The effect of catalyst film thickness on the magnitude of the electrochemical promotion of catalytic reactions
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The effect of catalyst film thickness on the magnitude of the effect of electrochemical promotion was investigated for the model catalytic reaction of C2H4 oxidation on porous Pt paste catalyst-electrodes deposited on YSZ. It was found that the catalytic rate enhancement ρ is up to 400 for thinner (0.2 μm) Pt films (40,000% rate enhancement) and gradually decreases to 50 for thicker (1 μm) films. The Faradaic efficiency Λ was found to increase moderately with increasing film thickness and to be described semiquantitatively by the ratio 2Fro/I0, where ro is the unpromoted rate and I0 is the exchange current of the catalyst–electrolyte interface. The results are in good qualitative agreement with model predictions describing the diffusion and reaction of the backspillover O2- species, which causes electrochemical promotion.
Keywordselectrochemical promotion NEMCA effect ethylene oxidation catalyst thickness effect promoter reaction-diffusion yttria-stabilzed zirconia support sacrificial promoter
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