Preparation And Photocatalytic Properties Of Porous TiO₂ And Its Cu_xO Composites

Photocatalytic water splitting for hydrogen production is effective way to solve energy and environmental problems.Among the numerous photocatalysts,TiO₂ has been extensively studied due to its excellent redox ability,good chemical stability and safety.However,as a photocatalyst,TiO₂ has the characteristics of narrow light absorption range,fast photocarrier recombination,small specific surface area and few active sites,which limit its further application and development.In view of this,this paper designs a scheme to improve and enhance the photocatalytic activity of TiO₂ from the preparation of TiO₂and its coupling with narrow-bandgap semiconductors.That is:firstly,porous TiO₂ was prepared by calcining MIL-125 to increase its specific surface area and reactive sites;then,porous TiO₂ was coupled with narrow-bandgap semiconductor to improve its light absorption ability and photogenerated carrier separation ability.The main research contents and results are as follows:（1）Porous TiO₂ was prepared by calcination using Ti-based MOF MIL-125 as the precursor.The structures and optical properties of the precursors and calcined products were analyzed by means of XRD,FT-IR,UV-vis DRS,and N₂ adsorption and desorption.The research shows that the light absorption range of the calcined products increases significantly,and the crystal phase of the material also changes with the temperature.With the increase of calcination temperature,the specific surface area of the derivatives gradually decreased,and the average pore size gradually increased.When the calcination temperature is 380℃,the obtained TiO₂ is pure anatase phase and has a large specific surface area(122.2 m²·g^-1),which is suitable as a catalyst for photocatalytic hydrogen production.（2）With pure anatase MT-380 as the substrate,porous Cu₂O/TiO₂ and CuO/TiO₂composites were prepared by glucose reduction method and chemical precipitation method,respectively.The structure and morphology of the materials were analyzed by XRD,XPS,SEM,TEM and other characterization methods.The change of the specific surface area of the samples was analyzed by the measurement of N₂ isotherm adsorption-desorption curves,and the results showed that the composites all had a high specific surface area and rich mesoporous structure.UV-Vis DRS,PL,EIS and photocurrent tests showed that the loading of Cu₂O and CuO not only enhanced the light absorption ability of the composite,but also improved the separation and transport efficiency of carriers.（3）The photocatalytic hydrogen production activity and stability of Cu₂O/TiO₂ and CuO/TiO₂ composites were tested under UV-visible light irradiation with triethanolamine as sacrificial agent.The photocatalytic hydrogen production test results show that the photocatalytic performance of the composites is significantly improved.Among them,the photocatalytic hydrogen production rate of 4%Cu₂O/MT-380 is as high as 14.39 mmol·h^-1·g^-1,which is 9.6 times that of pure TiO₂ and 24.8 times that of Cu₂O,respectively.The hydrogen production rate of 1%CuO/MT-380 is 10.05 mmol·h^-1·g^-1,which is 7 times that of pure TiO₂ and 17.8 times that of CuO and has good stability.The energy band structures of Cu₂O,CuO and TiO₂ were estimated by MS and UV-vis DRS tests,and the photocatalytic mechanism of Cu₂O/MT-380 and Cu₂O/MT-380 composites was further explored.