Tuning of the electronic band structure of fibrous silica titania with g-C3N4 for efficient Z-scheme photocatalytic activity

Abstract

Graphitic carbon nitride (g-C3N4)/fibrous silica titania (CNFST) catalysts are successfully synthesized via a simple solid-state microwave-assisted method under various loadings of g-C3N4 and then characterized by XPS, ESR, FTIR, TEM, UV–Vis DRS, FESEM, XRD and N2 adsorption-desorption analysis. The catalytic activity towards visible-light photodegradation of 2-chlorophenol is of the following order: 10 wt% CNFST (93%) ˃ 15 wt% CNFST (70%) ˃ g-C3N4 (67%) ˃ 5 wt% CNFST (49%) ˃ fibrous silica titania (40%). The highest activity of 10 wt% CNFST is due to high amount of defect sites, including SiON and SiOC bonds, oxygen vacancies and metal defects. These features narrow the band gap and tune the electronic band structure of fibrous silica titania, as well as acting as electron mediators which can induced charge carriers recombination and strong redox ability for the Z-scheme mechanism. Consequently, photogenerated holes play a major role in the degradation, as confirmed by a scavenger study. It is believed that the Z-scheme interfacial heterojunction of CNFST demonstrates an excellent potential toward the photocatalytic degradation of numerous phenolic compounds in wastewater treatment.