Non-Faradic Electrochemical Modifciation of Catalytic Activity

Non-Faradic Electrochemical Modification of Catalytic Activity, or the NEMCA effect, is used to describe the enhancement in catalytic activity (up to 9000% higher) and selectivity of a gas exposed electrode on a solid electrolyte cell upon application of a potential. This electrochemical promotion phenomena is well documented and has been observed on various surfaces (Ni, Au, Pt and Pd) supported by O^2-, Na⁺ and proton conducting solid electrolytes. As implied by the name, this phenomena does not follow Faraday's laws of electrolysis. The Faradic efficiency is defined as follows: E = (r-r₀)/(I/nF) where r is the catalytic rate at the applied potential and r₀ is the rate at open circuit conditions. I is the applied current, F is Faraday's Constant and n is the number of electrons transferred. Absolute efficiencies greater than 1 are said to exhibit the NEMCA effect. This effect is thought to occur by a back-spillover mechanism where ions from the solid electrolyte migrate onto the gas exposed electrode surface.

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References

• Vayenas, C.G.; S.I. Bebelis, I.V. Yentekakis, S.N. Neophytides (1997). "Electrocatalysis and Electrochemical Reactors", in P. Gellings, H. Bouwmeester: CRC Handbook of Solid State Electrochemistry. CRC Press. ISBN 0-8493-8956-9.