Investigating the Long-term Stability and Kinetics of Superoxide Ion in Dimethyl Sulfoxide Containing Ionic Liquids and the Application of Thiophene Destruction

The long-term stability of superoxide ion (O2) with four ionic liquids (ILs), namely 1-(2methoxyethyl)-1-methylpiperidinium tris(pentafluoroethyl)trifluorophosphate [MOEMPip][TPTP], 1-(3methoxypropyl)-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide [MOPMPip][TFSI], N-ethyl-N,Ndimethyl-2-methoxyethylammonium bis(trifluoromethylsulfonyl)imide [N112,1O2][TFSI], and ethyldimethyl-propylammonium bis(trifluoromethylsulfonyl)imide [EDMPAmm][TFSI], was studied for up to 24 h using two-second intervals. This was achieved by chemical generation of O2 by dissolution of potassium superoxide salt in dimethyl sulfoxide and the subsequent addition of the IL. The decrease in the concentration of O2 after the introduction of the IL was monitored using a UV-vis spectrophotometer. The ammoniumbased ILs were found to be more stable than piperidinium-based ILs. To the best of our knowledge, this was the first time that O2 stability with ILs has been monitored continuously for up to 24 h. This should provide a better insight into the stability and kinetics of O2 for industrial applications and its role in energy-storage devices. The most appropriate IL as a medium was [EDMPAmm][TFSI], and O2 generated in this IL was used to destroy nearly 90% of thiophene.