Why Use Ionic Liquids for Electrodeposition?

Abstract

With any great voyage of discovery the explorer should always be asked at the outset "Why are you doing this?" To answer the question "Why use ionic liquids for electrodeposition?" it is first necessary to look at current best practice and find its limitations.It is widely recognised that in 1805 Italian chemist, Luigi Brugnatelli made the first experiments in what we now know as electroplating. Brugnatelli used the newly discovered Voltaic Pile to deposit gold "I have lately gilt in a complete manner two large silver medals, by bringing them into communication by means of a steel wire, with a negative pole of a voltaic pile, and keeping them one after the other immersed in ammoniuret of gold newly made and well saturated" [1]. The process was later improved by John Wright who found that potassium cyanide was a beneficial electrolyte to add for silver and gold plating as it allowed thick adherent deposits to be obtained. Until the middle of the 19th century the production of jewellery and the gilding of decorative items were the main uses of electrodeposition.With an increased understanding of electrochemistry, the practice of metal deposition spread to non-decorative metals such as nickel, brass, tin, and zinc by the 1850s. Even though electroplated goods entered many aspects of manufacturing industry very little changed about the physical processes involved in electrodeposition for about 100 years. It was only with the advent of the electronics industry in the middle of the 20th century that significant changes occurred in the hardware and chemistry of the plating solutions. The post-war period saw an increase in gold plating for electronic components and the use of less hazardous plating solutions. This trend has continued with increased control of hazardous materials to the environment. Improved solution composition and power supply technology has allowed the development of fast and continuous plating of wire, metal strips, semiconductors and complex substrate geometries.Many of the technological developments seen in the electronics industry depend upon sophisticated electroplating including the use of exotic metals and this is one of the drivers for new technology within the electroplating sector. The other Electrodeposition from Ionic Liquids. Edited

Corrosion of carbon steel in the [P 14666 ][Br] ionic liquid: The effects of γ-radiation and cover gas

“…For many transition metals H2O is an effective oxidant and hence water can function as both an oxidant for the metal and an electrolyte medium that can transport the charged species in the corrosion reactions. The IL studied here (and generally other ILs) is not considered to be redox active with transition metals [18]. Hence, the complexity arising from the solvent molecule participating in the redox reaction is not present.…”

“…Ionic liquids vary considerably in their solvation properties for redox active species such as H2O and O2, and corrosion products such as metal ions and hydrogen [18]. Gamma-radiation can decompose IL molecules into redox active species.…”

“…For many transition metals H2O (and its dissociated ions, H + and OH − ) can be an effective oxidant and hence water can function as both an oxidant for the metal and a medium that can transport dissolved charged species from the corrosion reactions away from the reacting surface. Ionic liquid molecules are generally considered to be not redox active with transition metals and they are poorer solvents for transition metal ions [18].…”

“…For many transition metals H2O (and its dissociated ions, H + and OH − ) can be an effective oxidant and hence water can function as both an oxidant for the metal and a medium that can transport dissolved charged species from the corrosion reactions away from the reacting surface. Ionic liquid molecules are generally considered to be not redox active with transition metals and they are poorer solvents for transition metal ions [18].Hence, the complexity arising from the solvent molecule participating in the redox reaction is not present in an ionic liquid and electrochemical corrosion in an IL solution is the consequence of metal oxidation by dissolved redox active impurities in the IL.Ionic liquids vary considerably in their solvation properties for redox active species such as H2O and O2, and corrosion products such as metal ions and hydrogen [18]. Gamma-radiation can decompose IL molecules into redox active species.…”

Analysis of mass transport in ionic liquids: a rotating disk electrode approach

“…Besides, traditional solvents and ILs differ much in their mass transport properties. For instance, viscosity typically ranges around 1 cp, two orders of magnitude lower than most of the ILs 13 , 33 , 34 . The high viscosity also affects the diffusion coefficient.…”