Efficient oxygen evolution on spinel MFe2O4 (M = Zn and Ni) electrocatalysts

Electrochemical water splitting for the oxygen evolution reaction (OER) requires highly active, long-durable, and cost-effective catalysts to meet the needs of large-scale hydrogen production in the future. Herein, we studied the OER performance of spinel MFe2O4 (M = Zn and Ni) and NiOx. These metal oxides showed markedly different activities, which were closely related to their charge-transfer resistance and electrochemical surface area, attributing to the amount of oxygen vacancies. Particularly, ZnFe2O4 exhibits superior OER activity with an overpotential of 318 mV at the current density of 10 mA cm−2 (η10) and a Tafel slope of 50 mV dec−1. Furthermore, ZnFe2O4 also presents outstanding long-term stability for 100 h with negligible decay even at a high current density of 800 mA cm−2. This work provides a fundamental insight into the oxygen vacancy and spinel structure to help for the design of OER catalyst toward highly efficient water splitting.