Toward a Silver–Alumina Model System for NO<sub><i>x</i></sub> Reduction Catalysis

Martin, Natalia; Erdogan, Egemen; Grönbeck, Henrik; Mikkelsen, Anders; Gustafson, Johan; Lundgren, Edvin

doi:10.1021/jp507720h

Cited by 3 publications

(5 citation statements)

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“…However, the formation mechanism of isocyanate species is still debated. Previous studies reached similar conclusions that the initial step may be the dissociation of the NO molecule on the surface, and this may be followed by attack of a CO molecule to form the surface isocyanate species. − But more recent studies indicate that the breaking of the NO bond may be directly assisted by the attack of CO molecule to form a surface nitride species, which then reacts with CO to form the isocyanate NCO species. ,,, …”

Section: Introductionmentioning

confidence: 86%

“…13−21 But more recent studies indicate that the breaking of the NO bond may be directly assisted by the attack of CO molecule to form a surface nitride species, which then reacts with CO to form the isocyanate NCO species. 8,12,22,23 The reactions of metal atoms with NO and CO serve as the simplest model in understanding the intrinsic mechanism of catalytic NO and CO reduction processes. Previous matrix isolation infrared spectroscopic studies on the reactions of transition-metal atoms with CO and NO mixtures show that some metal atoms react with NO and CO to form unsaturated metal carbonyl nitrosyl complexes.…”

Section: ■ Introductionmentioning

confidence: 99%

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Isocyanate Formation from Reactions of Early Lanthanide Metal Atoms with NO and CO in Solid Argon

Jian

Zhang

et al. 2017

J. Phys. Chem. A

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The reactions of early lanthanide metal atoms (Ce, Pr, and Nd) with carbon monoxide and nitric oxide mixtures are studied by infrared absorption spectroscopy in solid argon. The reaction intermediates and products are identified via isotopic substitution as well as theoretical frequency calculations. The results show that the reactions proceed with the initial formation of inserted NLnO molecules, which subsequently react with CO to form the NLnO(CO) complexes on annealing. The NLnO(CO) complexes further isomerize to the more stable isocyanate OLnNCO species under UV light excitation.

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Section: Introductionmentioning

confidence: 86%

Section: ■ Introductionmentioning

confidence: 99%

Isocyanate Formation from Reactions of Early Lanthanide Metal Atoms with NO and CO in Solid Argon

Jian

Zhang

et al. 2017

J. Phys. Chem. A

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“…Among them, several formulations based on Ag/Al 2 O 3 catalysts have proved to be particularly active [44,[48][49][50] and although there is still some speculation about the mechanism for NO x reduction, -CN and -NCO species have been proposed as key…”

Section: Discussionmentioning

confidence: 99%

“…In order to reduce this concentration, heterogeneous catalysts that promote the reaction of NO x with reductant reagents in the atmosphere, like CO, hydrocarbons or alcohols have successfully been developed [51]. Among them, several formulations based on Ag/Al 2 O 3 catalysts have proved to be particularly active [48,[52][53][54] and although there is still some speculation about the mechanism for NO x reduction, -CN and -NCO species have been proposed as key intermediates [46]. According to these authors, when CO is used as reductant, the process starts with the adsorption of CO and NO x on the same Ag NP where they are both dissociated.…”

Section: Discussionmentioning

confidence: 99%

Formation of nitrile species on Ag nanostructures supported on a-Al₂O₃: a new corrosion route for silver exposed to the atmosphere

2017

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The aging of supported Ag nanostructures upon storage in ambient conditions (air and room temperature) for 20 months has been studied. The samples are produced on glass substrates by pulsed laser deposition (PLD); first a 15 nm thick buffer layer of amorphous aluminum oxide (a-AlO) is deposited, followed by PLD of Ag. The amount of deposited Ag ranges from that leading to a discontinuous layer up to an almost-percolated layer with a thickness of <6 nm. Some regions of the as-grown silver layers are converted, by laser induced dewetting, into round isolated nanoparticles (NPs) with diameters of up to ∼25 nm. The plasmonic, structural and chemical properties of both as-grown and laser exposed regions upon aging have been followed using extinction spectroscopy, scanning electron microscopy and x-ray photoelectron spectroscopy, respectively. The results show that the discontinuous as-grown regions are optically and chemically unstable and that the metal becomes oxidized faster, the smaller the amount of Ag. The corrosion leads to the formation of nitrile species due to the reaction between NO species from the atmosphere adsorbed at the surface of Ag, and hydrocarbons adsorbed in defects at the surface of the a-AlO layer during the deposition of the Ag nanostructures by PLD that migrate to the surface of the metal with time. The nitrile formation thus results in the main oxidation mechanism and inhibits almost completely the formation of sulphate/sulphide. Finally, the optical changes upon aging offer an easy-to-use tool for following the aging process. They are dominated by an enhanced absorption in the UV side of the spectrum and a blue-shift of the surface plasmon resonance that are, respectively, related to the formation of a dielectric overlayer on the Ag nanostructure and changes in the dimensions/features of the nanostructures, both due to the oxidation process.

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“…Recently, the Ni catalyst as an important electroactive material not only presents great adsorption ability for a gas molecule (such as the ethyne relative to Rh, Pd, and Pt) but also displays great catalytic potentials in steam-reforming hydrogenation of carbon dioxide, − NO dissociation, , and CH 3 OH dissociation . Among all the relevant low-cost deNO x catalysts that have been investigated by experimental and density functional theory (DFT) calculation methods, ,,− it is found that the Ni catalyst shows a much better low-temperature NO dissociation activity than the noble metals. For example, the experimental investigation for NO reduction by hydrogen showed that the Ni/Al 2 O 3 catalyst realized 95% NO conversion at low temperature .…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Nitric Oxide Reduction by Hydrogen on Ni(110) and Ir/Ni(110): First Principles and Microkinetic Modeling

et al. 2019

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The nitric oxide (NO) reduction by H2 on the pure Ni(110) and single-atom Ir-doped Ni(110) (Ir/Ni(110)) surfaces are investigated by density functional theory calculations coupled with microkinetic modeling. The stability of the single-atom alloy (SAA) Ir/Ni(110) in vacuum and under real conditions is considered. The results show that NO dissociation is very facile on the clean and H-predosed Ni(110) surface, and the dissociated N atoms is more likely to couple with the surface-adsorbed NO to produce N2O than with the N atom to form N2. However, the energy barrier for N2 formation is largely lowered by the doped Ir, whereas that for N2O formation is greatly increased. Thus, N2 is energetically preferentially formed on the Ir/Ni(110) surface. Microkinetic calculations further demonstrate that under ultrahigh-vacuum conditions, the selectivity toward N2O is 100% below 420 K and that toward N2 is over 80% above 460 K, in line with the experimental observation. In contrast, Ir/Ni(110) exhibits markedly improved selectivity toward N2 in a wide temperature range (>90% at 320 K and 100% at T ≥ 340 K). The present work shows that the SAA Ir/Ni(110) catalyst is very effective in promoting the reduction of NO into N2 while largely suppressing N2O formation.

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Toward a Silver–Alumina Model System for NO_x Reduction Catalysis

Cited by 3 publications

References 43 publications

Isocyanate Formation from Reactions of Early Lanthanide Metal Atoms with NO and CO in Solid Argon

Isocyanate Formation from Reactions of Early Lanthanide Metal Atoms with NO and CO in Solid Argon

Formation of nitrile species on Ag nanostructures supported on a-Al₂O₃: a new corrosion route for silver exposed to the atmosphere

Mechanism of Nitric Oxide Reduction by Hydrogen on Ni(110) and Ir/Ni(110): First Principles and Microkinetic Modeling

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Toward a Silver–Alumina Model System for NOx Reduction Catalysis

Cited by 3 publications

References 43 publications

Isocyanate Formation from Reactions of Early Lanthanide Metal Atoms with NO and CO in Solid Argon

Isocyanate Formation from Reactions of Early Lanthanide Metal Atoms with NO and CO in Solid Argon

Formation of nitrile species on Ag nanostructures supported on a-Al2O3: a new corrosion route for silver exposed to the atmosphere

Mechanism of Nitric Oxide Reduction by Hydrogen on Ni(110) and Ir/Ni(110): First Principles and Microkinetic Modeling

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Toward a Silver–Alumina Model System for NO_x Reduction Catalysis

Formation of nitrile species on Ag nanostructures supported on a-Al₂O₃: a new corrosion route for silver exposed to the atmosphere