Carbon defects in graphitic carbon nitride (g-CN) can modulate the electronic structure for efficient separation of electron–hole pairs, and thereby potentially enhance the photocatalytic H₂ generation. However, the mechanism on the separation of electrons and holes in C defect-modified g-CN still remains unclear. Here we report an autogenic ammonia gas route via in-situ urea decomposition to create carbon defects in g-CN for realizing increased photocatalytic H₂ generation rate of 36.62 µmol h⁻¹ under visible light exposure, which is 10 times higher than that of g-CN obtained in the absence of autogenic ammonia gas (~ 3.63 µmol h⁻¹). Illustrated by the density functional theory calculations, the C defects can not only reduce the band gap for increased light harvesting, but also delocalize the π electrons in valence band (VB) and conduction band (CB) for efficient charge transfer. Such delocalization of π electrons facilitates the efficient separation of electrons in LUMO and holes in HOMO, then promoting the photocatalytic H₂ generation. Therefore, the creation of C defects can be used as an effective route to delocalize the π electrons in g-CN for efficient photocatalytic H₂ generation.

Graphical Abstract

中文翻译：

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碳缺陷引起的π电子离域使能在石墨化氮化碳中进行有效的电荷分离，从而增加了光催化氢气的产生

石墨氮化碳（g-CN）中的碳缺陷可以调节电子结构以有效分离电子-空穴对，从而潜在地增强光催化H _{2 的}生成。然而，C缺陷修饰的g-CN中电子和空穴的分离机制仍不清楚。在这里，我们报告了一种通过原位尿素分解在 g-CN 中产生碳缺陷的自生氨气途径，以在可见光照射下实现36.62 µmol h ^{-1 的}光催化 H ₂生成率，这是g-CN 的10 倍-CN 在不存在自生氨气的情况下获得 (~ 3.63 µmol h ^-1）。密度泛函理论计算表明，C 缺陷不仅可以减小带隙以增加光收集，而且还可以使价带 (VB) 和导带 (CB) 中的 π 电子离域以实现有效的电荷转移。π 电子的这种离域化促进了 LUMO 中的电子和 HOMO 中的空穴的有效分离，从而促进了光催化 H _{2 的}生成。因此，C缺陷的产生可以作为使g-CN中的π电子离域以高效光催化H ₂生成的有效途径。

图形概要