An electrochemical investigation of oxygen adsorption on Pt single crystal electrodes in a non-aqueous Li+ electrolyte

Galloway, Thomas A, Attard, Gary and Hardwick, Laurence J ORCID: 0000-0001-8796-685X
(2020) An electrochemical investigation of oxygen adsorption on Pt single crystal electrodes in a non-aqueous Li+ electrolyte. Electrochemistry Communications, 119. p. 106814.

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Cyclic voltammetry has been used to probe the initial stages of oxygen reduction and oxidation in lithium-containing dimethyl sulfoxide at well-defined Pt single crystal electrodes in order to elucidate any catalytic effects ascribable to surface structure. In contrast to previous work involving sodium-oxygen, lithium-oxygen studies did not yield any significant differences for reaction on the three basal planes of platinum. Rather, all three planes generated a similar voltammetric response. However, by judicious use of various potential sweep limits, the formation of superoxide together with both a “conformal” or surface adlayer of lithium peroxide (Li2O2) together with a “microcrystallite” surface Li2O2 phase was resolved. Voltammetric peak intensity versus sweep rate measurements confirmed that superoxide electrooxidation was diffusion limited whereas electrooxidation of the two Li2O2 phases displayed behaviour typical of a surface-confined process. Under steady-state conditions for the formation of superoxide, it was found that for both the conformal and microcrystallite Li2O2 phases, electrooxidation followed zero-order kinetics, pointing to the importance of free surface sites in facilitating these reactions. A marked change in the rate of Li2O2 formation was found to coincide with a coverage of 0.25 monolayers, as measured by the charge density of the conformal Li2O2 electrooxidation peak. We postulate that electron tunnelling through both the conformal Li2O2 layer and microcrystallites deposited on this surface layer coincides with this coverage and accounts for such behaviour. This phenomenon of electron tunnelling through single conformal and mixed conformal/microcrystallite structures should prove vitally important in governing the overall electrooxidation rate.

Item Type: Article
Uncontrolled Keywords: Oxygen reduction reaction, Lithium-oxygen battery, Cyclic voltammetry, Single crystals, Platinum
Depositing User: Symplectic Admin
Date Deposited: 22 Sep 2020 09:11
Last Modified: 18 Jan 2023 23:32
DOI: 10.1016/j.elecom.2020.106814
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