Photocatalytic Reduction Of Carbon Dioxide Using Iodine Doped Titanium Dioxide With High Exposed(001) Facets Under Visible Light

In this study,titanium dioxide with high exposed?001?facets were synthesized by a hydrothermal method using tetrabutyl orthotitanate as titanium resource and hydrofluoric acid as a morphology controlling agent.After doping with iodine using iodic acid as iodine resource by the second step hydrothermal method,a series of iodine doped titanium dioxide with high exposed?001?facets were synthesized and the activities of the catalysts in the photocatalytic reduction of carbon dioxide were investigated,respectively.The morphology,structure,physicochemical property and the ablity to photoreduction of carbon dioxide of the photocatalysts were characterized by field-emission scanning electron microscopy,transmission electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy,Brunauer–Emmett–Teller analyzerand UV-visible absorption spectroscopy.In the present work,the behavior of all the iodine doped titanium dioxide with high exposed?001?facets to the photoreduction of carbon dioxide induced by visible light was investigated.The nano titanium dioxide photocatalysts with varieties of?001?facets percentage were synthesized through changing different molar ratio of F:Ti and the largest?001?facets percentage can reach 78%.After doping with different amount of iodine,all the titanium dioxide with high exposed?001?facets can be driven under visible light.The series of iodine doped titanium dioxide with high exposed?001?facets can reduce carbon dioxide with water vapor driven by visible light?wavelength>400 nm?and the production were CH₄ and minor CO.The sample which shows the best carbon dioxide reduction activity to produce CH₄ and CO and the yields can reach 31.8?mol g^-11 and 13.7?mol g^-1,respectively.The photocatalyst was stable and retained almost the same photoactivity after five repeated reaction cycles.The visible light response of the synthesized catalysts were attributed to the formation of I-O-I bond and I-O-Ti bond on the surface titanium dioxide lattice which can change the atomic configuration of the surface titanium dioxide leading to band gap narrowing.The photoreduction of carbon dioxide using catalysts with different?001?facets percentage indicated that the optimal ration of?001?to?101?was found to be 55:45which can reach the best reduction activity.Since the conduction band potential of?001?facets was higher than that of?101?facets,the photo-generated electrons can gather on the?101?facets to reduce the carbon dioxide while photo-generated holes can gather on the?001?facets to oxidize water vapor to produce oxygen.The process can improve the separation and utilization of photo-generated electrons and holes.