Synthesis, Characterization, and Photocatalytic Properties of SnO2/Rutile TiO2/Anatase TiO2Heterojunctions Modified by Pt

To improve the separation rate of photogenerated electrons and holes, a SnO2/rutile TiO2(R-TiO2)/anatase TiO2(A-TiO2) photocatalyst modified by Pt nanoparticles with three pairs of heterojunctions was fabricated by a facile hydrothermal method. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) clearly illustrated the structure of the three pairs of heterojunctions connected to each other. Heteronanostructure photocatalysts with increased specific surface area could offer more active sites when contacting pollutants, resulting in improved photocatalytic activity. The red shift in UV–vis diffuse reflectance spectra (DRS) indicated the utilization of visible-light. Photoluminescence (PL) and photoelectrochemical (PEC) measurements suggested the enhancement of electron and hole separation, in accordance with the results obtained for the photocatalytic oxidation of decomposing toluene over 4 h. A catalyst containing 1 wt % Pt/10 at. % SnO2/R-TiO2/A-TiO2exhibited the best photocatalytic mineralization rates of toluene: 40.9% and 72.3% under visible-light and UV-light irradiation, respectively. A proposed mechanism was elaborated to reveal the effective photocatalytic progress of charge transfer along multiple pathways along the three pairs of heterojunctions doped with Pt.