Photoelectrical Performance Of TiO₂ Doped With Nitrogen Or Carbon

Due to its large band gap energy, TiO₂ only can absorb UV light, which is less than 5ï¼…in solar spectrum. Therefore, the study on the TiO₂ photocatalyst with visible light-responsive property is the most challenging subject in the field of photocatalysis. In this paper, nitrogen or carbon-doped TiO₂ films were attempted to improve the visible-light-response performance. The structure, morphology, photo-response and photo-electrochemical properties of the as-prepared thin films were investigated.Firstly, TiO₂ photo-catalytic thin films were prepared by thermally oxidation of TiNi₃ hydrogen storage alloys in various oxidation temperature. The as-formed films in the temperature range from 500℃to 800℃are identified as rutile TiO₂ phase. The TiO₂ film prepared at 600℃exhibits the highest photo-catalytic activity and photo-current response. The discharge capacity of the TiO₂/TiNi₃ electrode charged under the light illumination has enhanced from 6.76mAh/g to 10.60mAh/g.Secondly, the TiO₂ films were formed on the surface of TiNi₃ alloys by thermal oxidation method, and then annealed at high temperature in nitrogen gas to obtain nitrogen-doped titanium oxide (TiO_2-xN_x) films. The results show that the UV-vis spectroscopy of the TiO_2-xN_x film has a remarkable red shift in the visible region of 400-600nm, as compared to the TiO₂. The TiO_2-xN_x film prepared at 600℃exhibits the highest photo-catalytic activity and photo-current response. The discharge capacity of the TiO_2-xN_x/TiNi₃ electrode charged under the light illumination has enhanced from 10.70mAh/g to 14.72mAh/g.Thirdly, metal Ti was doped with C by laser thermal treatment and then, TiO_2-xC_x film was formed on the surface of Ti sheet by thermal oxidation method under 600℃. The results show that the carbon-doped TiO₂ film has higher photo-catalytic activity and photo-current response, as compared to the TiO₂. The UV-vis spectroscopy of the TiO_2-xC_x film has a remarkable red shift in the visible region of 400-600nm. The discharge capacity of the TiO_2-xC_x/Ti electrode charged under the light illumination has enhanced from 7.36mAh/g to 9.20mAh/g. The TiO_2-xN_x film formed on the surface of TiNi₃ alloys exhibits higher photo-catalytic activity, photo-current response and discharge capacity than that of TiO_2-xC_x film prepared on the Ti sheet.