Rational Design And Photocatalytic Performance Of In₂O₃ Based Composites

The massive consumption of fossil fuels and the excessive emission of carbon dioxide have caused increasing concerns about energy shortages and climate change.Driven by sustainable solar energy,the use of photocatalytic technology to split water to generate hydrogen energy and reduce the carbon dioxide into hydrocarbon fuels are effective strategies to solve these problems.Indium oxide（In₂O₃）is an important semiconductor material.Due to its unique optical properties and electronic configuration,it has shown unique application prospects in the field of photocatalysis.However,the wide band gap of In₂O₃（2.6-3.6 e V）limits the effective use of sunlight,and the electron-hole pairs generated by light excitation also have a higher recombination rate.In order to improve the efficiency of In₂O₃ photocatalytic hydrogen production and the selectivity of carbon dioxide reduction,researchers have proposed measures such as construction of heterostructures,precious metal deposition,and metal/nonmetal doping.Although the traditional typeⅡIn₂O₃/In₂S₃heterojunction structure improves the photocatalytic hydrogen production efficiency,based on its charge transfer mechanism,it undoubtedly aggravates the photocorrosion of In₂O₃/In₂S₃ heterostructure materials.Depositing precious metal Pt on In₂O₃ can improve the selectivity of photocatalytic reduction of CO₂ to CH₄,but the high cost of metals severely limits the popularization and application of this technology.Based on the above problems,this paper proposes two effective ways to modify In₂O₃,rationally design In₂O₃/O_V/In₂S₃ and RGO/In₂O₃ composite photocatalytic materials,and achieve the purpose of improving the performance of photocatalytic water splitting and reducing carbon dioxide.The specific content is as follows:（1）A new type of In₂O₃/O_V/In₂S₃ photocatalyst was prepared by in-situ deposition method.The structure is a Z-scheme photocatalytic system with double close contact interfaces.In this system,oxygen vacancies grow in situ on In₂O₃ and can be used as an electron relays at the interface of the two semiconductor components of In₂O₃ and In₂S₃,and the in-situ generation of In₂S₃ also ensures that the two semiconductor components are in close contact.Such a double close contact interface maintains the continuity of the composition,so that the electron transfer rate of In₂O₃ to In₂S₃ through oxygen vacancies is significantly accelerated,which not only improves the photocatalytic efficiency but also inhibits the occurrence of photocorrosion.XPS and precious metal deposition prove that the charge transfer path of In₂O₃/O_V/In₂S₃ photocatalyst conforms to the Z-scheme mechanism.The results of photocurrent and fluorescence indicate that the rapid separation and transfer of carriers are the key to improving the activity of photocatalytic hydrogen production.The photocatalytic hydrogen production experiment shows that the rate of In₂O₃/O_V/In₂S₃ is 5.4 and 2.5 times that of In₂O₃/O_V and In₂S₃,respectively,and shows stable hydrogen production performance after the 14 h cycle experiment.In this work,an efficient and stable Z-scheme In₂O₃/O_V/In₂S₃ photocatalytic system was successfully designed and constructed based on the electronic relay function of oxygen vacancies,which provid research ideas for the modification of other oxide/sulfide photocatalysts.（2）The RGO/In₂O₃ composite photocatalytic material was prepared by a simple hydrothermal method and applied to the photocatalytic carbon dioxide reduction reaction.FTIR,TEM,XPS and other structural characterizations show that there is a strong chemical interaction between In₂O₃ and RGO.The electrons of In₂O₃ can be transferred to RGO,which significantly increases the surface charge density of RGO.On the other hand,the surface hydroxyl groups of RGO can induce the orientation of H protons.Therefore,the designed and synthesized RGO/In₂O₃ composite photocatalyst can effectively increase the surface charge density and proton concentration of the catalyst,which is beneficial to the multi-electron/proton coupling reaction of CO₂→CH₄.Under simulated sunlight,the RGO/In₂O₃ composite photocatalyst catalyzes CO₂ and H₂O to generate CH₄ at a rate of 0.025μmol/g/h and a selectivity of 76.6%,which is significantly better than the 0.014μmol/g/h and39.2%of single In₂O₃.The photocurrent and fluorescence detection results show that the complex has higher carrier separation efficiency.Furthermore,in-situ infrared technology is used to analyze and detect the intermediate species and products of RGO/In₂O₃ and In₂O₃ in the photocatalytic CO₂ reduction process,and the photocatalytic CO₂→CH₄ reaction path is proposed.This work proposes a new method to enhance the selectivity of photocatalytic CO₂ reduction to CH₄,reveals the role of RGO as an electron and proton trap,and is expected to replace precious metals in the future.In this work,we provide a reference for the development of high-performance photocatalytic materials for CO₂ reduction.