Vibrational spectroscopy on the PbO-PbSO 4 system and some related compounds : Part 1. Fundamentals, infrared and Raman spectroscopy

Abstract

The following compounds, lead sulphate (PbSO 4), lead oxide (PbO), lead dioxide (PbO 2), monobasic lead sulphate (PbO · PbSO 4), tribasic lead sulphate (3PbO · PbSO 4 · H 2O) and tetrabasic lead sulphate (4PbO · PbSO 4) can occur during the charge and discharge reactions of lead electrodes in lead acid batteries. These substances can also be detected in the active mass of lead acid battery plates throughout the different steps in the production process. The appearance of the basic lead sulphates and of lead oxide is an important indication of the passivation behaviour of the mechanism of the electrodes and points to the chemical and electrochemical oxidation reactions under the passive layer. For the investigation of this sensitive passive layer, it is important to avoid all the disadvantages of the predominantly used ex situ methods (especially x-ray analysis). Therefore, it is necessary to apply an in situ technique for the characterization of the lead electrode surfaces in contact with the commonly used aqueous sulfuric acid solution. For this reason, external reflection absorption FT-IR spectroscopy was applied to investigate lead electrodes under different electrochemical conditions. As a prerequisite for the planned in situ work, the vibrational spectra of the above mentioned compounds in the Pb-PbO-PbSO 4-H 2SO 4 system must be known, in order to allow the identification of these substances on the electrodes in the in situ investigations. This work presents the infrared and Raman spectroscopic characterization of PbO, Pb 3O 4, PbSO 4 PbO · PbSO 4, 3PbO · PbSO 4 · H 2O and 4PbO · PbSO 4.