金属氧化物和石墨烯双重修饰的新型高效Bi2WO6异质光催化剂研究

The project in the development of visible-light-active photocatalyst is of essential scientific significance and practical value to dissolve the problems of environmental pollution and energy crisis. The simplest Aurivillius-type oxide Bi2WO6 is a novel semiconductor photocatalyst which can be induced by visible light up to 460 nm and has received extensive attention. But its practicle application has been still limited by two key basic problems,that is, the narrow absorption in visible light region and the fast recombination of photogenerated holes and electrons. Based on the above-mentioned issues, Bi2WO6 heterostructure photocatalysts doubly modifed with metal oxide MxOy and graphene would be designed and fabricated. By compositing Bi2WO6 with well-matched metal oxide semiconductor, two objects can be achieved. On one hand, the visible light absorption range of Bi2WO6 can be expected to red shift due to the addition of MxOy semiconductor with narrower band gap. On the other hand, the photogenerated electron-hole would be effectively seperated for the inner electric field gnerated in the interface of heterosemicondrctor or for the effect of energy band match. By further introduction of graphen with uniquely high mobility of charge carriers to form ternary Bi2WO6 composite, the irreversible transport of excited electrons would be faster and more effective.Thus the upper limit of photocatalytic activity for singly modified MxOy/Bi2WO6 due to phase defects would be broken through. So the photo quantum efficency and thus the utilization of solar energy could be greatly enhanced to the most extent. In addition, the huge surface areas of graphene would increase the adsorption of photocatalyst to dye molecules and thus provide more active sites for photocatalytic reaciton. The visible light induced photocatalytic activity and the reaction mechanism in the degradation of typical organic pollutants would be systemically evaluated and revealed. In addition, the regulations and principles of the interfacial interaction between MxOy molecules, graphene and the Bi2WO6 substrate would also be disclosed in the assistance of various electro/photo- spectra and theoretical calculations to give instruction to the improvement of current photocatalysts and the design of novel photocatalysts. In the submitted project, visible light induced Bi2WO6-based heterostructre photocatalysts doubly modified by MxOy and graphene with characteristics of high efficiency, wide visible light absorption, and good reusability are expected to be developed. The work has essential meaning in the preparation and application of composite materials and would facilitate the blend of chemistry, materials, and enviroment disciplines.

Bi2WO6作为一种新型可见光光催化剂备受关注，但其有效利用仍受到两个瓶颈问题的限制，即可见光吸收范围窄和光生载流子复合速率快。鉴于此,本项目拟构筑金属氧化物MxOy和石墨烯双重修饰的Bi2WO6异质体系，选择能带匹配的窄带隙MxOy与Bi2WO6有效复合，既可拓宽催化剂的吸光范围，提高太阳能利用率，又可利用带隙耦合效应促进界面光生载流子分离。而具有超强电子传输能力石墨烯的双重修饰，可使光生电子更加快速有效地转移，从而突破MxOy单一修饰因晶相缺陷而导致的性能上限，更大程度上提高光量子效率；其巨大的比表面积还可为光催化反应提供更多活性位点。系统评价其可见光催化降解污染物的活性并揭示反应机理；借助各种光电谱学测试和理论计算深入研究MxOy和石墨烯与Bi2WO6基质的界面作用规律及机制，力争研制出高效稳定的Bi2WO6异质光催化剂。该项目对于解决环境污染和能源短缺具有重要的理论和现实意义。

出于对能源与环境问题的高度关注，开发高效可见光响应型半导体光催化剂，具有重要的理论及现实意义。钨酸铋Bi2WO6作为一种新型铋系光催化剂，在电子结构、晶体结构和稳定性方面均表现出独特的优势。尽管通过对其形貌和微结构的控制，光催化性能已得到部分提高，但要在此基础上进一步提高光催化活性，并使其逐步走向实用化，还面临两个瓶颈问题的限制：一是可见光响应范围较窄，二是光生载流子的复合速率较快。本项目主要围绕上述科学问题，开展了系列卓有成效的研究工作。分别为：采用浸渍-焙烧法和简单易行的室温化学沉积，成功对Bi2WO6进行了金属氧化物Fe2O3、Ag2O的表面沉积，有效构筑起了半导体异质结；利用AgNO3的光敏性，开展了Ag/Bi2WO6的“在线生成和原位光催化”研究，构筑了金属-半导体异质结；通过设计Bi源过量的一锅水热或醇-水溶剂热法，成功实现了铋系“类半导体”碱式硝酸铋及氢氧化铋对Bi2WO6的有效复合；通过一锅醇水溶剂热法，实现了还原氧化石墨对Bi2WO6的包覆修饰。详细表征了复合前后系列光催化剂的组成、形貌、微结构、比表面积、复合形态及界面特征，系统评价了可见光及模拟日光催化降解染料及酚类有机污染物的活性，发现通过上述异质结的有效构筑，同等条件下Bi2WO6的光催化反应动力学常数分别得到2.3-28倍的提高，并进一步借助光电谱学表征、高效液相色谱、电子自旋共振、甚至结合理论计算等手段，深入研究了光催化机理和活性得以提高的机制。此外，对光催化剂“构效关系”的探索一直是光催化材料领域的研究热点，本项目还对Bi基半导体的活性暴露晶面进行了研究，分别制备了具有高效活性晶面的铋基碱式盐和碳酸盐，通过严格控制实验参数，探索了“制备-结构-性能”之间的内在联系，发现了一些有趣的现象和规律。上述有关研究成果已在CrystEngComm、RSC Adv.、Catal. Commun.等国内外重要学术刊物发表研究论文17篇，其中影响因子大于3.0的论文10篇，授权中国发明专利4项，受到国内外同行的关注和好评，圆满完成了预期目标。