Enhanced Photocatalytic Degradation of Perfluorooctanoic Acid by Mesoporous Sb(2)O(3)/TiO(2) Heterojunctions.
Enhanced Photocatalytic Degradation of Perfluorooctanoic Acid by Mesoporous Sb(2)O(3)/TiO(2) Heterojunctions.
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DOI：
10.3389/fchem.2021.690520
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发表时间：
2021
影响因子：
5.5
通讯作者：
Qiu K
中科院分区：
文献类型：
--
作者：
Yao X;Zuo J;Wang YJ;Song NN;Li HH;Qiu K
全氟辛酸（PFOA）是一种典型的全氟羧酸，是受《斯德哥尔摩公约》监管的新兴一类永久性有机污染物。然而，PFOA 的降解相当具有挑战性，这主要是由于 C-F 键的超高稳定性。与其他技术相比，光催化降解具有操作简单、条件温和以及优异的分解和脱氟效率等潜在优势。二氧化钛 (TiO2) 是最常用的光催化剂之一，但迄今为止，原始纳米级 TiO2（例如商业 P25）被认为对 PFOA 降解效率低，因为 TiO2 光生羟基自由基无法直接攻击 C-F 键。因此，本工作合理设计了介孔Sb2O3/TiO2异质结，其中介孔TiO2骨架中受限的Sb2O3纳米粒子不仅可以调节能带结构，还可以增加PFOA降解的活性位点数量。结果发现，负载Sb2O3后，对紫外光的吸收增强，光利用效率更高；同时带隙减小，加速了光生载流子的分离；最重要的是，Sb2O3/TiO2异质结的价带边缘显着抬高，从而阻止了羟基自由基途径的发生。在 Sb2O3-TiO2 的最佳比例下，所得催化剂能够在 2 小时内去除 81.7% PFOA，其降解动力学比商业 P25 快 4.2 倍。清除剂测试和电子自旋共振谱进一步表明，这种改善主要归因于超氧自由基和光生空穴的形成，其中前者驱动C7F15COOH–C7F15•的脱羧，后者促进C7F15COO−–C7F15COO•转化的直接电子转移。 Sb2O3/TiO2光催化剂具有高度可回收性，连续5次循环后仍保留近90%的初始活性，保证了长期运行的可行性。
Perfluorooctanoic acid (PFOA), a typical perfluorinated carboxylic acid, is an emerging type of permanent organic pollutants that are regulated by the Stockholm Convention. The degradation of PFOA, however, is quite challenging largely due to the ultra-high stability of C-F bonds. Compared with other techniques, photocatalytic degradation offers the potential advantages of simple operation under mild conditions as well as exceptional decomposition and defluorination efficiency. Titanium dioxide (TiO2) is one of the most frequently used photocatalysts, but so far, the pristine nanosized TiO2 (e.g., the commercial P25) has been considered inefficient for PFOA degradation, since the photo-generated hydroxyl radicals from TiO2 are not able to directly attack C-F bonds. Mesoporous Sb2O3/TiO2 heterojunctions were therefore rationally designed in this work, of which the confined Sb2O3 nanoparticles in mesoporous TiO2 framework could not only tune the band structure and also increase the number of active sites for PFOA degradation. It was found that, after loading Sb2O3, the absorption of UV light was enhanced, indicating a higher efficiency of light utilization; while the band gap was reduced, which accelerated the separation of photo-generated charge carriers; and most importantly, the valence band edge of the Sb2O3/TiO2 heterojunction was significantly lifted so as to prevent the occurrence of hydroxyl radical pathway. Under the optimal ratio of Sb2O3–TiO2, the resulting catalysts managed to remove 81.7% PFOA in 2 h, with a degradation kinetics 4.2 times faster than the commercial P25. Scavenger tests and electron spin resonance spectra further revealed that such improvement was mainly attributed to the formation of superoxide radicals and photo-generated holes, in which the former drove the decarboxylation from C7F15COOH–C7F15 •, and the latter promoted the direct electron transfer for the conversion of C7F15COO−–C7F15COO•. The Sb2O3/TiO2 photocatalysts were highly recyclable, with nearly 90% of the initial activity being retained after five consecutive cycles, guaranteeing the feasibility of long-term operation.