Egerton Terry A, Kosa Samia A M, Christensen Paul A
Department of Chemical Engineering and Advanced Materials, Bedson Building, The University of Newcastle on Tyne, Newcastle NE1 7RU, UK.
Phys Chem Chem Phys. 2006 Jan 21;8(3):398-406. doi: 10.1039/b507516e. Epub 2005 Nov 14.
Photoelectrocatalytic disinfection of E. coli by an iron doped TiO(2) sol-gel electrode is shown to be more efficient than disinfection by the corresponding undoped electrode. Thus, the improvements in photocatalytic efficiency associated with selective doping have been combined with the electric field enhancement associated with the application of a small positive potential to a UV irradiated titanium dioxide electrode. The optimum disinfection rate corresponds to the replacement of approximately 0.1% of the Ti atoms by Fe. The enhanced disinfection associated with iron doping is surprising because iron doping decreases the photocurrent, and photocurrent is generally taken to be a good indicator of photoelectrocatalytic efficiency. As the level of iron is increased, the character of the current-voltage curve changes and the enhancement of photocurrent associated with methanol addition decreases. This suggests that iron reduces the surface recombination which in the absence of iron is reduced by methanol. Therefore the enhanced photocatalysis is interpreted as due to iron reducing surface recombination, by trapping electrons. It is proposed that at low iron levels the photo-generated electrons are trapped at surface Fe(III) centres and that consequently, because the electron-hole recombination rate is reduced, the number of holes available for hydroxyl radical formation is increased. It is also proposed that at higher iron levels, the disinfection rate falls because electron hole recombination at iron centres in the lattice reduces the number of holes which reach the surface. Our conclusion that the optimum electrode performance is a balance between surface and bulk effects is consistent with the proposal, of earlier authors for photocatalytic reactions, that the optimum dopant level depends on the TiO(2).
铁掺杂TiO₂溶胶 - 凝胶电极对大肠杆菌的光电催化消毒效果比相应的未掺杂电极更有效。因此，与选择性掺杂相关的光催化效率的提高与向紫外线照射的二氧化钛电极施加小正电位相关的电场增强相结合。最佳消毒速率对应于约0.1%的Ti原子被Fe取代。与铁掺杂相关的消毒增强令人惊讶，因为铁掺杂会降低光电流，而光电流通常被视为光电催化效率的良好指标。随着铁含量的增加，电流 - 电压曲线的特性发生变化，与甲醇添加相关的光电流增强降低。这表明铁减少了表面复合，在没有铁的情况下，甲醇会减少表面复合。因此，增强的光催化作用被解释为是由于铁通过捕获电子减少了表面复合。有人提出，在低铁含量下，光生电子被捕获在表面Fe(III)中心，因此，由于电子 - 空穴复合率降低，可用于形成羟基自由基的空穴数量增加。还提出，在高铁含量下，消毒速率下降是因为晶格中铁中心的电子 - 空穴复合减少了到达表面的空穴数量。我们关于最佳电极性能是表面和体相效应之间平衡的结论与早期作者关于光催化反应的提议一致，即最佳掺杂水平取决于TiO₂ 。
