Electrodeposition of palladium–indium from 1-ethyl-3-methylimidazolium chloride tetrafluoroborate ionic liquid

Abstract

Voltammetry at a glassy carbon electrode was used to study the electrochemical co-deposition of Pd–In from a chloride-rich 1-ethyl-3-methylimidazolium chloride/tetrafluoroborate air-stable room temperature ionic liquid at 120 °C. Deposition of Pd alone occurs prior to the overpotential deposition (OPD) of bulk In. However, underpotential deposition (UPD) of In on the deposited Pd was observed at the potential same as the deposition of Pd. The UPD of In on Pd was, however, limited by a slow charge transfer rate. Samples of Pd–In alloy coatings were prepared on nickel substrates and characterized by energy dispersive spectroscope (EDS), scanning electron microscope (SEM) and X-ray powder diffraction (XRD). The electrodeposited alloy composition was relatively independent on the deposition potential within the In UPD range. At more negative potentials where the OPD of Pd–In has reached mass-transport limited region, the alloy composition corresponds to the Pd(II)/In(III) composition in the plating bath. The Pd–In alloy coatings obtained by direct deposition of Pd and UPD of In on the deposited Pd appeared to be superior to the Pd–In alloys that were obtained via the co-deposition of Pd and bulk In at OPD potentials.