Simultaneous Modulation of Composition and Oxygen Vacancies on Hierarchical ZnCo₂ O₄ /Co₃ O₄ /NC-CNT Mesoporous...

Electrochemical water splitting is a promising way for the sustainable production of hydrogen, but the efficiency of the overall water-splitting reaction largely depends on the oxygen evolution reaction (OER) because of its sluggish kinetics. Herein, a series of hierarchical ZnCo₂ O₄ /Co₃ O₄ /NC-CNT (NC-CNT=nitrogen-rich carbon nanotube) mesoporous dodecahedrons grafted to carbon nanotubes have been synthesized from ZnCo bimetallic zeolitic imidazolate frameworks (ZnCo-ZIFs) through sequential pyrolysis in nitrogen and mild oxidation in air. The simultaneous modulation of oxygen vacancies, composition, and hierarchical mesoporous architecture remarkably enhanced their electronic conduction and the amount and reactivity of accessible actives; thus boosting their intrinsic activity in the OER. The optimal ZnCo₂ O₄ /Co₃ O₄ /NC-CNT-700 sample exhibited a large current density of 50 mA cm^-2 at a potential of 1.65 V, a small Tafel slope of 88.5 mV dec^-1 , and superior stability in alkaline media. This work should provide a facile strategy for the rational design of advanced OER catalysts by simultaneous engineering of oxygen vacancies and composition.