Zhu Yong, Li Xiaona, Wen Zhibing, Zhao Ran, Chen Zhi, Zhang Zihao, Gao Hua, Wang Siyao, Li Fei
State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, Dalian University of Technology, Dalian 116024, China.
School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
J Am Chem Soc. 2024 Aug 7;146(31):21903-21912. doi: 10.1021/jacs.4c06461. Epub 2024 Jul 24.
In photoelectrochemical (PEC) cells, selective oxidation of organic substrates coupled with hydrogen evolution represents a promising approach for value-added chemical production and solar energy conversion. In this study, we report on PEC epoxidation of alkenes at a ruthenium dye-sensitized photoanode in a CHCN/HO mixed solvent with LiBr as a mediator and water as the oxygen source. The dye-sensitized photoanode was found to exhibit significant advantages in the simultaneous improvement of charge separation and suppression of charge recombination. First, LiBr as a redox mediator plays a critical role in charge separation, leading to an excellent excited electron injection efficiency of 95% and a high dye regeneration efficiency of 87%. Second, the predominant charge recombination pathway on the dye-sensitized photoanode is efficiently blocked by the reaction between alkene and the generated bromine oxidant. As a result, the current system achieved a remarkable photocurrent density of over 4 mA cm with a record-high incident photo-to-current efficiency (IPCE) of 51% and extraordinary selectivity of up to 99% for the epoxidation of a wide range of alkenes. Meanwhile, nearly 100% Faradaic efficiency for hydrogen evolution was obtained. The performance shown here exceeds that obtained by metal oxide-based semiconductor photoanodes under comparable conditions, demonstrating the great potential of dye-sensitized photoelectrodes for organic synthesis owing to their diversity and tunability.
在光电化学（PEC）电池中，有机底物的选择性氧化与析氢反应相结合，是一种用于增值化学品生产和太阳能转换的很有前景的方法。在本研究中，我们报道了在以LiBr为介质、水为氧源的CHCN/H₂O混合溶剂中，钌染料敏化光阳极上烯烃的PEC环氧化反应。结果发现，该染料敏化光阳极在同时改善电荷分离和抑制电荷复合方面具有显著优势。首先，LiBr作为氧化还原介质在电荷分离中起关键作用，使得激发电子注入效率高达95%，染料再生效率高达87%。其次，烯烃与生成的溴氧化剂之间的反应有效地阻断了染料敏化光阳极上主要的电荷复合途径。因此，当前体系实现了超过4 mA cm⁻²的显著光电流密度，创纪录的高达51%的入射光-电流效率（IPCE）以及对多种烯烃环氧化高达99%的非凡选择性。同时，析氢反应的法拉第效率接近100%。此处展示的性能超过了在可比条件下基于金属氧化物的半导体光阳极所获得的性能，证明了染料敏化光电极因其多样性和可调性在有机合成方面具有巨大潜力。
