Preparation And Photocatalytic Reduction Of CO₂ Performances Of Pt/Bi₄Ti₃O₁₂/N-ACSs

Global warming and energy crisis caused by CO₂ from burning fossil energy have become two major problems restricting social development.Solar-semiconductor-driven CO₂ reduction,as one of the important research directions of new energy development,aims to convert clean renewable solar energy into chemical energy at lower,realizing CO₂ and H₂O as reactants to produce high-value hydrocarbons,which can not only reduce CO₂ content in the atmosphere,but also realize carbon resource utilization and alleviate energy shortage.Designing an efficient photocatalytic system is the core issue of this technology,and the adsorption and activation of reactant CO₂,the rapid recombination of photo-generated carriers,and the ability to respond to sunlight are still the main obstacles to current research.Based on this,this work takes Bi₄Ti₃O₁₂,a layered Bi-based semiconductor material,as the research subject,and selects activated carbon spheres（ACSs）as CO₂ adsorption carrier and electron transfer acceptor.Meanwhile,surface modification of the ACSs is carried out to create CO₂ adsorption and activation site.In addition,based on the Bi₄Ti₃O₁₂/N-ACSs composite catalyst,the local surface plasmon resonance effect and electron trapping characteristics of the noble metal Pt are used to further expand the photoresponse range,suppress the recombination of electron-hole pairs,and construct Pt/Bi₄Ti₃O₁₂/N-ACSs ternary composite photocatalyst with good photo-response ability,CO₂ adsorption capacity and photo-generated carrier separation ability.The specific research contents are as follows:（1）Nitrogen-modified activated carbon spheres（N-ACSs）was obtained by using urea as a nitrogen source and co-polymerization with formaldehyde in the suspension polymerization process,then Bi₄Ti₃O₁₂ was successfully loaded on the surface of N-ACSs by impregnation method.TG,FTIR,XPS and EA confirmed the successful introduction of nitrogen in the activated carbon spheres.XRD,SEM,EDS,N₂ adsorption/desorption curves and CO₂adsorption curves were used to analyze the crystal structure,microscopic morphology,pore structure properties and CO₂ adsorption capacity of Bi₄Ti₃O₁₂/N-ACSs,and it was proved that the CO₂ adsorption capacity of N-ACSS as the carrier was nearly 15 times higher than that of pure Bi₄Ti₃O₁₂.Compared with Bi₄Ti₃O₁₂ and Bi₄Ti₃O₁₂/ACSs under simulated sunlight,Bi₄Ti₃O₁₂/N-ACSs exhibited the highest photocatalytic reduction performance of CO₂（17.84μmol/g/h）.The enhanced activity mechanism of Bi₄Ti₃O₁₂/N-ACSs was proposed by means of assisted photoelectric analysis,PL,SPV and In-situ FTIR.The proper conduction band position of Bi₄Ti₃O₁₂ provides the basis for the reaction.The inherent microporous structure of millimeter N-ACSs increases the adsorption of CO₂,and it also acts as an electron acceptor to inhibit the recombination of photogenerated electron-hole pairs.Nitrogen rich surface modification is more conducive to the adsorption and activation of acidic CO₂,ultimately enhances the photocatalytic activity.（2）The Pt loading can be effectively controlled by changing the addition amount of H₂PtCl₆ in the solution during the process of photodeposition.With the theoretical loading increasing from 0.5 wt.%to 2.5 wt.%,1.5 wt.%Pt/Bi₄Ti₃O₁₂ showed better photocatalytic activity（16.41μmol/g/h）.The actual Pt loading,valence state,crystal structure and microstructure were determined by EA,XPS,XRD and TEM,then Pt/Bi₄Ti₃O₁₂ was wrapped on the surface of N-ACSs and the activity was further improved（19.80μmol/g/h）;TEM confirmed the existence of Pt.Combined with UV-visible diffuse reflectance spectroscopy,N₂adsorption/desorption curves,CO₂ adsorption curves to analyze the optical properties,pore structure properties and CO₂ adsorption capacity of Pt/Bi₄Ti₃O₁₂/N-ACSs.The mechanism of Pt promoting activity enhancement was proposed by assisting photoelectric and PL analysis:1)the surface plasmon resonance effect of noble metal Pt improves the optical response ability;2)the Pt with high power function can effectively capture electrons and reduce the photogenic electron-hole pairs recombination.