The Construction Of LDHs Nanoreactor And Its Performance In The Photocatalytic Co₂ Reduction-5-HMF Oxidation Coupling Reaction

With the acceleration of industrialization,energy consumption has increased sharply,and the problem of energy scarcity has become more prominent.The burning of traditional fossil energy coal,oil,and natural gas has caused environmental pollution and also produced a large amount of environmental pollution.CO2 gas,CO2 as a greenhouse gas threatens the survival of mankind.The technology of photocatalytic reduction of CO2 has been greatly developed.Generally,the photocatalyst is a semiconductor material,and the catalyst can convert CO2 into CO and other high value-added hydrocarbon products under the irradiation of sunlight.In addition,photocatalytic reduction of CO2 can provide feasible solutions for energy shortage and greenhouse gas emissions at the same time.In the traditional artificial photosynthesis process with H2O as the reducing agent,the H2O oxidation half-reaction not only has a slower rate,which limits the rate of the CO2 reduction half-reaction,but the oxidation product O2 does not have a large added value,which wastes the oxidation of photo-generated holes.ability.Hydroxyl groups in biomass molecules are more easily oxidized,and their oxidation products also have higher added value.Therefore,the CO2 reduction and the biomass oxidation process can be coupled to simultaneously achieve the increase of the CO2 reduction rate and the high value conversion of biomass.As a kind of biomass platform compound,5-Hydroxymethylfurfural(5-HMF)has received more and more attention.This paper mainly focuses on the photocatalytic CO2 reduction of 5-HMF oxidation coupling process.The nanoreactor provides a confined space isolated from the surrounding environment for the reaction.When the reaction system is confined to the nano-space,a series of changes will occur in the chemical reaction,even changing the mechanism of some chemical reactions.The rate of chemical reaction in the nanoreactor is accelerated.It can adjust the pore size for specific molecules in the reaction.The internal voids or hollow spaces can be adjusted to accommodate the reaction medium and buffer any volume expansion due to chemical reactions.The functionalized surface can be targeted at Specific species perform specific reactions.Layered Double Hydroxide(LDHs)provide a huge possibility for the development of high-performance nanoreactors due to their unique layered structure and adjustable layer composition and ratio.This paper by photocatalytic reduction of CO2 react with 5-HMF oxidation coupling results as the goal,by coprecipitation preparation of LDHs as the research object,and constructed a new type coupling process of photocatalytic reactor nanoparticles,and through the metal on the surface defects of regulation to achieve the purpose of improve the catalytic performance,further through the structure-activity relationship studies,results illustrate the photocatalytic reduction of CO2 and 5-HMF oxidation coupling reaction mechanism,expanded the research train of thought for the development of photocatalytic.This paper takes the photocatalytic reduction of CO2 and 5-HMF oxidation coupling as the target reaction,and takes LDHs prepared by the co-precipitation method as the research object,constructs a new type of photocatalytic coupling process nanoreactor,and achieves it by regulating the surface metal defects The purpose of improving the catalytic performance is to further study the structure-activity relationship to clarify the reaction mechanism of the coupling of photocatalytic reduction of CO2 and 5-HMF oxidation,which broadens the research ideas for the development of photocatalysis.Specifically,first of all,using the characteristics of LDHs layer plate metal elements can be adjusted,the CuCoAl-LDHs were successfully prepared by the co-precipitation method,and they were etched in KOH solution,and a series of catalysts with metal defects were prepared by controlling the etching time.Through a series of characterizations such as XRD,SEM,TGMS,ICP,XPS,Raman,EPR,CO-FTIR,etc.,it is proved that metal defects are formed on the surface of the catalyst after etching,and the concentration of metal defect vacancies increases with the extension of the etching time.The gap and energy band position of the catalyst are determined by UV-vis and valence band spectroscopy.The results show that the conduction band position of the catalyst is higher than the standard potential for reducing CO2 to CO,and the longer the etching time,the narrower the energy band gap of the catalyst.The more conducive the reaction takes place.The performance of the prepared catalyst was further evaluated under ultraviolet-visible light irradiation,and the results showed that CuCoAl-LDHs-etching 60 min had the highest catalytic performance,and the cumulative yield of CO reached 65.26 μmol/g after 4 h of photocatalytic reaction,The selectivity of FDCA reached 73.6%.Characterization of PL spectrum and photocurrent response proves that CuCoAl-LDHs-etching 60 min photogenerated electron holes have the weakest recombination ability and the strongest photoresponse ability.Through FTIR and carbon tracking,the activation site of 5-HMF and the CO32-cycle process between the catalyst layers were revealed,and the reaction mechanism of the reaction was explained.In addition,LDHs as a new type of nanoreactor can also play a role in the process.The role of capturing and storing CO2 in the air.In order to further explore the role of LDHs as a nanoreactor in the coupling reaction of photocatalytic reduction of CO2 and 5-HMF,CoFe-LDHs and defect-rich CoFe-LDHs(AIR)series without Na2CO3 were synthesized by co-precipitation.The catalyst,through a series of XRD,SEM,TG,XPS characterization,proved that the CoFe-LDHs(AIR)catalyst synthesized without Na2CO3 has a rich defect structure.The performance of the catalyst was evaluated,and the results showed that the defect-rich CoFe-LDHs(AIR)series catalysts had higher photocatalytic performance.The structure-activity relationship of the catalyst was characterized by UV-vis,PL spectroscopy and FTIR.The results showed that The CoFe-LDHs(AIR)catalyst has strong light absorption ability and weak photo-generated electron hole separation and recombination ability.The CO32-between the catalyst layers can be activated under light conditions,which is beneficial to improve the reaction efficiency and build a recyclable light.Catalyst provides new ideas.