MOF-derived S-doped NiCo₂O₄ hollow cubic nanocage for highly efficient electrocatalytic oxygen evolution

Inducing the surface reconstruction of spinels is critical for improving the electrocatalytic oxygen evolution reaction (OER) activity. Herein, S-doped NiCo₂O₄ hollow cubic nanocage was synthesized by anion etching Metal-Organic Frameworks (MOFs) template and air annealing strategies. The hollow structure possesses a large specific surface area and pore size, facilitating active site exposure and mass transport. S^2- doping regulates the electronic structure, reducing the oxidation potential of Ni sites during the OER process, thus promoting the surface reconstruction into γ-NiOOH active species. Meanwhile, S^2- doping enhances conductivity, accelerating interfacial charge transfer. As a result, S-NiCo₂O₄-6 exhibits superior OER activity (262 mV overpotential @ 10 mA cm^-2) and stability in 1.0 M KOH solution. Furthermore, 20 % Pt/C‖S-NiCo₂O₄-6 only needs 1.832 V to achieve 50 mA (the electrochemical active area is 4 cm²) in a homemade anion exchange membrane (AEM) electrolyzer. This work proposes a novel approach for preparing efficient anion-doped spinel-based OER electrocatalysts.