Circumventing the Sabatier Principle in Electrocatalysis: the Case of Oxygen Reduction Reaction on Au(100) in Alkaline Medium

19 May 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The barriers for elementary steps in the oxygen reduction reaction (ORR) catalyzed on Au(100) in alkaline solution are mapped out by ab initio molecular dynamics simulations. Due to the relatively weak binding energy of O2 and oxygenated species, the calculated O−O dissociation barrier at ~0.5 eV is indeed considerably higher than the association barrier (< 0.1 eV) to form adsorbed HOO*, pushing ORR towards the thermodynamically less favorable 2e− pathway. However, the kinetics is changed above the equilibrium potential for the association channel ~0.7 V (RHE) where the 2e− pathway is switched off. Thereafter, the 4e− pathway becomes active as the O−O dissociation barrier at ~0.5 eV is not prohibitive. For the subsequent reduction steps, the weak binding energies of oxygenated species on Au(100) are actually an advantage, making Au(100) as good an ORR catalyst as Pt. It also makes the outer sphere electron transfer to O2 as the eventual rate determining step, as supported by the j-E polarization curve, showing a small ORR current extending close to the overall 4e− ORR equilibrium potential of 1.23 V. It provides an example on how the ORR activity volcano curve based on the Sabatier Principle can be circumvented in electrocatalysis.

Keywords

Sabatier Principle
Oxygen Reduction Reaction
Au(100)
Alkaline Medium

Supplementary materials

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Title
Supplementary Materials for Circumventing the Sabatier's Principle in Electro-catalysis: the Case of Oxygen Reduction Reaction on Au(100) in Alkaline Medium
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Supplementary Materials
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