TiNi合金表面TiO_2薄膜的制备及光充电性能

Preparation and Photo-Rechargeable Properties of TiO_2 Film Thermally Formed on Surface of TiNi Alloys

采用热氧化方法在TiNi合金表面制备了TiO_2薄膜,并考察了TiO_2／TiNi电极在KOH溶液中的光电化学性能。结果表明,TiNi贮氢合金表面形成的TiO_2薄膜为金红石型,结晶度随氧化温度升高逐渐增大；TiO_2薄膜结构、光电流和界面阻抗之间存在良好的相关性,700℃制备的TiO_2薄膜光响应电流最大,电极阻抗谱与镍氢电池体系合金负极阻抗特征相似,高频区半圆对应于吸附氢的形成,而低频区Warburg线性关系则反映了氢在电极中的固态扩散过程：在光照射下具有特殊的光充电贮氢性能,放电容量从暗态时的5 mAh／g提高至光照时的15 mAh／g,对光充电反应机理作了初步分析。

TiO2 films were prepared by thermally oxidation of TiNi hydrogen storage alloys. The crystal structure and photo-electrochemical properties of the TiO2/TiNi electrode were investigated by using XRD and electrochemical measurement techniques. The results show that the film is futile TiO2 and the crystallization increases with increasing oxidation temperature. There is a good correlation between the structure of TiO2 films and the response of photocurrent and the interracial impedance. The TiO2 film electrode prepared at 700℃ gives the highest photocurrent response, and its EIS is similar to that obtained on the negative electrode in Ni-MH battery. The semicircle at high frequencies is ascribed to the formation of adsorbed hydrogen, and the linear part at low frequencies to the solid diffusive process of hydrogen in TiNi alloys. When charged by light irradiation, the charge potential slightly decreases and the discharge capacity increases from 5 mAh/g in dark to 15 mAh/g under illumination. Based on the experimental results, the possible photorechargeable reactions occurring at its TiNi/TiO2/electrolyte interface were also discussed.