An in-situ Raman study of the oxygen reduction reaction in ionic liquids

In-situ Raman spectroscopy is applied, for the first time, to elucidate the reaction products of oxygen reduction in two types of ionic liquids: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C(2)mimTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr(14)TFSI). The degradation of C(2)mimTFSI by superoxide attack is evidenced by the appearance of bands characteristic of amide and carbonate compounds. On the contrary, Pyr(14)TFSI is found to be resistant towards degradation. It is observed that superoxide is the first product of oxygen reduction in Pyr(14)TFSI, and the formation of Li2O2 is observed at longer times. (C) 2014 Published by Elsevier B.V.