In recent years, graphitic carbon nitride (g-C₃N₄) has attracted considerable attention because it includes earth-abundant carbon and nitrogen elements and exhibits good chemical and thermal stability owing to the strong covalent interaction in its conjugated layer structure. However, bulk g-C₃N₄ has some disadvantages of low specific surface area, poor light absorption, rapid recombination of photogenerated charge carriers, and insufficient active sites, which hinder its practical applications. In this study, we design and synthesize potassium single-atom (K SAs)-doped g-C₃N₄ porous nanosheets (CM-K_X, where X represents the mass of KHP added) via supramolecular self-assembling and chemical cross-linking copolymerization strategies. The results show that the utilization of supramolecules as precursors can produce g-C₃N₄ nanosheets with reduced thickness, increased surface area, and abundant mesopores. In addition, the intercalation of K atoms within the g-C₃N₄ nitrogen pots through the formation of K–N bonds results in the reduction of the band gap and expansion of the visible-light absorption range. The optimized K-doped CM-K₁₂ nanosheets achieve a specific surface area of 127 m² g^–1, which is 11.4 times larger than that of the pristine g-C₃N₄ nanosheets. Furthermore, the optimal CM-K₁₂ sample exhibits the maximum H₂ production rate of 127.78 μmol h^–1 under visible light (λ ≥ 420 nm), which is nearly 23 times higher than that of bare g-C₃N₄. This significant improvement of photocatalytic activity is attributed to the synergistic effects of the mesoporous structure and K SAs doping, which effectively increase the specific surface area, improve the visible-light absorption capacity, and facilitate the separation and transfer of photogenerated electron–hole pairs. Besides, the optimal sample shows good chemical stability for 20 h in the recycling experiments. Density functional theory calculations confirm that the introduction of K SAs significantly boosts the adsorption energy for water and decreases the activation energy barrier for the reduction of water to hydrogen.

中文翻译：

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层间钾单原子配位 g-C3N4 可显着提高可见光光催化氢气产量


近年来，石墨相氮化碳（g-C ₃ N ₄ ）因其含有地球丰富的碳、氮元素，且具有良好的化学稳定性和热稳定性而受到人们的广泛关注。其共轭层结构中的共价相互作用。然而，块状g-C ₃ N ₄ 存在比表面积低、光吸收差、光生载流子复合快、活性位点不足等缺点，阻碍了其实际应用。在本研究中，我们设计并合成了钾单原子（K SA）掺杂的 g-C ₃ N ₄ 多孔纳米片（CM-K _X ，其中 X代表通过超分子自组装和化学交联共聚策略添加的KHP的质量。结果表明，利用超分子作为前驱体可以制备厚度减小、表面积增加、介孔丰富的g-C ₃ N ₄ 纳米片。此外，通过形成 K-N 键，K 原子嵌入 g-C ₃ N ₄ 氮罐中，导致带隙减小和可见光的扩展。光吸收范围。优化后的K掺杂CM-K ₁₂ 纳米片的比表面积达到127 m ² g ^–1 ，是原始材料的11.4倍g-C ₃ N ₄ 纳米片。此外，最优的CM-K ₁₂ 样品在可见光（λ ≥ 420 nm）下表现出最大的H ₂ 产率127.78 μmol h ^–1 ，这比裸露的 g-C ₃ N ₄ 高近 23 倍。 光催化活性的显着提高归因于介孔结构和K SAs掺杂的协同效应，有效增加了比表面积，提高了可见光吸收能力，并促进了光生电子-空穴对的分离和转移。此外，最佳样品在回收实验中在20小时内表现出良好的化学稳定性。密度泛函理论计算证实，K SA 的引入显着提高了水的吸附能，并降低了水还原为氢的活化能势垒。