Ag改性提高TiO2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 TiO2 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＋.