Regulation of TiO2/ZSM-5 catalyst for enhanced photocatalytic toluene oxidation: Intensified light absorption, charge separation and toluene adsorption

Abstract

TiO2 has been widely studied in photocatalytic VOCs oxidation but its photocatalytic activity is still unsatisfied due to poor visible light absorption, serious charge recombination and weak toluene adsorption. Herein, a composite catalyst (TiO2/ZSM-5) was constructed between TiO2 and hierarchical ZSM-5 by ball milling for photocatalytic toluene oxidation. The optimal composite catalyst exhibited the toluene degradation efficiency of 91.08 %, which was 2.7 and 1.3 times than those of TiO2 and TiO2/commercial ZSM-5. It showed that the strong interaction between TiO2 and hierarchical ZSM-5 was established via the formation of Ti-O-Si bond, which decreased the band gap from 3.08 to 0.55 eV when compared with TiO2 and was helpful for the enhanced charge separation. In addition, the mesoporous volume of hierarchical ZSM-5 was regulated by a dual-template method, making the mesoporous volume increased from 0.23 to 0.38 cm−3 g−1 when compared with TiO2/commercial ZSM-5, which improved the toluene adsorption capacity from 0.12 to 0.16 cm−3 g−1. DFT calculation further indicated that the energy barrier of toluene oxidation and ring-opening reaction was reduced in the presence of hierarchical ZSM-5. This work provided a new catalyst design method to improve the photocatalytic activity by the synergy action of TiO2 and ZSM-5.