An investigation of silver electrodeposition from ionic liquids: Influence of atmospheric water uptake on the silver electrodeposition mechanism and film morphology

The electrodeposition of silver from two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm]BF₄]) and N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (C₄mPyr]TFSI]), and an aqueous KNO₃ solution on a glassy carbon electrode was undertaken. It was found by cyclic voltammetry that the electrodeposition of silver proceeds through nucleation–growth kinetics. Analysis of chronoamperometric data indicated that the nucleation–growth mechanism is instantaneous at all potentials in the case of BMIm]BF₄] and C₄mPyr]TFSI], and instantaneous at low overpotentials tending to progressive at high overpotentials for KNO₃. Significantly, under ambient conditions, the silver electrodeposition mechanism changes to progressive nucleation and growth in C₄mPyr]TFSI], which is attributed to the uptake of atmospheric water in the IL. It was found that these differences in the growth mechanism impact significantly on the morphology of the resultant electrodeposit which is characterised ex situ by scanning electron microscopy and X-ray diffraction.