催化学报 ›› 2024, Vol. 60: 219-230.DOI: 10.1016/S1872-2067(23)64645-5

• 论文 • 上一篇    下一篇

通过氟掺杂调控TiO2d带中心以增强光催化产H2O2活性

赵艳艳a, 张淑敏b, 吴珍c, 朱必成d, 孙国太d, 张建军d,*()   

  1. a商洛学院生物医药与食品工程学院, 陕西商洛 726000
    b长沙学院应用环境光催化湖南省重点实验室, 湖南长沙 410022
    c鄂尔多斯应用技术学院化学工程学院, 内蒙古鄂尔多斯 017000
    d中国地质大学(武汉)材料与化学学院, 太阳燃料实验室, 湖北武汉 430074
  • 收稿日期:2024-01-30 接受日期:2024-02-29 出版日期:2024-05-18 发布日期:2024-05-20
  • 通讯作者: 电子信箱: zhangjianjun@cug.edu.cn (张建军).
  • 基金资助:
    国家自然科学基金(52202375);国家自然科学基金(52372294);国家自然科学基金(22302183);国家自然科学基金(22362004);陕西省教育厅协同创新项目(22JY015)

Regulation of d-band center of TiO2 through fluoride doping for enhancing photocatalytic H2O2 production activity

Yanyan Zhaoa, Shumin Zhangb, Zhen Wuc, Bicheng Zhud, Guotai Sund, Jianjun Zhangd,*()   

  1. aCollege of Biology Pharmacy and Food Engineering, Shangluo University, Shangluo 726000, Shaanxi, China
    bHunan Key Laboratory of Applied Environmental Photocatalysis, Changsha University, Changsha 410022, Hunan, China
    cDepartment of Chemical Engineering, Ordos Institute of Technology, Ordos 017000, Inner Mongolia, China
    dLaboratory of Solar Fuel, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, Hubei, China
  • Received:2024-01-30 Accepted:2024-02-29 Online:2024-05-18 Published:2024-05-20
  • Contact: E-mail: zhangjianjun@cug.edu.cn (J. Zhang).
  • Supported by:
    National Natural Science Foundation of China(52202375);National Natural Science Foundation of China(52372294);National Natural Science Foundation of China(22302183);National Natural Science Foundation of China(22362004);Specialized Research Fund of Education Department of Shaanxi Province(22JY015)

摘要:

光催化产双氧水(H2O2)以太阳光、水和空气中的氧气作为原料, 将光能转变为化学能, 是一种绿色高效节能环保的新技术, 具有较好的应用前景. 光催化产H2O2主要包括三个关键步骤: (1) 催化剂在高能入射光激发下产生光生电子和空穴; (2) 光生电子-空穴对分离并迁移到催化剂表面; (3) 光生电子与催化剂表面吸附的氧气发生反应生成超氧自由基, 其继续与水和光生电子反应, 产生H2O2. 因此, 氧气在催化剂表面吸附性能的强弱对光催化产H2O2的性能有着重要影响. d带中心理论表明, 金属的d带能级高低决定了催化剂表面活性位点对小分子物质的吸附强度, 能级越高, 催化剂对小分子物质的吸附能力越强. TiO2具有制备简单、无毒、理化性质稳定、导价带位置跨越多个氧化还原电位等诸多优势, 在光催化生产H2O2领域具有较好的应用前景. 提升TiO2d带中心可以提高其对小分子物质如O2的吸附性能, 有效提升其光催化产H2O2的活性.

本文从氟离子掺杂提升TiO2d带中心增强对O2的吸附性能入手, 通过第一性理论计算、电子顺磁共振实验、飞秒瞬态吸收光谱等方法研究光生载流子的传输机理, 阐明F/TiO2光催化产H2O2活性增强机制, 并对TiO2光催化产H2O2的前景提出了展望. 首先, 分别以钛酸四异丙酯和氟化铵作为钛源和氟源, 通过溶胶-凝胶法结合高温煅烧制得了F/TiO2光催化剂. 第一性理论计算结果表明, F体相掺杂导致TiO2的电荷分布不均匀, 使得d带中心上移, 从而增强TiO2与表面吸附O2的相互作用, 降低表面氧的吸附能, 最终提高光催化生成H2O2的效率. 电子顺磁共振实验结果表明, 晶格中F离子的存在诱导了还原性Ti3+中心的形成, 这些还原性Ti3+中心可以提供电荷补偿所需的额外电子. O2温度程序解吸实验结果表明, F/TiO2对O2的化学吸附能力高于纯TiO2, 说明较低的反键轨道占用率可以增强Ti3+对O2的吸附. 飞秒瞬态吸收光谱结果表明, 光生电子从F/TiO2的导带转移到Ti3+表面态和表面F离子上, 加速了光生电子和空穴的分离; 光生电子与吸附在F/TiO2表面的O2发生反应, 加速了H2O2的生成. 光催化产H2O2性能实验结果表明, F掺杂TiO2后, 光催化生成H2O2的产率由277 μmol·g‒1·h‒1提高到了467 μmol·g‒1·h‒1. 循环实验结果表明, F/TiO2使用前后形貌和晶体结构几乎没有改变, 且循环实验后氧空位和Ti3+中心依然存在, 说明制得的F/TiO2光催化剂具有良好的稳定性.

综上所述, 本文借助第一性理论计算并结合实验结果, 从d带中心调控的角度揭示了F/TiO2光催化产H2O2活性提高的机理, 阐明了光催化产H2O2的反应机制. 本研究为优化光催化剂与氧气之间的吸附强度, 提高光催化产H2O2的性能提供了一种新策略, 可为后续光催化产H2O2技术的改进和应用提供参考.

关键词: 反键轨道, d带中心, 氧吸附, 电荷转移, 双氧水生成

Abstract:

Titanium dioxide (TiO2) has received extensive attention for photocatalytic hydrogen peroxide (H2O2) production, with the d-band center related to the adsorption performance, which affects the photocatalytic reaction process. Herein, an ingenious strategy to lower the antibonding-orbital occupancy in the Ti 3d orbital by fluoride ion (F) doping is proposed, with density functional theory calculations predicting that F-doping into TiO2 induces a non-uniform charge distribution and enables an upshift of the d-band center in F/TiO2. This manipulation provides accessible active centers with favorable d-band energy levels, which can improve the charge-transfer behavior, strengthen the interaction between the adsorbed oxygen and the photocatalyst, and reduce the adsorption energy of oxygen, eventually promoting the photocatalytic H2O2 production rate. The experimental results further confirm that a lower antibonding-orbital occupancy can intensify the adsorption of atomic oxygen at the Ti sites. Electron paramagnetic resonance experiment reveals that the presence of F ions in the lattice induces the formation of Ti3+ centers that localize the extra electron needed for charge compensation. Femtosecond transient absorption (fs-TA) spectroscopy suggests that photogenerated electrons are transferred from the conduction band of F/TiO2 to the Ti3+ surface states and surface F ions, expediting the separation of electrons and holes. Consequently, with F doping in TiO2, the photocatalytic H2O2 production yields improved from 277 to 467 μmol·g‒1·h‒1, with ethanol as a sacrificial reagent. This study provides a new strategy for regulating the d-band center to optimize the adsorption strength between the photocatalyst and oxygen atoms and achieve enhanced photocatalytic H2O2 production performance.

Key words: Antibonding orbital, d-Band center, Oxygen adsorption, Charge transfer, Hydrogen peroxide production