Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, 14476, Potsdam, Germany.
State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, Fuzhou, 350002, China.
Angew Chem Int Ed Engl. 2017 Oct 16;56(43):13445-13449. doi: 10.1002/anie.201706870. Epub 2017 Sep 18.
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 H evolution of optimal samples reaches 57 % and 10 % at 420 nm and 525 nm, respectively, which is significantly higher than in most previous experiments.
聚合物或有机半导体是光催化的有前途的候选材料，但由于激子结合较强和光吸收不足，它们大多只表现出中等活性。在此，我们报告了一种简便的自下而上策略，可将氮化碳的活性提高到可实际利用大部分光子来驱动光氧化还原化学的水平。尿素和草酰胺的共缩聚，然后在熔融盐中进行后煅烧，可得到具有最高π-π层堆积距离为 0.292nm 的六嗪单元的高结晶物种，这可改善横向电荷输运和层间激子离解。草酰胺的添加可将光学带隙从 2.74eV 降低至 2.56eV，这使得绿光也能有效地进行光化学。最佳样品的 H2 析出的表观量子产率（AQY）在 420nm 和 525nm 时分别达到 57%和 10%，明显高于大多数先前的实验。
