As a promising metal-free photocatalyst, graphitic carbon nitride (g-C₃N₄) has attracted increasing attention. However, from the viewpoint of practical application, the quantum efficiency of g-C₃N₄ needs to be further improved. In this article, carbon dots (C-dots) modified g-C₃N₄ hybrid was successfully prepared by a novel strategy using C-dots and dicyandiamide as starting materials. The photocatalyst was characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), FT-IR, UV–Vis diffuse reflectance spectrum (DRS), X-ray photoelectron spectroscopy (XPS), powder photoluminescence (PL) and surface photovoltage spectrum (SPS). Both the photocatalytic activity of C-dots modified g-C₃N₄ was evaluated by degradation of Rhodamine B under UV irradiation and photocatalytic hydrogen production under visible irradiation. The experimental results show that C-dots modification causes the lattice distortion of g-C₃N₄. With increase in the loading amount of C-dots, the photocatalytic activity of g-C₃N₄ increase first and then decrease. g-C₃N₄ modified with 0.25wt.% C-dots shows the highest photocatalytic activity, which is 3 times higher than pristine g-C₃N₄. C-dots act as electron-sinks, which prevent the recombination of photo-generated electron-hole pairs, enhancing the photocatalytic activity of g-C₃N₄. However, too much C-dots become recombination centers, which is detrimental to the photocatalytic activity of g-C₃N₄.

中文翻译：

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碳点修饰对g-C3N4结构和光催化活性的影响

作为有前途的无金属光催化剂，石墨氮化碳（gC ₃ N ₄）引起了越来越多的关注。但是，从实际应用的观点出发，需要进一步提高gC ₃ N ₄的量子效率。在本文中，碳点（C点）修饰了gC ₃ N ₄通过使用C点和双氰胺为起始原料的新策略成功制备了杂合体。通过扫描电子显微镜（SEM），透射电子显微镜（TEM），X射线衍射（XRD），FT-IR，UV-Vis漫反射光谱（DRS），X射线光电子能谱（XPS），粉末光致发光（PL）和表面光电压谱（SPS）。C-点修饰的gC ₃ N ₄的光催化活性均通过若丹明B在紫外线照射下的降解以及可见光照射下的光催化产氢来评估。实验结果表明，碳点修饰引起gC ₃ N ₄的晶格畸变。随着C点的负载量增加，gC ₃ N ₄的光催化活性先增加然后降低。用0.25wt。％的碳点改性的gC ₃ N ₄表现出最高的光催化活性，是原始gC ₃ N _4的3倍。C点充当电子吸收器，可防止光生电子空穴对的重组，从而增强gC ₃ N ₄的光催化活性。然而，太多的C-点成为重组中心，这不利于gC ₃ N ₄的光催化活性。