Dorotea Gajdek, Harald J Wallander, Giuseppe Abbondanza, Gary S Harlow, Johan Gustafson, Sara Blomberg, Per-Anders Carlsson, Justus Just, Edvin Lundgren, Lindsay R Merte
We have used grazing incidence X-ray absorption near edge spectroscopy (XANES) to investigate the behavior of monolayer FeO films on Pt(111) under near ambient pressure CO oxidation conditions with a total gas pressure of 1 bar. Spectra indicate reversible changes during oxidation and reduction by O and CO at 150 °C, attributed to a transformation between FeO bilayer and FeO trilayer phases. The trilayer phase is also reduced upon heating in CO+O , consistent with a Mars-van-Krevelen type mechanism for CO oxidation. At higher temperatures, the monolayer film dewets the surface, resulting in a loss of the observed reducibility. A similar iron oxide film prepared on Au(111) shows little sign of reduction or oxidation under the same conditions. The results highlight the unique properties of monolayer FeO and the importance of the Pt support in this reaction. The study furthermore demonstrates the power of grazing-incidence XAFS for in situ studies of these model catalysts under realistic conditions.
我们使用掠入射 X 射线吸收近缘光谱 (XANES) 研究了 Pt(111) 上的单层 FeOx 薄膜在总气压为 1 巴的近环境压力 CO 氧化条件下的行为。光谱显示了在 150ºC 下被 O2 和 CO 氧化和还原过程中发生的可逆变化,这些变化归因于 FeO 双层相和 FeO2 三层相之间的转变。在 CO+O2 中加热时,三层相也会还原,这与 Mars-van-Krevelen 类型的 CO 氧化机制相一致。在较高温度下,单层膜表面会产生露珠,从而失去观察到的还原性。在相同条件下,在 Au(111)上制备的类似氧化铁薄膜几乎没有还原或氧化的迹象。这些结果凸显了单层氧化铁的独特性质以及铂支撑在该反应中的重要性。该研究进一步证明了掠入射 XAFS 在实际条件下对这些模型催化剂进行原位研究的能力。
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John T. Kelly, Louis E. McNamara, William E. Gilbraith, Chelsea M. Goetzman, Megan E. Hoover, Robert J. Lascola
The Front Cover shows a complex relationship of acid–base chemistry in aqueous solutions. Here, Savannah River National Laboratory describes an elusive charge transfer between pyridine and the aqueous environment through Raman spectroscopy and computational chemistry. It builds on concepts that hydrogen bonding can induce blue-shifting features in vibrational spectra, and that excess protons found in acidic solutions are confined to acid–base pairing. More information can be found in the Research Article by J. T. Kelly, L. E. McNamara and co-workers (DOI: 10.1002/cphc.202400029). Image: Ella Maru Studio.