Construction of ternary rGO/1D TiO2 nanotubes/3D ZnIn2S4 microsphere heterostructure and mutually-reinforcing synergy for high-efficiency H2 production photoactivity under visible light

The novel ternary reduced graphene oxide/1D TiO2 nanotubes/3D ZnIn2S4 microspheres (rGO/TiO2/ZIS) heterostructured photocatalyst with high-efficiency H-2 production capacity under visible light illumination is designed and prepared in this work. In rGO/TiO2/ZIS system, the 1D TiO2 nanotubes are tightly inserted in the interspace of flower-like ZnIn2S4 microspheres, which are further covered by rGO, leading to an intimate contact among ZnIn2S4, TiO2 and rGO. The exquisite design of rGO/TiO2/ZIS makes it possess remarkable superiority in photocatalysis. Firstly, the unique 3D microsphere structure of ZIS increases the surface area and visible light absorption ability caused by their unique hollow structure. More importantly, the matched CB and VB positions between ZIS and TiO2 contribute to separate photogenerated holes and electrons of ZIS efficiently under visible light; then, the separated electrons on TiO2 are further transferred to rGO due to the superior-strong electron attracting ability of rGO. At last, the thoroughly suppressing recombination of photogenerated holes and electrons is achieved by the mutually-reinforcing synergy among ZIS, TiO2 and rGO, and thus the hydrogen generation capacity of ZIS is significantly enhanced. The H-2 production amount and rate of rGO/TiO2/ZIS (2.0 wt% rGO and 50 wt% ZIS) after 10 h are 4623 mu mol/g and 462.3 mu mol/g/h, respectively, which is 71.1 times of pristine TiO2 and 1.6 times of ZIS under the same condition. The apparent quantum yield of rGO/TiO2/ZIS (2.0 wt% rGO and 50 wt% ZIS) in 10 h is about 0.6888%. This excellent photocatalytic performance is ascribed to the mutually-reinforcing synergy among ZIS, TiO2 and rGO, which can be confirmed by X-ray photoelectron spectroscopy, photoelectrochemical measurements and photoluminescence spectrum. Based on the photo catalytic and characterization results, the corresponding mechanism is proposed.