Bridging the pressure gap in the electrochemical promotion of heterogeneously catalyzed reactions at metal/solid electrolyte interfaces: restructuring effects and morphological changes

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Porous metal electrodes interfaced to a solid electrolyte can be used for electrochemically promoting a heterogeneously catalyzed reaction (EPOC); applying an electric potential can increase the catalytic rate in a nonFaradaic way, that is the rate increase can surmount the amount of transported ions by more than a factor of 100,000. This EPOC effect has been demonstrated for about 100 reaction systems. In the preceding project we used ethylene oxidation over Pt/YSZ (= yttrium stabilized zirconia) as model system to elucidate the mechanism of electrochemical promotion. It was shown that the promotion effect is mainly due to the spillover of discharged oxygen ions onto the Pt metal surface. In this part we want to demonstrate that restructuring and morphological changes of the metal surface contribute to the activation of the catalyst. Using a socalled environmental scanning electron microscope (ESEM) which allows in situ studies of the metal surface with a resolution of nm up to a pressure of roughly 20 mbar we will use ethylene oxidation over Pt/YSZ and Ag/YSZ catalysts to verify the effects of reaction and potential-induced restructuring of the electrode surface.