placement for more cathodic values increased the cobalt reaction
contribution via a mechanism of direct reduction (Eq. (1)).
Results obtained for potentiostatic electrodepositions suggest
that, at pH5.40, cobalt reduction occurs by a direct reductionmech-
anism. For cobalt electrodeposition at pH 2.70 and in the presence
of the hydrogen detachment reaction, a simultaneous mechanism
of direct reduction and cobalt reduction occurs.
4. Conclusions
Using an EQCM, verified the mechanism for cobalt electrode-
position and correlated it with solution pH and electrochemical
conditions. The electrodeposition mechanism occurs via the direct
reduction of cobalt (Eq. (1)) for a pH of 5.40 and under potentiody-
namic or potentiostatic conditions. The relation valueM/z for cobalt
electrodeposition at pH 5.40 under potentiodynamic and potentio-
static conditionswas equal to 32.00 and 33.00 gmol
−1, respectively.
Potentiodynamic electrodeposition of cobalt at pH 2.70 occurs
via the mechanism of adsorbed hydrogen, and M/z values tend
towards 13.00 gmol
−1. The experimental M/z relation was lower
than that predicted by theory due to the hydrogen reduction
reaction, which decreases the cobalt electrodeposition efficiency.
Cobalt potentiostatic electrodeposition at pH2.70 occurs via simul-
taneous mechanisms of direct reduction and cobalt reduction in
the presence of adsorbed hydrogen. The M/z value was larger
for depositions accomplished at a more negative potential. This
demonstrates that a more cathodic potential increases the direct
cobalt reaction (Eq. (1)) contribution to the simultaneous mecha-
nism of direct reduction.