Peculiarities of copper underpotential deposition and nucleation on polycrystalline platinum in the presence of acetonitrile: Rotating ring-disk electrode

Abstract

The initial stages of copper electrocrystallization on polycrystalline platinum in 0.5 M H₂SO₄ + 10 mM CuSO₄ + 0–200 mM acetonitrile (AcN) solutions are studied by the methods of cyclic voltammetry and potentiostatic current transients on a ring-disk electrode. Adsorbed AcN molecules accelerate both the underpotential deposition and the bulk deposition of copper due to the local electrostatic effects on the charged interface. With the increase in the additive concentration in solution, the contribution of the production of copper ions Cu⁺ is observed to increase due to the formation of Cu(AcN) ⁺_x comlexes, particularly, for [AcN] ≥ 4 mM when the concentrations of acetonitrile and copper sulfate become comparable. In the presence of AcN, as well as in the copper sulfate supporting electrolyte, the adatomic layer is formed via the mechanism of the two-dimensional growth of Cu(1 × 1) phase islets.