On the catalytic and degradative role of oxygen-containing groups on carbon electrode in non-aqueous ORR
2021
Inozemtseva, Alina I. | Kataev, Elmar Yu | Frolov, Alexander S. | Amati, M. (Matteo) | Gregoratti, Luca | Beranová, Klára | Dieste, Virginia Pérez | Escudero, Carlos | Fedorov, A. V. (Aleksandr Viktorovich) | Tarasov, Artem V. | Usachov, Dmitry Yu | Vyalikh, Denis V. | Shao-Horn, Yang | Itkis, Daniil M. | Yashina, Lada V.
Oxygen reduction reaction (ORR) is a crucial process that drives the operation of several energy storage devices. ORR can proceed on the neat carbon surface in the absence of a catalyst, and its electrochemical activity is determined by its microstructure and chemical composition. Oxygen functional groups unavoidably existing on the carbon surface can serve as adsorption sites for ORR intermediates; the presence of some oxygen functionalities gives rise to an increase in the density of electronic states (DOS) at the Fermi level (FL). Both factors should have a positive impact on the electron transfer rate that was demonstrated for ORR in aqueous media. To study the O-groups effect on the aprotic ORR, which is now of interest due to the extensive development of aprotic metal-air batteries, we use model oxidized carbon electrodes (HOPG and single-layer graphene). We demonstrate that oxygen functionalities (epoxy, carbonyl, and lactone) do not affect the rate of one-electron oxygen reduction in aprotic media in the absence of metal cations since their introduction practically does not increase DOS at FL. However, in Li⁺-containing electrolytes, oxygen groups enhance both the rate of second electron transfer and carbon degradation due to its oxidation by LiO₂ yielding carbonate species.
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