Two-Dimensional COF with Rather Low Exciton Binding Energies Comparable to 3D Inorganic Semiconductors in the Visible Range for Water Splitting,The Journal of Physical Chemistry C

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Two-Dimensional COF with Rather Low Exciton Binding Energies Comparable to 3D Inorganic Semiconductors in the Visible Range for Water Splitting
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2019-10-01 , DOI: 10.1021/acs.jpcc.9b07403
Huizhong Ma ₁ , Min Wei _{1,

2} , Fan Jin _{1,

3} , Tingwei Chen ₁ , Yuchen Ma ₁

Affiliation

Many kinds of modification techniques have been developed to improve the quantum efficiency of the graphitic carbon nitride (CN) for photocatalytic water splitting in recent years. In this work, we theoretically propose to incorporate polyyne (−C≡C−)_n between the heptazine ring and the tertiary amino group of CN to form covalent organic frameworks (COFs) as a new strategy to further enhance the photocatalytic ability of CN. These COFs allow for a fine-tuning of their electronic and optical properties by altering the quantity of C≡C bonds. They could fulfill the three ultimate goals of an ideal photocatalyst for water splitting, i.e., broad optical absorption, overall water splitting, and low exciton binding energy. Most strikingly, in the visible region, these COFs possess a lot of strong dipole-allowed exciton transitions whose binding energies are just at the level of a few tens of meV and whose electron and hole are well separated in space by ∼10 nm. This extremely low exciton binding energy is of the same magnitude as that of many three-dimensional inorganic photocatalysts, which is an important characteristic that distinguishes from the conventional two-dimensional semiconductors. Functionalization of the C≡C bonds in the linkers of COFs can further enhance the driving force for water oxidation.

中文翻译：

二维COF具有相当低的激子结合能，在可见光范围内可与3D无机半导体媲美

近年来，已经开发了多种改性技术来提高用于光催化水分解的石墨氮化碳（CN）的量子效率。在这项工作中，我们理论上建议将多炔（-C≡C-）_n在庚嗪环和CN的叔氨基之间形成共价有机骨架（COFs）作为进一步增强CN的光催化能力的新策略。这些COF可以通过改变C≡C键的数量来微调其电子和光学性能。它们可以实现理想的水分解光催化剂的三个最终目标，即广泛的光吸收，整体水分解和低激子结合能。最引人注目的是，在可见光区域中，这些COF具有许多强大的偶极子激子跃迁，其结合能仅为几十meV，并且电子和空穴在空间中的间距约为10 nm。这种极低的激子结合能与许多三维无机光催化剂具有相同的强度，这是区别于常规二维半导体的重要特征。COF的接头中C≡C键的功能化可以进一步增强水氧化的驱动力。

更新日期：2019-10-02

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