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

Abstract Dark red ZnFe 2 O 4 (ZFO) nanoparticles (NPs) of ˜9 nm size and pale yellow WO 3 nanowire bundles (NWBs) with high porosity were prepared by hydrothermal reactions, respectively, and coupled to form novel ZFO/WO 3 heterojunctions. Tiny ZFO NPs and highly porous WO 3 NWBs successfully formed intimate heterojunctions, facilitating charge transport at their interfaces. Under visible-light, ZFO/WO 3 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 CO 2 evolved in 2 h during decomposition of IPA was 24.7 ppmv, which was 3.0 times that produced using typical nitrogen-doped TiO 2 (N-TiO 2 ). Moreover, its degradation rate constant of SA in the presence of ZFO/WO 3 was ˜7 times that of N-TiO 2 . It was determined that •OH and •O 2 - radicals were the major active species responsible for oxidation reactions, suggesting that the photocatalytic reactions of ZFO/WO 3 occurred via Z-scheme mechanism.