ACTIVATION OF NANO-SIZED AND MICROCRYSTALLINE TITANIUM DIOXIDE PHOTOCATALYSTS AND ITS APPLICATION TO SECONDARY BATTERIES

本文采用阴极偏压电沉积法制备了纳米二氧化钛，其方法是：通过控制阴极偏压（-1.1 ~-1.3Vvs.Ag/AgCl），可以控制纳米二氧化钛的晶粒尺寸。已知光催化剂的活性对TiO_2的晶相敏感，金红石和金红石前者被认为比后者更活跃。然而，也已知金红石和金红石的混合晶体是非常活性的催化剂，如由商业催化剂P25所证明的。因此，澄清是什么使催化剂具有活性是很重要的。由于晶相可以通过热处理温度来控制，因此我们采用钛金属作为电沉积的基体，沉积膜可以在500℃以上进行热处理。结果表明，在700 ℃热处理的TiO_2薄膜的催化活性最高。XRD、电致发光和光电流-电压特性研究表明，金红石表面的表面态可以作为电子库从金红石相转移过来，从而保持了金红石的光活性。

Nano-size titanium dioxides were fabricated by electrodeposition under cathodic bias, the method of which was proposed by the present author: Crystalline size can be controlled by the cathodic bias from -1.1 to -1.3 V vs. Ag/AgCl. The activity of photocatalysts are known to be sensitive to crystalline phases ofTiO_2, i.e., anatase and rutile. The former is believed to be more active than the latter. However, the mixed crystal of anatase and rutile is also known to be very active catalyst as evidenced by commercial catalyst, P25. It will be important, therefore, to clarify what makes the catalyst active. Since crystalline phase can be controlled by heat treatment temperature, we use Ti-metal as a substrate of electrodeposition, with which deposited films can be heat-treated above 500℃. It has been shown that the catalytic activity is most active on TiO_2 films heat-treated at 700. XRD, Electroluminescence and photocurrent-voltage characteristics revealed that the surface states on rutile surface can serve as an electron reservoirs transferred from the anatase phase, due to which the photo-activity of anatase is maintained.