Molecular adsorption of NO on PdO(101)

Choi, Jinwoo; Pan, Li; Zhang, Feng; Diulus, J. Trey; Asthagiri, Aravind; Weaver, Jason F.

doi:10.1016/j.susc.2015.01.010

Cited by 7 publications

(5 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As elaborated below, this scaling assumes that an NO molecule is adsorbed on each Fe cation of the FeO(111) monolayer at saturation of the NO layer. We have recently found that this scaling is reasonable for NO adsorbed on an FeO(111) monolayer grown on Ag(100), where the coverage scale in that case is based on NO TPD spectra obtained from Pd(111). , We estimate that the NO coverages reported here are accurate to within about 15%.…”

Section: Methodssupporting

confidence: 60%

See 1 more Smart Citation

Adsorption of NO on FeO_x Films Grown on Ag(111)

et al. 2016

Self Cite

View full text Add to dashboard Cite

We used temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS) to characterize the adsorption of NO on crystalline iron oxide films grown on Ag(111), including a Fe3O4(111) layer, an FeO(111) monolayer, and an intermediate FeO x multilayer structure. TPD shows that the NO binding energies vary significantly among the Fe cation sites present on these FeO x surfaces, and provides evidence that NO binds more strongly on Fe2+ sites than Fe3+ sites. The NO TPD spectra obtained from the Fe3O4(111) layer exhibit a dominant peak at 380 K, attributed to NO bound on Fe2+ sites, as well as a broad feature centered at ∼250 K that is consistent with NO bound on Fe3+ sites of Fe3O4(111) as well as NO adsorbed on a minority FeO structure. The NO TPD spectra obtained from the monolayer FeO(111) film exhibits a prominent peak at 269 K. After growing FeO x multilayer islands within the FeO(111) monolayer, we observe a new NO TPD feature at ∼200 K as well as diminution of the sharp TPD peak at 269 K. We speculate that these changes occur because the multilayer FeO x islands expose Fe3+ sites that bind NO more weakly than the Fe2+ sites of the FeO monolayer. RAIR spectra obtained from the NO-covered FeO x surfaces exhibit an N–O stretch band that blueshifts over a range from about 1800 to 1840 cm–1 with increasing NO coverage. The measured N–O stretching frequency is only slightly red-shifted from the gas-phase value, and lies in a range that is consistent with atop, linearly bound NO on the Fe surface sites. In contrast to the NO binding energy, we find that the N–O stretch band is relatively insensitive to the NO binding site on the FeO x surfaces. This behavior suggests that π-backbonding occurs to similar extents among the adsorbed NO species, irrespective of the oxidation state and local structural environment of the Fe surface site.

show abstract

Section: Methodssupporting

confidence: 60%

“…We have recently found that this scaling is reasonable for NO adsorbed on an FeO(111) monolayer grown on Ag(100), 17 where the coverage scale in that case is based on NO TPD spectra obtained from Pd(111). 31,32 We estimate that the NO coverages reported here are accurate to within about 15%.…”

Section: ■ Experimental Detailsmentioning

confidence: 58%

Adsorption of NO on FeO_x Films Grown on Ag(111)

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…To the best of our knowledge, there is no experimental data available on the thickness of the sulfate layer that forms on PdO after extensive SO 2 poisoning. However, compared to the XPS sampling depth, the thickness is probably on the scale of nanometers. , PdO(101) has been successfully modeled using multilayer slab models cleaved from bulk ,, and PdO(101) monolayer(s) on metallic Pd(100). ,, For the PdO(101) on Pd(100) models, adding a second PdO layer noticeably improves the activity . Each model has its advantages, and ultimately, it is debatable which model provides a more accurate description of the system.…”

Section: Resultsmentioning

confidence: 99%

“…However, compared to the XPS sampling depth, the thickness is probably on the scale of nanometers. 12,38 PdO(101) has been successfully modeled using multilayer slab models cleaved from bulk 9,43,44 and PdO(101) monolayer(s) on metallic Pd(100). 5,45,46 For the PdO(101) on Pd(100) models, adding a second PdO layer noticeably improves the activity.…”

Section: Resultsmentioning

confidence: 99%

PdSO₄ Surfaces in Methane Oxidation Catalysts: DFT Studies on Stability, Reactivity, and Water Inhibition

et al. 2020

View full text Add to dashboard Cite

Although it is experimentally difficult to observe, PdSO4 is considered to be the culprit for the reduced activity of SO2-poisoned methane oxidation catalysts. Density functional theory (DFT) predicts that the formation of bulk PdSO4 is unlikely, which explains the lack of X-ray diffraction (XRD) evidence for the PdSO4 phase. Instead, experimental observations support the idea of PdSO4 being formed on PdO as thin films. Our study found PdSO4(110) and PdSO4(111), corresponding to PdO(100) and PdO(101), respectively, to be the most likely surfaces to be found on a poisoned catalyst. On these sulfate surfaces, PdSO4(111) contains coordinatively unsaturated palladium, which enables catalytic activity. The first C–H dissociation of methane on PdSO4(111) was found to be rather accessible with an energy barrier varying between 0.74 and 0.87 eV, values similar to those reported for metallic Pd. However, the presence of hydroxyl groups increases the barrier height. Methane oxidation is also hindered by an exceptionally strong water adsorption of −1.45 eV on the PdSO4(111) surface, which causes site blocking. A significantly strong adsorption energy causes the combination of surface hydroxyl groups to form adsorbed water that is energetically favorable. The results provide a theoretical justification for the observation that SO2-poisoned PdSO4/Al2O3 catalysts produce proper methane conversion under dry conditions but perform poorly under wet feed.

show abstract

“…As such, we propose that only relative changes of coverage or desorption need be discussed. So long as we are confident that for any given species we can compare the relative intensity of a desorption peak from one experiment to the next, then the results are meaningful within the context of the discussion, as conventional surface science technology allows. − …”

Section: Introductionmentioning

confidence: 99%

Selective Catalytic Reduction of NO by Hydrocarbons on a Stepped Pt Surface: Influence of SO₂ and O₂

Griffiths

2015

J. Phys. Chem. C

View full text Add to dashboard Cite

The catalytic reduction of NO by hydrocarbons (C 2 H 4 and its derivatives) in the presence of both S 18 O 2 and O 2 on Pt(332) was investigated. S 18 O 2 -C 2 H 4 interactions are much stronger than NO-C 2 H 4 interactions. Co-adsorbed S 18 O 2 molecules consume most of the H atoms from C 2 H 4 dissociation before NO dissociation, a major cause for suppressing the NO-C 2 H 4 reaction. The S 18 O 2 molecules also reduce the reactivity of Pt(332) toward NO-C 2 H 4 reaction by passivating the metal surface and by blocking the step sites for NO adsorption. NO-C 2 H 4 reactions are also suppressed by co-adsorbed O(ads.) atoms due to the stronger Pt-O interaction and facile H-O reaction. However, when the coverage of O atoms is appropriate, the O atoms effectively lifts the suppressive effect of S 18 O 2 , a result of the facile O-S 18 O 2 reaction, which scavenges the S 18 O 2 related species and consequently gives the Pt(332) surface a more reactive pathway toward the NO dissociation (compared to that covered with sulfur oxides).

show abstract

Molecular adsorption of NO on PdO(101)

Abstract: 2016-11-02T18:49:00

Cited by 7 publications

References 42 publications

Adsorption of NO on FeO_x Films Grown on Ag(111)

Adsorption of NO on FeO_x Films Grown on Ag(111)

PdSO₄ Surfaces in Methane Oxidation Catalysts: DFT Studies on Stability, Reactivity, and Water Inhibition

Selective Catalytic Reduction of NO by Hydrocarbons on a Stepped Pt Surface: Influence of SO₂ and O₂

Contact Info

Product

Resources

About

Molecular adsorption of NO on PdO(101)

Abstract: 2016-11-02T18:49:00

Cited by 7 publications

References 42 publications

Adsorption of NO on FeOx Films Grown on Ag(111)

Adsorption of NO on FeOx Films Grown on Ag(111)

PdSO4 Surfaces in Methane Oxidation Catalysts: DFT Studies on Stability, Reactivity, and Water Inhibition

Selective Catalytic Reduction of NO by Hydrocarbons on a Stepped Pt Surface: Influence of SO2 and O2

Contact Info

Product

Resources

About

Adsorption of NO on FeO_x Films Grown on Ag(111)

Adsorption of NO on FeO_x Films Grown on Ag(111)

PdSO₄ Surfaces in Methane Oxidation Catalysts: DFT Studies on Stability, Reactivity, and Water Inhibition

Selective Catalytic Reduction of NO by Hydrocarbons on a Stepped Pt Surface: Influence of SO₂ and O₂