Coupled theoretical and experimental analysis of surface coverage effects in Pt-catalyzed NO and O2 reaction to NO2 on Pt(111)

Smeltz, Andrew; Getman, Rachel B.; Schneider, William F.; Ribeiro, Fabio H.

doi:10.1016/j.cattod.2007.12.139

Cited by 82 publications

(117 citation statements)

References 42 publications

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“…21 We conclude that O 2 activation on O*-covered surfaces is limited by the reaction of O 2 with a vacancy to form O* and mobile oxygen adatoms that rapidly migrate among strongly bound O* species. These data and conclusions suggest that the cleavage of O)O bonds occurs rapidly even without the assistance of coadsorbed reactants (e.g., NO* or CO*, as proposed elsewhere 15,22 Figure 3. NO oxidation rate constants increased monotonically with increasing cluster size, 6 concurrently with increases in isotopic oxygen exchange and NO 2 decomposition rates (Figure 2b).…”

Section: Experimental Methods 21 Catalyst Synthesis and Characterizsupporting

confidence: 74%

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NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

2009

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Kinetic and isotopic methods show that NO oxidation on supported Pt clusters involves kinetically relevant reaction of O 2 with vacancy sites on surfaces nearly saturated with oxygen adatoms (O*). The oxygen chemical potential at Pt surfaces that determines the O* coverage is rigorously described by an O 2 virtual pressure and determined by the thermodynamics of NO 2 -NO interconversion reactions. NO oxidation and oxygen isotopic exchange processes are described by the same rate constant, consistent with similar kinetically relevant O 2 dissociation steps for both reactions. NO oxidation, NO 2 decomposition, andO 2 exchange rates increased markedly with increasing Pt cluster size (1-8 nm); these clusters remain metallic at all O 2 virtual pressures prevalent during NO oxidation. These effects of cluster size reflect the higher vacancy concentrations and more facile oxygen desorption on larger Pt clusters, which bind oxygen adatoms weaker than more coordinatively unsaturated surface Pt atoms on smaller clusters. These trends are similar to those found for methane and dimethyl ether combustion on Pt and Pd catalysts, which also require vacancy sites on O*-saturated cluster surfaces in their respective kinetically relevant steps. Inhibition of NO oxidation by NO 2 persists to undetectable NO 2 concentrations; thus, NO oxidation turnover rates increase significantly when NO 2 adsorption sites present on BaCO 3 /Al 2 O 3 are placed within diffusion distances of Pt clusters. NO oxidation rates on intrapellet catalyst-adsorbent mixtures are described accurately by a simple reaction-adsorption model in which NO 2 adsorbs via displacement of CO 2 on BaCO 3 surfaces.

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Section: Experimental Methods 21 Catalyst Synthesis and Characterizsupporting

confidence: 74%

“…14 We consider the sequence of elementary steps previously proposed for NO oxidation 4,15 2 /NO ratios instead of O 2 pressures. As a result, rigorous comparisons between isotopic exchange and NO oxidation rates require that we measure both reaction rates at the same oxygen chemical potential.…”

Section: Experimental Methods 21 Catalyst Synthesis and Characterizmentioning

confidence: 99%

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

2009

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“…Theoretical models can be used to construct phase diagrams and predict surface conditions and the possibility of surface oxide or even bulk oxide formation [22][23][24][25] but in the end the state of the surface is a kinetic phenomenon as shown by Reuter et al [26]. Adsorbate-adsorbate interactions can have a significant effect on the energy of adsorption and desorption steps [27] and can alter the stability of transition states [15,28,29], and can therefore affect the catalytic rate substantially as shown recently by Schneider and coworkers [10,30,31]. The question therefore arises to what extend the state of the surface and in particular adsorbate-adsorbate interactions affect the trends in reactivity from one metal to the next.…”

Section: Introductionmentioning

confidence: 89%

Understanding Trends in Catalytic Activity: The Effect of Adsorbate–Adsorbate Interactions for CO Oxidation Over Transition Metals

2010

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Using high temperature CO oxidation as the example, trends in the reactivity of transition metals are discussed on the basis of density functional theory (DFT) calculations. Volcano type relations between the catalytic rate and adsorption energies of important intermediates are introduced and the effect of adsorbate-adsorbate interaction on the trends is discussed. We find that adsorbateadsorbate interactions significantly increase the activity of strong binding metals (left side of the volcano) but the interactions do not change the relative activity of different metals and have a very small influence on the position of the top of the volcano, that is, on which metal is the best catalyst.

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“…As was shown experimentally, the reaction of NO* + O* f NO 2 * controls the surface coverage of oxygen. 50,51 The temperature dependent steady-state coverages of NO*, N*, and O* averaged over the entire Pt particle are shown in Figure 6. The results indicate that the particle is predominately covered by oxygen which is consistent with experimental results reported for reduction 52 and NO oxidation.…”

Section: Facet-dependent Kineticsmentioning

confidence: 99%

First-Principles-Based Kinetic Monte Carlo Simulation of Nitric Oxide Reduction over Platinum Nanoparticles under Lean-Burn Conditions

Mei

Neurock

2010

Ind. Eng. Chem. Res.

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The kinetics for NO reduction over supported platinum under lean condition were investigated by firstprinciples-based kinetic Monte Carlo simulation over three-dimensional Pt nanoparticles. Model platinum nanoparticles with diameters ranging from 2.3 to 4.6 nm were constructed using a truncated octahedral cluster consisting of a two (100) facets and eight (111) facets. First-principles density functional theory (DFT) calculations were used to calculate the intrinsic kinetic parameters including the binding energies for all of the surface intermediates as well as the activation barriers and reaction energies that comprise the reaction mechanism over the (100) and (111) facets, as well as the (111)/(100) edge sites on the three-dimensional nanoparticle. Both intra-and inter-facet diffusion of adsorbates were included to model surface diffusion effects over the particle surface. The simulation results show that under lean conditions where there is excess oxygen, NO reduction to N 2 occurs solely on the (100) facets. The oxidation of NO to NO 2 , while much more favored on the (111) facets, can occur on both (100) and (111) facets. Only small amounts of N 2 O form over the (100) facets. The simulated apparent activation energies for N 2 and NO 2 formation over the entire particle are 45 and 42 kJ/mol, respectively. The latter is in agreement with experimentally measured value of 39 kJ/mol [Mulla, S. S., et al., Catal. Lett. 2005, 100, 267]. The effects of particle size on the activities of NO reduction to N 2 and NO oxidation to NO 2 depend upon the ratios of exposed surface sites. For the threedimensional model Pt nanoparticles examined here, the fractions of the (100) terrace sites are similar while the fraction of the (111) terrace sites increases with increasing particle size. As a result, the activity for NO reduction is somewhat insensitive to the particle size which symmetrically increases the numbers of (111) and (100) facets as the size increases. NO reduction, however, increases much more dramatically when the number of the (100) sites increases over the (111) sites. NO oxidation activity, on the other hand, appears to increase with increasing particle size regardless of the symmetry or shape of the particle as the reaction occurs predominantly over the (111) sites but can also take place on the (100) terrace sites. The structure insensitivity for NO oxidation is consistent with experimental results.

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Coupled theoretical and experimental analysis of surface coverage effects in Pt-catalyzed NO and O2 reaction to NO2 on Pt(111)

Cited by 82 publications

References 42 publications

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

Understanding Trends in Catalytic Activity: The Effect of Adsorbate–Adsorbate Interactions for CO Oxidation Over Transition Metals

First-Principles-Based Kinetic Monte Carlo Simulation of Nitric Oxide Reduction over Platinum Nanoparticles under Lean-Burn Conditions

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Coupled theoretical and experimental analysis of surface coverage effects in Pt-catalyzed NO and O2 reaction to NO2 on Pt(111)

Cited by 82 publications

References 42 publications

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO2Adsorption Sites

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO2Adsorption Sites

Understanding Trends in Catalytic Activity: The Effect of Adsorbate–Adsorbate Interactions for CO Oxidation Over Transition Metals

First-Principles-Based Kinetic Monte Carlo Simulation of Nitric Oxide Reduction over Platinum Nanoparticles under Lean-Burn Conditions

Contact Info

Product

Resources

About

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites