Novel ZnFe2O4/WO3, a highly efficient visible-light photocatalytic system operated by a Z-scheme mechanism

Dark red ZnFe2O4 (ZFO) nanoparticles (NPs) of (similar to)9 nm size and pale yellow WO3 nanowire bundles (NWBs) with high porosity were prepared by hydrothermal reactions, respectively, and coupled to form novel ZFO/WO3 heterojunctions. Tiny ZFO NPs and highly porous WO3 NWBs successfully formed intimate heterojunctions, facilitating charge transport at their interfaces. Under visible-light, ZFO/WO3 composites demonstrated outstanding catalytic activities for decomposing isopropyl alcohol (IPA) in the gas phase and salicylic acid (SA) in aqueous solution. In particular, the amount of CO2 evolved in 2 h during decomposition of IPA was 24.7 ppmv, which was 3.0 times that produced using typical nitrogen-doped TiO2 (N-TiO2). Moreover, its degradation rate constant of SA in the presence of ZFO/WO3 was (similar to)7 times that of N-TiO2. It was determined that center dot OH and center dot O-2-radicals were the major active species responsible for oxidation reactions, suggesting that the photocatalytic reactions of ZFO/WO3 occurred via Z-scheme mechanism.