Electrochemistry at negative potentials in bis(trifluoromethanesulfonyl)amide ionic liquids

The bis(trifluoromethanesulfonyl)amide (TFSA) anion is widely studied as an ionic liquid (IL) forming anion which imparts many useful properties, notably electrochemical stability. Here we present electrochemical and spectroscopic evidence indicating that reductive decomposition of the bis(trifluoromethanesulfonyl)amide (TFSA) anion begins at similar to -2.0 V vs. Fc(+)/Fc, well before the reported cathodic limit for many of these ILs. These processes are shown to be dependent upon the electrode substrate and are influenced by the water content of the IL. Supporting ab initio calculations are presented which suggest a possible mechanism for the anion decomposition. The products appear to passivate the electrode surface and the implications of this behaviour are discussed.