Study On CO₂ Catalytic Mechanism Of Lead Zirconate Titanate Piezoelectric Crystal Supported Catalyst

The catalytic conversion of carbon dioxide has become research focus in recent years.The built-in electric field generated by materials with spontaneous polarization can promote the separation of photo-generated electron holes of semiconductor catalysts,so it is considered to be an effective way to improve the catalytic conversion efficiency of CO₂.In this thesis,Pb Zi_0.52Ti_0.48O₃（PZT）semiconductor catalyst with perovskite structure is selected as the main research object.Using its own great polarization characteristics,the polarization conditions are adjusted by controlling the morphology and changing the pressure and temperature.To investigate the catalytic conversion performance and catalytic mechanism of PZT catalyst and its composite catalyst under polarized conditions.（1）PZT with different morphology is prepared by hydrothermal method,the influence of the concentration of mineralizer KOH and the amount of lead source on the morphology of PZT is studied.XRD,Raman,SEM are used to characterize the phase composition and morphology of PZT,and DRS is used to test its light absorption capacity.When the concentration of KOH is 2mol/L,the crystallinity of PZT is relatively low,and the morphology is irregular;When the concentration of KOH reaches4mol/L,PZT forms a tetragonal morphology,and as the concentration of KOH rises further,hydrothermally synthesized PZT gradually changes from square to spherical.By adding an appropriate excess lead source,the square shape PZT is transformed into a more uniform cubic shape.The results of electrochemical tests show that the photoelectric current of cubic PZT has a significant improvement over the square PZT,and it has strong carrier separation ability.The experimental results of PZT catalytic performance show that the cubic appearance of PZT had a certain hydrogen production capacity.Under normal pressure and high temperature,the hydrogen yield is 2.04μmol·h^-1·g^-1,and no CO₂ reduction products are detected in the experiment.（2）Based on the cubic morphology PZT research,PZT/g-C₃N₄ composite catalysts loaded with different ratios of g-C₃N₄ are prepared.The phase composition and morphology of the PZT/g-C₃N₄ composite catalyst are characterized by XRD,Raman and SEM,and DRS is used to test the light absorption capacity of the composite catalyst loaded with different proportions of g-C₃N₄.The experimental results show that the morphology of the PZT/g-C₃N₄ composite catalyst shows obvious agglomeration with the increase of g-C₃N₄ loading ratio.The light absorption capacity of the composite catalyst has been improved to a certain extent.The electrochemical test results show that the photocurrent intensity of the PZT/g-C₃N₄ composite catalyst had a certain attenuation relative to PZT,but it increases with the increase of the g-C₃N₄ loading ratio.The catalytic performance test results show that the hydrogen production capacity of the PZT/g-C₃N₄ composite catalyst has been further improved.When 10%g-C₃N₄was loaded,the hydrogen yield was 7.16μmol·h^-1·g^-1 under normal pressure and high temperature,no CO₂ reduction product is detected in the experiment.（3）Cu₂O/PZT composite catalysts with different ratios of Cu₂O are prepared.The phase composition and morphology of Cu₂O/PZT composite catalysts are characterized by XRD,Raman and SEM.The light absorption capacity of Cu₂O/PZT composite catalysts with different ratios is tested by DRS.The experimental results show that the loading of Cu₂O do not have much effect on the morphology of the Cu₂O/PZT composite catalyst,but the light absorption capacity is significantly improved.The results of electrochemical tests show that the photocurrent of Cu₂O/PZT composite catalyst was improved relative to PZT/g-C₃N₄,and as the proportion of Cu₂O load increases,the photocurrent further increases.The catalytic performance test results show that a certain amount of CO₂ reduction product CH₄ is detected in the catalyst loaded with 5%Cu₂O.Under high temperature and high pressure conditions,the CH₄yield is 24.53μmol·h^-1·g^-1;When the loading ratio of Cu₂O reached 10%,both CO and CH₄ are detected in the reduction product.Under the condition of high temperature and normal pressure,the CO yield is 25.55μmol·h^-1·g^-1,and the CH₄ yield is 55.2μmol·h^-1·g^-1.