Influence of alloying additives (Sb, Sn, Ca, Ag) on the oxygen evolution reaction on Pb/PbO/sub 2/ electrodes

When the lead-acid battery is charged over 70% SOC, oxygen is evolved on the positive plates due to water decomposition. In valve-regulated lead-acid batteries, the evolved oxygen forms a closed recombination cycle. The rate of O/sub 2/ evolution depends on potential, temperature and alloying additives. In this work, the influence of alloying elements (Sb, Sn, Ca, Ag) on oxygen overvoltage is studied and their effect on the activation energy of the process is determined using smooth model electrodes. It is established that Sn increases both the oxygen overvoltage and the activation energy, Ag and Sb have the opposite effect (weaker for Sb). Ca has a small influence on O/sub 2/ evolution. Besides, the additives increase the ratio /spl alpha/-//spl beta/-PbO/sub 2/ in the corrosion layer.