Doping Of Tio <sub> 2 </ Sub> Preparation And Properties Of Nanocrystalline Thin Film Electrodes

The porous nanocrystalline TiO₂ film electrode doped with Co²⁺, Ce³⁺, La³⁺ were prepared from Ti(OC₄H₉)₄ in alcohol by sol-gel and dip-coating method. The morphology, composition, optical and electrochemical property and photocatalysis of films were characterized by optical microscope, AFM, XRD, UV-Vis spectrophotometer, contact angle instrument and potentiostat. It showed that:The morphorlogy of film is greatly dependent on the molecular weight of PEG, viscosity of sol and the amount of dopant; The TiO₂ film with homogeneous pores was obtained when there is 20wt% PEG in the sol.(2) Energy band of TiO₂ shift to visible region because of rare-earth element and transition metal dopants. The largest bathoshift happened in films doped with Co²⁺ (1.98wt%), Ce³⁺ (1.98wt%) and tri-doped. The energy gap of tri-doped with 6.39wt%(Ce³⁺2.52wt%, Co²⁺ 1.89wt%, La³⁺1.98wt%) is the most evident which is 2.81 eV. The energy gap of bi-doped with Ce³⁺l .5wt% and La³⁺O.75wt% is 3.20eV, which exihibites obvious blue-shift.(3) Tri-doped TiC>2 was still anatase by annealing at 800℃. It indicated that tri-doped with rare-earth element and transition metal in TiO₂ films can restrain the transformation from anatase to rutile. It also changed the lattice of TiO₂ by tri-doping. So the photocatalysis of TiO₂ is improved. The best photocatalysis of TiO₂ is obtained in films doped with 1.98%Co²⁺ with a thickness of 400 nm.(4) The photoelectric properties of TiO₂ electrode was affected by doping and transient photocurrent can be enhanced. So the current response of TiO₂ electrode can be improved by doping. In this experiment, the maximum of photocurrent appears in tri-doped TiO₂ electrode of four layers, where little photocurrent is observed in pure TiO₂ membrane electrode.