A DFT-based study of enhanced photocatalytic performance in TiO₂ nanotubes by introducing nitrogen-doped models

Abstract In this theoretical study, we employed first-principles density functional theory calculations to investigate the structural, electronic, optical, and photocatalytic properties of pristine and nitrogen-doped (0,5) TiO 2 anatase nanotubes. Bandgap narrowing in nitrogen-doped TiO 2 nanotubes is attributed to the introduction of electronic states above the valence band, arising from the interaction between nitrogen dopants and the TiO 2 lattice. These states shift the valence band maximum to the higher values relative to the pristine nanotube, yielding optimal narrowed bandgaps of 2.8 eV, 1.0 eV, and 2.76 eV for substitutional, interstitial, and mixed doping models, respectively. Substitutional models with 0.83 at. % nitrogen demonstrates favorable band positions for comprehensive water splitting and CO 2 reduction. Based on the previous studies on the electronic structures of FePS 3 (Co 9 Se 8 ), we demonstrate the enhanced photocatalytic performance of the interstitial model in forming an S-scheme heterojunction, which promotes efficient hydrogen production and CO 2 reduction. These findings elucidate the critical role of nitrogen doping in augmenting the photocatalytic efficiency of TiO 2 nanotubes, providing a theoretical foundation for future experimental validation.