Ogbeifun Osemeikhian, Tichapondwa Shepherd M, Chirwa Evans M N
Water Utilization and Environmental Engineering Division, Department of Chemical Engineering, University of Pretoria, Pretoria, 0002, South Africa.
Discov Nano. 2023 Oct 31;18(1):137. doi: 10.1186/s11671-023-03915-4.
BiOCl is a potential photocatalyst in practical applications due to its excellent photostability, visible light activity, and competitive bandgap energy. However, the fast recombination of photogenerated charge carriers makes it impractical for pollution mitigation. Recently, aggregated porphyrins have emerged as photosensitizers in light-dependent applications such as photocatalysis. Although BiOCl and porphyrin can function as separate photocatalysts, their photocatalytic properties in terms of visible light adsorption, charge separation and transport, can be improved when they are combined to form heterostructure. In this study, rod-shaped aggregated 5,10,15, 20-Tetrakis (4-carboxyphenyl) porphyrin was synthesized by CTAB-assisted, self-assembly strategy and BiOCl by a facile microwave method. The porphyrin and BiOCl were combined to generate a series of x%Porphyrin@BiOCl having 0.02% wt., 0.1% wt., 0.4% wt., 1% wt. and 10% wt. as compositions of porphyrin. The materials' photocatalytic degradation efficiency was tested on Rhodamine B dye as a representative pollutant. The best and worst performances were reported for 1%Porphyrin@BiOCl and 10%Porphyrin@BiOCl, respectively, which are 3.1 and 0.5 times increases in efficiency compared to pure BiOCl. From the radical trapping experiment, electrons and superoxide were the dominant reactive species in the degradation process. The enhanced photocatalytic capability of the materials was attributed to the photosensitizing property of porphyrin and the heterojunction formation, which promotes the separation of photogenerated charge carriers. A plausible step-scheme (S-scheme) was proposed for the photocatalytic degradation mechanism. The S-scheme provided the high redox potential of the photogenerated charge carriers. The findings herein offer a new option for improving the photocatalytic performance of BiOCl for environmental applications through the photosensitization strategy.
由于具有优异的光稳定性、可见光活性和具有竞争力的带隙能量，BiOCl在实际应用中是一种潜在的光催化剂。然而，光生载流子的快速复合使得其在污染治理方面不切实际。最近，聚集卟啉已成为光催化等光依赖应用中的光敏剂。尽管BiOCl和卟啉可以作为单独的光催化剂发挥作用，但当它们结合形成异质结构时，其在可见光吸附、电荷分离和传输方面的光催化性能可以得到改善。在本研究中，通过CTAB辅助的自组装策略合成了棒状聚集的5,10,15,20-四（4-羧基苯基）卟啉，并通过简便的微波法合成了BiOCl。将卟啉和BiOCl结合，生成了一系列卟啉含量为0.02% wt.、0.1% wt.、0.4% wt.、1% wt.和10% wt.的x%卟啉@BiOCl。以罗丹明B染料作为代表性污染物测试了材料的光催化降解效率。分别报道了1%卟啉@BiOCl和10%卟啉@BiOCl的最佳和最差性能，与纯BiOCl相比，其效率分别提高了3.1倍和增加了0.5倍。从自由基捕获实验可知，电子和超氧化物是降解过程中的主要活性物种。材料光催化能力的增强归因于卟啉的光敏特性和异质结的形成，这促进了光生载流子的分离。提出了一种合理的分步方案（S-方案）用于光催化降解机理。S-方案提供了光生载流子的高氧化还原电位。本文的研究结果为通过光敏化策略提高BiOCl在环境应用中的光催化性能提供了新的选择。
