Electrodeposition of Nickel on Glassy Carbon Electrode from Protic Ionic Liquids with Imidazolium Cation

Abstract

The electrodeposition of nickel (Ni) on glassy carbon electrode was performed in a variety of six imidazolium based protic ionic liquids (PILs) like 2-methylimidazolium lactate ([Hmim][lactate]), 1-ethylimidazolium lactate ([Heim][lactate]), 1-butylimidazolium lactate ([Hbim][lactate]), 2-methylimidazolium glycolate ([Hmim][glycolate]), 1-ethylimidazolium glycolate ([Heim][glycolate]), 1-butylimidazolium glycolate ([Hbim] [glycolate]), respectively at various concentrations. While examining the course of the deposition process using cyclic voltammetry, the results demonstrate that all PILs possess high electrochemical stability with good electrochemical window ranging 1.61–3.6 V. In addition, [Hmim][lactate] and [Hmim][glycolate] showed greater cathodic stability, due to the replacement of C-2 acidic proton in imidazolium cation with methyl group. The Ni electrodeposition is found to be proceeding via one step—two electron transfer process that involved the irreversible reduction of Ni (II) to Ni (0). Also, it was found that by increasing Ni (II) concentration, nickel electrodeposition becomes more facile. Moreover, it was observed that owing to their high ionic conductance, the Ni electrodeposition was more facile in [Hmim][lactate] and [Hmim][glycolate] with diffusion co-efficient 1.8 × 10⁻⁵ and 5.1 × 10⁻⁷, respectively. The electrodeposited Ni was characterized using scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis. The distinctive uniform,sponge and gravel-like morphologies of Ni deposits were confirmed by SEM images and the EDX analysis endorse the presence of Ni element.