Tungsten carbide for gas-recombination electrodes

The review reports studies by scientists from IEES-BAS during the period 1980-1992, which have shown that the tungsten carbide (WC) may be used for the construction of catalytic electrodes for the recombination of hydrogen and oxygen evolved during the operation of lead/acid batteries. Similarly, the data indicate that the recombination reaction reaches a maximum rate at the stoichiometric ratio of 2:1 between hydrogen and oxygen. The results included in the review show, that WC possesses catalytic activity for the reduction of oxygen and oxidation of hydrogen - a topic, which is of great importance in our days. The oxidation of the tungsten carbide catalyst in recombination electrodes was investigated when the electrodes operated in an atmosphere of oxygen and hydrogen. It has been established that after a long operation period (4000 h) 60 to 70% of the catalysts, depending on the initial active surface of WC, may be oxidized to WOx, whereupon the rate of recombination decreases about three times. The performance of WC recombination electrodes in lead/acid batteries with flooded, gelled or immobilized electrolytes has been investigated under various operating conditions. However, as the recombination electrodes are not in contact with the electrolyte and the recombination rate reaches values higher than 200 cm(3).h(-1).cm(-2), the hydrogen/oxygen gas mixture may explode.