Fig. 1a shows a schematic illustration of oxygen vacancies in NiMoO4. Oxygen vacancies on the surface of NiMoO4 act as shallow carriers, which improve the electrical conductivity of the materials. When oxygen vacancies created in NiMoO4, the sample have strong absorption for water. Oxygen vacancies were responsible for the dissociation of water molecules into OH− [36]. Moreover, oxygen vacancies of NiMoO4 can adsorb OH− to accelerate the kinetics of electrochemical redox reactions. As shown in
