Summary Abstract: A comparison of nitric oxide decomposition on a variety of faces of platinum

Banholzer, W. F.; Gohndrone, John M.; Hatzikos, G. H.; Lang, Jiajia; Masel, Richard I.; Park, Y. O.; Stolt, Kaj

doi:10.1116/1.573169

Cited by 10 publications

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“…Ammonia adsorption and decomposition have been investigated experimentally on Pt{111}, Pt{210}, Pt{410}, Pt{557}, and polycrystalline Pt. − The decomposition shows only a moderate structure sensitivity. This is in sharp contrast to O 2 and NO adsorption and decomposition, which are highly structure-sensitive on Pt surfaces. − Earlier theoretical investigations of ammonia adsorption and decomposition on Pt{111} and Pt{100} have revealed adsorption sites and reaction barriers of ammonia and corresponding fragments on these surfaces. − Here we compare these results with investigations of ammonia dissociation reactions on the Pt{211} surface, which shares the geometrical properties of both (100) and (111) surfaces. This has led to important trends in the NH 3 dissociation reaction, which we expect to be generally valid for any platinum surface.…”

Section: Introductionmentioning

confidence: 80%

“…This is in sharp contrast to O 2 and NO adsorption and decomposition, which are highly structure-sensitive on Pt surfaces. [7][8][9][10][11][12][13] Earlier theoretical investigations of ammonia adsorption and decomposition on Pt{111} and Pt{100} have revealed adsorption sites and reaction barriers of ammonia and corresponding fragments on these surfaces. [14][15][16][17][18] Here we compare these results with investigations of ammonia dissociation reactions on the Pt{211} surface, which shares the geometrical properties of both (100) and (111) surfaces.…”

Section: Introductionmentioning

confidence: 99%

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Ammonia Dissociation on Pt{100}, Pt{111}, and Pt{211}: A Comparative Density Functional Theory Study

et al. 2007

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Density functional theory (DFT) calculations are performed to compare the dissociation of NH x (x = 1−3) species on the Pt{100}, Pt{111}, and Pt{211} surface. Pt{211} is a stepped surface, and Pt{100} consists of square arranged surface atoms. Both surfaces are less compact than Pt{111}. The question is addressed whether the Pt{100} and the Pt{211} surface promote the dissociation of NH x species by lowering the activation barriers with respect to Pt{111}. The NH dissociation reaction is promoted on Pt{100} but not on Pt{211}. The NH2 dissociation reaction is neither promoted by Pt{100} nor Pt{211}. The dissociation of NH3 is also not promoted and turns out to be a two-step reaction on the platinum surfaces. Atop-bonded NH2 is intermediate and equally stable on the three surfaces. The nature of the transition states, which is late in the formation and early in the rearrangement of this atop-bonded NH2, makes the barriers almost independent of the surface topology. Because the reaction energies of the NH x dissociation reactions do depend on the surface topology the findings are unexpected, but they are consistent with an experimentally found moderate structure sensitivity of the ammonia decomposition on platinum.

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Section: Introductionmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Ammonia Dissociation on Pt{100}, Pt{111}, and Pt{211}: A Comparative Density Functional Theory Study

et al. 2007

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“…As such, the adsorption and dissociation of NO have attracted great attention. In the earlier 1980s, Masel et al studied a series of platinum stepped surfaces for NO dissociation and found that this reaction was strongly dependent on the surface structure. − The {111} surface was found to be essentially inactive. The {410} surface, on the other hand, was shown to have significantly higher reactivity for NO decomposition.…”

Section: Introductionmentioning

confidence: 99%

Structure Dependence of NO Adsorption and Dissociation on Platinum Surfaces

Neurock

2004

J. Am. Chem. Soc.

118

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The influence of surface structure on NO chemisorption and dissociation on Pt[100]-(1x1), Pt[211], and Pt[410] has been studied using density functional theory slab calculations with the generalized gradient corrections. The presence of steps on Pt[211] strengthens the NO-surface chemisorption bond, but the barrier for NO dissociation remains high. On the other hand, the steps on Pt[410] help to stabilize the N and O adatoms that form upon dissociation and the transition state. The calculated barrier of 80.2 kJ/mol on Pt[410] is in good agreement with experiment. These results show that both the presence of steps and the nature of the steps are important to activate NO. An ensemble of square-arranged Pt atoms has been identified as an important feature in activating the N-O bond.

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“…Surface science studies have shown that the catalytic activity of Pt surfaces in the CO + NO reaction is related to the efficiency of dissociation of NO, which varies for different crystal planes . For example, NO partially decomposes to yield N 2 and O 2 on the Pt(100) surface, − whereas no dissociation occurs on Pt(111). ,, HREELS and infrared reflection absorption spectroscopy (IRAS) studies show that NO adsorbs molecularly on the reconstructed hex-Pt(100) surface at room temperature, but it initially adsorbs dissociatively on the (1 × 1)-Pt(100) surface prior to molecular adsorption at higher NO coverages. ,, …”

Section: Introductionmentioning

confidence: 99%

Influence of Alloyed Sn on Adsorption and Reaction of NO on Pt(100) Surfaces

Panja

Koel

2000

J. Phys. Chem. A

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Adsorption and reaction of NO on the (5 × 20)-Pt(100) surface and two Sn/Pt(100) surface alloys have been studied using temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS). On the (5 × 20)-Pt(100) surface, in the absence of Sn, NO is primarily reversibly adsorbed, and most of the chemisorbed NO desorbs molecularly from the surface during TPD. Approximately 25% of the adsorbed NO monolayer decomposes at temperatures higher than 400 K, and this leads to N 2 and O 2 desorption from the surface. Alloying Sn into the surface layer of Pt(100) forms two ordered surface alloys having c(2 × 2) and (3 2 × 2)R45°Sn/Pt(100) surface structures with θ Sn ) 0.5 and 0.67 ML, respectively. Alloying reduced the saturation coverage of NO in the chemisorbed monolayer from that on Pt(100) at 100 K, and it also reduced the adsorption energy of molecularly bound NO by more than a factor of 2. Alloyed Sn, which removes all pure-Pt 2-fold bridge and 4-fold hollow sites, completely changed the NO reaction pathway: nitrogen in NO was partially reduced to form N 2 O on these alloys so that N 2 O, along with NO and O 2 , desorption was observed in TPD. NO is bonded at the same site with a similar geometry on both Pt(100) and the Sn/Pt(100) alloyed surfaces at low NO coverages, based on the HREELS spectra. At saturation (monolayer) coverages, however, quite different HREELS spectra were observed on both of the Sn/Pt(100) alloyed surfaces compared to that on Pt(100). Vibrations were observed from adsorbed N 2 O, along with a shift of more than 60 cm -1 for two ν NO peaks on both of the Sn/Pt(100) alloys compared to Pt(100). The two ν NO peaks can be assigned either as (i) two ν s modes of bent (tilted) and linearly bonded atop NO or as (ii) ν s and ν as stretching modes of a surface dinitrosyl species, that is, two NO molecules bound to one Pt atom. Dinitrosyl species have been proposed as intermediates for N 2 O formation in reactions of NO on Mo(110) (Queeney and Friend, J. Chem. Phys. 1997, 107, 6432), and we suggest that a similar reaction mechanism occurs on Sn/Pt(100) alloys.

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Summary Abstract: A comparison of nitric oxide decomposition on a variety of faces of platinum

Cited by 10 publications

References 0 publications

Ammonia Dissociation on Pt{100}, Pt{111}, and Pt{211}: A Comparative Density Functional Theory Study

Ammonia Dissociation on Pt{100}, Pt{111}, and Pt{211}: A Comparative Density Functional Theory Study

Structure Dependence of NO Adsorption and Dissociation on Platinum Surfaces

Influence of Alloyed Sn on Adsorption and Reaction of NO on Pt(100) Surfaces

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