物理化学学报 >> 2019, Vol. 35 >> Issue (8): 850-857.doi: 10.3866/PKU.WHXB201811040

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通过g-C3N4担载MNi12 (Fe, Co, Cu, Zn)纳米团簇调节甲烷化

韩萌茹1,周亚男1,周旋1,储伟1,2,*()   

  1. 1 四川大学化学工程学院,成都 610065
    2 四川大学新能源与低碳技术研究院,成都 610065
  • 收稿日期:2018-11-28 录用日期:2019-01-11 发布日期:2019-01-16
  • 通讯作者: 储伟 E-mail:chuwei1965@scu.edu.cn
  • 基金资助:
    国家自然科学基金(21476145)

Tunable Reactivity of MNi12 (M = Fe, Co, Cu, Zn) Nanoparticles Supported on Graphitic Carbon Nitride in Methanation

Mengru HAN1,Yanan ZHOU1,Xuan ZHOU1,Wei CHU1,2,*()   

  1. 1 School of Chemical Engineering, Sichuan University, Chengdu 610065, P. R. China
    2 Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610065, P. R. China
  • Received:2018-11-28 Accepted:2019-01-11 Published:2019-01-16
  • Contact: Wei CHU E-mail:chuwei1965@scu.edu.cn
  • Supported by:
    This work is financially supported by the National Natural Science Foundation of China(21476145)

摘要:

新型二维材料g-C3N4由于其独特的电子结构和优异的化学性能受到了极大关注。根据金属载体间的相互作用以及合金的协同效应,本文应用密度泛函理论,对核壳结构MNi12 (Fe, Co, Cu, Zn)纳米团簇与载体g-C3N4的相互作用进行研究,并通过其对CO的吸附能研究新型催化剂的反应性能。结果表明d层电子越少的“核”原子与“壳”原子Ni的相互作用更强;当MNi12负载在g-C3N4上时,-9.40 eV到-8.39 eV之间的结合能说明MNi12可以很好的稳定在g-C3N4上;最后,通过MNi12以及MNi12/g-C3N4对CO的吸附行为发现,g-C3N4的引入导致CO的吸附能和C―O键长减小。根据电荷分析以及静电势(ESP)分析,发现其原因是因为g-C3N4担载以后,CO从MNi12获得的电子数更少。通过本次理论计算,可以得出结论:g-C3N4担载MNi12(Fe, Co, Cu, Zn)的新型催化剂不仅可以呈现高稳定性,还可以调变反应性能。

关键词: 金属-载体强相互作用, 核壳结构, CO, 吸附, 密度泛函理论

Abstract:

As a unique two-dimensional material, graphitic carbon nitride (g-C3N4) has received significant attention for its particular electronic structure and chemical performance. Its instinctive defect can provide a stable anchoring site for metals, potentially improving the surface reactivity. Ni-based catalysts are economical but their activity for CO2 methanation is lower than that of noble metal catalysts. Ni nanoparticles (NPs) supported on a substrate can further enhance the stability and activity of catalysts. Based on the principles of strong metal-support interaction (SMSI) and the synergistic effect on an alloy, MNi12/g-C3N4 composites as novel catalysts are expected to improve stability and catalytic performance of Ni-based catalysts. The configurations are established with core-shell structures of MNi12 (M = Fe, Co, Cu, Zn) nanoparticles (NPs) supported on g-C3N4 in this work. In the CO2 methanation reaction, the reactivity of CO on slab (ECO) is a critical factor, which is relative to the catalytic activity. Thus, the catalytic reactivity of these complexes via CO adsorption were explored using density functional theory (DFT). The values of cohesive energy (Ecoh) for MNi12 NPs range from -39.90 eV to -34.82 eV, suggesting that the formation of these NPs is favored as per thermodynamics, and Ecoh and partial density of state (PDOS) reveal that the central M atom with the less filled d-shell interacts more strongly with surface Ni atoms. Therefore, ZnNi12 is the most unstable structure among all the studied alloy, and the synergistic effect is also the weakest among them. When MNi12 NPs are supported on the g-C3N4 substrate, the binding energies (Eb) vary from -9.40 eV to -8.39 eV, indicating that g-C3N4 is indeed a good material for stabilizing these NPs. The PDOS analysis of pure g-C3N4 suggests the sp2 dangling bonds of N atoms in g-C3N4 can stabilize these transition metal NPs. Furthermore, the results of CO adsorbed on MNi12 NPs and MNi12/g-C3N4 composites show that ECO and dCO reduced with the introduction of g-C3N4. According to the results of the analysis of the Hirshfeld charges and electrostatic potential (ESP), the reason is that CO obtains less electrons from MNi12 NPs after deposition on the g-C3N4 substrate, which lowers the reactivity of CO on catalysts. Additionally, the deformation charge density is analyzed to investigate the interaction between the NPs and g-C3N4. With the introduction of g-C3N4, charge redistribution indicates the strong metal-support interaction, which further reduces the CO adsorption energy. In summary, MNi12 supported on g-C3N4 exhibit not only high stability but also tunable reactivity in CO2 methanation. These changes are beneficial for CO2 methanation reaction.

Key words: SMSI, Core-shell structure, CO, Adsorption, Density functional theory

MSC2000: 

  • O641