Scientists reveal how ultra-thin iron oxide catalysts switch chemical states at low temperatures
Researchers used advanced X-ray techniques to watch iron-oxide films toggle between two different forms while removing carbon monoxide at 150°C—a finding that could improve catalytic converter design and industrial pollution control. The discovery also shows that the underlying metal support critically determines whether such catalysts actually work, opening new avenues for materials engineering in emissions reduction.
Originaltitel: Operando XANES Reveals the Chemical State of Iron-Oxide Monolayers During Low-Temperature CO Oxidation
<p>We have used grazing incidence X-ray absorption near edge spectroscopy (XANES) to investigate the behavior of monolayer FeOx 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 O2 and CO at 150ºC, attributed to a transformation between FeO bilayer and FeO2 trilayer phases. The trilayer phase is also reduced upon heating in CO+O2, 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.</p>