Chemisorption of copper atoms on platinized platinum in sulphuric acid solution

Abstract

The cathodic formation and the anodic removal of chemisorbed layers of copper atoms was studied at room temperature on platinized platinum in 0.5 MH₂SO₄+X M CuSO₄ . 5 H₂O (3.10^–4⩽X⩽ 10^–1) at potentials positive to that of the reversible copper electrode in the respective solution. The initial rate of layer formation is controlled by mass transport processes and a slow step in the discharge reactions at small bulk concentrations (10^–3 M) of Cu²⁺ions. The maximum number of adsorption sites that are covered by Cu_ad at large bulk concentrations decreases with potential. It is equal to the number of sites for hydrogen adsorption at 0.3 V and to zero at 0.8 V. One Cu_ad covers one adsorption site for H_ad in a first approximation. When the coverage with copper atoms is about one half, the effect of Cu_ad on hydrogen adsorption can be described as repulsive between 0.2 and 0.3 V and as attractive between 0 and 0.2 V.