BiOCl/TiO2的氯化改性及其新式光生自由基催化反应

采用溶胶凝胶法制备了BiOCl/TiO₂复合催化剂，透射电镜（TEM）照片显示，两种半导体分布均匀、相互连接，形成的异质结可以为电子传导提供有效通道.经过氯化处理的复合材料具备更强的光催化能力，在紫外光条件下对苯的降解率达到90%，是原BiOCl/TiO₂的2倍、纯TiO₂的10倍.本文利用X射线光电子能谱、红外光谱和电子顺磁共振，对表面氯化的机理进行研究.结果表明，氯元素以Ti—Cl的方式吸附在催化剂表面，在光照条件下光生空穴夺取一个电子，使其生成氯自由基，进而配合超氧、羟基，构成一种新型的三自由基光催化体系，使催化降解能力大幅提升.最后，利用实验方法得到了光生氯自由基的直接证据，并构建了该体系的光催化反应机理.

The new free radical reaction of chlorinated BiOCl/TiO2

In this article, the BiOCl/TiO₂ composite has been successfully prepared via a sol-gel method and then modified by surface chlorination. According to the TEM images, two components were uniformly dispersed and connected to each other, which facilitated the transfer of photo-generated carriers. Under the UV light irradiation, the BiOCl/TiO₂ exhibited good photocatalytic activity and stability for gas-phase benzene oxidation and the surface chlorination would further enhance its performance. About 90% degradation was achieved over chlorinated BiOCl/TiO₂, which was twice as original BiOCl/TiO₂ and ten times compared to bare TiO₂. The prepared composites have been characterized by electronic chemistry station, Fourier transform infrared spectrometry (FT-IR), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) to explore the outstanding photocatalytic activity. As confirmed by XPS and FT-IR, the Cl was chemically adsorbed on the surface of catalyst (Ti-Cl), which would lead to a new mechanism for photocatalysis. Under the UV light irradiation, besides ·OH and ·O₂^- radicals, the photocatalytic reaction was also driven by photo-generated ·Cl radicals, which was confirmed by EPR analysis. Hence, the photocatalytic activity was significantly enhanced by synergistic effects of three radicals.