A novel NiO electrocatalyst with rich redox pairs and oxygen vacancies for methanol oxidation reaction: Mechanism and DFT study

This study introduces a synergistic engineering strategy by integrating oxygen vacancies and redox-active Ni³ ⁺/Ni²⁺ pairs within a three-dimensional walnut-like NiO nanostructure, achieving unprecedented methanol oxidation reaction (MOR) performance. Specifically, the optimized NiO-450 catalyst, derived via a facile hydrothermal-freeze-drying-sintering route, exhibits a record-low Tafel slope of 145.1 mV/dec, high current density of 5.63 mA/cm², and superior stability under high methanol concentrations (up to 5 mol/L). Density functional theory (DFT) calculations revealed that oxygen vacancies play a crucial role in enhancing the catalytic performance, which is further elaborated in the results section. This work represents a paradigm shift in non-precious metal catalyst design, demonstrating that rational defect engineering combined with redox pair optimization can enhance MOR performance while addressing critical challenges in DMFC practicality.