title: Pseudocapacitive mechanism of manganese oxide in 1-ethyl-3-methylimidazolium thiocyanate ionic liquid electrolyte studied using X-ray photoelectron spectroscopy.
abstract: The electrochemical behavior of anodically deposited manganese oxide was studied in pyrrolidinium formate (P-HCOO), 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6), and 1-ethyl-3-methylimidazolium thiocyanate (EMI-SCN) ionic liquids (ILs). The experimental data indicate that the Mn oxide electrode showed ideal pseudocapacitive performance in aprotic EMI-SCN IL. In a potential window of approximately 1.5 V, the oxide specific capacitance, evaluated using cyclic voltammetry and chronopotentiometry, was about 55 F/g. The electrochemical energy storage reaction was examined using X-ray photoelectron spectroscopy (XPS). It was confirmed that the SCN- anions, instead of the EMI+ cations, were the primary working species that can become incorporated into the oxide and thus compensate the Mn3+/Mn4+ valent state variation upon the charge-discharge process. According to the analytical results, a pseudocapacitive mechanism of Mn oxide in the SCN- based aprotic IL was proposed.
authors.affiliation: Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Jeng-Kuei
authors.initials: JK
authors.lastname: Chang
authors.forename: Ming-Tsung
authors.initials: MT
authors.lastname: Lee
authors.forename: Wen-Ta
authors.initials: WT
authors.lastname: Tsai
authors.forename: Ming-Jay
authors.initials: MJ
authors.lastname: Deng
authors.forename: Hui-Fang
authors.initials: HF
authors.lastname: Cheng
authors.forename: I-Wen
authors.initials: IW
authors.lastname: Sun