Ag改性提高TiO_2对Cr(VI)的光催化还原活性机理

在消除了质子缺乏、光生电子-空穴复合对Cr6 光催化还原负效应影响下,比较了TiO2和Ag/TiO2(Ag质量分数1.0％)光催化还原活性.结果表明,相同条件下Ag/TiO2表现出比TiO2更高的催化活性.EPR分析表明,对于Ag/TiO2,UV照射后Ag表面有活性物种O2生成,在TiO2上有活性中心表相Ti3 生成.光生电子通过表相Ti3 向Cr6 传递电子是cr6 光催化还原的速度控制步骤.较多的表相Ti3 参与还原反应是Ag/TiO2表现出较高催化活性的主要原因,担载Ag上积聚光生电子的较强流动性对反应也起到一定促进作用.

Mechanism of Silver Modification for the Enhanced Photocatalytic Activity of Cr(VI) Reduction on TiO_2 Photocatalyst

Under the condition that negative effects of proton starvation and photo-generated electron-hole recombination to the Cr6 photocatalytic reduction process were minimized for the photocatalytic activities of TiO2 and Ag/TiO2 for Cr6 reduction were comparatively investigated. Combined with the results of EPR, the mechanism of silver modification for the enhanced photocatalytic reduction of Cr6 on TiO2 was discussed. The result revealed that Cr6 reduction by the UV-Ag/TiO2 process was more effective than the UV-TiO2 process under the same conditions. Electron transfer from surface Ti3 to Cr6 was the key step for Cr6 reduction. Cr6 photocatalytic reduction by directly capturing photo-generated electrons is possible, but it occurs mainly indirectly by getting electrons from surface Ti3 . The higher reduction activity of Ag/TiO2 photocatalyst came mainly from the higher number of surface Ti3 .