BiOXs-氧化石墨烯的结构调控及其光催化氧化性能

Photocatalysis oxidization is the process of decomposing organic pollutants to minerals using semiconductor photocatalysts under solar light irradiation. The conventional TiO2 photocatalyst is confined by its wide band gap and responds only to UV light that accounts for less than 5% of sunlight energy, inducing lower degradation efficiency. Therefore, in order to take full advantage of the abundant solar energy, especially visible-light, it is of crucial significance to develop visible-light-driven photocatalysts with high efficiency. In the program, we will plan to prepare BiOC1xBryI1-x-y solid solution novel photocatalysts with three halogens through solvothermal methods. Moreover, Graphene possesses excellent properties of give-accepting and delivering electrons due to their hexagon π-conjugation system with delocalized electrons. To reduce the electron–hole recombination, we will futher plan to in-situ compose BiOXs with two halogens or three halogens with a series of selective reduced graphene oxides, which can improve the decomposition efficiency. Based on that, the electron delivery properties have been simulated and defined by electrochemistry impedance spectrum. The structure and surface fuctional groups of the so-prepared photocatalysts have been characterized by electron microscope, photo-electron energy spectroscopy, infrared and UV spectroscopy, and so on. The intrinsic relation between catalyst structures and catalysis efficiency has been constituted, which can provide necessary experimental data and theoretic support for designing and developing photocatalysts with high efficiency.

光催化氧化是通过半导体光催化剂在太阳光的照射下将环境中有机污染物完全矿化降解的过程。传统的TiO2光催化剂因其禁带宽度只能吸收小于太阳能5%的紫外光而使降解效率大大降低。因此，为了拓宽对太阳能尤其是可见光的吸收，开发高效的可见光激发的光催化剂具有重要的意义。本项目拟采用溶剂热法制备三卤素的卤氧化铋固溶体BiOC1xBryI1-x-y新型光催化剂。另外，由于石墨烯的六元环π共轭离域电子体系赋予其优异的电子授受和传输能力，为了降低电子-空穴对的复合率，本项目进一步将双卤素、三卤素的卤氧化铋固溶体（BiOXs）与经选择性还原的系列氧化石墨烯进行原位复合以提高其降解效率。并在此基础上，通过电化学阻抗谱拟合分析其电子传输性，通过电子显微镜、光电子能谱、红外和紫外光谱等表征所制备光催化剂的结构和表面官能团，从而建立催化剂的结构和催化效率的内在联系，为设计开发高效的光催化剂提供必要的实验数据和理论依据。

光催化氧化技术被认为是目前解决能源短缺和环境污染最具潜力的技术方案之一，然而传统的TiO2只能吸收小于太阳能5%的紫外光而使其催化氧化性能大大降低。因此，为了拓宽对太阳能尤其是可见光的吸收，开发高效的可见光激发的光催化剂具有重要的意义。本项目采用混合溶剂热法，通过调变反应条件，包括溶剂的配比、反应时间、原子配比及各种不同结构的鳌合助剂，制备了一系列单卤素、双卤素及三卤素的卤氧化铋（BiOXs，X=Cl、Br或I）光催化剂，并通过XRD、SEM、EDS、Mapping、TEM、XPS、UV-vis DRS、PL光谱、BET比表面测试仪对其结构及形貌进行了表征，结果显示以此方法可成功制备出结晶良好、纳米片状结构、光生电子-空穴复合率低、比表面高的单卤氧化铋及BiOXs固溶体。随后以双酚A、甲基紫、臧红、罗丹明B（RhB）、甲基橙（MO）或亚甲基兰（MB）为模拟物在可见光下对上述制备的催化剂进行了光催化氧化性能的评价，经筛选对比发现溶剂的体积比为1：1的条件下，冰醋酸的调控下，120℃反应10min制备BiOCl（60.800m2/g），反应12h制得的BiOCl0.33Br0.33I0.33, 柠檬酸调控下制备的BiOCl0.4Br0.6，BiOCl0.6I0.4以及乳酸调控下得到的BiOCl0.5I0.5和BiOCl0.33Br0.33I0.33固溶体均具有较优异的可见光催化氧化性能，其中乳酸调控下制备的BiOCl0.5I0.5和BiOCl0.33Br0.33I0.33固溶体的催化氧化性能更优，在可见光照180min，对15mg/L的MO降解率分别为83%和98%。在此基础上，将筛选出的卤氧化铋催化剂与制备的氧化石墨烯（GO）、还原GO、官能团化的GO、三维石墨烯（3D-G）以及氮杂三维石墨烯（N-3D-G）进行原位复合，并调节其相互的配比，对结构和催化氧化性能进行了表征和测试，通过对比发现，复合2%-3D-G的BiOCl0.5I0.5对15mg/L的MO降解率可达到95%，复合1%-N-3D-G的BiOCl0.33Br0.33I0.33对30mg/L的MO降解率可达到71%，进而对性能优异的催化体系进行电化学阻抗、光电流及自由基捕获实验分析考察了电子传输性、结构与催化性能之间的关联以及催化氧化机理，这些结果为设计开发高效的可见光催化剂提供必要实验数据和理论支持。