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The catalytic activity of an IrO 2 catalyst used as an electrode on a YSZ solid electrolyte cell for the gas-phase combustion of ethylene can be increased by electrochemical pretreatment. Thus, the polarization of the IrO 2 electrode during 90 min at 300 p.A, relative to a gold electrode, both deposited on YSZ, increases the activity of the IrO 2 catalyst after current interruption by a factor of 3. In situ catalyst work function measurements showed that after the electrochemical pretreatment the IrO 2 catalyst obtains higher work function. The activation of the catalyst is explained through the formation of a higher oxide, IrO2+,,.

In order to investigate the origin of the effect of non faradaic electrochemical modification of catalytic activity (NEMCA), a Kelvin probe was used to measure in situ the changes induced in the work function of an 1r02 catalyst film deposited on yttria-stabilized zirconia upon electrochemical supply of 02 to the catalyst under reaction conditions. Ethylene oxidation was chosen as a model reaction system. For this purpose an electrochemical reactor of novel design was used in which work function measurements could be carried out in situ during kinetic measurements. It was found that the changes in catalyst work function equal to changes in catalyst ohmic-drop-free potential and that the reaction rate depends exponentially on catalyst work function at low applied potentials.

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