Optimizing Optical Absorption, Exciton Dissociation, and Charge Transfer of a Polymeric Carbon Nitride with Ultrahigh Solar Hydrogen Production Activity.
Optimizing Optical Absorption, Exciton Dissociation, and Charge Transfer of a Polymeric Carbon Nitride with Ultrahigh Solar Hydrogen Production Activity.
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DOI：
10.1002/anie.201706870
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发表时间：
2017-10
影响因子：
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通讯作者：
Guigang Zhang;Guosheng Li;Zhi‐An Lan;Lihua Lin;Aleksandr Savateev;T. Heil;S. Zafeiratos;Xinchen Wang
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文献类型：
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作者：
Guigang Zhang;Guosheng Li;Zhi‐An Lan;Lihua Lin;Aleksandr Savateev;T. Heil;S. Zafeiratos;Xinchen Wang
聚合物或有机半导体是有希望的候选者，但由于强烈的束缚激子和不足的光吸收，大多数仅显示出中等的活性。在此，我们报告了一种简单的自下而上的策略，以提高氮化碳的活性，使大多数光子真正用于驱动光氧化还原化学。尿素和草酰胺的共缩合，然后在熔融盐中后煅烧，显示出导致高度结晶的物种，具有0.292 nm的七嗪单元的最大π-π层堆叠距离，这改善了横向电荷传输和层间激子解离。草酰胺的添加将光学带隙从2.74 eV降低到2.56 eV，这使得也能够利用绿色光进行有效的光化学。最佳样品在420 nm和525 nm处的析氢表观量子产率（AQY）分别达到57%和10%，这显著高于大多数先前的实验。
Polymeric or organic semiconductors are promising candidates for photocatalysis but mostly only show moderate activity owing to strongly bound excitons and insufficient optical absorption. Herein, we report a facile bottom-up strategy to improve the activity of a carbon nitride to a level in which a majority of photons are really used to drive photoredox chemistry. Co-condensation of urea and oxamide followed by post-calcination in molten salt is shown to result in highly crystalline species with a maximum π-π layer stacking distance of heptazine units of 0.292 nm, which improves lateral charge transport and interlayer exciton dissociation. The addition of oxamide decreases the optical band gap from 2.74 to 2.56 eV, which enables efficient photochemistry also with green light. The apparent quantum yield (AQY) for H2 evolution of optimal samples reaches 57 % and 10 % at 420 nm and 525 nm, respectively, which is significantly higher than in most previous experiments.