title: Direct Detection of the Superoxide Anion as a Stable Intermediate in the Electroreduction of Oxygen in a Non-Aqueous Electrolyte Containing Phenol as a Proton Source.
abstract: The non-aqueous Li-air (O2 ) battery has attracted intensive interest because it can potentially store far more energy than today's batteries. Presently Li-O2 batteries suffer from parasitic reactions owing to impurities, found in almost all non-aqueous electrolytes. Impurities include residual protons and protic compounds that can react with oxygen species, such as the superoxide (O2 (-) ), a reactive, one-electron reduction product of oxygen. To avoid the parasitic reactions, it is crucial to have a fundamental understanding of the conditions under which reactive oxygen species are generated in non-aqueous electrolytes. Herein we report an in situ spectroscopic study of oxygen reduction on gold in a dimethyl sulfoxide electrolyte containing phenol as a proton source. It is shown directly that O2 (-) , not HO2 , is the first stable intermediate during the oxygen reduction process to hydrogen peroxide. The unusual stability of O2 (-) is explained using density functional theory (DFT) calculations.
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022 (P.R. China). zqpeng@ciac.ac.cn.
authors.forename: Zhangquan
authors.initials: Z
authors.lastname: Peng
authors.affiliation: Department of Materials, University of Oxford, Oxford OX1 3PH (UK).
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Materials, University of Oxford, Oxford OX1 3PH (UK).
authors.forename: Peter G
authors.initials: PG
authors.lastname: Bruce
authors.affiliation: Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803 (USA). yexu@lsu.edu.
authors.forename: Ye
authors.initials: Y
authors.lastname: Xu
keywords: Li-air batteries; Raman spectroscopy; density functional theory calculations; oxygen reduction reactions; superoxide anion