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.

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.

No abstract