Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 14: Oxide Surfaces: Adsorption and Reactivity

O 14.3: Vortrag

Montag, 16. März 2015, 15:30–15:45, MA 042

Adsorption of carbon dioxide onto an iron oxide — •Petr Dementyev, Casey O'Brien, Francisco Ivars, Swetlana Schauermann, and Hans-Joachim Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

Carbon dioxide is likely to play one of the key roles in clean energy technologies. Its conversion into methanol or other chemicals is a promising way for renewable energy storage. Since carbon dioxide molecules are inert, an important issue is to activate them. Herein we employ a combination of single-crystal adsorption calorimetry (SCAC) and infrared reflection-absorption spectroscopy (IRAS) to study carbon dioxide adsorption on iron oxide Fe3O4. SCAC is a method for probing energetics of adsorbate-surface interactions, while IRAS allows identifying chemical nature of surface species. Both instruments contain molecular beams what enables to conduct careful adsorption experiments under clean UHV conditions.

We probe two well-defined Fe3O4 (111) and (100) thin films. Both substrates as well as FeO film are grown epitaxially on Pt single crystal. Low-temperature SCAC measurements reveal that carbon dioxide transiently sticks to Fe3O4 whereas it does not interact with oxygen-terminated FeO and bare Pt. IRAS confirms that CO2 does react with the iron oxide. There are many features in the region of C-O stretching vibrations indicating coexistence of different species such as physisorbed CO2 and carbonates. Surface chemistry of CO2 seems to be strongly kinetically limited. Co-adsorption experiments show that water surface species block CO2 adsorption.