Electrochemically engineered fabricated NiOOH/NiO nanospheres with oxygen vacancies for enhanced oxygen evolution reaction

Abstract

The demand for cost-effective and green hydrogen (H₂) has driven the development of high-performance, low-cost oxygen evolution reaction (OER) electrocatalysts. Herein, we combine electrodeposition and in-situ electrochemical oxidation to fabricate a novel and low-cost NiOOH/NiO composite structure supported on nickel foam (denoted as NiOOH/NiO(O_v)/NF), featuring a nanosphere structure with oxygen vacancies. The optimized catalyst exhibits an exceptionally low overpotential of 220/290 mV at 20/100 mA cm⁻² without iR correction and is remarkably stable for at least 120 h at 100 mA cm⁻² in 1 M KOH. Density functional theory (DFT) calculations reveal that oxygen vacancies in NiO narrow the bandgap, enhance conductivity, reduce intermediate adsorption energy, and accelerate charge transfer through spin polarization, thereby improving OER intrinsic activity. The synergistic coupling of oxygen-deficient NiO with highly active NiOOH species significantly enhances OER performance, while the superhydrophilic/aerophobic surface facilitates rapid bubble detachment and electrolyte contact. This work provides a cost-effective alternative to noble-metal catalysts, demonstrating promising potential for scalable green hydrogen production via water splitting.