催化学报 ›› 2025, Vol. 79: 205-218.DOI: 10.1016/S1872-2067(25)64847-9

• 论文 • 上一篇    下一篇

带隙工程调控的π共轭炔基聚合物/g-C3N4分子间S型异质结用于光催化过氧化氢合成

徐均如a, 程蕾a,*(), 苏通明b, 唐亚文a, 孙瀚君a,*()   

  1. a南京师范大学化学与材料科学学院, 江苏省新型动力电池重点实验室, 江苏省生物功能材料协同创新中心, 江苏南京210023
    b广西大学化学化工学院, 广西南宁530004
  • 收稿日期:2025-07-11 接受日期:2025-08-25 出版日期:2025-12-18 发布日期:2025-10-27
  • 通讯作者: 程蕾,孙瀚君
  • 基金资助:
    国家自然科学基金(22209076);国家自然科学基金(22422502);江苏省自然科学基金(BK20220369);江苏省高等学校自然科学基金(1020242193)

Band-gap engineered intermolecular S-scheme heterojunctions: π-conjugated acetylenic polymers/g-C3N4 with ultrafast charge transfer for solar-driven H2O2 synthesis

Junru Xua, Lei Chenga,*(), Tongming Sub, Yawen Tanga, Hanjun Suna,*()   

  1. aJiangsu Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Centre of Biomedical Functional Materials, School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, Jiangsu, China
    bSchool of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, Guangxi, China
  • Received:2025-07-11 Accepted:2025-08-25 Online:2025-12-18 Published:2025-10-27
  • Contact: Lei Cheng, Hanjun Sun
  • Supported by:
    National Natural Science Foundation of China(22209076);National Natural Science Foundation of China(22422502);Natural Science Foundation of Jiangsu Province(BK20220369);Natural Science Foundation of the Jiangsu Higher Education Institutions of China(1020242193)

摘要: 过氧化氢(H2O2)作为一种绿色氧化剂和能源载体, 其光催化合成近年来备受关注. 然而, 传统光催化剂在可见光吸收、电荷分离效率和氧化还原能力之间存在明显的制约关系. 相比而言, 构建S型异质结能够通过内置电场驱动电荷定向迁移, 在保留强氧化还原能力的同时提升载流子分离效率, 成为光催化剂设计的新策略. 其中, 石墨相氮化碳(g-C3N4)因其良好的化学稳定性和可见光响应特性, 被广泛用于构建S型异质结. 但由于g-C3N4自身导带位置的限制导致其还原能力较弱. 近年来, 富电子的共轭炔基聚合物(CAPs)因其可调的能带结构和强还原能力, 在光催化反应中显示出巨大潜力. 因此, 在分子水平精准调控CAPs与g-C3N4构建分子间S型异质结, 用于提升g-C3N4基光催化剂的还原能力, 并探究S型电荷转移与催化性能间的构效关系, 是一个有意义的研究方向.
本工作通过原位Glaser偶联反应在g-C3N4表面聚合1,4-二乙炔基苯(DEB), 成功构建了聚(1,4-二乙炔基苯)/氮化碳(pDEB/CN)分子间S型异质结. 通过不同氮原子数量的炔基单体(DEB, 2,5-二乙炔基吡啶和3,6-二乙炔基哒嗪)在g-C3N4表面原位聚合构建不同的S型异质结, 系统研究了电荷密度对聚合物能带结构的影响. 结果表明, 随着芳环上氮原子数量的增加, 吸电子效应限制电荷离域, 进一步导致炔基共轭聚合物的导带和价带位置正移; 而富电子的pDEB得益于拓展的离域范围, 因而具有最负的导带位置(-1.00 V vs. NHE), 与g-C3N4(价带+2.07 V vs. NHE)形成了理想的能带结构, 满足S型异质结的热力学要求. 为验证S型电荷转移机制, 通过双金属助催化剂(PtOx/MnOx)作为电子探针的原位X射线光电子能谱实验分析, 在光照下直接观测到Pt 4f和Mn 2p结合能分别负移0.3和0.6 eV, 证实了光生电子从CN向Pt、经界面电场驱动最终迁移至pDEB负载的MnOx的S型动态电荷转移路径. 此外, 飞秒瞬态吸收光谱进一步揭示了pDEB/CN-4中存在超快电荷转移过程(τ = 298.69 ps), 与CN相比异质结材料的载流子寿命得到显著延长, 载流子分离效率明显提升. 在可见光(λ ≥ 420 nm)照射下, pDEB/CN-4在纯水中无需牺牲剂即可实现246.8 μmol g-1 h-1的H2O2产率, 为纯CN的2.9倍. 更重要的是, 在放大10倍的连续流反应系统中, 该催化剂在24 h内仍保持394.27 μmol g-1 h-1的高活性, 在连续运行7 天后活性略有下降, 显示出该S型异质结催化氧气还原生成H2O2优异的稳定性和实际应用潜力. 机理研究表明, H2O2主要通过两步2e-氧还原反应路径生成, 电子顺磁共振和原位红外光谱证实了•O2-为关键中间体, 且该反应主要发生在pDEB芳香环的碳位点上.
综上, 本研究通过能带工程策略成功构建了具有强还原能力和高效电荷分离性能的分子间S型异质结光催化剂, 不仅解决了g-C3N4还原能力不足的限制, 深化了对S型电荷转移机制的理解, 而且为设计高性能有机光催化剂提供了新思路.

关键词: 共轭聚合物, 光催化, 能带工程, S型异质结, 超快电荷转移

Abstract:

All-organic intermolecular S-scheme heterojunction photocatalysts are promising for efficient and fast carrier separation, yet attaining strong reducing capacity and tracking directional charge transfer remain critical challenges. Herein, we unveiled an intermolecular S-scheme heterojunction through in-situ growth of conjugated poly(1,4-diethynylbenzene) (pDEB, reduction photocatalyst) on graphitic carbon nitride (g-C3N4, oxidation photocatalyst), forming the nanofiber-decorated nanosheet-like pDEB/CN architecture via π-conjugated polymer templating. By leveraging the electron-donating effect and the expanded π-electron delocalization range of electron-rich conjugated acetylenic polymers, pDEB with high energy band positions was introduced into the intermolecular S-scheme heterojunction with enhanced reducibility. The directional S-scheme charge migration is mechanistically demonstrated by deploying dual metal oxide cocatalysts as spatially resolved electron donor-acceptor probes, with light-modulated in-situ X-ray photoelectron spectroscopy capturing real-time interfacial charge migration. Femtosecond transient absorption spectroscopy further elucidates accelerated ultrafast electron transfer kinetics mediated by the S-scheme interfacial electric field. The S-scheme heterojunction attained an apparent quantum efficiency of 5.18% at 420 nm during the photocatalytic H2O2 production. Notably, pDEB/CN has demonstrated an excellent H2O2 yield for the first time in a continuous flow photocatalytic system, reaching 394.27 μmol g-1 h-1 within 24 h, which illustrates the stable interfacial charge transfer brought about by the rigid structure. The work demonstrated the transformative potential of architecting directional charge superhighways through band level engineering, while advancing S-scheme heterojunctions design with molecular precision.

Key words: Conjugated polymers, Photocatalysis, Band engineering, S-scheme heterojunctions, Ultrafast charge transfer