Electrochemical study on the structure of PbO₂ in mixed gel electrolytes during cycling by cyclic voltammetry

Abstract

Pb/PbO₂ electrodes are made by anodizing method from H₂SO₄ solution (1.26 g/cm³). The mixed gel electrolyte was prepared by mixing H₂SO₄ (1.37 g/cm³) with liquid glass (LG) in the presence of polyacrylamide (PAM), propylene glycol (PPG), and nano fumed silica (NFS). After finishing 150 cycles by cyclic voltammetry (CV) in different electrolytes at a scan rate of 100 mV/s, the structure of PbO₂, including morphology and the content of elements, were analysed by scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS), respectively, as well as by CV diagrams. There was found a huge difference in both the grain size and surface structure of PbO₂ electrodes. Among them, the morphology of PbO₂ electrode after cycling in mixed gel electrolyte using PAM with NFS is similar to that obtaining from H₂SO₄ solution (1.26 g/cm³). The appearance of α‐ and β‐PbO₂ forms depends on the combination of gelling agents. The existence of α‐PbO₂ form was found only by using separate PAM or PAM with PPG leading to small discharge densities, while both α‐ and β‐PbO₂ forms were clearly observed by combining PAM with NFS. The height of redox peak in this case is approximately the same as that in sulfuric acid solution.