Etude électrochimique du comportement des phases PbOx (x=1,33 à x=1,55) en milieu aqueux

Abstract

Intermediate oxides are synthesized by heating fresh lead dioxide obtained from industrial positive plates of used batteries. These oxides are soaked in H2SO4 with 1.28 s.g. under stirring for one hour. X-ray diffraction (XRD) results showed that the sample prepared from PbO1.55 only had a pattern similar to that of the starting PbO2 It is found that lead dioxide obtained from PbO1.55 is more active than the fresh sample. It shows an increase in the capacity of 17%. This is due to the increase of the quantity of structural water as given by the chemical and thermal analyses. Lead dioxide was extracted from used batteries, and used to synthesize the following intermediate oxides by heating at different temperatures: PbO1.55, PbO1.44, and PbO1.33. Each of the prepared intermediate oxide was subject to sulfuric acid with 1.28 g.cm-3. The measurements of H+ proton diffusion coefficient (DH+) of the different samples showed that the sample prepared from PbO1.55 had better electrochemical performances than the starting PbO2. This kinetics reflects the proton insertion mechanism in PbO2, i.e. the sample prepared from PbO1.55 has a large amount of structural water in OH- hydroxyl form. This amount contributes more in the PbO2 reduction mechanism. This work contributes to environment preservation by recycling of used lead dioxide and reducing the risk of groundwater pollution by lead oxides.