The effect of catalyst film thickness on the magnitude of the electrochemical promotion of catalytic reactions

Koutsodontis, C.; Katsaounis, Alexandros; Figueroa, Juan Carlos Sánchez; Cavalca, C.; Pereira, Candido; Vayenas, C.G.

doi:10.1007/s11244-006-0081-y

Cited by 24 publications

(18 citation statements)

References 24 publications

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“…7. This behaviour was already reported by Koutsodontis et al [28] and was attributed to the decrease in amount of promoter on the gas exposed catalyst surface due to the reaction of O d-with the hydrocarbons in good agreement with a developed mathematical model.…”

Section: Catalytic Activity Measurements Under Open-circuitsupporting

confidence: 88%

Electrochemical promotion of deep oxidation of methane on Pd/YSZ

et al. 2008

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Electrochemical catalysts based on Pd deposited by Physical Vapour Deposition on YSZ were used for methane deep oxidation. Different thicknesses of Pd films varying from 11 to 75 nm were catalytically characterized between 150 and 750°C. The Pd loadings were extremely low. Catalytic and EPOC experiments were carried out on those electrochemical catalysts. Their catalytic activities were compared with the performances of a reference catalyst. It was found that the catalytic activity can be in situ tuned by applying an anodic polarization thus supplying oxygen ions at the surface of the catalyst. Faradaic efficiency values up to 258 were observed and the induced modifications of the catalytic rate were typically 100 times higher than the corresponding ionic current. The influence of the polarization on the temperature of decomposition of the palladium oxide was also examined. The polarization was found to enhance the thermal stability of the oxide and turn palladium oxide into metallic palladium at higher temperatures.

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Section: Catalytic Activity Measurements Under Open-circuitsupporting

confidence: 88%

Electrochemical promotion of deep oxidation of methane on Pd/YSZ

et al. 2008

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“…This behaviour is expected, as in this system by increasing the oxygen partial pressure in the reaction chamber we decrease the oxygen chemical potential difference across the membrane and thus the driving force for oxygen migration that consequently affects the promoter supply to the catalyst. While for classic EPOC high rate enhancement ratios of ethylene oxidation on platinum have generally been reported under highly oxidising conditions [16], in the case of wireless EPOC higher rate enhancement ratios have so far been obtained under stoichiometric or mildly oxidising conditions [12,14]. Work is currently in progress to study wireless EPOC under reducing conditions (i.e.…”

Section: Kinetic Data Analysismentioning

confidence: 99%

Comparative studies between classic and wireless electrochemical promotion of a Pt catalyst for ethylene oxidation

Poulidi

Metcalfe

2008

J Appl Electrochem

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A comparative study between a classic and a wireless electrochemical promotion experiment was undertaken as a tool towards the better understanding of both systems. The catalytic modification of a platinum catalyst for ethylene oxidation was studied. The catalyst was supported on yttria-stabilised-zirconia (YSZ), a known pure oxide ion conductor, for the classic experiment and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-d -a mixed oxide ion electronic conductor-was used for the wireless experiment. The two systems showed certain similarities in terms of the reaction classification (in both cases electrophobic behaviour was observed) and the promotion mechanism. Significant difference was observed in the time scales and the reversibility of the induced rate modification.

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“…Besides the results which have been already reported in the literature till 2001 and reviewed by Professor Vayenas et al in the ''Electrochemical Promotion of Catalysis'' book [28] several new studies have been reported till the end of 2008 using various techniques and methods such as TPD [29,30,32,47,72], TPR [29], CV [21], FTIR [21], SEM-EDX [21], AC impedance spectroscopy [39], STM [73,74], work function measurements and theoretical considerations [18,75,76], transients experiments and kinetic studies [34,35], quantum mechanical calculations and Monte Carlo simulations [77] and general thermodynamic considerations [18,78,79]. The use of oxygen temperature programmed desorption both under UHV and atmospheric pressure conditions has proven [29,30] the existence of two different and distinct oxygen adsorption states on the catalyst surface when oxygen ion conductors used like YSZ.…”

Section: Electrochemical Promotion Of Reactions With Environmental Anmentioning

confidence: 99%

“…K values up to 3 9 10 5 and q values up to 150 [28] have been found for several systems. More recently q values between 300 [34,35] and 1,400 [36,37] have been observed for C 2 H 4 and C 3 H 8 oxidation on Pt/YSZ, respectively. In the experiment of Fig.…”

Section: Introductionmentioning

confidence: 97%

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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The effect of catalyst film thickness on the magnitude of the electrochemical promotion of catalytic reactions

Cited by 24 publications

References 24 publications

Electrochemical promotion of deep oxidation of methane on Pd/YSZ

Electrochemical promotion of deep oxidation of methane on Pd/YSZ

Comparative studies between classic and wireless electrochemical promotion of a Pt catalyst for ethylene oxidation

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

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