Synthesis of graphite-based lead composites and modification of their physicochemical and electrochemical properties.

ABSTRACT

The present work describes preparation of a graphite lead composite, its modification and the examination of basic physicochemical and electrochemical properties. Graphite lead composites are the products of reaction of lead chloride with flaky graphite performed in a molten salt system. The process was carried out at 450 °C for 96 hours. In the second stage, the obtained composites were subjected to thermal or chemical treatment in order to modify their physicochemical properties. The structure of the as prepared material has been examined by X-ray diffraction analysis. Transmission electron microscopy analysis (TEM) along with energy dispersive spectroscopy (EDS) have been used to determine the size as well as the distribution of Pb particles. To study the electrochemical properties of graphite-based lead composites, cyclic voltammetry and galvanostatic methods have been used. It has been proved that the thermally modified compound at 600 °C contains on its surface spherical particles of lead chloride and/or oxide with diameters varying from hundreds of nanometers to several micrometers. The acquired electrochemical results revealed that graphite/Pb composites exhibit good electrochemical activity towards the reversible reaction of Pb → Pb2+ oxidation. Charge associated with the reversible transformation of Pb to Pb2+ amounts to 15.72 C g-1 and 14.62 C g-1 for the original compound and the compound heated at 600 °C, respectively. It has been also proved that the highest level of structure modification of the composite is reached by its chemical treatment with hydrogen peroxide. However, the mentioned modification leads to the removal of the entire lead from the structure of the graphite matrix.