Hierarchical sheet-like W-doped NiCo2O4 spinel synthesized by high-valence oxyanion exchange strategy for highly efficient electrocatalytic oxygen evolution reaction

Limited specific surface area, active site amount, and intrinsic conductivity inhibit spinels' electrocatalytic oxygen evolution reaction (OER) activity. Herein, we proposed a high-valence oxyanion exchange strategy for preparing hierarchical sheet-like W-NiCo2O4-2 spinel OER electrocatalyst, which exhibits favorable activity (306 mV overpotential@10 mA cm−2) and durability in 1.0 M KOH solution, and shows an application prospect in a home-made anion exchange membrane (AEM) electrolyzer. BET results showed that the hierarchical structure increased specific surface area and corresponding edge active sites amount, accelerated mass transport and charge transfer. XPS, ex-situ Raman spectroscopy, and HRTEM characterizations dispicted that W6+ doping optimizes eg orbital electron filling and promotes M−OOH (M = Co, W) active species generation. DFT calculations reveal that W6+ doping modulates the adsorption of oxygen intermediates, improving the reaction kinetics, and increasing the density of electronic states nearby the Fermi level, thus enhancing conductivity. This work provides a universal pathway for modulating spinel-based OER electrocatalysts.