TiO 2 Electronic Properties Analysis: DFT Study of Ni and NiSe Doping Effect

Abstract

Titanium dioxide (TiO 2 ) is a promising photocatalyst for hydrogen generation, but its efficiency is severely restricted by a wide bandgap and rapid electron-hole recombination. This study employs Density Functional Theory (DFT) to investigate the structural and electronic effects of isovalent Ni⁴⁺ doping and substitutional Ni-Se co-doping on a 48-atom anatase TiO2 supercell. Results indicate that pure Ni doping induces localized lattice contraction, while NiSe co-doping causes structural expansion. Both modifications introduce new mid-gap states that significantly narrow the bandgap, with the 1NiSe configuration achieving a dramatic reduction from 2.68 eV (pristine) to 0.18 eV. While this indicates improved theoretical visible-light absorption potential, the known limitations of standard PBE functionals and the high dopant concentrations modelled must be considered. Furthermore, qualitative ground-state charge density analyses visually suggest that Se may act as an electron acceptor, creating a more uniform electron distribution. This observed charge delocalization suggests a potential mechanism for mitigating electron-hole recombination; however, quantitative charge analysis and explicit excited-state evidence are required to fully characterize these dynamics. Ultimately, these findings present Ni-Se co-doped TiO2 as a promising theoretical baseline model, warranting future calculations of absolute band-edge alignments and experimental evaluation to confirm its viability for clean energy applications.