Study On UV-induced Preparation Of Layered Bismuth-based Materials And Photocatalytic CO₂ Reduction Performance

In response to the policy of"carbon peaking and carbon neutrality",the conversion and utilisation of CO₂ is of great importance for green and low-carbon energy development.Photocatalytic technology is a green way to convert solar energy into chemical energy to reduce CO₂ into high value-added chemical fuels,solving the current energy shortage problem on the one hand,and alleviating the greenhouse effect caused by CO₂ emissions on the other hand,and fundamentally turning waste into treasure.In recent years,layered bismuth-based（LBB）materials have attracted the attention of researchers due to their unique layered crystal structure,diverse composition,rich atomic coordination and unique hybrid electronic band structure.BiOCOOH is a new type of layered bismuth-based photocatalyst that offers photocatalytic efficacy with less potential risk to the environment due to its"green"C,H and O elemental composition.Therefore,BiOCOOH in layered bismuth-based materials was chosen as the main target of this paper,and its photocatalytic performance was enhanced by two modifications:heterostructure construction and UV irradiation.（1）A 3D nanoflake shaped BiOCOOH was prepared by hydrothermal method,and its photocatalytic CO₂ reduction performance was tested by compounding with different molar ratios of g-C₃N₄ materials to construct S-scheme heterojunctions.The results showed that the photocatalytic performance of the composite（CNB）with a molar ratio of 1:1 between BiOCOOH and g-C₃N₄ was optimal.It was found that the S-scheme heterojunction formed by BiOCOOH and g-C₃N₄ expanded the range of BiOCOOH photoresponse,promoted the separation and transfer of photogenerated carriers,and improved the photocatalytic CO₂reduction activity.（2）On the basis of the above study,CNB was irradiated with UV light for different times.The results showed that the CO₂ reduction efficiency of CNB-10 was further improved,and the yield and selectivity of CO reached 71.96μmol g^-1 and 51.93%,respectively.Analytical characterization by SEM,HRTEM,XPS and EPR illustrated that UV irradiation introduced oxygen vacancies on the surface of BiOCOOH,which provided more active sites for the catalytic reaction and further effectively promoted the photocatalytic CO₂ reduction reaction.（3）BiOCOOH was irradiated with UV light for different times and its photocatalytic CO₂reduction performance was evaluated.The results showed that the sample irradiated with UV light for 50 min（B-50）exhibited superior performance with a cumulative CO yield of 88.84μmol g^-1,which was four times that of the original BiOCOOH,and a CO selectivity of 100%.Characterisation by XRD,SEM,TEM,XPS and EPR showed that BiOCOOH was photoreduced to OVs-Bi/Bi₂O₂CO₃.It was found that the presence of oxygen vacancy defect energy levels and Bi nanoparticles enhanced the separation migration efficiency of photogenerated carriers.Thus,the UV-induced generation of oxygen vacancies and the Bi surface plasmon effect jointly promote the CO₂ reaction.