Cathodic Corrosion at the Bismuth–Ionic Liquid Electrolyte Interface under Conditions for CO2 Reduction

Abstract

Bismuth electrodes undergo distinctive electrochemically induced structural changes in nonaqueous imidazolium ([Im]+)-based ionic liquid solutions under cathodic polarization. In situ X-ray reflectivity (XR) studies have been undertaken to probe well-ordered Bi (001) films which originally contain a native Bi2O3 layer. This oxide layer gets reduced to Bi0 during the first cyclic voltammetry (CV) scan in acetonitrile solutions containing 1-butyl-3-methylimidazolium ([BMIM]+) electrolytes. Approximately 60% of the Bi (001) Bragg peak reflectivity is lost during a potential sweep between −1.5 and −1.9 V vs Ag/AgCl due to a ∼ 4–10% thinning and a ∼40% decrease in lateral size of Bi (001) domains, which are mostly reversed during the anodic scan. Repeated potential cycling enhances the thinning and roughening of the films, suggesting that partial dissolution of Bi ensues during negative polarization. The mechanism of this behavior is understood through molecular dynamics simulations using ReaxFF and density fu...