Application of ionic liquids to the electrodeposition of metals

Abstract

The electrodeposition of most of technologically important metals has been shown to be possible from a wide range of room temperature molten salts, more commonly known today as 'ionic liquids'. These liquids are currently under intense scrutiny for a wide variety of applications some of which have already been commercialized. Despite the fact that electrodeposition was the first application studied in these liquids no metal deposition processes have as yet been developed to an industrial scale. This review addresses the practical and theoretical aspects that need to be considered when choosing ionic liquids for metal deposition. It details the current understanding of the physical and chemical properties of these interesting fluids and highlights the areas that need to be considered to develop practical electroplating systems. The effect of composition and temperature on viscosity and conductivity are discussed together with the fundamental approaches required to synthesise new liquids.

Electrofinishing of metals using eutectic based ionic liquids

“…A plethora of Al alloys have also been studied in imidazolium based chloroaluminates and a review of these has recently been published. 56 Endres has also recently written a review on the deposition of semiconductors, 14 primarily from eutectic based ionic liquids. None of these may seem technologically important, but one of the key advantages of ionic liquids is their ability to destabilise passive oxide films.…”

Ionic Liquids as Designer Solvents for the Synthesis of Metal Nanoparticles

“…Other metal nanostructures reported in ILs include anisotropic Au nanoparticles (Firestone et al, 2005), Au nanorods (Kumar et al, 2007), Pd nanowires (Kumar et al, 2007), Co nanocubes (Scariot et al, 2008) and Ag nanorods (Kim et al, 2009). Similarly electrochemical syntheses of metal nanostructures in the presence of ILs have also been reported, and readers are encouraged to look at associated references for a detailed understanding of these systems (Endres, 2002;Huang & Sun, 2004;Huang & Sun, 2005;Abbott & McKenzie, 2006;Dobbs et al, 2006;El Abedin & Endres, 2006;Yeh et al, 2006;Endres & El Abedin, 2008). It is however noteworthy that the use of ILs, particularly Imbased ILs as solvents for electrochemical reactions is predominantly dominated due to their electrochemical stability, excellent oxidative and reductive stability, and a large electrochemical potential window, which is typically notably larger than the electrochemical window of conventional molecular solvents (MacFarlane & Pringle, 2006;Endres et al, 2008).…”

Why use Ionic Liquids for Electrodeposition?

“…Others have sought to further divide the first generation liquids into separate types depending on the nature of the Lewis or Brønsted acid that complexes [18]. While there is some dispute whether eutectics with Brønsted acids constitute ionic liquids at all there are others who seek to widen the description of ionic liquids to include materials such as salt hydrates [19].…”

“…The species formed between the anion and the complexing agent becomes weaker when a Brønsted acid e.g. urea is used [18].…”

“…Details of these systems are given in the subsequent chapters and concise summaries exists in recently published reviews [18,25,26].…”