Redox Reaction of 2,2,6,6,-Tetramethylpiperidine-1-oxyl in Lithium Bis(trifluoromethylsulfonyl)amide-tetraglyme Solvate Ionic Liquid

The electrode reaction of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was investigated in a solvate ionic liquid composed of lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) and tetraglyme (G4), [Li(G4)]TFSA. A quasi-reversible redox reaction of the oxoammonium (TEMPO+) and TEMPO was observed with a formal potential of 0.19 V vs ferrocene vertical bar ferrocenium. The diffusion coefficient of TEMPO+ (2.1 x 10(-8) cm(2) s(-1)) was smaller than that of neutral TEMPO (1.3 x 10(-7) cm(2) s(-1)), reflecting the coulombic interaction between monovalent TEMPO+ and TFSA(-) in the solvate ionic liquid. The standard rate constant for TEMPO+/TEMPO redox reaction was estimated to be 1.9 x 10(-4) cm s(-1) at 25 degrees C by electrochemical impedance spectroscopy. The solubility of TEMPO in [Li(G4)]TFSA was found to be 4.4 M at 25 degrees C. (C) 2020 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited.