Electrochemical behavior of hexafluoroniobate, heptafluorotungstate, and oxotetrafluorovanadate anions in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide room temperature ionic liquid

Electrochemical behavior of hexafluoroniobate (Nb(V)F6−), heptafluorotungstate (W(VI)F7−), and oxotetrafluorovanadate (V(V)OF4−) anions has been investigated in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPyrTFSA) ionic liquid at 298 K by means of cyclic voltammetry and chronoamperometry. Cyclic voltammograms at a Pt electrode showed that Nb(V)F6− anion is reduced to Nb(IV)F62− by a one-electron reversible reaction. Electrochemical reductions of W(VI)F7− and V(V)OF4− anions at a Pt electrode are quasi-reversible and irreversible reactions, respectively, according to cyclic voltammetry. The diffusion coefficients of Nb(V)F6−, W(VI)F7− and V(V)OF4− determined by chronoamperometry are 1.34 × 10−7, 7.45 × 10−8 and 2.49 × 10−7 cm2 s−1, respectively. The Stokes radii of Nb(V)F6−, W(VI)F7−, and V(V)OF4− in BMPyrTFSA have been calculated to be 0.23, 0.38, and 0.12 nm, from the diffusion coefficients and viscosities obtained.