Abstract
Oxygen vacancy has been suggested to play a role in the electrochemical ability of NiMoO4. The band structure and density of state of NiMoO4 bulks with different concentrations of oxygen vacancy were investigated by the first-principles calculation. Original NiMoO4 shows semiconductive properties with a direct band gap of 0.136 eV. When one to three oxygen vacancies were introduced in the NiMoO4 supercell, the band structure of NiMoO4 transforms to metallic properties, and oxygen vacancies formation energy increases with the increased number of oxygen vacancies. The oxygen vacancies in NiMoO4 lead to the increased electron localization of Ni 3d and Mo 3d state nearby the Fermi level, resulting in higher concentration of carriers in NiMoO4 and thus increase in its electrical conductivity. The results demonstrate that introducing oxygen vacancies can improve the conductive property of NiMoO4.
Highlights
As a typical transition metal oxides semiconductor, NiMoO4 has attracted attention for its wide applications in electrochemical energy storage and conversion, such as supercapacitor and electrocatalytic water splitting (Du et al, 2018; An et al, 2019)
EO2 where Edefective is the total energy of a structure with oxygen vacancies, Eperfect is the total energy of the structure without oxygen vacancy, and EO2 is the elemental chemical potential of oxygen in the gas phase
The formation energy of two and three oxygen vacancies in NiMoO4 are 2.67 and 4.88 times than that of the one vacancy, respectively, which suggested that one vacancy is more formed in NiMoO4 crystal
Summary
As a typical transition metal oxides semiconductor, NiMoO4 has attracted attention for its wide applications in electrochemical energy storage and conversion, such as supercapacitor and electrocatalytic water splitting (Du et al, 2018; An et al, 2019). The poor conductivity and electrochemical activity of NiMoO4 limited its electrochemical energy storage performance. Defects engineering is a common method to change the physical chemistry property of transition oxide materials. As a typical representative of defects, oxygen vacancies can effectively modulate their electronic properties, tune their bandgaps, and optimize their electrical conductivity (Zhang et al, 2020a). Theoretical mechanism analysis of oxygen vacancies in NiMoO4 on its capacitance performance is still scarce
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
