镍族金属团簇在催化加氢过程中的应用（英文）

发布时间：2018-05-29 14:57

本文选题：团簇 + 过渡金属　；参考：《物理化学学报》2017年07期

【摘要】：贵金属纳米颗粒具有优异的催化活性,是异相催化反应中的重要角色。作为一种理想的研究模型,气相金属团簇被广泛应用于在原子和分子尺度探究催化反应的机理。在本专论中,我们将本课题组近年来关于氢气在镍族金属团簇上的解离吸附进行了回顾。首先,我们对比了不同金属团簇的结构演化规律和相对稳定性。随后,我们系统研究了H_2分子在金属团簇上的解离吸附行为,揭示了不同金属对H H键的解离能力。为了表征不同金属团簇的催化活性,我们定义了两个关键参数:氢气的解离吸附能(ΔE_(CE))和H原子的连续脱附能(ΔE_(DE))。结果显示,随着H覆盖度的增大,ΔE_(CE)和ΔE_(DE)都呈现显著的下降。由于在实际的催化反应中,氢气总是维持在一定的分压下,这就意味着催化剂金属应该总是处于较高的H覆盖度下。因此,通过处于H饱和状态下的ΔE_(CE)和ΔE_(DE)来评估金属团簇的催化能力是合理可行的。我们发现,在饱和H吸附状态下,每一个Pt原子可以容纳4个H原子,而每一个Pd或Ni原子则只能吸附2个H原子。考虑到H原子在这些团簇上的脱附能力相当,Pt团簇相对较高的H吸附量将极大提高其在加氢过程中的催化活性。最后,我们系统研究了带电状态对Pt团簇催化性能的影响规律。结果显示,在H覆盖度较低时,H2分子的解离以及H原子的脱附过程受Pt团簇带电状态的影响较大。在饱和H吸附时,由于大量H原子的吸附,电荷的影响被平均化到每个Pt H键上,导致ΔE_(CE)和ΔE_(DE)都收敛到一个非常小的区域。此外,当团簇的尺寸增大时,其所带的电荷被大量的Pt原子分摊,每个Pt原子仅携带极少的电荷,使得电荷的影响已经可以忽略。
[Abstract]:Noble metal nanoparticles have excellent catalytic activity and play an important role in heterogeneous catalytic reactions. As an ideal research model, gas phase metal clusters are widely used to explore the mechanism of catalytic reaction at atomic and molecular scales. In this monograph, we review the dissociation and adsorption of hydrogen on nickel metal clusters in recent years. First, we compare the structural evolution and relative stability of different metal clusters. Subsequently, we systematically studied the dissociation and adsorption behavior of H _ 2 molecules on metal clusters, and revealed the dissociation ability of different metals to H _ (H) bonds. In order to characterize the catalytic activity of different metal clusters, we have defined two key parameters: hydrogen dissociation adsorption energy (螖 E _ S) and H atom continuous desorption energy (螖 E _ S). The results showed that with the increase of H coverage, both 螖 E _ (C) and 螖 E _ (E _ (DEE) showed a significant decrease. In the actual catalytic reaction, hydrogen is always maintained at a certain partial pressure, which means that the catalyst metal should always be in high H coverage. Therefore, it is reasonable and feasible to evaluate the catalytic capacity of metal clusters by 螖 E _ S _ C and 螖 E _ S _ D _ (DEE) in H saturation state. It is found that each Pt atom can hold 4 H atoms while each PD or Ni atom can only adsorb 2 H atoms in saturated H adsorption state. Considering the desorption ability of H atoms on these clusters, the relatively high H adsorption capacity of Pt clusters will greatly improve their catalytic activity in the hydrogenation process. Finally, we systematically studied the influence of charged state on the catalytic performance of Pt clusters. The results show that the dissociation of H _ 2 and the desorption of H _ 2 atoms are greatly affected by the charged state of Pt clusters at low H coverage. In saturated H adsorption, due to the adsorption of a large number of H atoms, the effect of charge is averaged on each Pt H bond, leading to the convergence of 螖 E _ T _ CEE and 螖 E _ T _ D) to a very small region. In addition, when the size of the cluster increases, its charge is divided by a large number of Pt atoms, each Pt atom carries only a few charges, so the effect of charge can be neglected.
【作者单位】：中国地质大学(武汉)材料科学与化学学院可持续能源实验室;
【基金】：supported by the National Natural Science Foundation of China(21473164,21203169,21233006) the Fundamental Research Funds for the Central Universities,China University of Geosciences,China Air Products and Chemicals,Inc~~
【分类号】：O643.38

【相似文献】