In this work, nitrogen‐defective g‐C3N4 with different nitrogen defect densities is synthesized for ciprofloxacin photocatalytic degradation. Compared with pristine g‐C3N4, g‐C3N4 etched with NaBH4 for 1 h exhibits an approximately ten‐fold increase in the rate constant of ciprofloxacin (CIP) degradation. The combined experimental analysis and theoretical calculations reveal that nitrogen defects can be incorporated into g‐C3N4 in all nitrogen sites and that C─N═C is the most susceptible site. By incorporating nitrogen defects to induce defect states between the conduction band (CB) and valence band (VB), the electronic and band structures are tuned. The induced defect states can be downshifted to approach the valance band, reaching increased nitrogen defect density within optimum ranges to accommodate excited electrons to narrow the bandgap, extend the light absorption capability, and enhance the charge carrier separation and transfer efficiency. The g‐C3N4 etched by NaBH4 for 2 h with over‐introduced nitrogen defects exhibits a declined performance due to a deteriorated structure, and the over‐downshifted defect states turn out to be a new recombination center for charge carriers.

中文翻译：

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揭示缺陷 g-C3N4 中氮缺陷的存在和位置以改善有机光催化降解：来自实验和理论计算的见解


在这项工作中，合成了具有不同氮缺陷密度的氮缺陷g-C3N4，用于环丙沙星的光催化降解。与原始 g-C3N4 相比，用 NaBH4 蚀刻 1 小时的 g-C3N4 环丙沙星 (CIP) 降解速率常数增加了约十倍。实验分析和理论计算相结合表明，氮缺陷可以在所有氮位点并入g-C3N4中，其中C─N=C是最容易受影响的位点。通过引入氮缺陷来诱导导带 (CB) 和价带 (VB) 之间的缺陷态，从而调整电子和能带结构。诱导的缺陷态可以下移以接近价带，在最佳范围内达到增加的氮缺陷密度，以适应激发电子，从而缩小带隙，扩大光吸收能力，并提高载流子分离和传输效率。用NaBH4蚀刻2小时，过度引入氮缺陷的g-C3N4由于结构恶化而表现出性能下降，并且过度下移的缺陷态成为载流子的新复合中心。