Electrodeposition of Palladium in 1-Butyl-3-Methylimidazolium Chloride Ionic Liquid

Ionic liquids (ILs) have superior electrochemical properties that make them ideal for electrodeposition (1, 2). These properties include higher conductivity than non-aqueous solvents, wide electrochemical window and high solubility of metal salts. Moreover, complications due to air or water reaction at a metal/IL interface could be readily managed in air and water stable ILs (2).

Electrodeposition of a metal is strongly affected by IL properties such as viscosity and conductivity which are depended upon its cations and anions (3). Cations also adsorb on the electrode surface  and influence double layer structure at reduction potentials, while anions control the metal speciation (2). In addition, concentration of the dissolved metal ion affect the electrodeposition by changing the properties of ionic liquid and affecting the interactions at the metal/IL interface (2). Study of these phenomena on electrodeposition is limited (2).

            In this work, electrodeposition of Pd ions in 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) and 1-butyl-3-methylimidazolium dicyanamide ([Bmim][DCA]) was investigated for fission palladium recovery application. Deposition properties are strongly depended upon the IL selected. For example, Figure 1a shows a Ni flag electrode immediately after Pd electrodeposition in [Bmim][DCA] at -0.9 V vs Fc/Fc⁺  for 2 h at room temperature. On the Ni substrate, black deposits of Pd particles were found which was washed away upon insertion into methanol (Figure 1b) suggesting that the Pd particles formed were loosely attached onto the Ni surface. More studies on the effect of the ILs and substrate on the electrodeposition of Pd will be presented.       

Figure 1 (a) Black Pd particles on Ni flag electrode (0.25 cm²) after potential hold at -0.9 V vs Fc/Fc⁺ in 1-butyl-3-methylimidazolium dicyanamide at room temperature for 2 h. Pt wire served as the counter electrode. (b) Detachment of the Pd particles from the Ni electrode in methanol. 

References

1.             S. Z. E. Abedin, M. Polleth, S. A. Meiss, J. Janek and F. Endres, Green Chemistry, 9, 549 (2007).

2.             A. P. Abbott and K. J. McKenzie, Physical Chemistry Chemical Physics, 8, 4265 (2006).

3.             M. Galiński, A. Lewandowski and I. Stępniak, Electrochimica Acta, 51, 5567 (2006).