Abstract Rotating disc electrode voltammetry, cyclic voltammetry and chronocoulometry were used to test reversibility of the title system. The first technique revealed a deviation from reversible behaviour, when Cu(II) is reduced to Cu(I), which can be attributed to adsorption of the product Cu(I) with subsequent electrode coverage. The second technique gave evidence for the adsorption of both Cu(II) and Cu(I). The third technique confirmed that Cu(I) is adsorbed to a greater extent than Cu(II). An approximate adsorption isotherm was produced and a reaction mechanism proposed.