Selective catalytic ammonia oxidation to nitrogen by atomic oxygen species on Ag (111)
Author
Karatok, M.
Vovk, E. I.
Koc, A. V.
Ozensoy, E.
Date
2017Source Title
Journal of Physical Chemistry C
Print ISSN
1932-7447
Publisher
American Chemical Society
Volume
121
Issue
41
Pages
22985 - 22994
Language
English
Type
ArticleItem Usage Stats
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Abstract
Ammonia-selective catalytic oxidation was studied on the planar Ag(111) single-crystal model catalyst surface under ultra-high-vacuum (UHV) conditions. A variety of oxygen species were prepared via ozone decomposition on pristine Ag(111). Surface coverages of oxygen species were quantified by temperature-programmed desorption (TPD) and X-ray photoemission spectroscopy techniques. Exposure of ozone on Ag(111) at 140 K led to a surface atomic oxygen (Oa) overlayer. Low-energy electron diffraction experiments revealed that annealing of this atomic oxygen-covered Ag(111) surface at 473 K in UHV resulted in the formation of ordered oxide surfaces (Oox) with p(5×1) or c(4×8) surface structures. Ammonia interactions with O/Ag(111) surfaces monitored by temperature-programmed reaction spectroscopy indicated that disordered surface atomic oxygen selectively catalyzed N-H bond cleavage, yielding mostly N2 along with minor amounts of NO and N2O. Higher coverage O/Ag(111) surfaces, whose structure was tentatively assigned to a bulklike amorphous silver oxide (Obulk), showed high selectivity toward N2O formation (rather than N2) due to its augmented oxygen density. In contrast, ordered surface oxide overlayers on Ag(111) (where the order was achieved by annealing the oxygen adlayer to 473 K) showed only very limited reactivity toward ammonia. The nature of the adsorbed NH3 species on a clean Ag(111) surface and its desorption characteristics were also investigated via infrared reflection absorption spectroscopy and TPD techniques. Current findings demonstrate that the Ag(111) surface can selectively oxidize NH3 to N2 under well-defined experimental conditions without generating significant quantities of environmentally toxic species such as NO2, NO, or N2O.
Keywords
Absorption spectroscopyAmmonia
Atoms
Catalytic oxidation
Crystal atomic structure
Desorption
Electrons
Oxidation
Oxygen
Ozone
Photoelectron spectroscopy
Silver compounds
Silver oxides
Single crystals
Temperature programmed desorption
Ultrahigh vacuum
Desorption characteristics
Disordered surfaces
Experimental conditions
Infrared reflection absorption spectroscopy
Ozone decomposition
Selective catalytic oxidation
Temperature-programmed reaction spectroscopies
X ray photoemission spectroscopy
Silver
Permalink
http://hdl.handle.net/11693/37294Published Version (Please cite this version)
http://dx.doi.org/10.1021/acs.jpcc.7b08291Collections
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