Department of Chemical Engineering and Division of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH) , Pohang, Korea 37673.
Laboratory "Photoactive Nanocomposite Materials" Saint-Petersburg State University, Saint-Petersburg, Russia and "Photocatalysis and Nanotechnology", Institut fuer Technische Chemie, Gottfried Wilhelm Leibniz Universitaet Hannover , Hannover, Germany.
Environ Sci Technol. 2017 Apr 4;51(7):3973-3981. doi: 10.1021/acs.est.6b06303. Epub 2017 Mar 23.
We investigated a sequential photocatalysis-dark reaction, wherein organic pollutants were degraded on Ag/TiO under UV irradiation and the dark reduction of hexavalent chromium (Cr(VI)) was subsequently followed. The photocatalytic oxidation of 4-chlorophenol (4-CP), a test organic substrate, induced the generation of degradation intermediates and the storage of electrons in Ag/TiO which were then utilized for reducing Cr(VI) in the postirradiation period. The dark reduction efficiency of Cr(VI) was much higher with Ag/TiO (87%), compared with bare TiO (27%) and Pt/TiO (22%). The Cr(VI) removal by Ag/TiO (87%) was contributed by adsorption (31%), chemical reduction by intermediates of 4-CP degradation (26%), and reduction by electrons stored in Ag (30%). When formic acid, humic acid or ethanol was used as an alternative organic substrate, the electron storage effect was also observed. The postirradiation removal of Cr(VI) on Ag/TiO continued for hours, which is consistent with the observation that a residual potential persisted on the Ag/TiO electrode in the dark whereas little residual potential was observed on bare TiO and Pt/TiO electrodes. The stored electrons in Ag/TiO and their transfer to Cr(VI) were also indicated by the UV-visible absorption spectral change. Moreover, the electrons stored in the preirradiated Ag/TiO reacted with O with showing a sign of low-level OH radical generation in the dark period.
我们研究了一个连续的光催化-暗反应过程，其中有机污染物在 UV 照射下在 Ag/TiO 上降解，随后紧接着进行六价铬（Cr(VI)）的暗还原。作为测试有机底物的 4-氯苯酚（4-CP）的光催化氧化诱导了降解中间产物的生成和 Ag/TiO 中电子的储存，这些电子随后在辐照后时期用于还原 Cr(VI)。与 bare TiO（27%）和 Pt/TiO（22%）相比，Ag/TiO（87%）对 Cr(VI)的暗还原效率要高得多。Ag/TiO（87%）去除 Cr(VI)的贡献来自于吸附（31%）、4-CP 降解中间产物的化学还原（26%）和 Ag 中储存的电子还原（30%）。当甲酸、腐殖酸或乙醇被用作替代有机底物时，也观察到了电子储存效应。Ag/TiO 上 Cr(VI)的辐照后去除持续了数小时，这与在黑暗中 Ag/TiO 电极上存在持续的残余电势而 bare TiO 和 Pt/TiO 电极上几乎没有残余电势的观察结果一致。Ag/TiO 中储存的电子及其向 Cr(VI)的转移也通过 UV-可见吸收光谱的变化得到了证实。此外，储存在预辐照的 Ag/TiO 中的电子与 O 反应，显示出黑暗期内低水平 OH 自由基生成的迹象。
