Copper selenocyanate formation on the copper anode

The formation of CuSeCN on a copper anode was studied in 0.1 and 0.5 mol dm(-3) KSeCN solutions. A thin film of polycrystalline CuSeCN was produced with a midpoint potential between the anodic and cathodic peaks for 0.1 mol dm(-3) KSeCN at -0.253 V, close to the open-circuit potential of -0.249 V. A precursory anodic peak or shoulder was seen at about -0.210 V, and was ascribed to the formation of a primary (barrier) film. The anodic peak currents for the primary film were linearly dependent upon the sweep rate. Potential steps into the primary film region produced current transients, with the current decaying in proportion to the reciprocal of time. The anodic peak current and potential for the secondary polycrystalline film were proportional to the square root of the sweep rate, an effect which is consistent with a model for porous film growth controlled by the resistance across the underlying barrier film. A weak Raman band due to Se-bonded CuSeCN at 2164 cm(-1) was also observed in situ.