Water Formation under Silica Thin Films: Real-Time Observation of a Chemical Reaction in a Physically Confined Space

Mauricio J Prieto; Hagen W Klemm; Feng Xiong; Daniel M Gottlob; Dietrich Menzel; Thomas Schmidt; Hans-Joachim Freund

doi:10.1002/anie.201802000

Water Formation under Silica Thin Films: Real-Time Observation of a Chemical Reaction in a Physically Confined Space

Angew Chem Int Ed Engl. 2018 Jul 9;57(28):8749-8753. doi: 10.1002/anie.201802000. Epub 2018 Jun 6.

Authors

Mauricio J Prieto¹, Hagen W Klemm¹, Feng Xiong², Daniel M Gottlob¹, Dietrich Menzel^{1

3}, Thomas Schmidt¹, Hans-Joachim Freund¹

Affiliations

¹ Department of Chemical Physics, Fritz-Haber Institute of the Max-Planck Society, Faradayweg 4-6, 14195-, Berlin, Germany.
² Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026, P. R. China.
³ Physik-Department E20, Technical University München, 85778, Garching, Germany.

Abstract

Using low-energy electron microscopy and local photoelectron spectroscopy, water formation from adsorbed O and H₂ on a Ru(0001) surface covered with a vitreous SiO₂ bilayer (BL) was investigated and compared to the same reaction on bare Ru(0001). In both cases the reaction is characterized by moving reaction fronts. The reason for this might be related to the requirement of site release by O adatoms for further H₂ -dissociative adsorption. Apparent activation energies (Eaapp ) are found for the front motion of 0.59 eV without cover and 0.27 eV under cover. We suggest that the smaller activation energy but higher reaction temperature for the reaction on the SiO₂ BL covered Ru(0001) surface is due to a change of the rate-determining step. Other possible effects of the cover are discussed. Our results give the first values for Eaapp in confined space.

Keywords: LEEM; confined chemistry; heterogeneous catalysis; hydrogen oxidation; model systems.

Publication types

Research Support, Non-U.S. Gov't