Electrochemical mechanism of trivalent chromium reduction in 1-butyl-3-methylimidazolium bromide ionic liquid

The electrodeposition and electrocrystallization behaviour of chromium reduction in 1-butyl-3-methylimidazolium bromide (([BMIM]Br)) ionic liquid on a glassy carbon (GC) electrode is investigated. These results from cyclic voltammetry and linear sweep voltammetry show that the reduction of trivalent chromium (Cr3+) occurs by a two-step process, Cr3+ to Cr2+ and Cr2+ to Cr-0, respectively, the first step is an irreversible process with a diffusion coefficient of Cr3+ in solution of 2.3 x 10(-6) cm(2) s(-1) at 358 K, and the two-step reduction reaction has been identified by chronopotentiometry. The electrodeposits are characterized by SEM, EDS and XRD. XRD pattern of the electrodeposited layer reveals the characteristic peak of crystal Cr. Chronoamperometry results provide direct evidence that chromium electrodeposition in [BMIM]Br takes place through an instantaneous nucleation and diffusion-controlled three-dimensional growth mechanism. (C) 2014 Elsevier Ltd. All rights reserved.