Electrodeposition of chromium on single-crystal electrodes from solutions of Cr(II) and Cr(III) salts in ionic liquids

Abstract

Herein, we present a study on the initial stages of chromium electrodeposition on platinum and gold single-crystal surfaces from an ionic liquid containing dicyanamide anions. We employed conventional electrochemical techniques in combination with in situ and ex situ scanning probe microscopy (in situ scanning tunneling microscopy (STM), ex situ atomic force microscopy (AFM)) and ex situ X-ray photoemission spectroscopy (XPS). Cr electrodeposition was carried out from Cr(II) and Cr(III) solutions of low (10 mM) and high (250 mM) Cr concentrations. The microscopic and spectroscopic approaches clearly demonstrate the formation of a Cr deposit, although the voltammetric responses are difficult to interpret. The absence of a pronounced Cr dissolution peak in the backward scan of the cyclic voltammograms and a relatively low amount of Cr deposit (as confirmed by AFM) suggest the passivation of Cr and the substrate during deposition, thus hindering both further deposition of Cr and its anodic dissolution.