Sythesis And Modification Of TiO₂ Nanotube Array And Study On Their Photocatalytic Reduction Performance Of CO₂

How to solve the energy crisis and effectively reduce CO₂ to curb the global warming have become the major problems that need to be solved by all countries in the world.Photocatalytic CO₂ conversion technology has great potential in alleviating energycrisis and greenhouse effect because it can directly use solar energy and convert CO₂ into methanol,ethanol and other combustible compounds at room temperature and pressure.Nanotube array film has excellent photocatalytic properties due to its highly ordered tubular arrays,porous structures and large specific surface areas,so it has attracted much attention among researchers.In this paper,the TiO₂ nanotube array(TNTA)with controllable morphology were prepared on the pure titanium sheet substrate by anodic oxidation method,photocatalyticreduction gas-phase CO₂,Meanwhile,we studied the effects of different preparation process parameters of catalyst,volume flow rate of CO₂,light source and illumination intensityon products yield.We modified the TiO₂ nanotube array film.Formingelement,chemical state and absorption spectrum of the photocatalyst were characterized by SEM,TEM,XRD,XPS and UV-vis.Furthermore,the effects of themodifaction on the products yield of photocatalytic conversion CO₂ was deeply studied.Research contents and results will be briefly presentated as follows:(1)TNTA was prepared under different processparametersincludeing the concentration of NH₄F in the electrolyte,the applied voltage,the calcination temperature,and the properties of the sample were tested under 365nm-wavelength ultraviolet light.The effects of different content of NH₄F in the electrolyte,appliedvoltage,and the calcination temperature on performance of TiO₂ nanotube arrayswereresearched.The experimental results show that the TiO₂ nanotube array has excellent photocatalytic performance due to their good crystal shape,porousmorphology,and great specific surface area.The main product of CO₂ conversion is methanol.When NH₄F concentration is 0.25M,the applied voltage is 50V and the calcinationtemperature is 500 degree centigrade,the highest methanol yield is 138.23nmol/(cm²·h).(2)RGO-TNTA composite catalyst were synthesized by vapor-thermal treatment which made graphene oxide modifying on surface of uncrystallized TiO₂ nanotube arrays.Effects of different GO concentrations,lightsources,illuminationintensities and volume flow velocities of CO₂ on photocatalytic reduction performance of CO₂ were respectively studied.The experimental results show that the main product is methanol both under visible light and ultraviolet light.Photocatalytic performance of the RGO-TNTA composite catalyst under ultraviolet light and visible light respectively are1.26 times and 2.22 times as that of bare TNTA.The highest yields are up to 272.16nmol/(cm²·h)and 178.96nmol/(cm²·h)under ultraviolet light and visible light when the GO concentrations are 0.2mg/mL and 0.3mg/mL,the CO₂ volume flow velocities are 20.5mL/min and 25mL/min,the light intensity are36mW/cm² and 80mW/cm²,respectively.