Electrodeposition of Co was investigated in an amide-type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA), under an external magnetic field. Neodymium magnets were used as a source of the magnetic field, which was parallel to the ionic current during the electrodeposition of Co on a glassy carbon electrode. Potentiostatic cathodic reduction applying -1.6 and -2.0 V vs Ag|Ag(I) under the magnetic field in BMPTFSA containing Co(TFSA)2 at 25 C gave nanowire-shaped deposits on the electrode surface. The deposits were found to be composed of Co, which was confirmed by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. However, no diffraction peak was observed in the deposits by X-ray diffraction. The nanowires were further examined by transmission electron microscopy. The lattice fringe corresponding to (111) plane of Co was found in the deposits, indicating the nanowires were composed of metallic Co nanoparticles. Therefore, crystalline Co nanoparticles were considered to be formed in the presence of the magnetic field.
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