Electrodeposition of Cobalt from a Hydrophobic Room-temperature Molten Salt System

The electrodeposition of cobalt was investigated in a hydrophobic room-temperature molten salt, 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI), containing Co(TFSI)2 as a Co source. The cathodic reduction wave of Co(II) species was confirmed by cyclic voltammetry. The electrodeposit obtained by the potentiostatic reduction on a nickel substrate was found to be metallic Co by both XPS and EDX analyses. The diffusion coefficient of Co(II) was estimated to be 1.0 × 10−7 cm2 s−1 at 27.8°C. The electrodeposition of Co on the Pt substrate seemed to involve the three-dimensional instantaneous nucleation under diffusion control.