Scanning Tunneling Microscopy Study of C(2×4)-NO/Pt(001)

Song, Moon‐Bong; Momoi, Kazutaka; Ito, M.

doi:10.1143/jjap.36.l1528

Cited by 7 publications

(9 citation statements)

References 22 publications

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“…The experimental reduction charge for the stripping of saturated NO adlayers gives values between 710 and 740 μC cm -2 (before correction for hydrogen adsorption) for integration between 0.5 and 0.1 V. These values of the reduction charge and the corresponding coverage values agree well with estimations by the Alicante group. ,, The value of ca. 0.5 ML for the saturation coverage of NO under electrochemical conditions would coincide with the value for NO saturation coverage on Pt(100)-(1 × 1) surface under UHV conditions, as reported by different groups. ,, In more recent UHV studies, lower values for the NO saturation coverage were reported, particularly in connection with the possibility of NO dissociation even at room temperature. − The issue of NO dissociation under UHV and electrochemical conditions and the related issue of the saturation coverage and the structure of NO adlayer will be addressed in some detail in the Discussion section.…”

Section: Results and Data Analysissupporting

confidence: 64%

Mechanism of Electrocatalytic Reduction of Nitric Oxide on Pt(100)

Roşca

Koper

2005

J. Phys. Chem. B

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The mechanism of electrocatalytic reduction of nitric oxide on Pt(100)-(1 x 1) in acidic media has been studied using voltammetry, in-situ infrared spectroscopy, and on-line mass spectroscopy, considering the effect of surface defects, NO coverage, and the nature of the supporting electrolyte (sulfate vs perchlorate). Related mechanistic aspects of hydroxylamine (HAM) transformations on the same surface have been also examined. The adsorption of nitric oxide on Pt(100) results in the formation of an adlayer with a structure similar to that formed under ultrahigh vacuum (UHV) conditions. Ammonia was shown to be the main product of NOads reduction on Pt(100). The saturation coverage of NO adsorbate on Pt(100) was found to be around 0.5 ML, in agreement with previous UHV and electrochemical studies. Two features observed in the voltammetric profile for the electrocatalytic reduction of saturated and subsaturated NO adlayers were tentatively ascribed to reactions of NO species having different reactivity. The Tafel slope analysis of these voltammetric features gives values of ca. 60 mV decade(-1). This value was interpreted in terms of an EC mechanism, in which the first electron/proton transfer is at equilibrium, resulted in formation of HNOads intermediate, while the second reaction step is a chemical rate-determining step. This chemical step is assumed to involve the N-O bond breaking in HNOads intermediate, which most probably requires a free neighboring site. From a comparison with NOads reduction on Pt(111) and Pt(110), it follows that (i) the reaction mechanism is structure sensitive and (ii) Pt(100) is the most active surface for breaking the N-O bond, which is in agreement with the trend observed under UHV conditions. As suggested in our previous studies, the electrocatalytic reduction of HAM is likely to proceed through its partial dehydrogenation. In this study, we further develop this idea, and, based on the mechanism for NOads reduction proposed here, we suggest HNOads to be the intermediate appearing both in HAM reduction/oxidation and in NOads reduction.

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Section: Results and Data Analysissupporting

confidence: 64%

Mechanism of Electrocatalytic Reduction of Nitric Oxide on Pt(100)

Roşca

Koper

2005

J. Phys. Chem. B

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“…46,47 Up to now there has been one direct observation of this c͑4 ϫ 2͒ structure, by STM, and this clearly indicated a coverage of 0.25 ML. 48 This coverage has more recently been confirmed by XPS. 49 There have been extensive discussions on the exact nature of the c͑4 ϫ 2͒ ordered structure, and other studies have suggested a different coverage of NO of 0.50 ML.…”

Section: A Adsorption On the Fcc(100) Surfacementioning

confidence: 65%

“…Notwithstanding these arguments we are of the opinion that the STM images presented in Ref. 48 are the most direct observation of the c͑4 ϫ 2͒ structure reported so far. Our model III for adsorption on fcc͑100͒ surfaces thus also describes the case of NO adsorption on the Pt͑100͒ surface.…”

Section: A Adsorption On the Fcc(100) Surfacementioning

confidence: 85%

Bridge-bonded adsorbates on fcc(100) and fcc(111) surfaces: A kinetic Monte Carlo study

et al. 2006

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The adsorption of a bridge-bonded molecule onto fcc͑100͒ and fcc͑111͒ surfaces is studied using kinetic Monte Carlo simulations. The results are related to examples from both the electrochemical and the ultrahigh vacuum field. The lateral interaction model for the fcc͑100͒ surface with the least excluded neighbor sites does not cause ordering in the adlayer at saturation coverage. This is due to the availability of two equivalent bridge sites per surface atom. The model with the most excluded sites on the other hand causes the formation of a c͑4 ϫ 2͒ ordered structure with a coverage of 0.25 ML. Surprisingly, for the model with intermediate-ranged lateral interactions a one-dimensionally ordered structure is found. In this one-dimensionally ordered structure, bridge-bonded anions are aligned along the ͱ 2 direction. The spacing between these rows varies, since each new row can form at either one of the two kinds of bridge site per surface atom. The local distribution between these one-dimensional rows can be described by, respectively, a c͑2 ͱ 2 ϫ ͱ 2͒ or a ͑ ͱ 2 ϫ ͱ 2͒ unit cell ͓the latter one is also referred to as c͑2 ϫ 2͔͒. On the fcc͑111͒ surface, once again no ordered structure is found for the model with the smallest number of excluded sites. For the models with more excluded sites a c͑4 ϫ 2͒ ordered structure ͓also known as c͑2 ϫ ͱ 3͔͒ and a ͑ ͱ 3 ϫ ͱ 7͒ ordered structure are formed, the coverages being 0.50 and 0.20 ML, respectively. The simulated voltammograms generally show a broad peak due to adsorption in a disordered phase, and, if a two-dimensionally ordered structure is formed, a second sharp peak due to a disorder-order transition in the adlayer. The formation of the one-dimensionally ordered structure does not cause an additional current peak in the voltammogram.

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“…The experimental procedures for the UHV STM observations have been described elsewhere. 9 The microscope used is a JSTM-4610(JEOL). STM images were obtained in a constant height mode using tungsten tips.…”

Section: Methodsmentioning

confidence: 99%