Electrochemical behavior of rhodium(III) in 1-butyl-3-methylimidazolium chloride ionic liquid

Electrochemical behavior of rhodium(III) chloride in 1-butyl-3-methylimidazolium chloride was investigated by various electrochemical transient techniques at glassy carbon working electrode at different temperatures (343-373 K). Cyclic voltammogram of rhodium(III) in bmimCl consisted of a surge in reduction current occurring at a potential of -0.48 V (vs. Pd) is due to the reduction of Rh(III) to metallic rhodium and a very small oxidation wave occurring at -0.1 V. Increase of scan rate increases the peak current and remarkably shifts the cathodic peak potential (E-p(cl)) in negative direction indicating the irreversibility of electroreduction of rhodium(III). The diffusion coefficient of P rhodium(III) in bmimCl (similar to 10(-9) cm(2)/S) was determined and the energy of activation (similar to 25 kJ/mol) was deduced from cyclic voltammograms at various temperatures. The cathodic (tau(r)) and anodic (tau(o)) transition times were measured from chronopotential transients and the ratio tau(o)/tau(r) was found to be 1:7. Electrowinning of rhodium from bmimCl medium results in a deposition of metallic rhodium with lower (20-25%) Faradaic efficiency. A separation factor of rhodium from co-existing noble metal fission product palladium in bmimCl was determined during electrodeposition. (c) 2007 Elsevier Ltd. All rights reserved.