KINETICS OF HYDROGEN-EVOLUTION REACTION ON LEAD AND LEAD-ALLOY ELECTRODES IN SULFURIC-ACID ELECTROLYTE WITH PHOSPHORIC-ACID AND ANTIMONY ADDITIVES

The kinetics of the hydrogen-evolution reaction (HER) on smooth Pb, Pb -Ca-Sn and Pb-Sb-Se alloy electrodes is studied in H2SO4 (3-10 M) elec trolyte that contains phosphoric acid (0-40 g l(-1)) and antimony (0-1 0 mg l(-1)) using galvanostatic polarization in the Tafel domain. A di rect correlation is found between i(O,H) and i(cor) on lead and lead-a lloy electrodes with varying concentrations of H3PO4 and Sb(III) in H2 SO4. The maximum suppression of the HER occurs with 20 g l(-1) H3PO4 i n H2SO4 for both lead and lead alloys. The data are explained in the l ight of a model that employs adsorption of H3PO4 at the electrode/elec trolyte interface.