Structure, XAS analysis, and voltammetric study of copper–manganese-doped electrode materials obtained by recycling of a lead–acid battery

Electrode materials of x CuO∙5MnO 2 ∙(95 − x )[4PbO 2 ∙Pb] composition where x = 0–50 mol% CuO were prepared by melt quenching from spent plates of a car battery. Mixtures comprising the active mass of the anodic (as Pb source) and cathodic (as PbO 2 source) spent electrodes and MnO 2, and CuO powders were melted in corundum crucibles at 900 °C for 10 min. Manganese ions were used as dopant due to their significant role in hydrogen evolution reactions in sulfuric acid solution. The recycled and copper–manganese-doped samples were investigated by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopy (XAS). XRD and FTIR spectroscopy data show that by doping with the higher CuO content, the amount of sulfated crystalline phases was decreased. The IR spectra show the presence of sulfate ions and of [PbO n ] and [CuO n ] structural units in all the vitroceramic samples. EPR data indicate that the local structure around the Mn +2 and Cu +2 paramagnetic ions is dependent on the content of copper oxide, and the intensity of the resonance line corresponding to the Cu +2 ion was modified with the increase in the dopant content. XAS data analysis indicates that the lead atom has + 2 and + 4 oxidation states and that by increasing the dopant content there is a process of ordering of oxygen atoms around the lead atom similar to the PbO 2 theoretical model. In the cyclic voltammetry (CV) measurements, the recycled samples were used as working electrodes in a solution of sulfuric acid of the same concentration as that used in the car battery. The electrode material with x = 30 mol% CuO exhibited large oxidation and reduction waves and good reversibility of the cyclic voltammetry which improved the redox process in the lead–acid battery.