A Model for the Electroreduction of Molecular Oxygen

Document Type

Article

Subject Area(s)

oxygen, reduction (chemical), binding energy, adsorption, tunnelling, catalysis, platinum, discs (structures), electrochemical electrodes, reaction kinetics

Abstract

The kinetics of the oxygen reduction reaction (ORR) was studied by decomposing the polarization curves obtained using a polycrystalline platinum rotating disk electrode in an aqueous sulfuric acid electrolyte. The ORR model that is presented is novel in its expression of the pre-exponential factor in the traditional Butler–Volmer equation. It is postulated that this term can be described as an intrinsic kinetic frequency factor multiplied by a series of probability functions that describe the kinetic behavior based on spatial, energetic, and electron-transfer effects. Literature values are taken for the oxygen-binding energy to calculate the adsorption equilibrium behavior and both the activation energy and electron tunneling are used to quantify the kinetic probability functions. The frequency factors have been calculated as 2.0s−1" role="presentation" style="margin: 0px; padding: 0px; border: 0px; outline-style: none; font-family: inherit; line-height: normal; text-align: left; vertical-align: baseline; display: inline; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">2.0s−12.0s−1 for the four-electron reduction and 1.3×102s−1" role="presentation" style="margin: 0px; padding: 0px; border: 0px; outline-style: none; font-family: inherit; line-height: normal; text-align: left; vertical-align: baseline; display: inline; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">1.3×102s−11.3×102s−1 for the two-electron reduction. The model appears to simulate important features of the ORR, including the magnitude of the observed current and the activation overpotential, though slight deviations in the potential persist. Results of the model are used to discuss the potential to describe tailor-made catalysts for the ORR.

Rights

© Journal of The Electrochemical Society, 2007, Electrochemical Society

Mustain, W., & Prakash, J. (2007). A Model for the Electroreduction of Molecular Oxygen. Journal Of The Electrochemical Society, 154(7), A668-A676.

doi: 10.1149/1.2735915

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