Adsorption and Oxidation of n-Butane on the Stoichiometric RuO2(110) Surface
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- 作者：Tao Li ; Rahul Rai ; Zhu Liang ; Minkyu Kim ; Aravind Asthagiri ; Jason F. Weaver
- 刊名：Journal of Physical Chemistry C
- 出版年：2016
- 出版时间：May 12, 2016
- 年：2016
- 卷：120
- 期：18
- 页码：9863-9873
- 全文大小：537K
- 年卷期：0
- ISSN：1932-7455
文摘
We investigated the adsorption and oxidation of n-butane on a stoichiometric RuO2(110) surface using temperature-programmed reaction spectroscopy (TPRS) and density functional theory (DFT) calculations. At low coverage, molecularly adsorbed n-butane achieves a binding energy of ∼100 kJ/mol on RuO2(110), consistent with a strongly bound σ-complex that forms through dative bonding interactions between the n-butane molecule and coordinatively unsaturated (cus) Ru atoms. We find that a fraction of the n-butane reacts with the RuO2 surface during TPRS to produce CO, CO2, and H2O that desorb above ∼400 K and present evidence that adsorbed σ-complexes serve as precursors to the initial C–H bond cleavage and ultimately the oxidation of n-butane on RuO2(110). From measurements of the product yields as a function of surface temperature we estimate that the initial reaction probability of n-butane on RuO2(110) decreases from 9% to ∼4% with increasing surface temperature from 280 to 300 K and show that this temperature dependence is accurately described by a precursor-mediated mechanism. From kinetic analysis of the data we estimate a negative, apparent activation energy of −35.1 kJ/mol for n-butane dissociation on RuO2(110) and an apparent reaction prefactor of 6 × 10–8. The low value of the apparent reaction prefactor suggests that motions of the adsorbed n-butane precursor are highly restricted on the RuO2(110) surface. DFT calculations confirm that n-butane forms strongly bound σ-complexes on RuO2(110) and predict that C–H bond cleavage is strongly favored energetically. The n-butane binding energies and energy barrier for C–H bond cleavage predicted by DFT agree quantitatively with our experimental estimates.