From Fig. 2b, it was observed that experimental M/z values
obtained during cobalt electrodeposition in a solution of pH 5.40
moved toward a value of 32.00 gmol
−1 as the deposition advanced
in the cathodic direction. This result suggests that deposition is
occurring in agreement with Eq. (1). Already at pH 2.70,M/z values
tended toward a value of 13.00 gmol
−1.
This result suggests that cobalt electrodeposition might be
occurring via the formation reaction of Co(OH)2 or by the mecha-
nismof adsorbed hydrogen. As observed byMatsushima et al. [11],
however, the formation of Co(OH)2 does not occur in solutions of
pH< 2.70. Therefore, the decrease in observed M/z values might be
associated with the formation of adsorbed hydrogen. This reaction
occurred in solutions with pH< 2.70 when H3BO3 was added as a
buffer to prevent local pH variations in the solution. Experimental
M/z values were lower than theoretical values owing to the hydro-
gen reduction reaction, which decreases the efficiency for cobalt
electrodeposition.
The voltammograms curves for cobalt electrodissolution at both
analyzed pHvalues are shown in Fig. 2a.According to Soto et al. [23],
peak I canbe associatedwithcobalt oxidationcontaininghydrogen-
rich phase. The shoulder of current II can be related with cobalt
electrodissolution without adsorbed hydrogen.