Roles of Oxygen Vacancies in NiMoO4: A First-Principles Study

Oxygen vacancy has been suggested to play a role in the electrochemical ability of NiMoO 4 . The band structure and density of state of NiMoO 4 bulks with different concentrations of oxygen vacancy were investigated by the first-principles calculation. Original NiMoO 4 shows semiconductive properties with a direct band gap of 0.136 eV. When one to three oxygen vacancies were introduced in the NiMoO 4 supercell, the band structure of NiMoO 4 transforms to metallic properties, and oxygen vacancies formation energy increases with the increased number of oxygen vacancies. The oxygen vacancies in NiMoO 4 lead to the increased electron localization of Ni 3d and Mo 3d state nearby the Fermi level, resulting in higher concentration of carriers in NiMoO 4 and thus increase in its electrical conductivity. The results demonstrate that introducing oxygen vacancies can improve the conductive property of NiMoO 4 .