Construction of hybrid Z-scheme graphitic C3N4/reduced TiO2 microsphere with visible-light-driven photocatalytic activity

A novel Z-scheme graphitic C3N4/reduced TiO2 microsphere (g-C3N4/r-TiO2) has been successfully synthesized by a solvothermal method. The as-prepared samples with different contents of g-C3N4 were characterized by X-ray diffraction, electron paramagnetic resonance, scanning electron microscope, UV–vis. diffuse reflectance and photoluminescence spectra. The r-TiO2 microspheres are aggregated on the surface of g-C3N4 sheets in the as-prepared g-C3N4/r-TiO2 composites. All g-C3N4/r-TiO2 catalysts show enhanced photocatalytic activity for the degradation of rhodamine B under visible light irradiation. It could be attributed to these influences of oxygen vacancy (changing the band gap of TiO2), the large specific surface area (providing much more active sites for photocatalytic reaction), and the synergetic effect between g-C3N4 and r-TiO2 (promoting the separation for photoinduced electron-hole pairs). Moreover, the Z-scheme carriers transfer mechanism in the photocatalytic process has been discussed through trapping experiments of active species. The work demonstrates the strategies of the construction of Z-scheme carriers transfer system, the introduction of oxygen vacancy and structure designing are beneficial to design materials toward solar energy conversion like contaminant degradation.