含氧空位BiOCl纳米片可见光活化分子氧降解五氯酚的研究

In recent years, photocatalytic degradation of pentachlorophenol (PCP) on semiconductor has received much attention. However, it is difficult to measure the contributions of various active species on its degradation pathway because multiple active species (h+, e-, •O2-, •OH and so on) participate in the photocatalytic reaction， not beneficial for the exploration of PCP degradation pathway. Very recently, it is found that although electrons on the valance band of BiOCl can not be excited directly under visible light, oxygen vacancies on BiOCl surface could induce sub-band excitation from defect states to the conduction band for molecular oxygen activation, which could produce measurable •O2- and •OH for PCP degradation. Based on this find, we would employ BiOCl nanoplates with oxygen vacancies for degrading PCP under visible light, and try to adjust the concentration of •O2- and •OH by controlling the ratio of exposed (001) and (010) facets on BiOCl and the concentration of their surface oxygen vacancies. We will study the contributions of the concentration and ratio of •O2- and •OH on PCP degradation pathway, and analyze the relationship between degradation pathway and efficiency. On the basis of the above result, we will explore the contributions of •O2- and •OH on PCP dechlorination and mineralization reactions for illustrating PCP degradation pathway and reaction mechanism on BiOCl with surface oxygen vacancies. By this way, we demonstrate that PCP can be removed efficiently via a photocatalytic molecular oxygen activation route and propose a novel strategy for removing PCP by utilizing molecular oxygen in air.

近年来半导体光催化降解五氯酚备受关注，但反应中多种活性物种（h+、e-、•O2-和•OH等）的参与增加了研究PCP降解路径中活性物种各自贡献的难度,不利于探明PCP光催化降解路径。最新研究发现，含氧空位BiOCl在可见光下不会发生价带电子直接激发，而是通过氧空位缺陷导致Sub-band在可见光下激发活化分子氧生成浓度易于检测的•O2-和•OH。基于这一发现，本项目拟采用含氧空位BiOCl纳米片可见光催化降解PCP，通过调控BiOCl纳米片(001)和(010)晶面比例及氧空位浓度来调节光催化体系中•O2-和•OH的浓度；研究•O2-和•OH浓度及比例对五氯酚降解的影响，分析五氯酚降解路径与效率之间的关系，深入揭示•O2-和•OH在PCP脱氯和开环过程中作用，阐明含氧空位BiOCl纳米片可见光降解PCP的途径和机理，实现高效PCP光催化降解，为利用空气中分子氧去除环境中五氯酚开辟一条新途径。

针对半导体光催化降解五氯酚反应中多活性物种（h+、e-、•O2-和•OH等）的参与增加了研究PCP降解中活性物种各自贡献的难度,不利于高效PCP光催化剂的设计。本研究选择BiOCl为目标催化剂，含氧空位BiOCl在可见光下不会发生价带电子直接激发，而是通过氧空位缺陷导致Sub-band在可见光下激发活化分子氧生成浓度易于检测的•O2-和•OH。基于这一事实，本项目首先通过低温液相法采取调控pH或者改变反应溶液浓度的方法调控BiOCl纳米片(001)晶面暴露比例，(001)晶面暴露越多，越有利于•O2-的生成，从而调控可见光照下反应溶液中•O2-和•OH的比例关系，探明•O2-和•OH的比例关系对五氯酚钠降解效率的影响。结果显示反应体系中高比例•O2-能提高五氯酚钠的降解效率，而在保证高浓度•O2-的前提下提高•OH浓度是进一步提高五氯酚钠降解效率的关键。在此基础上进一步通过I-和Br-掺杂不同晶面暴露的BiOCl，发现I-和Br-掺杂分别对(001)和(010)晶面暴露为主的含氧空位BiOCl光催化活性的提高更有利。此外，还制备了BiOClxBr1-x，BiOCl/BiOBr, 金属酞菁，In2S3等光催化剂，选择研究了他们在催化酚类污染物或者染料的效率及催化机制。本研究为制备高效BiOCl基光催化剂利用空气中分子氧去除环境中五氯酚提供了切实可行的方向。