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Thissen, Peter; Grundmeier, Guido; Wippermann, Stefan Martin; Schmidt, Wolf Gero

doi:10.1103/physrevb.80.245403

Cited by 78 publications

(97 citation statements)

References 39 publications

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“…Temperature programmed desorption experiments on Al2O3 in [27,28] have shown that water still desorbs at temperatures above the here-tested 300 °C. Nanosized ceria is able to sorb water as well [29].…”

Section: Microwave-based Detection Of Aging State Dependent Water Adsmentioning

confidence: 61%

In operando Detection of Three-Way Catalyst Aging by a Microwave-Based Method: Initial Studies

2015

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Initial studies on aging detection of three way catalysts with a microwave cavity perturbation method were conducted. Two physico-chemical effects correlate with the aging state. At high temperatures, the resonance frequencies for oxidized catalysts (λ = 1.02) are not influenced by aging, but are significantly affected by aging in the reduced case (λ = 0.98). The catalyst aging state can therefore potentially be inferred from the resonance frequency differences between reduced and oxidized states or from the resonance frequency amplitudes during lambda oscillations. Secondly, adsorbed water at low temperatures strongly affects the resonance frequencies. Light-off experiment studies showed that the resonance frequency depends on the aging state at temperatures below the oxygen storage light-off. These differences were attributed to different water sorption capabilities of differently aged samples due to a surface area decrease with proceeding aging. In addition to the aging state, the water content in the feed gas and the temperature affect the amount of adsorbed water, leading to different integral electrical material properties of the catalyst and changing the resonance properties of the catalyst-filled canning. The classical aging-related properties of the catalyst (oxygen storage capacity, oxygen storage light-off, surface area), agreed very well with data obtained by the microwave-based method. OPEN ACCESSAppl. Sci. 2015, 5 175

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Section: Microwave-based Detection Of Aging State Dependent Water Adsmentioning

confidence: 61%

In operando Detection of Three-Way Catalyst Aging by a Microwave-Based Method: Initial Studies

2015

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“…This is very similar to the effect of water adsorption at the nonpolar Al 2 O 3 (0001) surface, which was recently found to significantly disrupt the clean Al 2 O 3 surface geometry. 34 We notice that another configuration of very similar energy can be created. In this case, the oxygen of the water molecule again adsorbs close to a surface Li…”

Section: A Zero-coverage Adsorptionmentioning

confidence: 86%

Polarization-dependent water adsorption on the LiNbO3(0001) surface

2012

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The effect of ferroelectric poling on the adsorption characteristics of water at lithium niobate surfaces is investigated by ab initio calculations. Thereby we model the adsorption of H 2 O monomers, small water clusters, and water thin films on the LiNbO 3 (0001) surface. The adsorption configuration and energy are determined as a function of the surface coverage on both the positive and negative (0001) surfaces. Confirming the results of temperature programed desorption measurements [Garra, Vohs, and Bonnell, Surf. Sci. 603, 1106 (2009)], polarization-dependent adsorption energies, geometries, and equilibrium coverage are found. Our calculations predict the adsorption to occur mainly nondissociatively, independently of the coverage. The water structures formed at the surface are coverage-dependent, though. The different affinity of water to the two surfaces is explained in terms of electrostatic interactions between the substrate and polar molecules. Water adsorption accentuates the surface relaxation, thus increasing the microscopic surface roughness.

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“…It indicates that water adsorption on the ␥-Al 2 O 3 surfaces are stronger than on Cu 2 O surface. On the Al-terminated ␣-Al 2 O 3 (0 0 0 1) surface [45], dissociative adsorption is favored at low water coverage and the formation of hexagons of alternating dissociatively and molecularly adsorbed water monomers is found at high coverage from first principles DFT calculations. The computed free energy profiles from first principles MD simulations show that molecularly adsorbed water is metastable and dissociates readily, even in the absence of defects, by a kinetically preferred pathway at low water coverage [46], while rapid dissociation and unanticipated collective effects, including water-catalyzed dissociation and proton transfer reactions between adsorbed water and hydroxide have been observed at higher water coverage.…”

Section: Water Adsorption On Other Metal Oxide Surfacesmentioning

confidence: 94%