The previous studies on K-doped g-C3N4 suggest a simple correlation between the increased potassium content and the improved photocatalytic activity due to a shift of the valence band potential to more positive values, leading to the direct oxidation of hydroxyl ions to hydroxyl radicals by holes. In this study, we investigated the influence of different potassium precursors on the properties and photocatalytic efficiency of K-modified g-C3N4 materials in Rhodamine B degradation. Detailed characterization revealed that the choice of precursor significantly affects the structural and optoelectronic properties with complex correlations rather than superficial relationships between potassium content and photocatalytic activity. Notably, KCl-based samples, despite having a lower specific surface area, exhibited enhanced photocatalytic properties due to prolonged carrier lifetimes and improved charge transfer efficiency compared to KOH-based samples. Higher precursor concentrations resulted in more recombination centers, increasing Urbach energy and reducing photocatalytic activity. These findings underscore the importance of precise synthesis control, revealing that both K and Cl atoms act as charge transfer bridges, improving the material’s photocatalytic properties beyond mere surface area enhancement. In addition, even smaller amounts of Cl atoms in g-C3N4 showed much higher impact on the final position of conduction and valence band potentials than K atoms.

中文翻译：

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通过战略性钾前驱体选择优化 g-C3N4 中的 Urbach 能量和电荷载流子动力学：见解和挑战


先前对 K 掺杂 g-C3N4 的研究表明，由于价带电位向更正的值转变，导致羟基离子通过空穴直接氧化为羟基自由基，钾含量增加与光催化活性提高之间存在简单的相关性。在本研究中，我们研究了不同钾前驱体对 K 改性 g-C3N4 材料降解罗丹明 B 性能和光催化效率的影响。详细的表征表明，前驱体的选择显着影响结构和光电性质，钾含量和光催化活性之间存在复杂的相关性，而不是表面的关系。值得注意的是，尽管基于 KCl 的样品具有较低的比表面积，但由于载流子寿命延长和电荷转移效率提高，与基于 KOH 的样品相比，表现出增强的光催化性能。较高的前驱体浓度导致更多的复合中心，增加 Urbach 能量并降低光催化活性。这些发现强调了精确合成控制的重要性，揭示了 K 和 Cl 原子都充当电荷转移桥，提高了材料的光催化性能，而不仅仅是增加表面积。此外，g-C3N4 中少量的 Cl 原子对传导和价带电位的最终位置的影响也比 K 原子大得多。