Abstract:

TiO₂/C₃N₅ heterojunction photocatalyst was prepared by reflux method using isopropyl titanate and nitrogen-rich carbon nitride （C₃N₅） as raw materials. XRD, FT-IR, TEM, UV-vis DRS and PL were used to characterize the photocatalyst in phase composition, chemical composition, microstructure, light-response absorption, and the separation and recombination of photogenerated carriers. Methylene blue （MB） was used as the target pollutant to evaluate the activity and stability of the TiO₂/C₃N₅ heterojunction photocatalyst. The photocatalytic mechanism was proposed based on the free radical quenching and energy band theory. The results showed that the construction of heterojunction between TiO₂ and C₃N₅ enhanced the visible-light-response absorption ability and effectively promoted the separation of photogenerated carriers. The TiO₂/C₃N₅ heterojunction photocatalyst with the mass ratio of 1:2 showed excellent photocatalytic activity, and the degradation percentage of MB reached 98.60% under visible light irradiation. After 5 cycles, the degradation percentage of MB still reached 98.30%. In the S-scheme photocatalytic mechanism, the holes （h⁺） and electrons （e^-） with high oxidation activity and reduction activity, respectively, were retained, and efficient charge separation was achieved through energy-band bending and the construction of internal electric field. Therefore, a large amount of superoxide radicals （·O₂^-） were generated in the system to achieve efficient degradation of MB.

Key words: C₃N₅, TiO₂, heterojunction, photocatalysis, methylene blue, S-scheme