Band Gap Engineering of TiO2 Anatase through Cobalt and Nitrogen Co-doping: A Periodic Hybrid-DFT Study

Nowadays photocatalysts are widely used to degrade industrial and waste by-products. Among different catalysts, anatase is the most applied one due to its abundance and low cost. However, its large band gap (3.2 eV) limits its efficiency. Many metal and non-metal atoms have been used experimentally to reduce the band gap of anatase. In this paper, we tried to use a hybrid periodic density functional theory (DFT) method to model the solid-state phase of anatase photocatalyst and investigate nitrogen and cobalt substitutional doping on the band gap reduction. In addition to the band gap value, the magnetic properties of defected anatases are also studied. Results show that Co-doping by itself reduces the band gap from 3.56 (for pristine anatase) to 2.4 eV. The band gap reduction for (N, Co) dual-doping depends on the relative positions of N and Co to each other. If Co and N are located far from each other, the band gap reduces from 3.56 to 2.5 and 2.0 eV for spin-up and spin-down, respectively. If they are nearest neighbors, the band gap reduces from 3.56 to 3.2 and 2.6 eV for spin-up and spin-down, respectively.