[论文解读] Structural flexibility dictates reactivity of single-atom catalysts

Jakub Planer, Dominik Hrůza+4 more|arXiv (Cornell University)|Mar 12, 2026

Electrocatalysts for Energy Conversion被引用 0

一句话总结

研究表明在相同电子结构下，Fe-N3 与 Fe-N4 单原子催化位点因结构灵活性而导致 CO 吸附能不同，凸显配位几何作为关键反应性因素。

ABSTRACT

Unravelling the origins of single-atom catalyst reactivity is a central challenge in heterogeneous catalysis research. A key question is whether the activity arises solely from atomic isolation or from distinct structural and electronic configurations of the single atoms. Here, we use precisely defined Fe-N$_3$ and Fe-N$_4$ model catalyst sites synthesized on an inert support to quantify the effect of coordination geometry on chemical reactivity. Both the Fe-N$_3$ and Fe-N$_4$ models have the same electronic configuration (high-spin Fe$^{2+}$ with S=2), and even their d-orbital occupancies and positions with respect to Fermi level are almost identical. Despite this electronic similarity, the adsorption energy of CO differs by more than 0.6 eV between the Fe-N$_3$ and Fe-N$_4$ sites, as indicated by density functional theory computations and confirmed by atomically-resolved scanning tunneling microscopy experiments. We trace this reactivity difference to the structural flexibility of the Fe-N$_3$ sites, which allows strengthening of the Fe 3d$_{xz/yz}$-CO 2$π$* back-bonding by lifting the Fe atom from the -N$_3$ plane. These results demonstrate that coordination geometry plays a crucial role in defining the reactivity of single-atom catalysts, and that such effects cannot be predicted by analysis of the sites' electronic structures alone.

研究动机与目标

• 理解单原子催化剂活性是否仅来自原子分离，还是来自结构/电子配置。
• 量化配位几何在 Fe-N3 与 Fe-N4 模型位点中的化学反应性影响。
• 确定相似电子结构是否因结构灵活性而导致不同的反应性。

提出的方法

• 在惰性载体上构建精确定义的 Fe-N3 和 Fe-N4 模型催化位点。
• 使用密度泛函理论（DFT）计算吸附能与电子结构。
• 采用原子分辨的扫描隧道显微镜（STM）实验验证理论预测。
• 比较 Fe 3d 轨道占据及其与 CO 回键的关系。
• 把反应性的差异归因于结构灵活性，而非仅电子构型。

实验结果

研究问题

• RQ1 单原子 Fe 位点的配位几何（N3 与 N4）是否在不改变电子配置的前提下改变反应性？
• RQ2 结构灵活性如何影响 Fe 3d 轨道与 CO 之间的回键？
• RQ3 相同的高自旋 Fe2+ 电子配置是否因位点几何而产生不同的吸附能？

主要发现

• Fe-N3 与 Fe-N4 模型具有相同的电子配置：高自旋 Fe2+，S=2。
• DFT 和 STM 显示 Fe-N3 与 Fe-N4 之间 CO 吸附能相差超过 0.6 eV。
• Fe-N3 的结构灵活性使 Fe 能从 N3 平面上升，增强 Fe 3d_xz/yz-CO 2π* 回键。
• 配位几何从根本上影响反应性，超出单纯电子结构分析范围。