Electrochemical preparation of palladium nanoparticles in bis(trifluoromethylsulfonyl)amide ionic liquids consisting of pyrrolidinium cations with different alkyl chain lengths

Electrochemical preparation of palladium nanoparticles has been investigated in the bis(trifluoromethylsulfonyl) amide (TFSA–) ionic liquids composed of 1-butyl-1-methypyrrolidinium (BMP+), 1-hexyl-1-methylpyrrolidinium (HMP+) and 1-decyl-1-methylpyrrolidinium (DMP+) containing [PdBr4]2–. Cathodic reduction of [PdBr4]2– on a carbon electrode below –2.2 V vs. Ag|Ag(I) in the ionic liquids resulted in formation of palladium nanoparticles, which were confirmed by transmission electron microscopy and electron diffraction. The average particle sizes of the nanoparticles obtained at –2.6 V in BMPTFSA, HMPTFSA and DMPTFSA were 2.9 ± 0.6, 3.0 ± 0.8 and 3.2 ± 0.8 nm, respectively, indicating the average particle size was slightly dependent on the ionic liquid. The nanoparticles dispersed in the ionic liquids are considered to form by inhibition of crystal growth with the organic cations accumulated on the negatively polarized electrode surface.