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

采用阴极偏压电沉积法制备了纳米二氧化钛，作者提出的方法是在-1.1~-1.3V的阴极偏压下控制纳米二氧化钛的晶粒度。众所周知，光催化剂的活性对锐钛矿型和金红石型的二氧化钛晶相很敏感。前者被认为比后者更活跃。然而，工业催化剂P25证明，锐钛矿和金红石的混合晶体也是非常活跃的催化剂。因此，重要的是要弄清楚是什么使催化剂活性。由于晶相可以通过热处理温度来控制，所以我们使用金属钛作为电沉积的衬底，用它可以对沉积的薄膜进行500℃以上的热处理。结果表明，700℃热处理的二氧化钛薄膜的催化活性最高。X射线衍射、电致发光和光伏特性表明，金红石表面的表面态可以作为锐钛矿相转移的电子储存库，从而保持锐钛矿的光活性。

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.