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(@ + 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-02-Co(NH3)5]+4. The electroactivity 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 ~ cm2 s-I. The decomposition of the peroxo complex to form a mononuclear complex of Co(n1) was a slow process (k = 3 . 0 ~ s-l).

Catalysis of Oxygen Cathodic Reduction in Cobalt Ammoniacal Solutions

“…In a previous work (8), we have shown that use of the peroxo complex [ (NH3) ~Co-Oe-Co (NH3) s] +4 increases the limiting current of oxygen reduction on a platinum electrode without decreasing the overpotential. This homogeneous effect was explained as an increase of dissolving oxygen capacity of the cobaltammoniacal solution.…”

“…Two types of electrodes (1.0 • 2.8 cm each) were prepared (1): the noncatalytic electrode (type A) was a Ni gauze on which carbon was deposited, and the catalytic one (type B) was a similar electrode but impregnated with Fe(III)-PhC. The instrumentation is described elsewhere (6,8).…”