Regulating oxygen vacancies in Co ₃ O ₄ by combining solution reduction and Ni ²⁺ impregnation for oxygen evolution reaction

Abstract Oxygen vacancies are considered to be an important factor to influence the electronic structure and charge transport of electrocatalysts in the field of energy chemistry. Various strategies focused on oxygen vacancy engineering are proved to be efficient for further improving the electrocatalytic performance of Co ₃ O ₄ . Herein, an optimal Co ₃ O ₄ with rich oxygen vacancies have been synthesized via a two-step process combining solution reduction and Ni ²⁺ impregnation. The as-prepared electrocatalyst exhibits an enhanced oxygen evolution performance with the overpotential of 330 mV at the current density of 10 mA cm ⁻² in alkaline condition, which is 84 mV lower than that of pristine one. With the increasing of oxygen vacancies, the charge transfer efficiency and surface active area are relatively enhanced reflected by the Tafel slope and double-layer capacitance measurement. These results indicate that combination of solution reduction and heteroatom doping can be a valid way for efficient metal oxides-based electrocatalyst development by constructing higher concentration of oxygen vacancy.