Preparation And Performance Of Indium-based Sulfide Composite Photocatalyst

Photocatalytic splitting water hydrogen production is the key technology to solve energy shortage and environmental pollution.Because TiO₂ has the advantages of chemical stability,non-toxicity and low price,it has become the most ideal photocatalyst.However,TiO₂ has a large band gap?3.2 eV?and can only absorb ultraviolet light.In this paper,three indium-based sulfide semiconductors are used to modify TiO₂,and In₂S₃/TiO₂,ZnIn₂S₄/TiO₂ and CaIn₂S₄/TiO₂composite photocatalysts were constructed.The crystal structure,micromorphology,and optical characteristics of the catalysts were characterized by XRD,EDX,SEM,TEM and UV-vis absorption spectra.The photocatalytic activity of three composite materials was investigated by photoelectrochemical test and photocatalytic degradation of methyl orange.The details are as follows:1.A simple hydrothermal method was used to synthesize TiO₂ nanosheet arrays on the FTO substrate,and then hydrothermally grown In₂S₃ nanoparticles to form In₂S₃/TiO₂ composite films.The effects of hydrothermal reaction time on the light absorption and photoelectric properties of the films were studied.The results show that the current density of In₂S₃/TiO₂ composite films with a hydrothermal reaction time of 120 min is the largest,reaching 0.25 mA·cm^-2,which is 4.2times that of TiO₂ nanosheets.The mechanism of charge transfer is discussed.2.The ZnIn₂S₄/TiO₂ composite thin film was prepared by two hydrothermal methods.By adjusting the reaction time to change the thickness of the ZnIn₂S₄ nanosheets,and then adjusting the band gap width of the composite film.This further enhances the light absorption intensity in the visible light region and improves its photoelectrochemical performance.The results show that the ZnIn₂S₄ nanosheets and TiO₂ nanosheets form a heterostructure.It provides more paths for the transmission of photo-generated carriers and reduces the probability of carrier recombination.Thus,the photocurrent density is improved.3.A new visible light-driven CaIn₂S₄/TiO₂ composite photocatalyst was synthesized,and the TiO₂ microspheres were uniformly coated with CaIn₂S₄ nano-flowers to build a heterostructure.The optimal photocatalytic activity was found by changing the TiO₂ loading.Photocatalytic activity of CaIn₂S₄/TiO₂ composites was evaluated by photocatalytic degradation of MO.The results showed that the best degradation rate of CaIn₂S₄/TiO₂-0.05 within 30 min was 97%.Through a series of characterization analysis,it is known that the improvement of optical properties is conducive to the generation of more photo-generated carriers,and then the heterostructure of CaIn₂S₄/TiO₂ is used to achieve carrier separation and transfer.Finally,the degradation ability of the catalyst is improved.