The effects of biaxial strain and sulfur/boron doping on the photocatalytic performance of the g-C3N5 system: A first-principles study

Strain and doping are effective methods for enhancing the intrinsic properties of the photocatalyst g- C₃N₅. This paper investigates the electronic properties, optical characteristics, and changes in Gibbs free energy of g-C₃N₅ under the combined effects of biaxial strain and sulfur/boron (S/B) doping through first-principles calculations. By calculating the formation energy of the doping system, the optimal doping positions for B/S are identified. The results indicate that intrinsic g-C₃N₅ exhibits indirect band gap semiconductor properties with a band gap of 1.851 eV. In contrast, S/B doping reduces the band gap, with the S-doped g-C₃N₅ system (S-g-C₃N₅) displaying direct band gap semiconductor properties and a band gap of 1.677 eV. The application of tensile or compressive strain induces a red shift or blue shift in the absorption spectra of both the intrinsic g-C₃N₅ system and the doped system. Tensile strain positions the band edges of all systems favorably, enhancing carrier mobility and redox capability. This study provides valuable insights for the development of photocatalytic carbon nitride through atomic doping and strain modulation.