Theoretical study of the origin of the enhanced visible light photocatalytic activity of N-doped CsTaWO6: Charge compensation effects modulated by N and other defects

First-principles calculations were used to investigate the origin of the enhanced visible light photocatalytic activity of N-doped CsTaWO6. The studies of the interactions of N and other defects found three kinds of charge compensation forms might be better. When NH-codoping is in CsTaWO6, the H atom acted as a charge donor to compensate the hole state caused by N-doping and induced the band gap narrowing of about 0.507 eV. For a higher N-doping concentration, a particular N–N cluster structure was formed. The electron transition energy from N–N π⁎ states to conduction band minimum decreased by 1.627 eV. When oxygen vacancy existed in the lattice, two electrons were transferred to compensate for two adjacent N acceptors and the band gap narrowed about 0.874 eV. The thermodynamics calculations indicated the formations of N and other defects were mutually promoted.