Study On The Controllable Preparation And Photocatalytic CO₂ Reduction Performance Of Lead-Free Halide Perovskite Catalysts

The concentration of carbon dioxide（CO₂）in the atmosphere is ever-increasing along with the excessive consumption of fossil fuels,leading to growing energy and climate problems.Mimicking the photosynthesis process of plants,and using solar energy to reduce CO₂ to chemicals over catalysts is one of the ideal ways to achieve carbon neutrality.The photocatalytic CO₂ reduction efficiency is mainly governed by the combination of light absorption efficiency,photogenerated carrier separation efficiency and surface catalytic efficiency of the catalyst.Low-cost metal halide perovskites（MHP）have attracted extensive attention in the field of photocatalysis in recent years due to their good light absorption properties.However,the lack of highly active sites on the surface of MHP catalysts and insufficient separation of photogenerated carriers limit their photocatalytic CO₂ reduction efficiencies.In response to these problems,this thesis achieved a significant improvement in the photocatalytic CO₂ reduction efficiency of MHP-based catalysts through cocatalyst loading and structure modulation.The details are as follows:（1）A series of composite catalysts were successfully prepared by loading cobalt phthalocyanine molecules（Co Pc）with different groups on the surface of conventional lead-free double perovskite Cs₂Ag Bi Br₆ nanosheets（CABB）containing surface ligands through electrostatic attraction.The influence rule of Co Pc with different groups on the efficiency of photocatalytic CO₂ reduction was systematically studied.Compared with pristine Co Pc without substituent,amino-substituted Co Pc（Co TAPc）and carboxyl-substituted Co Pc（Co TCPc）have stronger electronic coupling with CABB and higher charge separation efficiency.Therefore,CABB@Co TAPc and CABB@Co TCPc exhibit significantly improved photocatalytic efficiencies of CO₂ reduction with respect to CABB@Co Pc.The photoreduction CO₂-to-CO yield of CABB@Co TCPc can reach up to 150.1±6.3μmol g^-1 h^-1,which is 8.2 times that of pristine CABB.（2）Considering that the MHP surface ligands would hinder the separation of photogenerated carriers and inhibit CO₂ adsorption,A novel ligand-free and lead-free halide perovskite hollow nanosphere（H-Cs3Sb2Br9）was developed by a template-free in situ conversion method,and employed it as a photocatalyst for CO₂ photoreduction.It is shown that the ligand-free H-Cs3Sb2Br9 has a hollow inner cavity,which can improve the specific surface area,light-harvesting,and CO₂ adsorption capacities,and shorten the carrier migration distance.More importantly,the enrichment of Br vacancies in H-Cs3Sb2Br9 facilitates the exposure of active sites and charge separation,thus significantly enhancing the catalytic performance.Furthermore,the electronic coupling between ligand-free H-Cs3Sb2Br9 and cocatalyst is stronger compared with conventional Cs3Sb2Br9 nanocrystals with surface ligands.In combination with the previously developed binuclear cobalt molecular catalyst,the yield of H-Cs3Sb2Br9 for photocatalytic CO₂ reduction to CO can reach up to 1876.3±12.2μmol g^-1 h^-1,which is 28 times that of traditional Cs3Sb2Br9 nanocrystals,and is also the highest efficiency of MHP-based catalysts.