Leicester Ionic Liquids Group
Green Solutions
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Research

The main research interests of the group are firmly based around green chemistry with particular emphasis on electrochemical processes. It is active in developing novel solvent systems with industrial applications such as metal deposition and dissolution. It collaborates strongly with industry and much of the work to date has been in the development of novel processes using ionic liquids.

Electroplating

Electrodeposition of metals is essential for a variety of industries including electronics, optics, sensors, automotive and aerospace to name but a few. The main metals of interest include Cr, Ni, Cu, Au, Ag, Zn and Cd together with a number of copper and zinc-based alloys. The electroplating industry, which dates back well over 100 years, is based solely on aqueous solutions due to the high solubility of electrolytes and metal salts resulting in highly conducting solutions. Water does, however, suffer from the drawback that it has a relatively narrow potential window, and hence the deposition of metals with large negative reduction potentials such as Cr and Zn is hindered by poor current efficiencies and hydrogen embrittlement of the substrate. The main driving force for non-aqueous electrolytes has been the desire to deposit refractory metals such as Ti, Al and W. As ionic liquids have developed, the key advantages of the liquids have become:
Cr plating demonstrator unit (part of the Ionic Liquids Demonstrator ild) and brass items electroplated with nickel and silver.

Due to their low vapour pressures ionic liquids are well suited to perform electrodeposition at a range of temperatures. At elevated temperatures there is less concern about viscosity and conductivity and phenomena such as nucleation, surface diffusion and crystallisation associated with metal deposition can be accelerated. The use of ionic liquids heralds not only the ability to electrodeposit metals that have hitherto been impossible to reduce in aqueous solutions but also the capability to engineer the redox chemistry and control metal nucleation characteristics.

Aluminium plated mild steel and copper rods (left); Nickel coated brass rods (right).