Electrochemical promotion of catalysis
The electrochemical promotion of catalysis (EPOC) effect in the realm of chemistry refers to the pronounced enhancement of
The EPOC effect can also be utilized in a reverse manner in order to influence the selectivity of versatile heterogeneous catalytic reactions. In most cases, the electronically conductive catalyst is in metallic or
Examples and research fields
The EPOC effect can be observed in a wide range of catalytic reactions with several kinds of metal or metal oxide catalysts mostly coupled with solid electrolytes. Versatile catalytic reactions including hydrogenations, dehydrogenations, oxidations, reductions, isomerizations, and chemical decompositions have been known to be promoted electrochemically on various transition metal and oxide catalysts (e.g., Pt, Pd, Rh, Ag, Au, Ni, Cu, Fe,
Mechanistic origins
Earlier mechanistic proposals for the EPOC phenomenon with
Aqueous electrolyte solution at ambient temperatures
In contrast to solid electrolyte systems under high temperatures (usually higher than 200 °C), EPOC has rarely been reported in low-temperature aqueous systems (particularly at room temperature). Only a few examples have been demonstrated for the EPOC in an aqueous electrolyte solution at ambient temperature: H2 oxidation at Pt catalyst surface in alkaline solutions,[6][7] hydrocarbon isomerization reaction occurring at the nanoparticulate Pt catalyst,[8] hydrazine oxidation operating at the Ni alloy catalyst in alkaline media,[9] and CO2 reduction at the Pd-based gas diffusion electrode.[10] Even though the perturbation of the local work function and tuning of surface binding strengths of intermediate species were suggested as the origin for the EPOC effects in the liquid electrolyte systems as similar to the EPOC examples of high-temperature solid electrolyte systems, thorough theoretical studies supported by clear experimental evidence have not been addressed. Very recently, it was additionally hypothesized for the cases of the hydrazine oxidation and the CO2 reduction that the mechanistic origin of the EPOC phenomena observed in these cases can be contributed to structurally non-disparate transition states and/or surface bound intermediate species for the corresponding bifurcated faradaic and non-faradaic reactions.[9][10]
See also
References
Further reading
- Vayenas, C.G.; S.I. Bebelis; I.V. Yentekakis; S.N. Neophytides (1997). "Electrocatalysis and Electrochemical Reactors". In P. Gellings, H. Bouwmeester (ed.). CRC Handbook of Solid State Electrochemistry. CRC Press. OCLC 35033723.