新型碱式硝酸铋系光催化剂的微结构可控合成及其高度有序异质结的构建

Different from other bismuth-based compounds, basic bismuth nitrates, having more negative conduction band potentials (<-0.69 eV), are promised to possess good photocatalytic activity for hydrogen evolution from water splitting. Nevertheless, they have not been completely developed due to difficult isolation resulting from the presence of crystal water. Based on previous studies, this project is going to prepare several novel basic bismuth nitrates with controllable morphology and good photocatalytic activity for both hydrogen evolution from water splitting and degradation for pollutants. Moreover, the construction of heterojunctions is promised to enlarge light absorption range and inhibit recombination of the photo-generated electrons and holes, and consequently increase the photocatalytic efficiency. Based on semiconducting theories, except that the conduction and valence bands of heterojunction semiconductors are required to match each other and the interface should closely contact, it is very important that the heterojunctions must possess long-range-order microstructures and suitable surface energy to ensure the carriers to transport orientedly without quenching. To the best of our knowledge, little study has been carried out on the relationship between the structures and performance of the heterojunction photocatalysts. Herein, two kinds of heterojunctions will be designed: layered structure BiOBr/Bi2O2(OH)(NO3) and [Bi6O6(OH)2](NO3)4·2H2O/[Bi6O5(OH)3](NO3)5·3H2O containing [Bi6Ox(OH)8-x]10-x entities. They possess similar lattice parameters for each other, and would grow epitaxially along with each other to generation heterojunctions with ordered interfacial microstructures. Besides, thanks to surface plasmon resonance effect of metal Bi and photo-sensitive property of Bi2S3, some visible-light-driven photocatalysts will be prepared via in-site reduction or sulfide. The purpose of the project is to find a correlation between the heterojunction microstructures and photocatalytic activity, and to provide scientific basis for developing highly efficient visible-light-driven photocatalysts.

碱式硝酸铋系化合物无毒、种类多，但由于分离困难尚未充分开发。不同于其它铋基光催化剂，它们的导带电位（<-0.69 eV)低，理论上应具有光催化水分解制氢活性。项目拟鉴于前期研究，微结构可控地制备兼具优异的光催化水分解制氢活性及污染物降解活性的碱式硝酸铋，并基于理论计算，设计晶体结构等匹配度高的碱式硝酸铋基异质结，层状结构的BiOBr/Bi2O2(OH)(NO3)及具有[Bi6Ox(OH)8-x]10-x结构的[Bi6O6(OH)2](NO3)4·2H2O/[Bi6O5(OH)3](NO3)5·3H2O等。采用液相外延生长法等制备，以确保异质结的界面紧密结合且高度有序，利于载流子在界面上定向迁移而不很快淬灭，大大提高光催化效率。进一步在表面沉积高度分散的Bi2S3或Bi，改善可见光催化性能。最后，探讨异质结及表面沉积物的微结构与光催化性能之间的构效关系，为开发高效可见光催化剂提供科学依据。

作为一种解决能源与环境问题的有效绿色手段，利用光催化技术处理废水、废气及光解水制氢的研究引起了广泛关注。但由于还存在不能充分利用太阳光、光催化效率低及催化剂的回收再利用等问题，实现光催化剂在实际生产中的应用还存在差距，获得高效、价廉的光催化剂是解决光催化剂实用化的瓶颈。.考虑到TiO2光催化剂仍存在禁带宽度大不能充分利用太阳光及光催化效率低等不足，开发新型可见光催化剂成为重要的研究方向。铋系半导体材料因其来源丰富、对可见光响应良好及光催化性能优异，备受研究者关注。尽管已有大量文献报道，但由于便宜易得的原料Bi(NO3)3·5H2O易水解，在室温下难以制备获得形貌及微结构均匀的产物，所以合成反应大多在水热法条件下进行，不利于大规模生产。另外，单一材料作为光催化剂存在光响应范围窄、光生载流子易复合等缺点。本项目的创新点及突破的关键技术之一，通过选择合适的溶剂，使得大部分合成反应在室温下进行，解决了硝酸铋容易水解而难以进行均相合成的问题；创新点及关键技术之二，室温下一步法制备了几种铋基光催化剂的异质结，包括碱式硝酸铋等构建的异质结，特别是能同时保留高氧化还原性能与载流子分离效率的Z-及S-异质结，详细探讨了异质结的微结构及电子结构等匹配度对光催化性能的影响；创新点及关键技术之三，通过微结构调控，获得了性能优异的几种铋基光催化剂，详细研究了铋系催化剂的微观结构、粒径及形貌与光催化性能的构效关系，并探讨了光催化机理。.在该项目经费支持下，以该项目作为唯一标注，在国际一流期刊Nanoscale, Chem.Eng.J等上发表SCI收录论文27篇，获批专利1件。超额完成了合同所预期的指标。培养硕士及博士研究生共12名。