Electrochemical Generation of Superoxide Ions in five different Fluorine rich Room Temperature Ionic Liquids

Abstract-Stable superoxide ion O2- is electrochemically generated in five room temperature ionic liquids namely 1-hexyl-3-methylimidazolium hexafluorophosphate [hmim][PF6], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [bmim] [btfmsi], 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [bdmim] [btfmsi], N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [N-Bu-N-MePyrr] [btfmsi], 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [bdmim] [BF4]. Cyclic voltammetry studies were used to check for the short-term stability of O2- in these RTIL’s. In the absence of impurities, especially water, the O2- is stable in these three RTIL’s in the timescale of the cyclic voltammetry. The formal potential for the O2/ O2- couple is found to be -0.86 V vs. Ag/AgCl reference electrode. Hydrophobicity, Viscosity, Oxygen Solubility and Electrical Conductivity were found to be key parameters in the generation of stable superoxide ions in RTILs.