed a facile method to synthesize a three-dimensional (3D) honeycomb porous CoMoO₄@pNi (porous nickel) catalyst with ultra-thin nanosheet, the generated oxygen vacancies and mesoporous structures with defects as active sites. We also precisely tuned the thickness and array structure to investigate its catalytic performance. The as-prepared CoMoO₄@pNi catalyst delivers the overpotential of 377 mV for HER and 410 mV for OER, respectively, and only demands 1.99 V to reach a large current density of 1000 mA cm⁻² for overall water splitting. CoMoO₄@pNi catalyst is also operated for 200 h under 500 and 1000 mA cm⁻², respectively, and both showed an ignorable current decrease. The excellent activity and stability are ascribed to the high surface area, short transport path for electrons and protons, the full contact between the exposed active sites and electrolyte, and the inherent stable nanohoneycomb porous structure of the ultra-thin nanosheet.