催化学报

催化学报

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Na2CO3辅助合成钠掺杂结晶/非晶g-C3N4 S型同质结光催化剂用于增强H2O2合成

谭丽红a, 吴新鹤a,*, 许家超a, Mahmoud Sayedb,c,*, 王国宏a,*   

  1. a湖北师范大学化学化工学院, 污染物分析与再利用技术湖北省重点实验室, 黄石 435002;
    b中国地质大学（武汉）材料科学与化学学院, 太阳能燃料实验室, 武汉 430074;
    c法尤姆大学理学院, 法尤姆 63514
  • 通讯作者: *电子信箱: wuxinhe@hbnu.edu.cn (吴新鹤); mahmoud@cug.edu.cn (Sayed Mahmoud); wanggh2003@163.com (王国宏)
  • 基金资助:
    国家自然科学基金(22302061、22578106、W2433135、22402126)

Na2CO3-assisted synthesis of Na-doped crystalline/amorphous g-C3N4 S-scheme homojunction photocatalyst for enhanced H2O2 production

Lihong Tana, Xinhe Wua,*, Jiachao Xua, Mahmoud Sayedb,c,*, Guohong Wanga,*   

  1. aHubei Key Laboratory of Pollutant Analysis and Reuse Technology, College of Chemistry and Chemical Engineering, Hubei Normal University, Huangshi, 435002, P. R. China;
    bLaboratory of Solar Fuel, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430074, P. R. China;
    cChemistry Department, Faculty of Science, Fayoum University, Fayoum 63514, Egypt
  • Contact: *E-mail: wuxinhe@hbnu.edu.cn (X. Wu); mahmoud@cug.edu.cn (M. Sayed); wanggh2003@163.com (G. Wang)

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摘要： 近年来,光催化技术由于其反应条件温和,操作简便、对环境友好而成为一种理想的可持续性技术。在众多提升光催化性能的策略中,结晶/无定形g-C3N4同质结的构建是一种具有广泛应用前景的策略,可用于制备界面匹配性更优、载流子传输阻力更低的同质结光催化剂,从而显著提升光催化性能。然而,传统的促进g-C3N4结晶的方法通常涉及复杂的多步处理操作及有毒化学品的使用,因而限制了其实际应用的可行性。例如,现有方法大多采用有毒化学品——氯化锂（LiCl）作为缩合反应溶剂。此外,此前的g-C3N4结晶体系大多需要采用双盐,且所使用的两种盐的共熔点必须低于550℃,才能作为调控g-C3N4聚合过程的溶剂,这极大限制了共熔盐的选择及该方法的发展。
针对上述瓶颈,本文提出了一种创新的碳酸钠（Na2CO3）诱导结晶度调控策略,成功实现了钠掺杂结晶/无定形g-C3N4 S型同质结光催化剂的一步构筑。该方法以三聚氰胺与三聚氰酸分子的预组装为基础,通过调控二者的比例实现对分子组装程度及表面组成（如是否暴露氨基基团,-NH2）的精确控制。在煅烧前引入Na2CO3,利用体系中过量三聚氰胺分子所提供的充足-NH2基团,通过氢键作用与Na2CO3有效结合,从而在后续的一步煅烧过程中同步实现结晶度调控与钠离子掺杂,最终获得钠掺杂结晶/无定形g-C3N4 S型同质结光催化剂。所制备的光催化剂在H2O2合成中表现出优异的光催化性能,最优的H2O2生成速率达到444.6 μmol·L-1·h-1,相较于块体g-C3N4提升6.1倍。通过X射线衍射（XRD）、X射线光电子能谱（XPS）、傅里叶变换红外光谱（FT-IR）、电化学测试等实验表征和密度泛函理论（DFT）计算研究表明,S型同质结的构建有效促进了光生载流子的空间分离与高效传输;与此同时,钠离子掺杂优化了O2吸附与*OOH中间体转化等过程,从而显著增强了界面H2O2生成动力学,二者协同作用显著提升了钠掺杂结晶/无定形g-C3N4 S型同质结光催化剂的H2O2光催化生成活性。
综上所述,本研究不仅提供了一种高效、简便、环保的一步煅烧法构建g-C3N4基S型同质结的新策略,还通过结晶/无定形复合结构与金属掺杂的协同作用,为设计高活性光催化剂提供了新思路,在太阳能燃料合成和光催化等领域具有重要的应用潜力。

关键词: 光催化, S型同质结, 结晶/无定形g-C3N4, 结晶度调控, H2O2合成

Abstract: The construction of crystalline/amorphous g-C3N4 homojunctions presents a versatile strategy to obtain all-organic homojunction photocatalysts with better interface matching and lower interface charge carrier movement resistance for optimized photocatalytic activity. However, the process entails a complex multi-step workup, which compromises its feasibility. To overcome this challenge, this work provided an innovative Na2CO3-induced crystallinity modulation strategy to construct a Na-doped crystalline/amorphous g-C3N4 S-scheme homojunction photocatalyst in a single step. The approach involves the initial pre-assembling of melamine and cyanuric acid molecules, and subsequent introduction of Na2CO3 before the calcination. Na2CO3 plays key roles to induce in-situ crystallinity modulation during the calcination and as a source for Na-doping. The prepared g-C3N4 S-scheme homojunction photocatalyst demonstrated a prominent H2O2-production rate of 444.6 μmol·L-1·h-1, which is 6.1-fold higher than that of bulk g-C3N4. The enhanced activity was attributed to the synergistic effect of charge carrier separation induced by the S-scheme homojunction system, and the optimized interfacial H2O2 generation kinetics. The latter was fostered by the Na-doping. This study provides an innovative approach for the one-step construction of g-C3N4 S-scheme homojunction and its integration in photocatalytic applications.

Key words: Photocatalysis, S-scheme homojunction, Crystalline/amorphous g-C3N4, Crystallinity modulation, H2O2 production