The effect of hydroxyl group grafting on the photocatalytic phenolic compounds oxidation ability of g-C3N4 prepared by a novel H2O2-alkali hydrothermal method

The hydroxyl group grafted g-C3N4 with outstanding photocatalytic phenolic compounds oxidation ability was prepared by H2O2-alkaline hydrothermal treatment. [Display omitted] •The hydroxyl grafted g-C3N4 is prepared by H2O2-alkaline hydrothermal treatment.•The catalyst has stronger adsorption capacity, leading to the higher phenol degradation and mineralization rate.•The main oxide species of phenol degradation is •OH. The treatment of phenol-containing wastewater is a hot topic in the field of environmental chemistry. In this work, the hydroxyl grafted graphite phase carbon nitride (g-C3N4) was prepared by H2O2-alkaline hydrothermal treatment, and its degradation of phenol under visible light was investigated. XRD, UV–Vis, FT-IR, XPS, N2 adsorption, SEM, TEM, PL, ESR, TPD and EIS were used to characterize the as-prepared catalysts. The results showed that the hydroxyl group grafting does not influence the crystal structure, optical property and specific surface area of catalyst. Compared with the single H2O2 treatment, the H2O2-alkali hydrothermal treatment can graft more hydroxyl groups onto the g-C3N4 surface, leading to the higher electron-hole separation efficiency. The as-prepared catalyst by this method had more surface negative charge and stronger adsorption capacity for the reaction substrate phenol. The DFT calculation results also supported the above conclusions. The g-C3N4 prepared by this H2O2-alkali hydrothermal treatment displayed the phenol degradation rate constant of 0.254 h−1, which was 4.3 times and 1.8 times higher than that of neat and single H2O2 treated g-C3N4, as well as excellent catalytic stability and structural stability. The possible reaction mechanism was proposed.