The Non-metal Doping Study Of TiO₂ Photoelectrocatalyst

As an important photoelectric functional material, the doped TiO₂ has attracted more and more attention. In this paper, Sol-gel method and magnetron sputtering method were used to prepare nitrogen-doped TiO₂ photocatalyst. Laser-plasma method was adopted to prepare carbon-doped TiO₂ particles. The structure, morphology, optical absorption edge and photo-electrochemical properties of the as-prepared materials were investigated by XRD, SEM, UV-vis absorption spectrum and electrochemical test methods.During the Sol-gel synthesis of nitrogen-doped TiO₂ powder, the effect of water and triethanolamine amount to the gelation time, UV-vis absorption spectrum and crystal structure was investigated thoroughly for the first time. It was found that the increase of water content resulted in the reduction of the gelation time and the blue-shift phenomenon of the optical absorption edge. We also found that the increase of the amount of triethanolamine led to the extension of gelation time, the phase transformation from the mixed crystal of anatase and rutile to pure anatase and the refinement of the crystal grain. The optical absorption edge reached at 430 nm when 7 ml of triethanolamine was used. The crystal grain grew and the structure transformed to rutile phase with the increase of the heat-treat temperature. The as-prepared materials treated at 500℃and 800℃were investigated by cyclic voltammetry, photocurrent curve and AC impedance. The TiO₂ treated at 500℃exhibited much higher photoelectrocatalytic activity and photocurrent response. The open circuit potential curves and current curves in illumination/dark showed that the sample synthesized at 500℃had more effective photoresponse.Nitrogen-doped TiO₂ film was prepared by magnetron sputtering method, using ITO glass as base plate. The TiO₂ films were pure anatase phase. The surface of two kinds of samples consisted of small compact particles. SEM images proved that the grain of TiO₂ film treated at 600℃was smaller than that treated at 700℃. Compared with pure TiO₂ film, the optical absorption edge of as-prepared materials appeared remarkable red-shift phenomenon, which approached 420 nm. The photocurrent of TiO₂ film enhanced from open circuit potential, which was more obviously in the sample treated at 700℃.The C-doped TiO₂ particles were synthesized for the first time via laser heating treatment of the mixture of TiO₂ gel and polypropylene powders in air. The crystal grain grew and the phase transformed from the mixed crystal of anatase and rutile to pure anatase along with the increase of the heat-treat temperature. The laser treatment had obvious effects on the crystal phase composition of TiO₂. It could be observed the grain size of the C-doped TiO₂ was smaller than that of the undoped sample according to the SEM images. EDS results revealed the precence of abundant oxygen vacancy and the atomic ratio of doped carbon was about 2.6 %. In comparison with pure TiO₂ synthesized by a sol-gel process, the optical absorption edge of the C-doped TiO₂ red-shifted 50 nm and the photoelectrochemical response was significantly improved. AC impedance proved that the Photoelectrode made of C-doped TiO₂ showed high perfomance in the electrode reaction under illumination.