石墨烯基Z型光催化体系对多溴联苯醚的光催化还原降解研究

Polybrominated diphenyl ethers (PBDEs), a class of persistent organic pollutants widely existed in environment, were placed into Annex A of the Stockholm Convention in 2009. Therefore, a growing need existed for developing efficient PBDEs degradation technology to ensure the environemental satefy and Stockholm Convention implementation. Photocatalytic reduction technology over semiconductor photocatalyst by utilizing sunlight is an advantage process for PBDEs degradation. The challenge in developing this photocatalytic system lies in keeping the photoexcited electrons at a sufficient high reduction potential for achieving efficient reductive debromination of PBDEs. Herein, we propose the fabrication of graphene based Z-scheme photocatalytic system that inspired by natural photosynthesis in green plants for photocatalytic debromination of PBDEs. The phtocatalytic performance of the graphene based Z-scheme system could be optimized by the modulation of photosystem I (PS I)/graphene/PS II contact interface, which could overcome the "bottleneck" problem of photocatalytic degradation of PBDEs by holding photoexcited electrons in PS I at a high red-/ox- potential, and reducing the probability of charge recombination as a result of vectorial electron transfer driven by the two-step excitation of PS I and PS II. The strategy represents a versatile approach to design novel photocatalytic system by mimicking natural concepts, which provides new perspectives for photocatalytic debromination technology.

多溴联苯醚（PBDEs）是一类在环境介质中广泛存在的持久性有机污染物，2009年斯德哥尔摩公约将PBDEs列入受控名单，因此，寻求高效的PBDEs降解技术对确保环境安全和履行公约具有重要的意义。基于太阳光利用的光催化还原技术是实现PBDEs脱溴降解的有效途径，其关键是设计具有高光生电子还原能力的半导体光催化体系。本项目提出以石墨烯作为电子传递链构建模拟绿色植物光合作用机制的Z型光催化体系来实现PBDEs的光催化还原降解。通过调控光系统Ⅰ-石墨烯-光系统Ⅱ的界面性质，定性研究并优化体系的光催化性能，增强光催化体系内光生电子还原能力、电子-空穴对分离效率和催化剂表面吸附污染物能力，实现PBDEs的高效光催化还原脱溴降解。本研究采用仿生学的方法设计Z型光催化体系，将为有效提高光催化剂的还原脱卤性能提供新思路，进一步丰富光催化体系设计理论。

基于太阳光利用的光催化还原技术是实现PBDEs脱溴降解的有效途径，其关键是设计具有高光生电子还原能力的光催化体系。本研究以石墨烯作为电子传递链，CdS、TiO2分别作为光系统I和光系统II，通过溶剂热的方法构建了模拟绿色植物光合作用机制的Z型光催化体系来实现PBDEs的光催化还原降解。与传统异质结构体系(CdS/TiO2)相比，在模拟太阳光的照射下Z型光催化体系CdS-RGO-TiO2实现了对多溴联苯醚(PBDE-47)的更高效光催化还原降解。对降解中间产物的鉴定分析表明PBDE的光催化还原降解是一个逐步脱溴过程，最终生成联苯醚。通过Pt纳米晶的光还原沉积实验验证了体系内的Z型电子传递过程(TiO2 → graphene → CdS)。进一步分析表明PBDE-47的光催化还原降解过程可能是一个串联反应过程：即光照下首先在Z型催化剂表面产生氢气，随后在催化剂表面原位进行脱溴加氢反应，实现PBDE的光催化还原降解。本研究采用仿生学的方法设计Z型光催化体系，将为有效提高光催化剂的还原脱卤性能提供新思路。