Preparation And Modification Of ZnTi-LDH And Its Photocatalytic CO₂ Reduction Performance

With the continuous depletion of fossil fuels and the increasingly serious environmental problems,the use of clean and renewable resources has attracted great attention.The use of artificial photosynthesis to reduce CO₂ to carbon-based fuels is considered a promising and challenging method to alleviate the energy crisis and environmental pollution problems.A series of molecular or semiconductor-based catalysts have been developed for the photocatalytic reduction of CO₂.However,due to the poor adsorption of CO₂,the rapid electron-hole recombination during photocatalytic reactions,and the limited light absorption range of the catalyst itself,most catalysts The photocatalytic performances of all are far from satisfactory.Therefore,there is an urgent need to explore new photocatalysts to enhance the performance of photocatalytic reduction of CO₂.In this paper,double metal hydroxide ZnTi-LDH is used as the catalyst,and a series of modifications are carried out on it.The prepared catalyst is used to reduce CO₂ under simulated sunlight conditions.The main research contents are as follows:1.The ZnTi-LDH photocatalyst was prepared by hydrothermal method,and the photosensitizer TCPP was introduced to explore the performance of the composite material for photocatalytic reduction of CO₂.First,synthesize ZnTi-LDH with different ratios of zinc to titanium,and determine the best ratio of zinc to titanium through a series of characterization and photocatalytic activity tests.When Zn:Ti=2:1,pure ZnTi-LDH has the most excellent photocatalysis performance.On this basis,the photosensitizer TCPP is introduced to form the composite material TCPP/ZT.The two materials construct an organic-inorganic heterojunction,which improves the photocatalytic activity of the material.Among TCPP/ZT with different mass ratios,2%wt TCPP/ZT showed excellent performance in photocatalytic reduction of CO₂.The cumulative output of CH₄ and CO reached 8.65μmol?g^-1 and 1.72μmol?g^-1 under 5hours of light.They are 2.50 times and 1.56 times that of pure ZnTi-LDH,respectively.The principle of the reaction is discussed through a series of characterization,photoelectrochemical testing and DFT calculation.2.The CuO nanoparticles were prepared by the phase transfer method,and CuO and 2%TCPP/ZT（PZnTi-LDH）were composited.The combination of the two materials constructed a CuO/PZnTi-LDH composite with a Z-type heterojunction successfully.The construction of the Z-type heterojunction improves the separation efficiency of photogenerated carriers and the redox capability of the material,and at the same time realizes a broad spectrum response and high stability,and enhances the photocatalytic reduction capability of the composite material.The 5wt%CuO/PZnTi-LDH composite photocatalyst has the best reduction activity and excellent selectivity for the reduction of CH₄.Under the condition of full-wavelength light for 5 hours,the output of CH₄ was 15.45μmol?g^-1,which was 4.46 times that of ZnTi-LDH and 1.78times that of PZnTi-LDH.It is proved that after the introduction of TCPP,the introduction of CuO can further improve the photocatalytic reduction performance of ZnTi-LDH.