TiO_2锐钛矿晶化度对其光生电荷性质及光催化活性的影响

采用溶胶-水热法合成掺杂La、Zn以及La和Zn共掺杂的纳米TiO2。重点调控纳米TiO2的热稳定性及改善锐钛矿相的晶化度,在维持与P25型TiO2具有相似晶相组成条件下,考察锐钛矿相晶化度对光生电荷分离及光催化活性的影响。结果表明,La或Zn离子的引入能抑制晶相转变过程,且前者的抑制作用明显大于后者,相转变温度从500℃升高至750℃。表面光电压谱证实,锐钛矿相的晶化度越高,光生电荷越易分离。虽然La或Zn的引入可以提高纳米TiO2单位面积上的光催化活性,但却不能超过P25的活性。此结果表明锐钛矿晶化度强烈影响光生电荷的性质和光催化活性。

Effects of anatase crystallinity on photoinduced charge properties and photocatalytic activity of nano-sized TiO_2

Un-doped, La-doped, Zn-doped and La-Zn-co-doped nano-sized TiO_2 samples were prepared by sol-hydrothermal processes, aiming to controllably obtain different TiO_2 samples with the similar phase composition, but with different anatase thermal stability and crystallinity. On the condition of similar phase composition to the P25 TiO_2, the effects of the anatase crystallinity on photoinduced charge separation and photocatalytic activity of nanocrystalline TiO_2 were mainly investigated. The results show that La doping or Zn doping can inhibit the phase transformation process of TiO_2, and the former has much greater effect than the latter. The beginning temperature of phase chage is changed from 500 to 750℃ after doping La. The surface photovoltage responses well demonstrate that the increase in the anatase crystallinity is in favor of the separation of photoinduced electron-hole pairs, which is responsible for the result that the unit-surface-area photocatalytic activity of the as-prepared TiO_2 crystallities is improved by doping La or Zn, in spite of still with lower activity than P25 TiO_2. It is suggested that the anatase crystallinity has great effects on the photoinduced charge properties and photocatalytic activity of TiO_2, and the surface photovohage technique is an effective tool to reveal the separation situation of photoinduced charges of semiconductor photocatalysts.