Fabrication of Bi2O3 QDs decorated TiO2/BiOBr dual Z-scheme photocatalysts for efficient degradation of gaseous toluene under visible-light

Abstract

Weak visible-light capture ability, ultrahigh charge recombination rate, and poor redox ability are crucial constraints to improve the photocatalytic performance for toluene degradation under visible-light. Hence, a dual Z-scheme of Bi2O3 quantum dots decorated TiO2/BiOBr photocatalysts (Bi2O3 QDs@TiO2/BiOBr) were prepared by a two-step hydrothermal method. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were performed to identify the existence of Bi2O3 QDs and TiO2 that loaded on the surface of BiOBr. The introducing of oxygen vacancies in TiO2 broadened its light absorption region to the visible-light. The constitutes of Bi2O3 QDs and BiOBr were regulated and the optimized photocatalyst BT1-B10 exhibited 94.1 % of removal rate for gaseous toluene degradation after 150 min irradiation of visible-light (>420 nm) as well as good recoverability and durability. This result was obviously superior to other comparison samples. In-situ DRIFTs spectra and Gas Chromatography-Mass Spectrometry (GC-MS) were carried out to provide a possible pathway for the toluene degradation. Additionally, a dual-channel electron transfer model based on the Z-scheme was proposed, which presented desirable visible-light response region, efficient charge separation efficiency, and enhanced redox ability. Notably, hydroxyl radicals (•OH) served as the dominant active species was confirmed by electron spin resonance (ESR) and gas-phase capture tests, that was beneficial to the ring-opening of toluene degradation. This dual Z-scheme heterojunction of Bi2O3 QDs@TiO2/BiOBr photocatalyst showed great potential for the degradation of toluene under visible-light irradiation.