Electroreduction of cobalt-amino peroxo complexes. Part 1.—The reduction of oxygen in the Co(II)+ ammonia system

Abstract

The electroreduction of O₂ in Co(II)+ NH₃ solutions has been investigated using the rotating disc electrode technique. It was found that the electroactive species, in the potential range 0 to –1 V against s.c.e., are O₂ and the peroxo complex [(NH₃)₅Co—O₂—Co(NH₃)₅]⁺⁴. The electro-activity of the complex was shown by the appearance of a new cathodic wave and by the linear increase of the limiting current of this wave with the peroxo complex concentration. It is suggested that four electrons are involved in the reduction of the complex on a Pt rotating disc electrode. Its diffusion coefficient was calculated to be 8.6 × 10^–6 cm² s^–1. The decomposition of the peroxo complex to form a mononuclear complex of Co(III) was a slow process (k= 3.0 × 10^–6 s^–1).