Reduction of nitric oxide with carbon monoxide on the Rh(100) single crystal surface

Technical Report · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5335147

Hendershot, R E

Steady-state kinetic measurements, at 688/sup 0/K and in the pressure range of 1.0 to 1800 Pa, indicate that this process proceeds via a Langmuir-Hinshelwood type mechanism and is selective towards the production of N/sub 2/ and CO/sub 2/. The CO kinetic order varied continuously from +1 to -1 as the partial pressure of CO was increased from 1 to 250 Pa, at a constant NO partial pressure of 57.5 Pa. In a similar manner, the NO kinetic order varied continuously from +3/2 to -1 as the partial pressure of NO was increased from 1 to 1800 Pa, at a constant CO partial pressure of 44.0 Pa. The catalyst surface was characterized with Auger AES, LEED, and thermal desorption spectroscopy (TDS). Initial Auger analysis illustrated surface contamination by S, P, and B. The S and P contaminants were removed by ion beams of H and O, respectively. The B contaminant was identified by AES and by the formation of a B (3 x 1) or (3 x 3) ordered overlayer. This impurity was removed via cycles of Ar ion bombardment and high temperature annealing. NO adsorbed with a high sticking coefficient and formed a c(2 x 2) ordered overlayer at saturation. The NO adsorbate dissociated upon slow stepwise heating as indicated by the production of a surface oxide and the lack of surface nitrogen. Thermal desorption experiments indicated, however, that most of the adsorbed NO desorbed molecularly in a first order process with a peak at 401/sup 0/K, during the temperature flash. CO adsorbs molecularly in two distinct surface sites both of which follow first order desorption kinetics, with TDS peaks at 373 and 425/sup 0/K. A kinetic model was developed which is consistent with both the steady-state kinetic and surface characterization results.

• Research Organization: Ames Lab., IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5335147
• Report Number(s): IS-T-1081; ON: DE84007199
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
500200 -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ADSORPTION
AUGER ELECTRON SPECTROSCOPY
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
CRYSTALS
DESORPTION
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
HIGH TEMPERATURE
METALS
MONOCRYSTALS
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
REDUCTION
RHODIUM
SCATTERING
SORPTION
SPECTROSCOPY
SURFACES
TRANSITION ELEMENTS