The direct dissolution of Ce_2(CO_3)_3 and electrochemical deposition of Ce species using ionic liquid trimethyl-n-butylammonium bis(trifluoromethanesulfonyl)imide containing bis(trifluoromethanesulfonyl)imide

摘要

Ionic liquids (ILs) are solutions comprised of cation/anion pairs that are not limited by the electrochemical side reactions common to aqueous solution. The high stability of the ionic liquid provides large potential windows that can encompass the thermodynamic potentials for the reduction of f-elements such as cerium to metal. The direct dissolution of Ce_2(CO_3)_3·xH_2O into the ionic liquid trimethyl-n-butylammonium bis(trifluoromethanesulfonyl)imide [Me3NBu][TFSI] using conjugate acid bis(trifluoromethanesulfonyl)imide [HTFSI] is demonstrated. The displacement of carbonate ligand and formation of carbonic acid facilitates the in situ dissolution. The subsequent coordination of Ce with the TFSI ion in the IL is monitored using UV/vis spectroscopy and emergent ligand to metal transitions below 300 nm. Further evidence of the coordination of Ce in the ionic liquid is based on changes in the IR spectra for absorbance bands related to the sulfonyl functional groups of the TFSI anion. The reduction/oxidation of soluble Ce in IL is examined at Au, Pt, and GC (glassy carbon) electrodes. Multi-wave voltammetry at all three electrodes is consistent with the reductive deposition of Ce species from the IL solution. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) confirm the deposition of Ce species at mica/Au electrodes.