Wang Hong, He Wenjie, Dong Xing'an, Wang Haiqiang, Dong Fan
Chongqing Key Laboratory of Catalysis and New Environmental Materials, College of Environment and Resources, Chongqing Technology and Business University, Chongqing 400067, China.
Department of Environmental Engineering, Key Laboratory of Polluted Environment Remediation and Ecological Health of Ministry of Education, Zhejiang University, Hangzhou 310027, China.
Sci Bull (Beijing). 2018 Jan 30;63(2):117-125. doi: 10.1016/j.scib.2017.12.013. Epub 2017 Dec 16.
The g-CN with different structures was prepared by heat treatment using urea (CN-U) and thiourea (CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were analyzed with advanced tools. The results showed that the CN-U has a porous structure, a high specific surface area and a wide band gap in comparison with CN-T. The in situ FT-IR technique was used to monitor the adsorption and reaction process of visible photocatalytic NO oxidation on g-CN. The corresponding reaction mechanism was proposed based on the results of reaction intermediate observation and electron paramagnetic resonance (EPR) radical scavenging. It was revealed that (1) the presence of defective sites favored the adsorption of gas molecules and electronically compensated it leading to promoted formation of the final products; (2) the high separation efficiency of photogenerated electron-hole pairs enhanced the production of radicals during the photocatalytic reaction; (3) the hydroxyl radicals (OH) are not selective for the decomposition of pollutants, which are favorable to the complete oxidation of the reaction intermediates. The above three aspects are the main reasons for the CN-U possessing the efficient visible light photocatalytic activity. The present work could provide new insights and methods for understanding the mechanism of photocatalysis.
在相同条件下，以尿素（CN-U）和硫脲（CN-T）为前驱体，通过热处理制备了具有不同结构的石墨相氮化碳（g-CN）。采用先进工具对光催化剂的微观结构和光学性质进行了分析。结果表明，与CN-T相比，CN-U具有多孔结构、高比表面积和宽带隙。采用原位傅里叶变换红外光谱（FT-IR）技术监测了可见光光催化NO在g-CN上氧化的吸附和反应过程。基于反应中间体观察结果和电子顺磁共振（EPR）自由基捕获，提出了相应的反应机理。结果表明：（1）缺陷位点的存在有利于气体分子的吸附并对其进行电子补偿，从而促进最终产物的形成；（2）光生电子-空穴对的高分离效率增强了光催化反应过程中自由基的产生；（3）羟基自由基（OH）对污染物的分解没有选择性，有利于反应中间体的完全氧化。上述三个方面是CN-U具有高效可见光光催化活性的主要原因。本工作可为理解光催化机理提供新的见解和方法。
