Electrodeposition study of simulated and dissolution solutions of the positive electrode of a spent Ni-MH battery using the electrochemical quartz crystal microbalance and inductively coupled plasma optical emission spectrometry

The use of electrochemical quartz crystal microbalance (EQCM) and inductively coupled plasma optical emission spectrometry (ICP-OES) as well as potentiodynamic and potentiostatic methods has revealed the electrodeposition mechanism from simulated solutions containing Ni 2+ , Co 2+ , Zn 2+ , and Mn 2+ , and a leached solution from cathodes of spent Ni-MH batteries. For simulated solutions, electrodeposition occurs via direct reduction, involving two electrons. Zn 2+ addition in the solution containing Ni 2+ and Co 2+ leads to a change in the electrodeposition potential for more negative values. Mn 2+ addition in the bath containing Ni 2+ , Co 2+ , and Zn 2+ does not change the electrodeposition process. The electrodeposition from the leached solution occurs in parallel with the hydrogen and oxygen reduction, with the passage of 4 mol of electrons. The MM/ z ratios calculated using ICP-OES are very similar to those obtained by EQCM measurements, revealing the appropriateness of the mechanisms proposed in this work.