Synthesis and structural analysis of electrodeposited Pb-Co films for oxygen evolution applications

Abstract

Pb-Co films have been studied due to the reduced oxygen overpotential at which they operate. However, the synthesis of these films is not trivial because Pb and Co are known to be immiscible metals. Thus, with the aim of understanding the process behind the formation of Pb-Co films, full structural characterization of such films is done. Moreover, to ease the electrodeposition of the films, ascorbic acid is used as a complexing agent. Various concentrations of ascorbic acid were studied. The sample grown in the presence of 90 mM showed the most compact morphology, free of voids and cracks. Further, the analysis of polarization curves revealed that this coating is the best suited as an electrocatalyst for the oxygen evolution reaction, allowing operation at a lower overpotential compared to that of conventional Pb-Ca-Sn anodes. The structure of the samples was studied employing X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). It was encountered that the obtained coatings were composed of nanocrystallites of lead immersed in a pseudo-amorphous matrix of lead and cobalt. By differential scanning calorimetry (DSC) analysis, the amorphous nature of the matrix was demonstrated. This nanocrystalline nature favors the electrocatalytic activity of the coating as every point in the surface of the electrode (anode) acts as a catalyst.