Correlation Between the Electrochemical Activity and the Crystallite Size of PbO 2 : A Comparative Study Between the Che
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Correlation Between the Electrochemical Activity and the Crystallite Size of PbO2: A Comparative Study Between the Chemical and the Electrochemical Routes L. Zerroual1 · I. Derafa1 Received: 19 March 2020 / Accepted: 7 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Lead dioxide was prepared by chemical and electrochemical routes. The chemical samples were obtained by dissolving lead tetra-acetate in distilled water at room temperature. The electrochemical samples were obtained by oxidizing cured plates in sulfuric acid containing different concentrations of surfactant. The discharge of the different samples in sulfuric acid showed that the capacity of the chemical electrodes is independent of the crystallite size. In contrast the capacity of the electrochemical powders decreases with the increase of the crystallite size. Thermal analyses of the different samples were investigated to show the difference between the two methods. Keywords Lead dioxide · X-ray diffraction · Capacity · Crystallite size · Structural water
1 Introduction The positive plate of lead-acid battery contains two forms of lead dioxide α and β-PbO2. It is commonly known that the α form is stable in alkaline solution whereas β is stable in acidic solution. Numerous studies have been reported in the literature concentrating on the differences between chemically and electrochemically prepared lead dioxide. Compared with chemically prepared P bO2, which are reputed to be electrochemically inactive forms, material prepared by electrochemical formation of positive plates of lead-acid batteries exhibits high electrochemical activity. It was found that, in general electrochemically prepared lead dioxide is non-stoichiometric, whereas chemically prepared PbO2 is nearly stoichiometric. The origin of the electrochemical activity was essentially linked to the presence of hydrogen species [1]. Lead dioxide active mass is a gel-crystal system with proton and electron conductivity. The anodic layer formed on lead electrodes in H2SO4 solution contains
* L. Zerroual [email protected] 1
Laboratoire D’Energétique Et Electrochimie du Solide (LEES), Faculté de Technologie, Université Ferhat ABBAS, Sétif-1, 19000 Sétif, Algeria
hydrated structures. At a given potential, P b4+ ions are formed on the electrode surface. These are unstable in aqueous solutions and form Pb(OH) 4. The Pb(OH) 4 is dehydrated partially or completely giving PbO(OH)2 and P bO2. The electrode surface is covered by a layer of PbO2, PbO(OH)2 and Pb(OH)4, which layer has gel-like properties. During the discharge of the positive battery plate, the reduction of PbO2 and PbO(OH)2 to P bSO4 proceeds in two stages. The first is electrochemical and occurs in the bulk of the agglomerates and particles and gives Pb(OH)2. During the second stage, P bSO 4 formation takes place through a chemical reaction between Pb(OH)2 and H2SO4. In our previous work [2], using an all solid state system exempt of H 2SO4, the kinetic tests and coulometric dat
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