Electrocatalytic Materials and Techniques for the Anodic Oxidation of Various Organic Compounds

Treimer, Stephen E.

doi:10.2172/803741

Cited by 1 publication

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References 16 publications

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“…Where j K corresponds to the current in the absence of electrolyte mass-transfer limitation (c y = 0 = c * ), limited by any other kinetics type (physical, chemical or electrochemical). 29,34,35 When the limiting kinetics is surface diffusion and electrosorption, the corresponding KL expression can be obtained from Eq. 38, accounting for diffusion area overlapping:…”

Section: Modelmentioning

confidence: 99%

Current at a Rotating Disk Electrode under Electrosorption and Surface Diffusion Limitation

Chaparro

2017

J. Electrochem. Soc.

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Following a model for the current limited by adsorption and surface diffusion at a rotating disk electrode (rde), the case is analyzed when surface diffusion is preceded by adsorption with charge transfer. The electrode surface consists of a distribution of reaction sites embedded in a supporting phase where electrosorption and surface diffusion take place. Electrosorption is described by five parameters, an equilibrium potential (E 0 ad ), a microscopic partial charge transfer (z ad ), a charge transfer coefficient (β ad ), and the rate constants for desorption and adsorption (k 1 and k 2 , respectively). Analytical expressions for the current -overpotential (j vs η ad ) and the Koutecký -Levich (KL) relation (1/j vs 1/ω 1/2 ) are provided as a function of electrosorption parameters and surface diffusivity (D s ). The KL relation is linear, with the same slope as for a classical rde, whereas the intercept (1/ j K ) depends on electrosorption parameters and D s . Tafel relations for the intercept current (log j K vs. η) are provided for the general and limiting cases. Effects of the radial convective transport in the electrolyte over reaction sites, and of the overlapping of surface diffusion areas are included in the model. The analytical expressions can be used to determine surface diffusion kinetics parameters from rde results. Reactivity at electrode surfaces is in most cases localized on active sites. On single crystalline surfaces, active sites favor the interaction with electrolyte species, 1-4 or expose appropriate electronic orbitals that enhance reactivity. 5,6 Localized reactivity is more remarkable on composite material surfaces, like supported catalysts and partially blocked surfaces, and when the reactions are mediated by an interaction with the electrode surface, like electrocatalyzed reactions, 1,3 electroadsorption, 7 and electrodeposition. 4,8 Unlocalized reactivity is less usual and requires the participation of non-interacting reactants. 9Areas surrounding active sites, called supporting or inactive areas, may participate in the electrochemical reaction in different ways. If adsorption is favored, the inactive areas concentrate reactants and become a parallel path for the supply of species to active sites. Predominance of the adsorption path over the direct electrolyte path is very probable in this case, even at low adsorbabilities, by a pure concentration effect.10 After adsorption, the species diffuse toward the actives sites leading to adsorption-surface diffusion mediated mechanisms, like the spillover, 11-18 and the bifunctional mechanisms. 19,20 Surface diffusion mediated reactions require an optimal degree of interaction of the adsorbed species with inactive areas, which should lead to a 'volcano' dependence of reaction rate with the adsorption energy like the encountered for many catalytic reactions. 21The rotating disk electrode (rde) technique is very appropriate for the study of surface kinetics in electrochemical reactions because it provides controlled and well defined hydrodynam...

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Section: Modelmentioning

confidence: 99%

Current at a Rotating Disk Electrode under Electrosorption and Surface Diffusion Limitation

Chaparro

2017

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

Electrocatalytic Materials and Techniques for the Anodic Oxidation of Various Organic Compounds

Cited by 1 publication

References 16 publications

Current at a Rotating Disk Electrode under Electrosorption and Surface Diffusion Limitation

Current at a Rotating Disk Electrode under Electrosorption and Surface Diffusion Limitation

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