3.2. Potentiostatic and electrochem

3.2. Potentiostatic and electrochemistry quartz crystal
microbalance measurements
Chronoamperogram plots and the corresponding variations of
M/z as functions of time are shown in Fig. 3. In this case, the
potentiostatic electrodeposition of cobalt in a pH 5.40 solution,
with −0.90V applied potential, presented a similar behavior in
comparison with potentiodynamic electrodeposition. M/z values
for deposition in this pH 5.40 solution tended towards a value
of 33.00 gmol
−1, which corresponds to the cobalt direct elec-
trodeposition mechanism (Eq. (1)). For electrodeposition in a
pH 2.70 solution, M/z values were already near 10.00 gmol
−1 at
the initial deposition stage. The M/z relation continued increas-
ing as the deposition advanced, reaching 22.00 gmol
−1 by the
end of the electrodeposition. The M/z value for cobalt reduc-
tion at pH 2.70 was intermediary between direct reduction
(M/z = 29.50 gmol
−1) and reduction togetherwith adsorbed hydro-
gen formation (15.25 gmol
−1). This result demonstrates that, in
some electrode regions, the direct reduction reaction occurs and
that, in others, the cobalt reduction reaction,with adsorbed hydro-
gen formation, occurs.