Its value of the M/z when the cobalt is being deposited with 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 precipitation, 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.
From Fig. 2b, it was observed that experimental M/z values obtained during cobalt electrodeposition in a solution of pH5.40
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 mechanismof adsorbed hydrogen. As observed by Matsushima 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 hydrogen reduction reaction, which decreases the efficiency for cobalt electrodeposition.