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          Institute: Fritz-Haber-Institut     Collection: Physical Chemistry     Display Documents

ID: 219338.0, Fritz-Haber-Institut / Physical Chemistry
Catalytic oxidation of ammonia on RuO2(110) surfaces: Mechanism and selectivity
Authors:Wang, Yuemin; Jacobi, Karl; Schöne, Wolf-Dieter; Ertl, Gerhard
Date of Publication (YYYY-MM-DD):2005-03-24
Title of Journal:Journal of Physical Chemistry B
Journal Abbrev.:J. Phys. Chem. B
Issue / Number:16
Start Page:7883
End Page:7893
Copyright:© 2005 American Chemical Society
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The selective oxidation of ammonia to either N2 or NO on RuO2(110) single-crystal surfaces was investigated by a combination of vibrational spectroscopy (HREELS), thermal desorption spectroscopy (TDS) and steady-state rate measurements under continuous flow conditions. The stoichiometric RuO2(110) surface exposes coordinatively unsaturated (cus) Ru atoms onto which adsorption of NH3 (NH3-cus) or dissociative adsorption of oxygen (O-cus) may occur. In the absence of O-cus, ammonia desorbs completely thermally without any reaction. However, interaction between NH3-cus and O-cus starts already at 90 K by hydrogen abstraction and hydrogenation to OH-cus, leading eventually to N-cus and H2O. The N-cus species recombine either with each other to N2 or with neighboring O-cus leading to strongly held NO-cus which desorbs around 500 K. The latter reaction is favored by higher concentrations of O-cus. Under steady-state flow condition with constant NH3 partial pressure and varying O2 pressure, the rate for N2 formation takes off first, passes through a maximum and then decreases again, whereas that for NO production exhibits an S-shape and rises continuously. In this way at 530 K almost 100% selectivity for NO formation (with fairly high reaction probability for NH3) is reached.
Free Keywords:
External Publication Status:published
Document Type:Article
Communicated by:Gerhard Ertl
Affiliations:Fritz-Haber-Institut/Physical Chemistry
Identifiers:URL: [Abstract]
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