Sulfur vacancy enhances the electronic and optical properties of FeS2 as the high performance electrode material

Abstract FeS2 disulfide is a fascinating electrode material for the application of sodium ion batteries (SIBs). However, the band width of FeS2 restricts the electronic jump near the Fermi level and weakens the catalytic activity. Essentially, the sulfur vacancy induced charge carrier trap is an effective method to improve the electronic transfer between the valence band and conduction band. Here, we apply the first-principles to investigate the S-vacancy mechanism in FeS2. Two FeS2 phases: cubic and orthorhombic are considered. The influence of S-vacancy on the electronic and optical properties of FeS2 is deeply studied. The result shows that the cubic FeS2 has better stability compared to the orthorhombic FeS2. Furthermore, it is found that these S vacancies are stability in FeS2 whether cubic or orthorhombic FeS2. The cub-S(1) is more thermodynamically stable than the orth-S(1) and orth-S(2) vacancies. In particular, the S-vacancies improve the electronic jump of FeS2 between the valence band and the conduction band. Therefore, it is concluded that the S-vacancies improve the electrical jump and catalytic activity of FeS2 because the band gap of S-vacancies is much lower than the corresponding FeS2. In addition, the S-vacancies enhance the photocatalytic properties of FeS2 based on the adsorption spectrum. Therefore, we believe that the introduction of S-vacancy is an effective method to improve the electrical conductivity and catalytic activity of FeS2 electrode material.