Photocatalytic Reduction Of CO₂ Using Inverse-opal TiO₂ And Its Modified Structures

Greenhouse environmental pollution and energy shortages are two major problems that our society needs to solve.Based on the principle of plant photosynthesis to convert CO2 and H2O into organic matter,we use chemical reactions to reduce CO2 and H2O to methanol and methane under the action of photocatalysts,which not only alleviates the greenhouse effect but also addresses the energy crisis.TiO2 semiconductor materials non-toxic harmless green and cheap and easy to obtain is very good semiconductor photocatalytic materials widely used in photocatalytic degradation and photolysis of water hydrogen.TiO2 inverse opal photonic crystal structure has a modulation effect,and the porous structure has a relatively large specific surface area is conducive to the absorption of light.In this paper,we studied the photocatalytic reduction of CO2 by TiO2 inverse opal photonic crystals.At the same time,in order to improve the photocatalytic efficiency,the use of visible absorption of more Cu2O and mature photocatalytic material ZnO to modify the TiO2 inverse opal.The process of Cu2O and ZnO modified TiO2 inverse opal and the structural properties after modification were studied.The main contents of this thesis are as follows:(1)Photonic crystal templates with different particle diameters were prepared by vertical deposition.The TiO2 inverse opal photonic crystals with different particle sizes were prepared by using ALD method on the photonic crystal structure,and the heterojunctions of TiO2 inverse opal photonic crystals were prepared.The surface morphology of TiO2 inverse opal and heterojunction was characterized by SEM.The characteristics of photonic bandgap are characterized by reflection spectroscopy,and the absorption range of light is characterized by absorption spectroscopy.The photocatalytic activity was characterized by photocurrent.The photocurrent density of TiO2 inverse opal photonic crystal heterojunction is larger than that of pure TiO2 inverse opal.The yield of methanol was 5.06?mol/h using a photocatalytic system and a gas chromatograph.(2)Cu(hfac)2 was used as the copper source by CVD method at 300 ? with oxygen and water to prepare Cu2O.At the same time,Cu2O was prepared by electrochemical deposition at 65 ?.Cu2O was prepared by the above two methods,and the composition of Cu2O was determined by Auger electron spectroscopy.The absorption range of Cu2O modified TiO2 inverse opal prepared by two kinds of deposition methods was characterized by absorption spectroscopy.It was found that the Cu2O-modified TiO2 inverse opal prepared by CVD vapor deposition had more absorption of visible light.And the photocatalytic activity was characterized by photocurrent.(3)The ZnO was prepared by hydrothermal method and ALD atomic layer deposition method respectively.The surface morphology of ZnO modified TiO2 inverse opal was characterized by SEM.The effect of ZnO on the photocurrent reaction at different time and the effect on the photocurrent density were compared.It was found that the photocatalytic activity of ZnO was modified by hydrothermal reaction for 2 hours.The absorption range of ZnO modified TiO2 inverse opal was characterized by absorption spectroscopy.The photocatalytic activity of ZnO modified TiO2 inverse opal has a good photocatalytic activity and 1.2 times higher photocatalytic efficiency.The heterogeneous junction between TiO2 and ZnO improves the separation efficiency of photogenerated carriers and inhibits the recombination between electron holes,thus improving the photocatalytic activity of the material.