In-situ hydrothermal synthesized γ-Al2O3/O-g-C3N4 heterojunctions with enhanced visible-light photocatalytic activity in water splitting for hydrogen

In this work,γ-Al₂O₃ and hydrogen peroxide treated g-C₃N₄（O-g-C₃N₄） were combined through a novel in-situ hydrothermal method to form heterojunction structured photocatalysts.These photocatalysts were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy（PL）.FT-IR results indicate that oxygen functional groups can be grafted on the surface of O-g-C₃N₄ by hydrogen peroxide treatment.The visible light photocatalytic hydrogen evolution rate was investigated in 10 vol% TEOA aqueous solution.The optimal Al₂O₃ mass content is set to be 20 wt% and the corresponding hydrogen evolution rate is 1288 μmol/h/g which is approximately 6,3 folds that of pristine g-C₃N₄ and O-g-C₃N₄ respectively and 1.6 folds that of mechanical mixed composite with the same Al₂O₃ mass content.The photocurrent density–time curves were carried out under visible light illumination for four on–off cycles.The electrochemical impedance spectroscopy（EIS） measurements verified the enhanced separation efficiency of electron–hole pairs.This work raised a new method to form the heterojunction structured photocatalysts and achieved a remarkable improvement of the photocatalytic activity in water splitting for hydrogen under visible light irradiation.