Electrochemical enhancement of a catalytic reaction in aqueous solution

Abstract. The effect of Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA effect) or Electrochemical Promotion (EP) was used to promote the methane oxidation reaction to CO2 and H20 over Pd polycrystalline films interfaced with yttria-stabilized zirconia in galvanic cells of the type: CH4, O2, CO 2, Pd/YSZ/Au, CH 4, 02, CO2It was found that by applying positive potentials or currents and thus, supplying O 2-onto the catalyst surface, up to 90-fold increases in CH 4 oxidation catalytic rate can be obtained. The induced changes in catalytic rate were two orders of magnitude higher than the corresponding rate of ion transfer to the catalyst-electrode surface, i.e. faradaic efficiency A values above 100 can be attained. The reaction exhibits electrophobic behavior under the experimental conditions of the investigation. The results can be rationalized on the basis of the theoretical considerations invoked to explain NEMCA behavior, i.e. the effect of changing work function on chemisorptive bond strengths of catalytically active electron donor or acceptor adsorbates.

Section: Introductionmentioning

confidence: 93%

Electrochemical promotion of CH4 oxidation on Pd

Giannikos

Frantzis

Pliangos

et al. 1998

“…It has been found that the catalytic and chemisorptive properties of polycrystalline metal films ( e.g. Pt, Pd, Ag, Ni, Au, Rh, IrO2) interfaced with O 2-, Na +, F-, and H + conducting solid electrolytes [9][10][11][12][13][14][15][16][17][18][19], with aqueous alkaline solutions [20], and with mixed ionic-electronic conductors [21,22], can be affected dramatically and reversibly by electrically polarising the metal-solid electrolyte interface. The effect has been shown to be due to an electrochemically induced and controlled backspillover of promoting species (e.g.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical promotion of Pd for the hydrogenation of C2H2

Giannikos

Petrolekas

Pliangos

et al. 1998

Abstract. The effect of Non-Faradaic Electrochemical Modification of Catalytic Activity, or insitu controlled promotion, was investigated during Acetylene selective hydrogenation on Pd films deposited on 13"-A1203, a Na + conductor, at temperatures from 60 to 100 ~ and GHSVs from 103 to 104 h -1, i.e., under conditions similar to those used in industrial processes. It was found that both acetylene conversion and hydrogenation selectivity can be affected by means of externally applied potentials, i.e., by supplying or removing sodium ions to or from the catalyst surface. Electrochemical sodium supply to the Pd catalyst surface was found to supress both the rate of acetylene hydrogenation and, to a larger extent the rate of ethylene hydrogenation to ethane. Consequently electrochemical sodium supply was found to enhance the selectivity to ethylene. Thus, 13"-A1203 can act as an active catalyst support causing enhanced performance of the Pd catalyst. Acetylene conversion and hydrogenation selectivity values up to 90 % and 95 %, respectively, were obtained.

“…Previous Eleclxochemical Promotion studies, involving both solid electrolytes [1,2,4,6,7] and aqueous solutions [5] have shown that x can be estimated from…”

Section: Introductionmentioning

confidence: 99%

“…electrolyte electrode reactants or air This effect, described by the acronym NEMCA (Nonfaradaic Electrochemical Modification of Catalytic Activity), or Electrochemical Promotion (EP), has been studied for over 50 catalytic systems [1,2] using metal or metal oxide [3] catalysts on a variety of solid electrolytes including 02. conductors (Y203 -stabilized-ZrO2), Na § conductors (IY'-A1203), H + conductors (CaZr0.9In0.xO3.a, Nation), F-conductors (CaF2), mixed electronic -ionic conductors (ZiO2) [4] and aqueous alkaline solutions [5].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical promotion of electronically isolated and dispersed Pt catalysts

Marwood

Balomenou

Tsiliras

et al. 1998

Abstract. In this paper we discuss the first attempts to induce the effect of Electrochemical Promotion or Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA) on highly dispersed catalyst-electrodes systems which can compete in terms of dispersion and surface area with industrial catalysts. Three systems are discussed: 1. Electrochemical promotion of CEH 4 oxidation on electronically isolated Pt catalysts on YEO3-stabilized-Zirconia (YSZ) where NEMCA is induced via potential application between two terminal Au electrodes also supported on the solid electrolyte (bipolar design). Electrochemical promotion of C2H4 oxidation on a finely dispersed Pt catalyst deposited on aAu electrode which is supported on YSZ. 3. Induction of NEMCA during CHaOH oxidation on Pt without external voltage application by utilizing the potential difference developed between the catalyst and a catalytically inert counter electrode. In all cases significant non faradaic behavior has been obtained. The underlying catalytic/electrocatalytic phenomena are discussed together with some of the engineering challenges for potential practical applications.