Formamidinium Lead Bromide Nanocrystals And Titanium Carbide Compistes:Preparation And Research Of Solar-Driven Photocatalytic CO₂ Reduction

Photocatalytic carbon dioxide(CO₂)reduction to renewable fuels is regarded as one of the effective strategies to solve energy issues.Organic-inorganic hybrid perovskite photocatalyst,formidine lead bromide(FAPbBr₃),has been applying in the field of photocatalysis due to its high absorption coefficient and adjustable band gap.However,the efficiency of photocatalytic CO₂ reduction is limited by its drawbacks such as the fast recombination rate of the photogenerated charge carriers and the lack of active sites on the surface.Among the structured two-dimensional(2D)materials,titanium carbide(Ti₃C₂)has been considered as the most promising for co-catalysts.It is ascribed to several advantages such as chemical stability,large specific surface area,excellent electronic conductivity,and abundant active sites.Herein,FAPbBr₃ cubic-and sheet-nanocrystals were prepared,respectively.They were further combined with few-layer Ti₃C₂ to construct Schottky heterojunction photocatalysts.The photocatalytic CO₂ reduction performance was systematically studied,and the following conclusions were drawn:(1)Cubic CsPbBr₃ and FAPbBr₃ quantum dots were prepared by hot injection method,and their photocatalytic CO₂ reduction in three different media were compared.It was found that the two kinds of quantum dots exhibited the excellent photocatalytic performance in the ethyl acetate/deionized water mixture.The photoluminescence intensity of cubic FAPbBr₃ quantum dots has been retained 40%after 520 min illumination(750?W).The intensity of cubic CsPbBr₃ quantum dots decreased to 31%of the initial intensity after 180 min.Under irradiation for 1 h,the CO yield of FAPbBr₃(181.25?mol·g^-1·h^-1)was superior that of CsPbBr₃(11.23?mol·g^-1·h^-1).It was deduced that the charges in FAPbBr₃ could separate and transfer in a long time by the carrier dynamics characterization.Therefore,compared with all inorganic CsPbBr₃ quantum dots,FAPbBr₃ quantum dots are more suitable as catalysts for photocatalytic CO₂reduction.(2)Cubic FAPbBr₃ quantum dots were anchored on Ti₃C₂ nanosheets to construct0D/2D FAPbBr₃/Ti₃C₂ Schottky heterojunction composite via high injection combined with in-situ growth method.In this composite structure,Ti₃C₂ nanosheets not only acted as the electron acceptors to accelerate the separation of excitons,but also supplied specific catalytic sites.Thus,the photocatalytic activity was improved.Upon visible light illumination for 1 h,FAPbBr₃/Ti₃C₂ composite photocatalyst showed significant improvement.The optimal CO yield was 283.41?mol·g^-1·h^-1 with 0.2 mg Ti₃C₂,which was 1.84 times that of the original FAPbBr₃.Besides,the significant improvements on photocurret density(from 0.034 to 0.170?A·cm^-2)and decrease on impedancewere were achieved by the FAPbBr₃/0.2-Ti₃C₂ composite.(3)2D FAPbBr₃ nanosheets were fabricated by changing the ligand ratio and preparation temperature of FAPbBr₃.2D/2D FAPbBr₃/Ti₃C₂ Schottky heterojunction composites were further prepared to increase the contact area between FAPbBr₃ and Ti₃C₂,shorten the transport distance of carriers,and improve the separation efficiency.It was demonstrated that FAPbBr₃ nanosheets were anchored on Ti₃C₂,which not only significantly improved the stability of FAPbBr₃ nanosheets,but also increased the specific surface,accelerated the charges transfer,and increased the carrier density.The results showed that the average CO yield of optimized 2D/2D FAPbBr₃/0.2 mg-Ti₃C₂ was 93.82?mol·g^-1·h^-1,which was 1.25 times that of FAPbBr₃ nanosheets under simulated solar irradiation for 4 h.