Preparation And Photocatalytic Properties Of TiO₂ Nanotubes Modified With Transition Metal Elements

In recent years,Tatanium dioxide?Ti O₂?nanotubes have such advantages due to its highly ordered structure,stable chemical properties,non-toxicity and large specific surface area.Ti O₂ nanotubes have broad application prospects in dye-sensitized solar cell,biosensors and hydrogen production.In this paper,we prepared Ti O₂ nanotubes by anodic oxidation,and selected appropriate transition metal elements to modify Ti O₂ nanotubes.The Cu₂O/Ti O₂nanotubes and Co/Ti O₂ nanotubes were prepared by direct impregnation-calcination method and electrodeposition method.The effects of the precursor concentration,current and voltage on the micromorphology,elemental composition,crystalline structure and photocatalytic activity of Ti O₂ nanotubes were studied.The Ti O₂ nanotubes were prepared under oxidation voltage of 50 V,oxidation time of 2 h,and the obtained Ti O₂ nanotube array was arranged regularly.The average diameter of Ti O₂nanotubes was 130-150 nm,and the average tube length was 2-3?m.After modification,no significant mico-morphology change was observed in Ti O₂ nanotubes.Firstly,the Cu₂O/Ti O₂nanotubes were prepared by direct impregnation-calcination method.A large amount of Cu₂O nanoparticles accumulated on the surface of Ti O₂ nanotubes and filled the pores for relatively high precursor concentrations.When the concentration of Na OH was 0.2 mol/L,the photocurrent density of Cu₂O/Ti O₂ nanotubes was the highest.When the concentration of Na OH was 0.3 mol/L,the composite catalyst has the best degradation effect on Rh B.It can be seen from the PL spectrum that Cu₂O nanoparticles reduce the electron-hole pair recombination efficiency and improve the utilization rate of photo-generated electrons.Secondly,Cu₂O/Ti O₂ nanotubes were prepared by electrochemical deposition method.The SEM images show that,Cu₂O nanoparticles are small,they can be observed at inside and outside of the tube wall.The photocatalytic current density of Cu₂O/Ti O₂ nanotubes was 1.0m A/cm²when the electrolyte p H was 11.And photoelectric conversion efficiency reached22.6%.The degradation rate of Rh B was the highest after 120 min under ultraviolet light irradiation.Indicating that,Cu₂O loaded reduce the width of band gapand improve its utilization in the area where the light can be used.Co/Ti O₂ nanotubes were prepared by electrochemical deposition method.The catalyticwere mainly composed of Ti,O,C and Co,with trace amounts of C from external contamination during the test.According to the SEM results,the average particle size of Co nanoparticles decreased with the increase of deposition time.When deposition time was 60 s and deposition voltage was 1 V,the photoelectric conversion efficiency reached 14.92%.According to PL spectrum and EIS characterization results known that anappropriate amount of Co can enhance the electron-hole pair separation effect.When the deposition time was constant and the voltage changed,the diameter of Co nanoparticles gradually decrease.When the deposition voltage was 2 V,the degradation efficiency reach 76.3%.Compared to pure Ti O₂ nanotubes which was significantly improved.Doped with Co particles can improve the photocatalytic activity,and reduce the band gap of the catalyst.