Enhanced oxygen evolution performance of iron-nickel oxide catalyst through dual-defect engineering

A dual-defect strategy of creating oxygen vacancies and phosphorus filling was developed to enhance the electrocatalytic activity and stability of NiFe2O4, and the optimal NiFe2O4-Vo-P exhibits outstanding OER performance [Display omitted] •A strategy of filling oxygen vacancies with phosphorus dopants is developed to enhance the catalytic activity and stability of NiFe2O4.•Phosphorus atoms filling enables optimized electronic structure, thus reducing the reaction energy barrier of the rate-determining step and improving the activity of the catalyst.•Phosphorus filling could reduce the band gap and enhance the conductivity of the NiFe2O4 oxide.•The optimal NiFe2O4-Vo-P exhibits fascinating OER activity with low overpotential of 306 mV to deliver a high current density of 200 mA cm−2.•The phosphorus filling strategy could effectively stabilize the oxygen vacancies in NiFe2O4, thereby improving the cycling stability of the catalyst. Transition metal oxides have been extensively investigated for oxygen evolution reaction (OER). While the introduction of oxygen vacancies (Vo) was found to be an effective way to enhance the electrical conductivity and the OER electrocatalytic activity of transition metal oxides, the oxygen vacancies are easily damaged during the long-term catalytic process, resulting in rapid decay of the electrocatalytic activity. Herein, we proposed the strategy of dual-defect engineering to enhance the catalytic activity and stability of NiFe2O4 by filling the oxygen vacancies of NiFe2O4 with phosphorus atoms. The filled P atoms could form coordination with iron and nickel ions to compensate the coordination number and optimize the local electronic structure, which not only enhances the electrical conductivity but also improves the intrinsic activity of the electrocatalyst. Meanwhile, the filling of P atoms could stabilize the Vo and thus improving the cycling stability of the material. The theoretical calculation further demonstrates that the improvement in conductivity and intermediate binding by P refilling remarkably contributes to enhancing the OER activity of NiFe2O4-Vo-P. Benefiting from the synergistic effect of filled P atoms and Vo, the derived NiFe2O4-Vo-P exhibits fascinating activity with ultra-low OER overpotentials of 234 and 306 mV at 10 and 200 mA cm−2, together with the good durability for 120 h at relatively high current density of 100 mA cm−2. This work sheds light on the design of high-performance transition metal oxide