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

Abstract

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 Ni2+, Co2+, Zn2+, and Mn2+, and a leached solution from cathodes of spent Ni-MH batteries. For simulated solutions, electrodeposition occurs via direct reduction, involving two electrons. Zn2+ addition in the solution containing Ni2+ and Co2+ leads to a change in the electrodeposition potential for more negative values. Mn2+ addition in the bath containing Ni2+, Co2+, and Zn2+ 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.