超细钴掺杂二氧化钛的制备、表征及气相光催化性能

PREPARATION AND CHARACTERIZATION OF ULTRAFINE TiO_2 DOPED WITH Co AND ITS PERFORMANCE IN GAS-PHASE PHOTOCATALYTIC OXIDATION

以四氯化钛为原料、硝酸钴为掺杂剂,制备了粒径10nm～30nm的钴掺杂超细二氧化钛并进行了XRD、TEM和FT IR表征及气相光催化性能的评价。钴掺杂造成了锐钛矿向金红石相的转变温度明显降低,掺杂量从0增加到4%时,相变温度下降了90℃左右。制备过程中的pH值对相变也有影响,pH值很小时相变在较低的温度下就能发生。当pH<3,500℃焙烧的样品中就基本是金红石型TiO2;红外光谱分析证明掺杂样品比纯样品有更强的吸水性;以苯作为反应物在一个固定床光反应器中考察了钴掺杂二氧化钛的光催化活性。结果表明,钴掺杂对催化剂的光催化性能有影响。反应初期掺杂样品与纯二氧化钛样品相比活性相差不大,但随着反应的进行活性差别逐渐增大。在实验条件下160min后纯样品基本失活,掺杂样品的活性仍大于50%。

Ultrafine particles (10?nm～30?nm) of TiO_2 doped with Co were prepared by titanic chloride hydrolysis. Cobaltous nitrate was used as dopant. The properties of the samples were characterized by means of XRD (X-ray dif- fraction), TEM (transmission electron microscopy) and FT-IR (Fourier transform infrared spectroscopy) techniques, and the evaluations of photocatalytic activity in gas-phase were performed, as well. It was found that after doping with Co, the temperature of transition from anatase to rutile was reduced obviously. When the dopant amounted to 4%, the phase-transition temperature dropped about 90?℃. The effects of pH on the phase transition were also observed. The smaller the pH value was, the lower the phase-transition temperature was. The sample calcined at 500?℃ consisted of basically rutile at pH<3. It is proved by IR analysis that the sample doped with Co has very good hygroscopicity. The effects of doping Co on catalytic activity were studied by photocatalytic reaction of benzene in a fixed-bed photoreactor. It is showed that doping Co enhanced the catalyst activity and especially was favorable to the decomposition of benzene, which is hard to decompose. Under the experimental conditions, benzene led to deactivation of the pure TiO_2 after 160?min time-on-stream, but activity of Co doped catalyst is still 50%.