Preparation And Photocatalytic Properties Of Indium Sulfide-based Photocatalysts

Photocatalytic technology has attracted the attention of researchers from all over the world for nearly half a century because of its environmental friendliness,mild response conditions,solar-driven,high efficiency and safety.Many studies have proved that semiconductor photocatalysts have excellent oxidation reduction ability under the irradiation of light,and have shown satisfactory performance in the fields of photodegradation of pollutants,photoreduced carbon dioxide and photoreduced ammonia.Nowadays,as a gentle and convenient environment-friendly technology,researchers have found a number of semiconductor materials that can be applied to photocatalytic reactions,and modified them by means of doping,materials compounding,introduction of vacancies,noble metal deposition and so on.As a semiconductor material with visible light response,indium sulfide has been widely used in the field of photocatalytic technology due to its narrow band gap,excellent photosensitivity and low toxicity.However,indium sulfide has some disadvantages such as easy recombination of photogenerated electron and hole,and low quantum efficiency.In order to make full use of the advantages of In₂S₃and further overcome the existing shortcomings to improve its photocatalytic efficiency,various materials based on In₂S₃with different morphologies and modifications through different methods have been reported.Each section of this paper explores the photocatalytic nitrogen fixation properties of indium sulfide,which are introduced sulfur vacancies and compounded with semiconductor and non-semiconductor materials,and is divided into three parts:In the first part,using MOF material,MIL68-（In）as the precursor and template of indium sulfide,the indium sulfide tubes with hollow and mesoporous structure are prepared by a solvothermal method.It is then calcined in nitrogen atmosphere to introduce different concentrations of sulfur vacancies into indium sulfide.The characterization of origin indium sulfide and with different concentrations of sulfur vacancies were characterized,and the effect of sulfur vacancies on the photocatalytic nitrogen fixation properties of the material was investigated.Using MOF as a template can make good use of its porous properties to expand the surface area of the catalyst,thus increasing the contact area of the catalyst with the reaction medium and shortening the distance of the carrier transmission during the photocatalytic reaction,making photocatalytic reactions easier to occur.When light irradiate on the indium sulfide tubes,the hollow structure enables it to reflect and refract light inside the tube,making full use of the light energy.After introducing sulfur vacancies with different concentrations in the indium sulfide,the optical and photocatalytic properties of the obtained materials were significantly improved in different degrees compared to samples without the sulfur vacancies,which proved that when sulfur vacancies existed in the material,the effect of improving the photocatalytic properties of the material could be achieved.However,only when the sulfur vacancies concentration is in an appropriate range can the photocatalytic properties of indium sulfide be improved optimally.Among them,SV-In₂S₃-200photocatalytic nitrogen fixation performance is the best,photocatalytic nitrogen fixation rate of 52.49μmol·h^-1·g^-1.In the second part,the MOF material MIL68-（In）is prepared by solvent thermal method,and using it as a template for calcination in nitrogen atmosphere to prepare indium oxide with carbon as the substrate.Subsequently,the solvent thermal method was used again to convert indium oxide into indium sulfide,obtained indium sulfide with carbon as the substrate.After converting the indium oxide in the sample into indium sulfide,the photocatalytic properties of the material were significantly improved,and the optical properties of the material were greatly improved by carbon.Compared with the C-In₂O₃sample,the C-In₂S₃sample was not only has better photo absorption,lower electrons-holes compounding rate,stronger photoresponse,etc.,but also has higher photocatalytic nitrogen fixation efficiency under the same reaction conditions.The results show that under the same conditions,the conversion of indium oxide into indium sulfide can improve its photocatalytic properties,while the optical properties of indium sulfide added carbon as the substrate can also be improved as 41.12μmol·h^-1·g^-1.In the third part,the carbon nitride with a flaky structure is first prepared,the carbon nitride and indium sulfide are prepared by a solvothermal method.The photocatalytic properties of different composite proportions of materials are investigated,and the pristine samples of the two materials are compared to verify the improvement of the photocatalytic properties of the composite structure to the material.The experimental results show that the photocatalytic nitrogen fixation performance of composite materials is stronger than that of origin In₂S₃and C₃N₄,in which when the ratio of In₂S₃ and C₃N₄is 1:1,the photocatalytic nitrogen fixation efficiency of the sample is the highest,and the results show that the composite of In₂S₃ and C₃N₄ material can significantly improve its photocatalytic properties.