Electrodeposition of Tin in an Amide Type Ionic Liquid Containing Chloride Ion

Abstract

Electrochemical behavior of Sn was investigated on a GC electrode in an aprotic ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing BMPCl and SnCl₂ at 298 K. SnCl₂ was found to dissolve as [SnCl₄]²⁻ by potentiometry. The formal potential of [SnCl₄]²⁻/Sn was −1.67 V vs. Ag|Ag(I) (−1.24 V vs. ferrocene|ferrocenium), which was more negative than that in BMPTFSA without chloride ions. Electrodeposition of Sn was possible by reduction of [SnCl₄]²⁻ in the ionic liquid. The dissociation of [SnCl₄]²⁻ was suggested from the diffusion coefficient of [SnCl₄]²⁻. Tubular deposits with an inner diameter of 1–1.5 µm were obtained in addition to granular deposits by potentiostatic cathodic reduction at −2.0 V.