Electrodeposition of lead-cobalt anodes: The effect of electrolyte pH on film properties

Electrodeposited lead (Pb)-cobalt (Co) coatings are an effective electrocatalyst in the oxygen-evolution reaction. We studied the effect of an electrolytic bath pH on the electrodeposition of Pb-Co coatings, and the coating properties were analyzed. The pH was varied from 1 to 6 for a solution without and with ascorbic acid as complexing agent. Cathodic polarization curves show that the deposition conditions have a greater effect on the reduction potential of Co2+ than the reduction potential of Pb2+. Energy-dispersive X-ray spectrometer analysis shows that a pH higher than 4 promotes Co deposition and yields a [Pb]/[Co] film ratio lower than 1. Scanning electron micrographs showed that samples grown at a pH higher than 2 were covered with Co dendrites, and that the sample grown with ascorbic acid at pH 1 exhibited a compact morphology. Anodic polarization curves showed that Pb-Co-coated anodes grown at pH 1 with a complexing agent evolved oxygen at c.a. 1.6 V vs. normal hydrogen electrode, which lead to a 40% reduction in the required overpotential (η) for the oxygen-evolution reaction compared with conventional Pb-Ca-Sn anodes.SCOPUS: ar.j