Creutzburg Marcus, Sellschopp Kai, Tober Steffen, Grånäs Elin, Vonk Vedran, Mayr-Schmölzer Wernfried, Müller Stefan, Noei Heshmat, Vonbun-Feldbauer Gregor B, Stierle Andreas
DESY NanoLab, Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany.
Department of Physics, University of Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany.
J Phys Chem Lett. 2021 Apr 22;12(15):3847-3852. doi: 10.1021/acs.jpclett.1c00209. Epub 2021 Apr 14.
We report a novel heterogeneous adsorption mechanism of formic acid on the magnetite (111) surface. Our experimental results and density functional theory (DFT) calculations give evidence for dissociative adsorption of formic acid in quasibidentate and chelating geometries. The latter is induced by the presence of iron vacancies at the surface, making oxygen atoms accessible for hydrogen atoms from dissociated formic acid. DFT calculations predict that both adsorption geometries are energetically favorable under our experimental conditions. The calculations prove that the locally observed (√3 × √3) 30° superstructure consists of three formate molecules in a triangular arrangement, adsorbed predominantly in a chelating geometry. The results show how defects can stabilize alternative adsorption geometries, which is a crucial ingredient for a detailed atomistic understanding of reaction barriers on magnetite and other oxide surfaces, as well as for the stability of carboxylic acid based nanocomposite materials.
我们报道了甲酸在磁铁矿（111）表面一种新型的非均相吸附机制。我们的实验结果和密度泛函理论（DFT）计算为甲酸在准双齿和螯合几何构型中的解离吸附提供了证据。后者是由表面铁空位的存在所诱导的，使得氧原子可被来自解离甲酸的氢原子所接近。DFT计算预测，在我们的实验条件下，两种吸附几何构型在能量上都是有利的。计算证明，局部观察到的（√3 × √3）30°超结构由三个呈三角形排列的甲酸盐分子组成，主要以螯合几何构型吸附。结果表明缺陷如何能够稳定替代吸附几何构型，这对于从原子层面详细理解磁铁矿和其他氧化物表面的反应势垒以及基于羧酸的纳米复合材料的稳定性而言是一个关键因素。
