Reactive carbon dioxide desorption on stepped Pt(112)

Ohno, Yuichi; Barrera, A.; Rar, A.; Yamanaka, Toshiro; Sugimura, H.; Matsushima, Toshiyasu

doi:10.1016/0039-6028(96)00265-8

Cited by 11 publications

(8 citation statements)

References 12 publications

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“…͑The N 2 peak from Pd͑110͒ was directed 37°from the surface normal.͒ A highly collimated desorption pattern has also been observed for CO 2 desorption from Pt͑112͒. 42 However, even with an infinitely sharp distribution for N 2 and a cos() distribution for NO, if the mass spectrometer accepts a cone with angular radius of 20 deg then the sensitivity enhancement for N 2 is only a factor of 10, not enough to explain fully the observed difference.…”

Section: Terrace Nomentioning

confidence: 92%

Reactions of N and NO on Pt(335)

Wang

Tobin

DiMaggio

et al. 1997

The Journal of Chemical Physics

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As part of a study of species important in automotive exhaust chemistry, the reactivity of atomic N and NO on Pt͑335͒ at low temperature has been studied. The atomic N was produced by dissociating adsorbed NO with a 76 eV electron beam. Cross sections for electron-stimulated desorption and dissociation are estimated for NO on terrace and step sites. Terrace NO is at least five times more likely to desorb than to dissociate.Step NO has a lower desorption cross section than terrace NO, but probably a higher dissociation cross section. Temperature-programmed desorption was used to monitor desorption, dissociation, and the formation of N 2 and N 2 O from adsorbed N and NO. Five distinct desorption states of N 2 formed by NO dissociation are identified. The dominant N 2 peak ͑435 K͒ comes from electron-dissociated step NO; its desorption temperature is higher than the N 2 peaks from electron-dissociated terrace NO. Coadsorbed N and NO react to form N 2 O even below 100 K, with an activation barrier of ϳ6 kcal/mol. Only terrace NO participates in this reaction; step NO does not react to form N 2 O. This site dependence resembles that for CO oxidation on Pt͑112͒ and Pt͑335͒ and can be rationalized with simple steric considerations. All of the forms of atomic N participate in N 2 O formation, but that formed by the dissociation of step NO exhibits the lowest reaction temperature. Hence, the same N atoms that only recombine to form N 2 at 435 K, react with NO to form N 2 O at 100 K. We found no evidence for an NO reaction with N atoms to form N 2 and adsorbed O, or for NO formation from the recombination of adsorbed N and adsorbed O 2 .

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Section: Terrace Nomentioning

confidence: 92%

Reactions of N and NO on Pt(335)

Wang

Tobin

DiMaggio

et al. 1997

The Journal of Chemical Physics

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“…For a comparison, the collimation angles of desorbing CO 2 in the thermal CO oxidation are also listed, where three CO 2 peaks are observed at around 400 K (P 1 -CO 2 ), 300 K (P 2 -CO 2 ) and 230 K (P 3 -CO 2 ). 37,38 The third column shows the translational temperature of these species at the collimation position. The collimation angle shifts closer to the local normal at higher kinetic energy as predicted.…”

Section: Terrace Normal Desorptionmentioning

confidence: 99%

Desorption of products in 193 nm photo-induced reactions in (O2+ CO) adlayers on Pt(112)

Han

Matsushima

2005

Phys. Chem. Chem. Phys.

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The spatial distributions of desorbing products were examined in 193 nm photo-induced reactions in O2 + CO adlayers on stepped Pt(112) = [(s)3(111) x (001)]. At high coverage of O2(a) and CO(a), both O2 and CO2 desorption collimated closely along the (111) terrace normal. The results were compared with those in thermal CO oxidation, and the origin of the collimation angle shift in the latter is discussed. On the other hand, at low CO(a) coverage, O2 and CO2 desorption collimated in inclined ways in the plane along the surface trough. At these collimation positions, the kinetic energy of desorbing 02 and CO2 was maximal, confirming the hot-atom collision mechanism.

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“…In CO oxidation on noble metals at the steady state, oxygen and CO molecules first adsorb as O(a) and CO(a), and then the reaction subsequently proceeds via a Langmuir−Hinshelwood mechanism, i.e., CO(a) + O(a) → CO 2 (g) . The product CO 2 carries a high energy in translational and internal modes. − The reaction site for CO 2 formation can be identified by the spatial and velocity distributions of the desorbing product because of its highly repulsive desorption. , Some research has already been published on the dynamics on individual sites by using AR-TDS (angle-resolved thermal desorption spectroscopy) combined with the TOF (time-of-flight) technique. − In such TDS work, however, the coverage of CO(a) and O(a) decreases with increasing surface temperature, as these are removed as CO 2 . It is difficult to study either the coverage effect at fixed temperatures, or the temperature effect at fixed coverages.…”

Section: Introductionmentioning

confidence: 99%

“…AR-TDS has been applied to both site identification and switching in the CO oxidation on stepped surfaces, Pt(112), (113), (335), and (557). ,− ,− The resultant CO 2 spatial distribution shows that the product is desorbed from narrow terraces or steps. On Pt(113), CO 2 is predominantly formed on the (111) site at high CO(a) coverage, while at high O(a) coverage, the contribution from the (001) site is enhanced and the site preference is reversed.…”

Section: Introductionmentioning

confidence: 99%

Dynamics on Individual Reaction Sites in Steady-State Carbon Monoxide Oxidation on Stepped Platinum(113)

et al. 1999

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The reaction kinetics and dynamics of carbon monoxide oxidation on a stepped Pt(113) = (s)2(111) × (001) surface were studied by angle-resolved kinetic and velocity measurements at the steady state. CO2 desorption sharply collimated nearly along either the (111) site normal or the (001) site normal. Only two reaction sites, the (111) and (001) sites, were operative. The translational energy of CO2 was characteristic of each site throughout a site switching. At surface temperatures above 520 K in the active region, where the reaction was first order in CO, the preference of the (111) site was suppressed with increasing CO pressure. Below 520 K, on the other hand, site switching slowly took place under limited conditions, in which both sites considerably contributed to the reaction and a meta-stable adsorbed phase seemed to be formed. The preference for the (111) site over the (001) site was caused by the former's higher reactivity of oxygen.

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Reactive carbon dioxide desorption on stepped Pt(112)

Cited by 11 publications

References 12 publications

Reactions of N and NO on Pt(335)

Reactions of N and NO on Pt(335)

Desorption of products in 193 nm photo-induced reactions in (O2+ CO) adlayers on Pt(112)

Dynamics on Individual Reaction Sites in Steady-State Carbon Monoxide Oxidation on Stepped Platinum(113)

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