碱土金属钛酸盐-TiO_2异质结型复合光催化活性研究

Photocatalytic property of MTiO_3-TiO_2(M=Mg,Ca,Sr,Ba) heterojunction photocatalyst

采用溶胶-凝胶法制备碱土金属钛酸盐MTiO3(M=Mg,Ca,Sr,Ba),并进一步与TiO2固相法复合制备MTiO3-TiO2异质结型复合光催化剂。以光催化降解亚甲基蓝(MB)为探针,评价了MTiO3和MTiO3-TiO2光催化剂的活性变化。结果表明,紫外光条件下碱土金属钛酸盐MTiO3的光催化活性顺序为:CaTiO3>BaTiO3>SrTiO3>MgTiO3,钙钛矿化合物的容忍因子、电负性以及催化剂的吸附性能都影响催化剂的降解效率。MTiO3与TiO2复合后形成的异质结复合光催化剂的催化活性得到显著的提高,催化剂浓度1.0g/L时,光催化反应1h后,MB(25mg/L)的降解率分别为82.6%,99.8%,93.7%,97.3%,异质结复合光催化剂活性顺序与MTiO3一致。光催化活性的提高与异质结界面形成电荷定向流动,促进光生电子、空穴的分离有关。

Alkaline earth titanates MTiO3 （M = Mg, Ca, Sr, Ba） were prepared by an sol-gel methods and MTiO3 -TiO2 heterojunction catalysts were then synthesized by MTiO3 and titanium dioxide. The photocatalytic degradation of methylene blue （MB） in aqueous solution were used as a probe reaction to evaluate the photocatalytic activity of MTiO3 and MTiO3-TiO2. The results show that the photoeatalytie activity of alkaline earth titanates ： CaTiO3 〉 BaTiO3 〉 SrTiO3 〉 MgTiO3. The tolerance factor of perovskite type oxide, eleetronagativity and absorption property of catalysts had important influence on the photocatalytic performance of photocatalysts. The photocatalytie activities of MTiO3 -TiO2 heterojunetion catalyst were greatly enhanced after combination. The degradation rate of MB（25 mg/L） solution was 82. 6%, 99. 8%, 93. 7%, 97. 3%, respectively after lh UV irradiation, when used these heterojunetions as photocatalyst （ 1.0 g/L）. The activity sequence of the heterojunction was consistent with that of MTiO3. The improvement of photocatalytic activity was attributed to the directional flow of the photogenerated eharges at the interface of heterojunetion,which promoted the separation of photogenerated electrons and holes.