Design And Construction Of Dye Intercalated Transition Metal Based LDHs Composites And Study On Visible Light Catalytic Reduction Of CO₂

Due to excessive exploitation of energy,energy depletion and environmental issues are becoming increasingly prominent.As the main greenhouse gas,converting CO₂into fuel with added value can solve both of the above problems simultaneously.Therefore,the topic of reducing CO₂has become a hot topic for researchers worldwide.Among them,photocatalysis technology uses clean energy,solar energy,as a driving force,and has the advantages of sustainability and simple operation.It is considered to have great potential in CO₂reduction.In recent years,although scientific researchers have made significant progress in developing luminescent catalysts,there are still problems with the inability of catalysts to utilize visible and near-infrared light and low quantum efficiency,and the efficiency of catalytic products is also difficult to support large-scale industrial applications.Therefore,fully consider the content of each step of photocatalytic reaction,improving light absorption ability,inhibiting photogenerated carrier recombination,and promoting surface reactions are important issues that need to be paid attention to in current photocatalysis research.This thesis focuses on the first two parts of the photocatalysis trilogy,which optimize and modify LDHs in terms of broadening the optical absorption range and improving the separation rate of electron hole pairs,it also explores the performance and mechanism of photocatalytic reduction of CO₂.The main research contents and results are as follows:1.Construction of phycocyanin（PC）sensitized Zn Al LDHs composites and their visible light catalytic reduction of CO₂:PC is a light absorbing substance of blue algae living in the deep sea.Its structure is a tetrapyrrole structure with large conjugated chains.Considering its stability,a series of composite materials with different intercalation ratios of PC were designed and synthesized using an optimized constant p H coprecipitation method and Zn Al LDHs as the main body.Guided by the performance of photocatalytic reduction of CO₂,the optimal intercalation ratio of PC was explored to be40%,the yield of CO is 9.6μmol·g^-1·h^-1and 9.6 times higher than that of Zn Al LDHs,and the 8-electron reduction product CH₄is produced.After three cycles of reaction,the main product CO yield remained at 97%,indicating good catalyst stability.The improvement in performance is attributed to the fact that the presence of PC broadens the light absorption range of the material,improves its light absorption ability,and constructs a composite material with a conductive band position that meets the reduction potential required for CO₂reduction.2.Study on the construction of purpurin（pp）sensitized Zn Al LDHs composites and their visible light catalytic reduction of CO₂performance:As an organic dye molecule with anthraquinone structure,pp has good absorption at 550 nm in the visible light region.Through hydrothermal coprecipitation,it was compounded with LDHs to synthesize a series of composite materials with different pp intercalation ratios,significantly improving the light absorption performance of LDHs,thereby achieving a certain breakthrough in the performance of photocatalytic reduction of CO₂,the yield of CO is 11.9μmol·g^-1·h^-1and 12 times higher than that of Zn Al LDHs.Moreover,the yield of CH₄is 2.5μmol·g^-1·h^-1.After three cycles of reaction,the main product CO yield remained 90.3%.Material stability is a prerequisite for stable performance,and the limiting effect of LDHs laminates provides a guarantee for the stability of the composite.In addition,the performance improvement is attributed to the improvement of the overall light absorption ability of the material and the matching energy level relationship with LDHs,promote electron transfer,which is beneficial for catalytic reactions。3.Construction of SDS-pp（3%）/LDHs loaded Pt composite and its visible light catalytic reduction of CO₂performance:Based on the sensitization of LDHs by pp,the carrier defect vacancies were constructed by acid etching,and then Pt in H₂Pt Cl₆·6H₂O was reduced by Na BH₄through immersion reduction.Through characterization methods such as XRD,FTIR,mapping,XPS and etc,it was proved that Pt was successfully reduced and anchored to LDHs,and the existence of pp and SDS was confirmed,as well as the retention of the intercalated structure of LDHs.Through the comparison of photocatalytic experimental results,it was found that,The CO product of Pt@SDS-pp（3%）/LDHs is 1.4 times than that of SDS-pp（3%）/LDHs,and the CH₄product is 1.8 times than that of SDS-pp（3%）/LDHs.The performance improvement is due to the addition of Pt promoting the separation of photogenerated carriers.