Preparation And Photocatalytic CO₂ Reduction Performances Of Bi₂MO₆（M=W,Mo）/ACSs

Converting CO₂ into high value-added chemicals and fuels via solar semiconductor photocatalysis technology can not only reduce CO₂ emissions and solve greenhouse effect in environmental issue,but also realize the cyclic utilization of carbon resource on the basis of renewable energy,which has become one of important research orientations for the development of new energy in the future.However,it is difficult for a single photocatalyst to take into account good light response,CO₂ adsorption and carrier separation capability.Therefore,it will be significant scientifically for the design and development of an efficient photocatalyst system to achieve CO₂photoreduction and improve the directional conversion and yield of CO₂photoreduction products.In the thesis,based on the intrinsic material properties and CO₂photoreduction reaction principle,the Bi₂MO₆（M=Mo,W）photocatalysts with reasonable band gap structures are firstly selected,and satisfy with the scientific utilization of sunlight and the coordination between valence-conduction band potentials and reactant potentials.Secondly,the activated carbon spheres（ACSs）,with high CO₂ adsorption capacity and large specific surface area,are chosen to support high-efficiency Bi₂MO₆photocatalysts and optimize the separation efficiency of photogenerated electron-hole pairs,constructing the Bi₂MO₆/ACSs photocatalyst system with highly efficient solar light response,CO₂ adsorption and CO₂ reduction performances.The main research contents are as follows:（1）Preparation and CO₂ photoreduction performances of Bi₂WO₆/ACSs.Firstly,the phenolic resin spheres are prepared by suspension polymerization and further carbonized and activated to obtain ACSs supporter with good sphericity.In the process of hydrothermal synthesis of Bi₂WO₆,the customized carrier ACSs is introduced to prepare Bi₂WO₆/ACSs composite photocatalyst.Secondly,XRD,SEM,UV-Vis DRS,PL,BET and CO₂adsorption isotherms are used to investigated contrastly the phase structures,chemical compositions,structural morphologies,optical absorption capacities,photoelectric properties and CO₂ adsorption activities of pure Bi₂WO₆ and Bi₂WO₆/ACSs samples.Thirdly,the photocatalytic CO₂ reduction performances and cyclic stability of Bi₂WO₆ and Bi₂WO₆/ACSs are studied for comparations under the simulated sunlight irradiation.Lastly,the enhanced mechanism of photocatalytic CO₂ reduction activity for Bi₂WO₆/ACSs is prop,which is should be the synergistic effects between Bi₂WO₆,with the energy band structure and excellent redox potentials of,and ACSs,with good CO₂ absorption capacity and electrical conductivity.Our findings indicate that ACSs can be used as an excellent support for the construction of high efficiency CO₂ photoreduction catalyst system.（2）CO₂ photoreduction performances of ACSs assisting 3D Bi₂MoO₆microspheres.Accorrding to excellent CO₂ adsorption and electronic conductivity of ACSs,the photocatalyst system of ACSs assisted 3D Bi₂MoO₆ microspheres is designed.First of all,3D Bi₂MoO₆ microspheres are loaded on the surface of ACSs via simple and mild impregnation method so as to obtain Bi₂MoO₆/ACSs samples.In addition,the analysis results of XRD and SEM show that Bi₂MoO₆ crystal phase is good and uniformly loaded on the surface of ACSs.The structure and particle size of Bi₂MoO₆ have no obvious change before and after loading ACSs.Then,the XPS,EDX,DRS,BET,CO₂adsorption isotherms,EIS and transient photocurrent of the samples are analyzed and compared in detail.Finally,the photocatalytic CO₂ reduction performances of samples are evaluated under the simulated sunlight irradiation,and the Bi₂MoO₆/ACSs reveal excellent activity,selectivity and stability of CO₂ photoreduction.The CO yield of Bi₂MoO₆/ACSs is 1.8 times than that of pure Bi₂MoO₆,and after four cycles,one of less than 10%only reduces.The photocatalytic CO₂ reduction mechanism of Bi₂MoO₆/ACSs is proposed.Our findings reveal that millimeter grade ACSs can effectively improve the CO₂ reduction activity and stability of Bi₂MO₆ catalyst,which should be expanded to support other Bi-based semiconductor materials and the construction of other powder catalyst systems,providing good basic scientific data for promoting the engineering research of solar photocatalytic CO₂ green conversion.