Study On The Modification Of TiO₂ Nanotube Arrays And Their Photocatalytic Performance Of CO₂ Aqueous Solution

As the main composition of greenhouse gases,CO₂ has caused wide attention around the world,and governments are considering to reduce its emission and achieve its utilization.With solar power,TiO₂ photocatalysis technology is used to convert CO₂ into hydrocarbons,which can not only reduce the greenhouse effect but also relieve the problem of energy crisis,attracting more and more attention of researchers all over the world.Due to the bigger forbidden band width,highly ordered TiO₂ nanotube arrays that is prepared via the method of twice anodic oxidation can only absorb ultraviolet light,leading to a lower light utilization efficiency,and the catalyst normal electronics are prone to compound.In order to solve these problems,precious metal of Ag,Au,Pt,and metal of Fe are deposited to the TiO₂ nanotube arrays by means of photoelectric deposition method and the method of anodic oxidation,preparing compound TiO₂nanotube arrays doped with precious metal and transition metal.The obtained TiO₂nanotube arrays are characterized by SEM,EDS,UV-Vis DRS,and are also utilized to catalyze CO₂ aqueous solution electrically under the normal temperature of 300 W ultraviolet light irradiation,work electrode of TiO₂ nanotube arrays,counter electrode of foil,reference electrode of Ag/AgCl,reaction liquid of NaHCO₃.After a certain period of reaction,the reduction product is analyzed by gas chromatograph and the photoelectric catalytic activity of TiO₂ nanotube arrays before and after the modification is compared.The results demonstrate that structure of TiO₂ nanotube arrays doped with precious metal and transition metal has no change,however,light response of which is apparently enhanced.Besides,light absorption range is larger and the occurrence of red shift is observed.Under the 300 W uv lamp irradiation,TiO₂ nanotube arrays doped with Ag can convert CO₂ aqueous solution into Methanol and ethanol.The optimum photoelectric catalytic activity of Ag/TiO₂ nanotube arrays is obtained at deposition voltage of-2 V,sediment concentration of 0.001 mol·L^-1,obtaining a methanol yield of 4.34mg·cm^-2·h^-1 of space and time,ethanol yield of 4.35 mg·cm^-2·h^-1 of space and time after 2 h reaction time.The optimum photoelectric catalytic activity of Pt/TiO₂nanotube arrays is obtained at deposition voltage of-2 V,sediment concentration of1.93×10^-3 mol·L^-1,obtaining a methanol yield of 5.24 mg·cm^-2·h^-1 of space and time,ethanol yield of 9.13 mg·cm^-2·h^-1 of space and time.The optimum photoelectric catalytic activity of Au/TiO₂ nanotube arrays is obtained at d sediment concentration of 0.10×10^-3 mol·L^-1,obtaining a methanol yield of 4.39 mg·cm^-2·h^-1 of space and time,ethanol yield of 8.43 mg·cm^-2·h^-1 of space and time.The optimum photoelectric catalytic activity of Fe/TiO₂ nanotube arrays is obtained at sediment concentration of0.10 mol·L^-1,obtaining a methanol yield of 5.55 mg·cm^-2·h^-1 of space and time,ethanol yield of 10.9 mg·cm^-2·h^-1 of space and time.