Preparation And Photoelectrochemical Properties Of TiO_2-xN_x/NiO Double-layer Thin Tilms

In order to develop a new kind of photo-electric function materials, N-dopedTiO₂ thin films were synthesized on indium-tin oxide (ITO) conducting glass substrateby DC reactive magnetron sputtering and sol-gel method, respectively. Then highporous NiO was deposited onto the N-doped TiO₂ layer by chemical bath deposition(CBD) to obtain TiO_2-xN_x/NiO bilayer thin films electrode. The microstructure, photoelectrochromicproperties and photoelectrochemical energy storage ability of theTiO_2-xN_x/NiO thin film were investigated by XRD,SEM,XPS,UV-vis adsorptionspectra and eletrochemial test technology.N-doping TiO₂ films were prepared on ITO conducting glass by dc-reactivemagnetron sputtering using Ti target in O2+N2/Ar gas mixture in combination with afollowing heat-treatment at 300-500℃. The results showed that the TiO_2-xN_x filmannealed at 400℃showed the highest photocurrent response under Xe lightirradiation. The bilayer films were irradiated with Xe lamps at a closed circuit for 1 h,the color of the TiO_2-xN_x/NiO electrode turned from colorless to brown, and thetransmittance varied from 79.0% to 12.6% at 500 nm. After photo-charging, thedischarge current was controlled at 100 nA and the duration time was about 11 h.And also, the N-doped TiO₂ film was synthesized on indium-tin oxide (ITO)conducting glass substrate by sol-gel method. As compared to the undoped TiO₂, thesynthesized N-doped TiO₂ had visible light photoresponse and exhibited a significantincrease in the photocurrent under Xe light irradiation. It was found that theTiO_2-xN_x/NiO electrode exhibited excellent photoelectrochromic properties. After 2 hirradiation, the color of the TiO_2-xN_x/NiO electrode changed from colorless to brown,and the transmittance varied from 83.5% to 32.9% at 400 nm. The discharge currentwas controlled at 100 nA and the duration time was about 4.2 h.Additionally, TiN thin films were prepared on ITO by dc reactive magnetronsputtering technique and then directly annealed in 300-500℃in air for thepreparation of TiO_2-xN_x thin film electrode. Under the same light irradiation, thephotocurrent of the TiO_2-xN_x electrode is four times larger than that of pure TiO₂ electrode. The as-fabricated TiO_2-xN_x/NiO electrode exhibited a noticeablephotoelectrochromism. After 3 h irradiation, the transmittance varies from 71.4% to26.5% at 400 nm. The discharge current was controlled at 100 nA and the durationtime was about 18 h.