| Photocatalytic CO2 reduction technology is a kind of green means to reduce CO2into a variety of products.As a visible light responsive polymer,g-C3N4 has attracted extensive attention due to its layered structure,high chemical and thermal stability,low cost and easy preparation.However,the CO2 conversion rate of single g-C3N4 is usually very low,which is mainly limited by two factors:the lack of visible light absorption caused by medium band gap and the low quantum efficiency caused by rapid charge recombination.These problems have certain limitations on its photocatalytic performance.In order to improve its photocatalytic performance,the g-C3N4 composite photocatalyst（Ag-g-C3N4/BN-C）and the g-C3N4 photocatalyst modified by biomass-carbon and Sn S2 were prepared respectively for the photocatalytic reduction of CO2.The following is the concrete research content:（1）A novel Ag-doped g-C3N4/biomass-derived carbon composite with hollow bird’s nest-shape（Ag-g-C3N4/BN-C）was designed and synthesized by means of a simple yet effective one-step pyrolysis method.After 5h irradiation without addition of any sacrificial reagents and photosensitizers,the CO maximum yield is 166.5μmol·g-1.This could be due to the conductive quasi-spherical hollow structure of BN-C doubles the specific surface area with multiple reflections of light,providing abundant active sites and more utilization efficiency of light energy.Furthermore,the highly-dispersed Ag with the surface plasmon resonance（SPR）effect acts as a significant cocatalyst not only to efficiently trap the photogenerated electrons from g-C3N4 to boost the separation of photogenerated electrons but also to produce additional active“hot electrons”.Therefore,the efficiency of carrier transfer and separation can be improved,and the active site of surface reaction can be increased,thus significantly increasing the CO yield.（2）The C/g-C3N4/Sn S2 composite photocatalyst modified by biomass carbon was prepared by calcination and hydrothermal method.The materials prepared were characterized by different test methods.The activity of the catalyst was evaluated by the yield of CO from photocatalytic reduction of CO2.Under visible light irradiation,the C/g-C3N4/Sn S2 photocatalyst showed better CO2 reduction ability,and the yield of CO reached 204.29μmol g-1 after 5h,which was 5.5 times of that of pure g-C3N4. The C/g-C3N4/Sn S2 photocatalyst combined with biomass carbon has a higher photocatalytic activity.The introduction of biomass carbon can increase the active sites of the reaction.Meanwhile,the C/g-C3N4/Sn S2 Z-type heterojunction structure formed can provide sufficient interface contact for charge migration,thus improving the photocatalytic activity... |
