[论文解读] The key role of antibonding electron transfer in surface chemisorption and heterogeneous catalysis

Liping Yu, Qimin Yan+1 more|arXiv (Cornell University)|Dec 5, 2018

Electrocatalysts for Energy Conversion参考文献 53被引用 10

一句话总结

本文提出反键电子转移——即电子从高能反键态跃迁至费米能级——是驱动表面化学吸附与多相催化的关键机制，为吸附能趋势提供了新描述符。基于MoS₂的第一性原理计算揭示了反键电子转移能量与氢吸附之间存在线性关系，解释了硫空位和边缘位点的催化活性。

ABSTRACT

The description of the chemical bond between a solid surface and an atom or a molecule is the fundamental basis for understanding a broad range of scientific problems in heterogeneous catalysis, semiconductor device fabrication, and fuel cells. Widespread understandings are based on the molecular orbital theory and focused on the degree of filling of antibonding surface-adsorbate states that weaken bonding on surfaces. The unoccupied antibonding surface-adsorbate states are often tacitly assumed to be irrelevant. Here, we show that most antibonding states become unoccupied because the electrons that would occupy these antibonding states are transferred to the lower-energy Fermi level. Such antibonding electron transfer goes beyond molecular orbital theory. It leads to an energy gain that largely controls the trends of surface adsorption strength and can serve as a primary descriptor for bonding on surfaces. This finding is illustrated from the first-principles study of hydrogen adsorption on MoS$_2$ surfaces. A clear linear relationship between the energies of antibonding electron transfer and hydrogen adsorption is identified. The hydrogen evolution reaction on MoS$_2$ is found to originate from the in-gap states induced by sulfur vacancies or edges. The effects of surface inhomogeneity (e.g., defects, step edges) on surface catalysis can be understood from the corresponding different energies gained from antibonding electron transfer. The emerging picture also offers a physically different explanation for the well-known $d$-band theory for hydrogen adsorption on transition metal surfaces.

研究动机与目标

• 重新评估反键态在表面化学吸附中的作用，挑战传统上对反键态占据数的关注。
• 识别一种新的物理机制——反键电子转移，该机制控制表面吸附能强度。
• 为过渡金属及MoS₂等二维材料中的催化趋势提供统一解释。
• 从新的电子转移视角重新诠释d带理论，提供一个在物理上截然不同的理论框架。
• 通过反键电子转移的能量收益，将表面缺陷与非均质性与催化活性联系起来。

提出的方法

• 采用第一性原理密度泛函理论（DFT）计算，模拟氢在MoS₂表面的吸附行为。
• 分析电子结构，量化从反键态转移至费米能级的电子能量。
• 将反键电子转移的能量收益作为吸附能强度的描述符进行计算。
• 绘制硫空位和边缘位点诱导的隙态分布，以关联其与催化活性的关系。
• 建立反键电子转移能量与氢吸附能之间的线性关系。
• 与d带中心模型进行比较，重新诠释其物理基础。

实验结果

研究问题

• RQ1 从反键态转移的电子如何影响表面吸附能？
• RQ2 未占据的反键态在决定化学吸附强度中起什么作用？
• RQ3 反键电子转移能否解释MoS₂上析氢反应（HER）活性的趋势？
• RQ4 表面缺陷与边缘如何通过该机制影响催化活性？
• RQ5 该机制能否提供比d带中心理论更根本的替代解释？

主要发现

• 反键电子转移带来显著的能量收益，从而控制表面吸附能强度。
• 在MoS₂上，反键电子转移能量与氢吸附能之间存在清晰的线性相关性。
• MoS₂上的析氢反应源于硫空位或边缘位点所形成的隙态。
• 表面非均质性（如缺陷与台阶边缘）通过增强反键电子转移的能量收益，提高了催化活性。
• 该机制为d带中心理论提供了在物理上截然不同的解释，将其起源重新诠释为电子转移而非仅d带填充。
• 基于反键电子转移的描述符在预测过渡金属及二维表面吸附趋势方面优于传统模型。