NON-FARADAIC ELECTROCHEMICAL MODIFICATION OF CATALYTIC ACTIVITY .4. THE USE OF BETA''-AL2O3 AS THE SOLID ELECTROLYTE

It was found that the catalytic activity of polycrystalline Pt films deposited on β″-Al2O3, a Na+-conducting solid electrolyte, can be altered dramatically and reversibly by polarizing the catalyst-solid electrolyte interface. The observed decrease in the rate of ethylene oxidation on Pt is typically 103 - 5 × 104 times larger than the rate of supply of Na+ to the catalyst-electrolyte interface. A Na coverage of 0.015 suffices to cause a 70% decrease in catalytic rate which varies exponentially with catalyst work function. The latter was measured both potentiometrically and by means of a Kelvin probe. The behavior is qualitatively similar to that observed when using O2--conducting solid electrolytes and shows that the newly found effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) is not restricted to any particular metal or solid electrolyte. This supports the proposed explanation of the effect which is based on the change in catalyst work function and concomitant change in chemisorptive bond strengths as a result of ion spillover upon polarization of the catalyst-solid electrolyte interface. © 1991.