Electronic and optical properties of nitrogen and sulfur doped strontium titanate as efficient photocatalyst for water splitting: A DFT study

One of the most effective option of photocatalysts for water splitting is doped strontium titanate, SrTiO₃. It has a high rate of photo-generated charge transfer and limited photocatalytic activity for water splitting. The search of an appropriate photocatalyst having a high visible light absorption as well as fast charge transportation is extremely needed, however it is a difficult task. The structural, electronic and optical properties of sulfur-doped SrTiO₃ and nitrogen-doped SrTiO₃ are investigated using calculations based on density functional theory (DFT). According to the band structure calculations, the O-2p states represented the higher levels of the valence band of pure SrTiO₃. When S and N atoms are introduced into the SrTiO₃ structure on the O site, electronic structure findings indicate that doping the Sulfur (S) atoms reduced the band gap significantly, whereas doping of N atoms increased the bandgap of SrTiO₃. According to our results, the N-doped SrTiO₃ has a sufficient band gap of 2.03 eV, as well as suitable high visible light absorption and charge carrier transportation. The optical properties showed that N-doped SrTiO₃ has good photosensitivity for visible light. In addition, we have found a significant impurity state that differs from O 2p-states, which can increase photocatalytic efficiency. The results of studies of electronic band structure showed that electron-hole transportation was well consistent with the experimental data. Thus, the N-doped SrTiO₃ in this study is indeed an attractive candidate for hydrogen evolution throughout the visible light range, providing a logical base for the establishment of innovative photocatalysts.