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Heterojunctions for Photocatalytic Wastewater Treatment: Positive Holes, Hydroxyl Radicals and Activation Mechanism under UV and Visible Light
International Journal of Chemical Reactor Engineering ( IF 1.6 ) Pub Date : 2020-02-19 , DOI: 10.1515/ijcre-2019-0159
José Alfonso Pinedo Escobar 1 , Edgar Moctezuma 2 , Benito Serrano Rosales 1
Affiliation  

Abstract Forming heterojunctions by coupling two or more semiconductors is an important strategy to develop stable and efficient photocatalysts able to operate both under near-UV and visible light. Five novel heterojunction systems were synthesized in the present study, using a modified sol-gel method: Bi2Mo3O12/TiO2, ZnFe2O4/TiO2, FeTiO3/TiO2, WO3(US)/TiO2 and WO3/TiO2. These heterojunction semiconductors were characterized by using XRD, SEM and EDX, UV–Vis diffuse reflectance spectroscopy and BET. Their photocatalytic activities were evaluated using methyl orange (MO) degradation under both near-UV and visible light. From the various heterojunctions developed, the WO3(US)/TiO2 photocatalyst was the one that showed the highest photocatalytic efficiency with this being assigned to the formation of a double heterojunction involving anatase, rutile and monoclinic WO3 phases. On this basis, a photocatalyst activation mechanism applicable to near-UV and visible light irradiation was proposed. This mechanism explains how the photogenerated electrons (e–) and positive holes (h+) can be transferred to the various phases. As a result, and given the reduced holes and electron recombination surface, hydroxyl radicals found were more abundant. To confirm this assumption, hole formation in the valence band was studied, using hole-scavenging reactions involving ion iodine (I–), while hydroxyl radical production used fluorescence spectroscopy.

中文翻译:

用于光催化废水处理的异质结:紫外线和可见光下的正空穴、羟基自由基和活化机制

摘要 通过耦合两个或多个半导体形成异质结是开发能够在近紫外和可见光下工作的稳定高效光催化剂的重要策略。在本研究中,使用改进的溶胶-凝胶法合成了五种新型异质结系统:Bi2Mo3O12/TiO2、ZnFe2O4/TiO2、FeTiO3/TiO2、WO3(US)/TiO2 和 WO3/TiO2。通过使用 XRD、SEM 和 EDX、UV-Vis 漫反射光谱和 BET 对这些异质结半导体进行了表征。在近紫外和可见光下使用甲基橙 (MO) 降解来评估它们的光催化活性。从开发的各种异质结来看,WO3(US)/TiO2 光催化剂是表现出最高光催化效率的光催化剂,这归因于形成涉及锐钛矿的双异质结,金红石和单斜 WO3 相。在此基础上,提出了一种适用于近紫外和可见光照射的光催化剂活化机制。这种机制解释了光生电子 (e-) 和空穴 (h+) 如何转移到各个相。结果,鉴于空穴和电子复合表面的减少,发现的羟基自由基更加丰富。为了证实这一假设,研究了价带中的空穴形成,使用涉及离子碘 (I-) 的空穴清除反应,而羟基自由基的产生使用荧光光谱。这种机制解释了光生电子 (e-) 和空穴 (h+) 如何转移到各个相。结果,鉴于减少的空穴和电子复合表面,发现的羟基自由基更丰富。为了证实这一假设,研究了价带中的空穴形成,使用涉及离子碘 (I-) 的空穴清除反应,而羟基自由基的产生使用荧光光谱。这种机制解释了光生电子 (e-) 和空穴 (h+) 如何转移到各个相。结果,鉴于空穴和电子复合表面的减少,发现的羟基自由基更加丰富。为了证实这一假设,研究了价带中的空穴形成,使用涉及离子碘 (I-) 的空穴清除反应,而羟基自由基的产生使用荧光光谱。
更新日期:2020-02-19
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