Insights into Reaction Kinetics in Confined Space: Real Time Observation of Water Formation under a Silica Cover

Mauricio J. Prieto, Thomas Mullan, Mark Schlutow, Daniel M. Gottlob, Liviu C. Tǎnase, Dietrich Menzel, Joachim Sauer, Denis Usvyat, Thomas Schmidt, Hans Joachim Freund

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

We offer a comprehensive approach to determine how physical confinement can affect the water formation reaction. By using free-standing crystalline SiO2 bilayer supported on Ru(0001) as a model system, we studied the water formation reaction under confinement in situ and in real time. Low-energy electron microscopy reveals that the reaction proceeds via the formation of reaction fronts propagating across the Ru(0001) surface. The Arrhenius analyses of the front velocity yield apparent activation energies (Eaapp) of 0.32 eV for the confined and 0.59 eV for the nonconfined reaction. DFT simulations indicate that the rate-determining step remains unchanged upon confinement, therefore ruling out the widely accepted transition state effect. Additionally, H2O accumulation cannot explain the change in Eaapp for the confined cases studied because its concentration remains low. Instead, numerical simulations of the proposed kinetic model suggest that the H2 adsorption process plays a decisive role in reproducing the Arrhenius plots.

Original languageEnglish
Pages (from-to)8780-8790
Number of pages11
JournalJournal of the American Chemical Society
Volume143
Issue number23
DOIs
StatePublished - 16 Jun 2021

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