Electrodeposition parallel reactions

Because the electrodeposition process involves the transfer of electrons to an electrode, by measuring the current in the electrochemical cell, it is in principle possible to calculate the amount of material deposited. If no other reaction occurs in parallel, then we can assume that the reaction at the working electrode in aqueous electrolyte is just the simple reduction of a metal (M)... 

Irregular or powdered copper deposits are formed by electrodeposition from acid sulfate solutions at current densities and overpotentials corresponding to the plateau of the limiting diffusion current density and at higher ones. At these overpotentials and current densities, parallel to copper electrodeposition processes, hydrogen evolution reaction occurs [30]. Hence, it is very clear that the formation of powdered copper deposits is closely related with hydrogen evolution reaction as the second reaction in copper electrochemical deposition processes at high overpotentials and current densities [38]. 

With the applied cathodic current density pulses larger than the limiting diffusion current density, parallel to copper electrodeposition hydrogen evolution reaction occurs [52]. On the other hand, there was not any gas evolution during anodic pulses indicating that the overall gas evolution corresponds to hydrogen evolution. Then, Eq. (4.22) can be modified by Eq. (4.25) ... 

---