Preparation Of Transition Metal Modified Composite Semiconductor Materials And Its Photocatalytic Research Of C0₂ Conversion

Environmental pollution and energy shortages have been a serious threat to the survival and development of mankind,and the major problems to be solved urgently in the 21st century.CO2,as one of the main gases leading to the greenhouse effect,has caused severe damages on the future human living environment and the Earth's ecosystem Therefore,the use of CO2 as raw material to synthesize high value-added organic matter has become an important research direction of CO2 utilization.The photocatalytic reduction of CO2 to hydrocarbon raw materials using photocatalyst with high catalytic performance is also of great significance for environmental protection and energy reutilization.The BiVO4/g-C3N4 photocatalyst and the noble metal Au,Pt and Pd supported BiVO4/g-C3N4 composite photocatalyst were prepared by mixed calcination and photodeposition methods respectively,and the Z-type Au-BiVO4/g-C3N4 catalyst was prepared by changing the steps.The catalysts were characterized by X-ray diffraction(XRD),UV-Vis,SEM,TEM,FT-IR,PL and XPS to analysis the elemental composition,morphology and optical properties.Then the photocatalytic effect of the photocatalytic reduction of CO2 into CH3OH reaction was investigated.In addition,the effects of catalyst dosage,irradiation time,noble metal loading,reaction pressure,sacrificial agent concentration,NaOH concentration and the reaction mechanism on the photocatalytic reduction of CO2 were also investigated.The results show that BiVO4/g-C3N4 photocatalyst prepared by calcination has good visible light response,and 50wt%BiVO4/g-C3N4 shows the best photocatalytic activity.The noble metal Au,Pt and Pd can be well supported on the BiVO4/g-C3N4 by photoprecipitation,and the BiVO4-Au/g-C3N4 catalyst shows the best photocatalytic performance among them.When the reaction time was 5h,the reaction pressure was 5 MPa,NaOH concentration was lmol/L and the concentration of Na2SO3 was 0.1mol/L,the photocatalytic reduction of CO2 to produce CH3OH had the best effect,and CH3OH yield was 19.76?mol·h-1·g-1,2.47 times as high as that of the 50wt%BiVO4/g-C3N4 and 1.49 times as high as that of the 1 wt%Au-50wt%BiVO4/g-C3N4 respectively,which indicates that the efficiency of photocatalytic reduction of CO2 is improved remarkably.