RuC@g-C3N4(H+)/TiO2 visible active photocatalyst: Facile fabrication and Z-scheme carrier transfer mechanism

Abstract

The protonated g-C3N4 bonded with ruthenium complexes as photosensitizer, and then was loaded on TiO2 to form RuC@g-C3N4(H+)/TiO2 by solvothermal method. The morphology and structure of photocatalyst were characterized by high-resolution transmission electron microscopy (HRTEM) with element mapping, X-ray diffraction (XRD) and (BET) surface area measurements. The chemical composition was analyzed by X-ray photoelectron (XPS) and Fourier transform infrared (FTIR). Photoluminescence (PL) emission intensity was employed to determine the separation efficiency of photogenerated electron-hole pairs. The results suggested that the protonation of g-C3N4 could improve both photocatalytic performance of g-C3N4 and the content of ruthenium complexes loaded on the g-C3N4(H+) by 1.33 times that for the g-C3N4(without protonation). Thus, the photocatalytic kinetic constant k of optimal RuC@g-C3N4(H+)/TiO2 (N16-1) was enhanced 1.7 times than that of RuC@g-C3N4/TiO2 (G12-1) without protonated treatment. Through analyzing three scavengers for BQ, t-BuOH, and EDTA-2Na trapping active species of the O2−, h+ and OH respectively in MB aqueous solution during light irradiation, the transfer of photogenerated electron-hole of g-C3N4(H+)/TiO2 hybrids could be described as classic Z-scheme photocatalytic mechanism, and further confirmed that the ruthenium complexes, performing as a pump to transfer electron, could improve effectively the separation of photogenerated electron-hole. The main significance of this paper is providing analysis of photogenerated electron-hole pairs transfer through scavenging active species in aqueous solution, and working mechanism of photosensitizer.