Well-designed 3D ZnIn2S4 nanosheets/TiO2 nanobelts as direct Z-scheme photocatalysts for CO2 photoreduction into renewable hydrocarbon fuel with high efficiency

Abstract A 3-dimensional (3D) ZnIn 2 S 4 /TiO 2 Z-scheme system has been designed and constructed for photocatalytic reduction of CO 2 into renewable hydrocarbon fuels without the use of a solid-state electron mediator. The unique 3D morphology, achieved by assembling 2D ZnIn 2 S 4 nanosheets onto 1D TiO 2 nanobelts, not only provides large surface area but also improves the separation and transfer efficiency of photogenerated electrons and holes. The 3D ZnIn 2 S 4 /TiO 2 Z-scheme photocatalysts show excellent light-harvesting properties demonstrated in photocatalytic reduction of CO 2 , resulting in generation of desired hydrocarbons. The CH 4 production rate of the 3D ZnIn 2 S 4 /TiO 2 can reach up to 1.135 μmol g −1  h −1 , which is about 39-times higher than that of bare ZnIn 2 S 4 (0.029 μmol g −1  h −1 ). The enhanced photocatalytic activity is attributed to effective separation of the charge carriers between ZnIn 2 S 4 and TiO 2 through the direct Z-scheme instead of a type-II heterojunction. The photogenerated electrons in TiO 2 nanobelts recombine with the holes in ZnIn 2 S 4 nanosheets, and the unrecombined electrons/holes on different active sites have stronger reduction/oxidation abilities, leading to higher photocatalytic activity for CO 2 reduction.