Electrochemical Behavior of Cadmium in 1-Butyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)amide Room-temperature Ionic Liquid

Electrodeposition of cadmium (Cd) was investigated in an amide-type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) amide (BMPTFSA) containing Cd(TFSA)2 as a Cd source with cyclic voltammetry and chronoamperometry on a glassy carbon electrode. The infrared spectroscopy showed Cd(II) in BMPTFSA is octahedrally coordinated with three TFSA–. Electrochemical reduction of Cd(II) to Cd(0) was suggested to be an electrochemically irreversible process involving 2 one-electron transfer steps. The diffusion coefficient of Cd(II) at 25 °C was estimated to be 0.95 × 10−7 cm2 s−1. Electrodeposits obtained by galvanostatic and potentiostatic electrolysis were confirmed to be metallic Cd by X-ray diffraction and energy dispersive X-ray analysis. The nucleation process and the surface morphology of the electrodeposited Cd were found to depend on the applied potential, probably due to the change in the electric double layer structure by accumulation of BMP+ at the negatively polarized electrode surface. Furthermore, Cd nanoparticles were obtained in the ionic liquid by potentiostatic cathodic reduction at −2.6 V vs. Ag/Ag(I).