Design Of Layered Double Hydroxide Based Hybrid Materials And Study On Photocatalytic Reduction Of CO₂

At present,using solar energy to simulate plant photosynthesis and convert CO₂into high value-added products is one of the effective methods to solve the greenhouse effect and energy crisis.However,photocatalytic CO₂reduction still faces many challenges and opportunities in broadening the efficiency of the solar spectrum and fully utilizing the oxidation terminal.As a two-dimensional material,layered double hydroxides（LDHs）possess the advantages of adjustable host layer elements,and adjustable band structure,and are considered a potential photocatalytic catalyst for CO₂reduction.In this paper,a series of catalysts with high catalytic activity and selectivity were prepared by hybridization of LDHs and other materials.Furthermore,the problem of spectral extension and effective utilization of oxidation end of photocatalytic CO₂reduction was successfully solved.The research contents are as follows:1.LDH/TiC was used for photocatalytic reduction of CO₂to syngas at long wavelengths:Firstly,DFT calculation results show that different concentration of TiC and LDH is beneficial to regulate the adsorption energy of CO and H₂,and thus adjust the syngas ratio.Furthermore,we carried out the photocatalytic CO₂reduction experiment and found that CO:H₂=1:1～1:4can be successfully achieved in visible light（λ>400 nm）with LDH/TiC-x.More importantly,the different ratios of syngas can be modulated in LDH/TiC-x atλ=550 nm.The reaction path of LDH/TiC-x was further confirmed by in-situ infrared spectroscopy.The work offers a new strategy for using solar energy to convert CO₂and H₂O into syngas at a long wavelength.2.NiAl-Ru-LDH achieves a photocatalytic reduction of CO₂under infrared light:In order to avoid the use of homogeneous photosensitizer molecules,we successfully prepared Ru-based photosensitive molecular intercalated LDH materials（denoted as NiAl-Ru-LDH）by taking advantage of the interlayer anion tunability of LDHs.Under the irradiation ofλ=1200 nm,NiAl-Ru-LDH exhibits activity in photocatalytic CO₂reduction,and the CO selectivity of NiAl-Ru-LDH can reach 86.70%.In addition,NiAl-Ru-LDH shows good stability and can be recycled at least 50 times.The CO selectivity of NiAl-Ru-LDH has almost no obvious change,indicating that NiAl-Ru-LDH exhibits good stability and catalytic activity.Furthermore,by studying the band structure of NiAl-Ru-LDH,it is found that the bandgap of NiAl-Ru-LDH is 0.98 e V,which can drive the reaction atλ=1200 nm.Subsequently,the characterization of fine structure found that NiAl-Ru-LDH possesses metal defects and oxygen defects,which is conducive to the inhibition of electron-hole recombination.This work provides a new strategy for converting CO₂and H₂O into CO under infrared light conditions.3.LDH/QDs were used to realize the organic oxidation reaction and photocatalytic CO₂reduction:CdSe/CdS quantum dots（QDs）and NiAl-Ru-LDH were added into the reaction system to form LDH/QDs in order to make full use of the oxidation end and avoid the use of sacrificing reagents.Under the irradiation of LED=450 nm,photocatalytic CO₂reduction can be carried out without the addition of a sacrificial reagent.Firstly,the sacrificial reagent（TEOA）was replaced by 1-phenyl ethanol to realize the oxidation end from 1-phenyl ethanol to pinacol,and the photocatalytic CO₂reduction to CO and CH₄can be achieved in the reduction ends.In addition,we found that the photocatalytic CO₂reduction reaction can be driven when the sacrificial reagent is replaced by H₂O.Compared with QDs,LDH/QDs can significantly inhibit H₂production.This study provides a new method for fully the utilization of the oxidation terminal.