Electrochemical promotion of deep oxidation of methane on Pd/YSZ

Roche, Virginie; Karoum, R.; Billard, Alain; Revel, Renaud; Vernoux, P.

doi:10.1007/s10800-008-9569-4

Cited by 30 publications

(17 citation statements)

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“…Conse- quently, the catalytic reaction rate was increased by anodic polarisation, exhibiting electrophobic behaviour [8]. This result totally agrees with other electrochemical promotion studies on methane combustion, reported by Giannikos et al [17] and Roche et al [34]. These authors also observed electrophobic behaviour under oxidising conditions over palladium catalysts prepared by paste and sputtering, respectively.…”

Section: Original Research Papersupporting

confidence: 87%

“…As shown in Figure 8, the rate enhancement ratio was of 5.6. The Faradaic efficiency value was found to be 764 (the highest value reported for the electrochemical promotion of this reaction [17,[33][34][35]). This difference could be explained by the role of ceria film.…”

Section: Original Research Papermentioning

confidence: 99%

“…SEM, XRD and AC impedance spectroscopy were used to study the double electrolyte system. Electrochemical promotion of methane has been mainly reported on palladium supported over YSZ [17,33,34], but also on platinum [35]. Under oxidising conditions, it was observed in the literature that the reaction exhibited electrophobic behaviour, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical Promotion of CH₄ Combustion over a Pd/CeO₂–YSZ Catalyst

et al. 2010

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The phenomenon of electrochemical promotion of catalysis (EPOC) has been demonstrated on palladium supported catalysts using ceria and yttria‐stabilised zirconia as solid electrolyte. SEM, XRD, linear voltammetry and AC impedance spectroscopy have been used to study this double electrolyte system. Electrochemical catalysts were also used to promote the methane combustion reaction leading to one of the highest faradaic efficiency reported for this reaction (Λ = 764). Thus, the catalytic activity of palladium was found to increase over 450% via electrochemical transference of oxygen promoting ions from the solid electrolyte to the catalyst film.

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Section: Original Research Papersupporting

confidence: 87%

Section: Original Research Papermentioning

confidence: 99%

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Electrochemical Promotion of CH₄ Combustion over a Pd/CeO₂–YSZ Catalyst

et al. 2010

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“…conductivity are also under investigation. Methane oxidation was studied by Roche et al [38] using Pd on YSZ prepared by physical vapour deposition (PVD) where under positive polarization Faradaic efficiencies up to 258 and rate enhancement ratios up to 50 were observed. Propene oxidation is another reaction studied using various working electrodes deposited on several solid electrolytes.…”

Section: Electrochemical Promotion Of Reactions With Environmental Anmentioning

confidence: 99%

Recent developments and trends in the electrochemical promotion of catalysis (EPOC)

Katsaounis

2009

J Appl Electrochem

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Electrochemical Promotion of Catalysis (EPOC or NEMCA effect) is one of the most exciting discoveries in Electrochemistry with great impact on many catalytic and electrocatalytic processes. According to the words of John O'M. Bockris, EPOC is a triumph, and the latest in a series of advances in electrochemistry which have come about in the last 30 years. It has been shown with more than 80 different catalytic systems that the catalytic activity and selectivity of conductive catalysts deposited on solid electrolytes can be altered in a very pronounced, reversible and, to some extent, predictable manner by applying electrical currents or potentials (typically up to ±2 V) between the catalyst and a second electronic conductor (counter electrode) also deposited on the solid electrolyte. The induced steady-state change in catalytic rate can be up to 135 9 10 3 % higher than the normal (open-circuit) catalytic rate and up to 3 9 10 5 higher than the steady-state rate of ion supply. EPOC studies in the last 7 years mainly focus on the following four areas: Catalytic reactions with environmental impact (such as reduction of NO x and oxidation of light hydrocarbons), mechanistic studies on the origin of EPOC (using mainly oxygen ion conductors), scale-up pf EPOC reactors for potential commercialization via development of novel compact monolithic reactors and application of EPOC in high or low temperature fuel cells via introduction of the concept of triode fuel cell. The most recent EPOC studies in these areas are discussed in the present review and some of the future trends and aims of EPOC research are presented.

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“…It is also worth noting that heat-transfer and mass transfer limitations are coupled directly via the Lewis number [16] and thus, in the absence of mass-transfer limitations (which is a necessary condition for obtaining large L and 1 values, [2,3,[17][18][19][20] for example, L as high as 3 10 5[2-5, 17-20] and 1 as high as 1400, [17,18] as reported by many authors in the literature for extremely fuel-lean conditions), [2][3][4][16][17][18][19] there should be no concern about heat-transfer limitations and concomitant catalysttemperature increases. Thus, the first issue which must be ad-dressed in any EPOC study-and in any catalytic study in general-is the absence of mass-transfer limitations.…”

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confidence: 99%

Note on “The Electrochemical Promotion of Ethylene Oxidation at a Pt/YSZ Catalyst”

Vayenas

Vernoux

2011

ChemPhysChem

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Can a single oxygen spillover species on Pt explain the effect of electrochemical promotion of catalysis (EPOC or NEMCA, non-Faradaic electrochemical modification of catalytic activity, effect) with O 2À conductors such as YSZ (yttria-stabilized ZrO 2 ), as suggested in a recent paper published in this journal by Toghan, Rçsken and Imbihl, [1] or is it necessary to use the longtested sacrificial promoter mechanism, [2][3][4][5] which involves two oxygen species or-equivalently-two different oxygen adsorption states, a regular chemisorbed oxygen and a more ionic, more strongly bonded and less reactive spillover oxygen species (or state), commonly denoted aspoles, in the EPOC literature? [2][3][4][5] This question has been addressed in great detail by numerous older [6][7][8] and more recent [9][10][11][12] papers, which were unfortunately not cited by the authors of ref. [1]. For example, Figure 1 from ref. [9] shows oxygen temperature-programmed desorption (TPD) spectra obtained from a Pt-catalyst electrode deposited on YSZ and using 18 O 2 for gaseous O 2 adsorption. One observes that the more weakly bonded state b 2 is populated primarily by 18 O oxygen atoms resulting from the adsorption of 18 O 2 from the gas phase while the more strongly bonded state b 3 , which desorbs at 100 K higher temperature, is occupied almost exclusively by 16 Oatoms resulting from the spillover of lattice 16 O from the YSZ support. The existence of the two different states is also evident from the 16 O 18 O desorption peak, resulting from some isotopic scrambling in the catalyst surface, which takes place during the long timescale (~1400 s) of the experiment.[9] This time is much longer than the time (inverse of turnover frequency, TOF) associated with the catalytic process, which is electropromoted and is typically in the 0.1-10 s range. [3,10] Thus, this figure and many others [9,10] leave little room for any reasonable doubts about the validity of the sacrificial promoter, that is, a two-oxygen-species (or states) EPOC mechanism. [3,9] However, it is always useful to examine alternate mechanisms if data contradicting the sacrificial promoter mechanism are obtained. Þvalues up to 2.4] only under fuel-rich conditions where in situ X-ray photoelectron spectroscopy (XPS) showed that the surface is predominantly covered by a carbonaceous CH x layer [1] resulting from the adsorption of C 2 H 4 . They proposed that their data can be explained by an "ignition" mechanism, where "electrochemical O 2À pumping causes an ignition from an unreactive carbon-poisoned state of the surface to an active state with less carbon and clarified that the term "ignition" just refers to "a transition initiated by perturbation of a metastable state, but not to a temperature increase accompanying this transition". The authors criticized the currently accepted sacrificial promoter two-oxygen-species mechanism of electrochemical promotion [3][4][5] not for failing to explain their data, which is not at all the case as discussed Figure 1. Temperature-programm...

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Electrochemical promotion of deep oxidation of methane on Pd/YSZ

Cited by 30 publications

References 30 publications

Electrochemical Promotion of CH₄ Combustion over a Pd/CeO₂–YSZ Catalyst

Electrochemical Promotion of CH₄ Combustion over a Pd/CeO₂–YSZ Catalyst

Recent developments and trends in the electrochemical promotion of catalysis (EPOC)

Note on “The Electrochemical Promotion of Ethylene Oxidation at a Pt/YSZ Catalyst”

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Electrochemical promotion of deep oxidation of methane on Pd/YSZ

Cited by 30 publications

References 30 publications

Electrochemical Promotion of CH4 Combustion over a Pd/CeO2–YSZ Catalyst

Electrochemical Promotion of CH4 Combustion over a Pd/CeO2–YSZ Catalyst

Recent developments and trends in the electrochemical promotion of catalysis (EPOC)

Note on “The Electrochemical Promotion of Ethylene Oxidation at a Pt/YSZ Catalyst”

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Electrochemical Promotion of CH₄ Combustion over a Pd/CeO₂–YSZ Catalyst

Electrochemical Promotion of CH₄ Combustion over a Pd/CeO₂–YSZ Catalyst