Electrochemically induced surface changes on microstructured Pt films on a Solid YSZ electrolyte

Poppe, J.; Schaak, A.; Janek, Jürgen; Imbihl, R.

doi:10.1002/bbpc.19981020806

Cited by 32 publications

(15 citation statements)

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“…9b͒. Equation 2 has been previously reported both by our group 19,20 and by several other groups using both the Kelvin probe technique [21][22][23][24][25][26] and UPS. 27 This is shown in Fig.…”

Section: Figures 7 Andmentioning

confidence: 75%

Electrode Work Function and Absolute Potential Scale in Solid-State Electrochemistry

Tsiplakides

Vayenas

2001

J. Electrochem. Soc.

111

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A two-Kelvin-probe arrangement was used to measure, for the first time in situ, the work functions, ⌽, of the gas-exposed surfaces of porous Pt, Au, and Ag working and reference electrodes exposed to O 2 -He, H 2 -He and O 2 -H 2 mixtures, and deposited on 8% Y 2 O 3 -stabilized ZrO 2 ͑YSZ͒ in a three-electrode solid electrolyte cell. It was found that at temperatures above 600 K the potential difference, U WR , between the working ͑W͒ and reference ͑R͒ electrode reflects the difference in the actual, spillover, and adsorption-modified work functions, ⌽ W and ⌽ R of the two electrodes eU WR ϭ ⌽ W Ϫ ⌽ R ͓1͔ This equation, typically valid over 0.8-1 V wide U WR ranges, was found to hold for any combination of the Pt, Au, and Ag electrodes. It is consistent with the previously reported equation e⌬U WR ϭ ⌬⌽ W ͓2͔ which is also confirmed here, and allows for the definition of a natural absolute electrode potential U O 2 (abs) in solid-state electrochemistry fromwhere ⌽ is the work function of the gas-exposed electrode surface of the metal ͑any metal͒ electrode in contact with the YSZ solid electrolyte. It expresses the energy of solvation of an electron from vacuum to the Fermi level of the solid electrolyte. The value U O 2 0 (abs͒ ϭ 5.14 Ϯ 0.05 V was determined as the standard U O 2 (abs) value at p O 2 ϭ 1 bar and T ϭ 673 K.

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Section: Figures 7 Andmentioning

confidence: 75%

Electrode Work Function and Absolute Potential Scale in Solid-State Electrochemistry

Tsiplakides

Vayenas

2001

J. Electrochem. Soc.

111

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“…It is well-known that the Y 2 O 3 -stabilized ZrO 2 (YSZ) solid electrolyte is a typical ionic conductor for O 2-. 3,[7][8][9][20][21][22][23][24][25] Although the anions of O 2can form and conduct in the bulk of YSZ, there is no evidence that O 2exists in the gas phase according to our investigations. This implies that the transient anions of O 2are very unstable on the electrode surface.…”

Section: Electron and Omentioning

confidence: 88%

“…3,[7][8][9][20][21][22][23][24][25] When the anions of O 2-are supplied to a metal-catalyst film deposited on YSZ and exposed to C 2 H 4 -O 2 or CO-O 2 mixtures, it causes a dramatic increase of the catalytic oxidation rate, which reaches 10 2 -10 5 times higher than the supply rate of O 2-to the catalyst. 6 This indicates that each O 2-supplied to the catalyst will cause 10 2 -10 5 absorbed O atoms to react with C 2 H 4 or CO and form CO 2 and H 2 O.…”

Section: Introductionmentioning

confidence: 99%

“…It is well-known that the Y 2 O 3 -stabilized ZrO 2 (YSZ) electrolyte, possessing significant ionic conductivity for the transient anion of O 2- , has been widely used for electrochemical promotion catalyst reactions, fuel cells, and oxygen sensors. ,− ,− When the anions of O 2- are supplied to a metal-catalyst film deposited on YSZ and exposed to C 2 H 4 −O 2 or CO−O 2 mixtures, it causes a dramatic increase of the catalytic oxidation rate, which reaches 10 2 −10 5 times higher than the supply rate of O 2- to the catalyst . This indicates that each O 2- supplied to the catalyst will cause 10 2 −10 5 absorbed O atoms to react with C 2 H 4 or CO and form CO 2 and H 2 O.…”

Section: Introductionmentioning

confidence: 99%

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Desorption of the C₂^- Anion from the Au−C-Deposited Y₂O₃-Stabilized ZrO₂ Surface

Nishioka

Kashiwagi

et al. 2003

J. Phys. Chem. B

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Carbon dimer anions (C 2 -) and atomic oxygen radical anions (O -) desorbed from an Au-C-deposited Y 2 O 3 -stabilized ZrO 2 (YSZ) surface have been observed. Both the emitted anions and electrons were found to be strongly dependent on the surface temperature and applied extraction field. The Arrhenius plots for the anions and electrons exhibit double-linear behavior, resulting in lower apparent activation energies in the hightemperature region (>913 K). It was found that the apparent activation energies can be reduced by the extraction field. Measurements of the absolute emission current density show similar temperature and field features as derived by TOF (time-of-flight) spectroscopic investigations. The observed anions of O -are attributed to the detachment of the transient anions of O 2-(s) (i.e., O 2-(s) f O -(s) + e -(s)), which migrate from the YSZ bulk onto the emission surface. The C 2 -(s) anions are attributed to the surface anion-exchange reactions between O -(s) and surface carbon atoms. An emission mechanism is proposed to account for the observed temperature dependence, field characteristics, and emission branch ratios of the desorbed anions and electrons.

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“…Πρόσφατα η μέθοδος αυτή χρησιμοποιήθηκε για την μελέτη του φαινομένου NEMCA από τους Imbihl et al 174 Εξετάσθηκαν πορώδη ηλεκτρόδια Pt που παρασκευάσθηκαν με την χρήση οργανομεταλλικής πάστας, αλλά και μικροηλεκτρόδια Pt πάχους ~500 Å που παρασκευάσθηκαν με την μέθοδο της μικρολιθογραφίας. Και για τους δύο τύπους ηλεκτροδίων οι Imbihl et al 46,174…”

Section: μικροσκοπία εκπομπής φωτοηλεκτρονίων (Peem)unclassified

Νέοι Ηλεκτροχημικά Ενισχυόμενοι Αντιδραστήρες Και Κυψέλες Καυσίμου

Μπαλωμένου¹

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Electrochemical promotion, or non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA), was discovered at the beginning of 1980s by Vayenas and Stoukides, when the first nonfaradaic enhancement in heterogeneous catalysis was reported for the case of ethylene epoxidation on Ag electrodes deposited on a ceramic O 2conductor, via electrical potential application between the catalyst and a counter electrode.Since then Electrochemical Promotion of Catalysis has been proven to be a general phenomenon at the interface of Catalysis and Electrochemistry. During the last ten years its importance has grown on the academic level and more than seventeen groups around the world have made important contributions in this area and this number is reasonably expected to grow further as the phenomenon of electrochemical promotion has very recently been found to be intimately related not only to chemical (classical) promotion and spillover, but also to the "heart" of industrial catalysis, i.e. metal-support interactions of classical supported catalysts.The effect of Electrochemical Promotion is due to an electrochemically induced and controlled migration (backspillover) of ions (O δin the case of YSZ, Na δ+ in the case of β"-Al 2 O 3 ) from the solid electrolyte onto the gas-exposed, catalytically active, surface of metal electrodes. It is these ions which, accompanied by their compensating (screening) charge in the metal and forming dipoles ([Ο δ--δ + ] or [Na δ+ -δ -]) that migrate and form an effective electrochemical double layer on the entire gas-exposed catalyst surface, change its work function and affect the catalytic phenomena taking place there in a very pronounced, reversible, and controlled manner.The change in catalytic activity or selectivity of the active phase with varying catalyst support is usually termed Metal-Support Interaction (MSI). Metal-support interactions can influence in a very pronounced way the catalytic and chemisorptive properties of metal and metal oxide catalysts. An alternative interpretation of the phenomenon of metal-support interactions induced by doping of semiconductive carriers with aliovalent cations is based on the theory of electrochemical promotion or the NEMCA effect. According to this interpretation, the charge carriers which are transported from the carrier to the metal particles are oxygen ions which diffuse to the surface of the metal particles thus altering the surface work function and, subsequently, chemisorptive and catalytic parameters.Recent studies have shown that, at least for the cases of ZrO 2 -, TiO 2 -and CeO 2 -based supports, the mechanism of the metal-support interaction is identical with that of NEMCA when using YSZ. Small metal crystallites on these supports are covered during catalytic reactions with backspillover promoting O 2species which are Λ times less reactive than normally chemisorbed O and which are continuously replenished in the O 2--or mixed-conducting support by gaseous O 2 . Overall, in both cases O 2backspillover to the catalyst surface i...

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Electrochemically induced surface changes on microstructured Pt films on a Solid YSZ electrolyte

Cited by 32 publications

References 14 publications

Electrode Work Function and Absolute Potential Scale in Solid-State Electrochemistry

Electrode Work Function and Absolute Potential Scale in Solid-State Electrochemistry

Desorption of the C₂^- Anion from the Au−C-Deposited Y₂O₃-Stabilized ZrO₂ Surface

Νέοι Ηλεκτροχημικά Ενισχυόμενοι Αντιδραστήρες Και Κυψέλες Καυσίμου

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Electrochemically induced surface changes on microstructured Pt films on a Solid YSZ electrolyte

Cited by 32 publications

References 14 publications

Electrode Work Function and Absolute Potential Scale in Solid-State Electrochemistry

Electrode Work Function and Absolute Potential Scale in Solid-State Electrochemistry

Desorption of the C2- Anion from the Au−C-Deposited Y2O3-Stabilized ZrO2 Surface

Νέοι Ηλεκτροχημικά Ενισχυόμενοι Αντιδραστήρες Και Κυψέλες Καυσίμου

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Desorption of the C₂^- Anion from the Au−C-Deposited Y₂O₃-Stabilized ZrO₂ Surface