Electrochemical specific adsorption of halides on Cu 111,100, and 211: A density functional theory study

Abstract The specific adsorption of ions onto electrode surfaces can affect electrocatalytic reactions. Density functional theory is used to investigate the specific adsorption of aqueous F^-, Cl^-, Br^-, and I^- onto Cu (111), (100), and (211) surfaces. The adsorption is increasingly favorable in the order of F^- < Cl^- < Br^- < I^-. The adsorption has a weak dependence on the surface facet, with adsorption most favorable on Cu (100) and least favorable on Cu (111). Potential ranges where specific adsorption would be expected on each facet are reported. The thermodynamics of bulk copper halide (CuX, CuX₂) formation are also investigated as a function of potential. CuX formation occurs at potentials slightly more positive of halide specific adsorption and of copper oxidation in aqueous electrolytes. Specifically adsorbed halides and bulk CuX may be present during a variety of electrochemical reactions carried out over a Cu electrode in halide containing electrolyte solutions.