To study the cobalt electrodeposition mechanism, a curve of
mass/charge (M/z) as a function of the potential was constructed
for the both solutions (Fig. 2b). ExperimentalM/z valueswere com-
pared with theoretical values obtained for mechanisms of more
probable reactions, such as: (i) the direct electrodeposition reac-
tion of cobalt (Eq. (1)), (ii) the deposition reaction of metallic
cobalt with adsorbed hydrogen (Eq. (4)), and (iii) the reduction of
cobalt from Co(OH)2 (Eq. (8)). The theoretical M/z values for reac-
tions (i) through (iii) were, respectively, 29.50 gmol
−1 (MCo
2+/2e−;
Eq. (1)), 15.25 gmol
−1 (MCo
2+ +2H+/4e−; Eq. (4)), and 14.80 gmol
−1
(MCo
2+/4e−; Eq. (8)).
Its value of theM/zwhen the cobalt is being depositedwith 100%
efficiency, i.e., without any other parallel process on the surface
of the electrode. If electrochemical processes occur with parallel
chemical processes as for example with deposit of mass by pre-
cipitation, the ratio M/z will be higher value than theoretical. If
electrochemical process occur with lower or no mass change, the
experimental M/z will be lower than the theoretical value for the
reaction considered.