Enhancement of Carrier Separation and Overall Water Splitting Performance by Nitrogen Doping in SrTiO₃

Enhancing the photocatalytic performance of SrTiO 3 through bandgap modification via nitrogen doping is a widely used approach. However, our study reveals that N-doped SrTiO 3 may exhibit additional mechanisms contributing to its improved performance. In this study, SrTiO 3 was synthesized via a hydrothermal method. N doping significantly improved the photocatalytic efficiency of SrTiO 3 in water splitting, with average hydrogen and oxygen production rates of 36.79 μmol h –1 and 18.66 μmol h –1, respectively, which is approximately 3.4 times higher than that of pure SrTiO 3 . First-principles calculations combined with diffuse reflectance spectroscopy demonstrated that under conventional doping conditions, N doping does not lead to a reduction in the bandgap of SrTiO 3, indicating that the primary reason for the enhanced photocatalytic activity differs from that of N-doped TiO 2 and is not due to an enhanced response to visible light. Further studies showed that upon introduction of nitrogen into the SrTiO 3 lattice, the difference in electronegativity between N and O increased the charge density around the Ti 3d orbitals, causing an upward shift in the Fermi level, increased the depletion layer thickness, and promoted carrier transport and separation. This suggests that the primary reason for the performance improvement may be the enhanced efficiency of carrier transport and separation. This finding could contribute to a more comprehensive understanding of the effects of nonmetal ion doping on the properties of SrTiO 3 and its potential applications.