Effect of room temperature ionic liquids on the electrochemical dissolution and deposition of nickel in the Watts solution

Abstract

Ionic liquids have been extensively investigated in recent years either as a main medium or as an additive for various applications. In the present study, we have synthesized four room temperature ionic liquids (RTILs) of the 1-butyl-3-methylimidazole (BMIM) family with different anions, including BF4−, PF6−, SCN−, and C2H6NO3S− (taurinate, denoted as Tau), and investigated their effect as additives on the electrochemical dissolution and deposition of Ni in the conventional Watts solution. Our electrochemical studies revealed that the addition of BMIM[SCN] significantly lowered the electrode potential for Ni dissolution compared to the rest of the RTILs as well as the Watts solution. The Ni anodes after the electrochemical dissolution and the Ti cathodes after the electrochemical deposition were further characterized using cyclic voltammetry to assess their electrochemical active surface areas (EASAs). It was found that the sample anodically dissolved in the Watts solution containing BMIM[SCN] had the highest EASA and that the nickel deposited on the Ti substrate in the Watts solution with BMIM[Tau] additive exhibited the highest EASA compared with the Ni deposition in all the other tested solutions. Our study has also shown that the addition of RTILs may affect the electrochemical nickel dissolution and deposition processes adversely or beneficially depending on the compositions of the RTILs.