Na⁺掺杂g-C₃N₄通过NaHCO₃辅助策略用于高效光催化产H₂O₂

Na⁺ Doped g-C₃N₄ Prepared via a NaHCO₃ Assisted Strategy for Efficient Photocatalytic H₂O₂ Production

摘要: 光催化制备过氧化氢(H₂O₂)因其绿色、可持续的特点，被认为是替代传统蒽醌法的重要途径之一。针对石墨相氮化碳(g-C₃N₄)存在比表面积有限、光生载流子复合严重及氧还原活性不足等问题，本研究采用碳酸氢钠(NaHCO₃)作为改性剂，通过一步高温热缩聚法制备Na⁺掺杂改性g-C₃N₄(CN-Na)光催化材料。结果表明，NaHCO₃的引入在材料形成过程中起到结构调控作用，使块体g-C₃N₄发生部分剥离与破碎，比表面积显著提升，同时晶体结构发生轻微膨胀，证明Na⁺成功掺入骨架结构。紫外-可见漫反射光谱显示，CN-Na的吸收边发生红移，禁带宽度减小，可见光响应能力增强。光电化学测试表明，CN-Na具有更高的瞬态光电流响应和更低的电荷转移阻抗，说明其光生电子–空穴分离与迁移效率得到显著改善。在可见光照射下，CN-Na表现出优异的H₂O₂生成性能，其产率达到未改性样品的10倍以上，并随反应时间稳定增长。电子顺磁共振(EPR)结果进一步表明，Na改性促进了超氧自由基($\cdot O_2^{-}$ )的生成，从而增强了两电子氧还原路径的反应效率。综上，NaHCO₃辅助的Na⁺掺杂策略能够实现g-C₃N₄结构与电子性质的协同优化，显著提升其光催化H₂O₂生成性能，为高效太阳能驱动绿色过氧化氢合成提供了有效思路。

Abstract: Photocatalytic production of hydrogen peroxide (H₂O₂) is considered a green and sustainable alternative to the conventional anthraquinone process. However, graphitic carbon nitride (g-C₃N₄) suffers from limited specific surface area, severe photogenerated charge carrier recombination, and insufficient oxygen reduction activity, which restrict its practical photocatalytic performance. In this work, sodium bicarbonate (NaHCO₃) was employed as a modifying agent to construct Na⁺-doped g-C₃N₄ (CN-Na) via a one-step high-temperature thermal polycondensation method. The results indicate that the introduction of NaHCO₃ plays a crucial role in regulating the material structure, leading to partial exfoliation and fragmentation of bulk g-C₃N₄, thereby significantly increasing the specific surface area. Meanwhile, a slight lattice expansion confirms the successful incorporation of Na⁺ into the g-C₃N₄ framework. UV-vis diffuse reflectance spectroscopy reveals a red shift of the absorption edge and a narrowed band gap, indicating enhanced visible-light harvesting ability. Photoelectrochemical measurements show that CN-Na exhibits a higher transient photocurrent response and lower charge transfer resistance, demonstrating improved separation and migration efficiency of photogenerated electron–hole pairs. Under visible-light irradiation, CN-Na displays excellent H₂O₂ production performance, with a yield more than 10 times higher than that of pristine g-C₃N₄ and maintaining stable growth over time. Electron paramagnetic resonance (EPR) analysis further confirms that Na modification promotes the generation of superoxide radicals ($\cdot O_2^{-}$ ), thereby enhancing the two-electron oxygen reduction pathway. In summary, the NaHCO₃-assisted Na⁺ doping strategy enables synergistic optimization of both the structure and electronic properties of g-C₃N₄, significantly improving its photocatalytic H₂O₂ production performance and providing an effective approach for efficient solar-driven green hydrogen peroxide synthesis.