Semiquinone Intermediates in the Two‐Electron Reduction of Quinones in Aqueous Media and their Exceptionally High Reactivity towards Oxygen Reduction

Abstract

We report the catalytic anthraquinone-mediated reduction of oxygen at a boron-doped diamond electrode. Scheme of squares modelling confirms the existence of and reveals the role of the semiquinone intermediates, which are shown to have an exceptional reactivity towards oxygen (as compared to the di-reduced anthraquinone).

The electrochemical reduction of oxygen at boron-doped diamond and glassy carbon electrodes: A comparative study in a room-temperature ionic liquid

“…5 is that the reduction of O 2 on BDD is much more irreversible than that on GC. The decreased kinetics of oxygen reduction on BDD has previously allowed for the electrochemical investigation of species whose Faradaic features would normally be obscured by the interference of atmospheric oxygen [32]. Also of note is the significantly smaller double-layer capacitance observed for the BDD electrode in the ionic liquid, as reported previously for BDD [13].…”

Faradaic electro-swing reactive adsorption for CO2 capture

“…20 While the presence of oxygen can cause the oxidation of some reduced quinones with a sufficiently negative reduction potential, through the formation of the superoxide radical anion O 2 À , it is possible to avoid any reactions with oxygen in the feed stream by carefully tuning the electron density of the quinone polymer. 42 The cyclic voltammogram (CV) of the PAQ-CNT composite on the electrode substrate in [Bmim][TF 2 N] saturated with N 2 , the green line in Fig. 3, shows two redox couples corresponding to the two reduction potentials of anthraquinone.…”

The anthraquinone mediated one-electron reduction of oxygen in acetonitrile

“…The significantly larger peak-to-peak separation for the reduction of oxygen observed on the BDD electrode, as compared to the glassy carbon substrate, leads to the potential ability of studying the anthraquinone mediated reduction of oxygen within the non-aqueous media. Comparable experiments have been performed under aqueous conditions, where the semi-quinone species was observed to be highly reactive towards the reduction of oxygen [24]. However, due to the smaller potential range available for study in the present case (relative to that in aqueous media), careful selection of the electrocatalyst is required.…”