Interface-vacancy synergy of Co(OH)2/CoN to boost alkaline water splitting

Developing bifunctional electrocatalysts with high performance that are easily available, low-cost, and long-term stable is challenging. Interface engineering and vacancy engineering are two effective methods for constructing excellent catalysts. Based on the integration of these two strategies, a heterostructured catalyst with abundant oxygen vacancies was built via electrodeposition. The as-prepared catalyst, V O -Co(OH) 2 /CoN, had long-term stability in alkaline electrolyte and demonstrated excellent bifunctional activity with low overpotentials of 52 mV for the hydrogen evolution reaction and 206 mV for the oxygen evolution reaction at 10 mA cm −2 . The electrolytic cell constructed by V O -Co(OH) 2 /CoN only required a cell potential of 1.518 V at 10 mA cm −2 . According to both the results of experiments and density functional theory computations, the outstanding bifunctional activity of V O -Co(OH) 2 /CoN is attributed to the synergistic effect of heterointerface and oxygen vacancies. A Co atom and an oxygen vacancy formed an active Co-vacancy pair near the heterointerface, which synergistically boosted water splitting by changing the reaction path. Oxygen vacancy not only participated in catalysis as an active site, but also effectively adjusted the electron densities to improve the catalyst conductivity. Our work is vital to guide the design of highperformance catalysts and understand the catalytic mechanism.