An Experimental and Theoretical Study on The S-doped g-C3N4 Nanosheets

Using sunlight as a permanent energy source and free of contamination in photocatalytic processes is the best solution to solve the energy crisis and environmental pollution. In recent years, g-C3N4 (graphitic carbon nitride) has been considered as a visible light photocatalyst. It is low-cost and biocompatible photocatalyst with high thermal and chemical stability [1]. It is used in various photocatalytic fields such as water splitting, CO2conversion to fuel, degradation of pollution. However, the photocatalytic activity of g-C3N4 is not significant, due to the relatively large band gap and high recombination rate of e--h pairs. In this work, S-doped modification method is used to improve the g-C3N4 photocatalytic efficiency, which is examined theoretically and experimentally. Both bare and S-doped g-C3N4 nanosheets were synthesized by thermal condensation technique. The XRD patterns and FT-IR spectra confirmed the synthesis of the gC3N4 structure for bare and S-doped g-C3N4. ICP-AES analysis confirmed the presence of sulfur in the S-doped g-C3N4.TEM and SEM image for g-C3N4 showed layer structure of g-C3N4 nanosheet. UV-vis spectra and Tauc plots showed that sulfur doping of the g-C3N4 decreases band gap and increases visible light absorption.DFT calculation showed that doping of g-C3N4 with sulfur decreases band gap and thus visible light absorption is modified. On the other hand, S doping increases delocalization and photogenerated carriers can freely move between heptazine units that decreases recombination rate of e--h pairs. Generally, experimental and theoretical results indicate that S doping of g-C3N4 improves the photocatalytic activity of the g-C3N4.