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 2Fr o/I 0, where r o is the unpromoted rate and I 0 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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