LAUSR

Abstract Electrocatalytic water splitting, including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is an ideal method to produce hydrogen energy source. Stable electrocatalysts with good electrolytic activity are crucial for long-term water splitting. In this work, we show that MoO2 nanosheets can be grown directly on nickel foam substrate with oxygen vacancies decorated on the surface, acting as an excellent electrocatalyst for practical water splitting. In comparison to the pristine sample, the optimized MoO2, treated by 2% N2H4 solution for 20 min, exhibits a relatively low onset potential of −60 mV vs. reversible hydrogen electrode (RHE) for HER and a cell voltage of about 1.6 V vs. RHE to achieve a current density of 85 mA cm−2 for OER, which are attributed to the enhanced conductivity and improved surface active sites facilitated by oxygen vacancies. With the accelerated hydrogen generation process and activated water oxidation reaction, MoO2 is demonstrated to be a suitable and stable bifunctional electrode for full water splitting, and the post-treatment process for oxygen vacancies also provides an effective strategy for improving electrocatalysis.