ИСТИНА

Air- and water-stable room-temperature ionic liquids (ILs) are an excellent alternative medium for electrodeposition of metals, alloys, and semiconductor materials [1]. They offer great opportunities for improvement of electrodeposition processes that are inefficient or difficult to realize in aqueous solutions or solutions based on organic solvents. ILs possess good intrinsic ionic conductivity, nonvolatility, high thermal stability, and a wide electrochemical window. These features caused vast interest in studying ILs as deposition electrolytes [2], but the fundamental understanding of the electrodeposition processes in ILs is only at a preliminary stage [3]. Here, we focus on the study of initial stages of metallic chromium and copper electrodeposition on Pt and Au single crystal surfaces in ILs with dicyanamide anion. For this study we employed conventional electrochemical techniques in combination with in situ and ex situ scanning probe microscopy (in situ STM and ex situ AFM) and ex situ XPS technique. Cr electrodeposition was tested from Cr(II) and Cr(III) solutions employing low (10 mM) and high (250 mM) concentrations of chromium salts. The microscopic and spectroscopic methods demonstrate the formation of chromium deposit, although the voltammetric responses are not so obvious to interpret. In case of copper electrodeposition from 10 mM Cu(I) solutions, clear voltammetric cathodic waves of copper deposition are observed followed by a peak of metallic copper dissolution on a reverse anodic scan (Fig. 1a). Microscopic investigation shows (quasi)two-dimensional growth of copper on the Au(111) and Pt(111) electrode surfaces at moderate overpotentials (Fig. 1b,c). At high overpotentials copper deposition proceeds via formation of a large number of three-dimensional crystallites. This observation is in agreement with the shape of voltammetric and chronoamperometric responses. [1] A.P. Abbott, I. Dalrymple, F. Endres, D.R. Macfarlane, in: Electrodeposition from Ionic Liquids,Wiley-VCH Verlag GmbH & Co. KGaA, 2008. [2] Q. Zhang, Q. Wang, S. Zhang, X. Lu, X. Zhang, ChemPhysChem, 17 (2016) 335. [3] Sebastián, P.; Climent, V.; Feliu, J. M.; Gómez, E. Ionic Liquids in the Field of Metal Electrodeposition. In Encyclopedia of Interfacial Chemistry, Wandelt, K., Ed. Elsevier: Oxford, 2018; pp. 690. The work is supported by the Russian Foundation for Basic Research (project no. 17-03-00602).