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In situ controlled promotion of catalyst surfaces via solid electrolytes: Ethylene oxidation on Rh and propylene oxidation on Pt

Kaloyannis, Antonis, Pliangos C. A. , Gentekakis Ioannis, Vayenas, Costas G

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Περίληψη

The kinetics of C2H4 oxidation on Rh and C3H6 oxidation on Pt were investigated on polycrystalline metal films interfaced with ZrO2(8mol%Y2O3) solid electrolyte in galvanic cells of the type:C2H4,O2,Rh/YSZ/Pt,O2andC3H6,O2,CO2,Pt/YSZ/Au,C3H6,O2,CO2It was found that by applying positive potentials and thus, supplying O2- to the catalyst surface, up to 100-fold increases in catalytic rate can be obtained (electrophobic NEMCA effect) for the case of C2H4 oxidation on Rh. For the case of C3H6 oxidation on Pt, up to 6-fold increases in catalytic rate were observed by negative potentials, i.e. removing of O2- from the catalyst surface (electrophilic NEMCA effect).The induced changes in catalytic rates for both reactions were found to be 103 to 5×104 higher than the rates of ion transfer to or from the catalyst-electrode surface. For both reactions it was found that varying the catalyst potential, and thus work function, causes pronounced changes in activation energy and preexponential factor, leading to an interesting demonstration of the well-known “compensation” effect.The results can be rationalized on the basis of the theoretical considerations invoked to explain previous NEMCA studies, i.e. the effect of changing work function on chemisorptive bond strengths of electron acceptor and electron donor adsorbates.

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