OXYGEN DISCHARGE ON NICKEL AND COBALT ANODES IN 30 W/O KOH AT 70-DEGREES-C IN THE PRESENCE OF DISSOLVED IRON AND VANADIUM

The oxygen evolution reaction (OER) has been investigated on polished pure nickel and cobalt anodes in 30 w/o KOH at 70-degrees-C. The anodes were preanodized at an anodic current density i(a) of 5 or 0.44 A cm-2 for 20 min before the kinetic parameters of the OER were determined. The electrocatalytic activity decreases significantly in the case of cobalt anodes but remains pratically unaffected in the case of nickel anodes when i(a) is shifted from 0.44 to 5 A cm-2, in the case of prepurifed electrolytes. The behaviour of both substrates is slightly affected by the presence of 1 mM vanadium in the electrolyte. The presence of 0.25mM iron in the electrolyte strongly improves the OER due to (i) a significant decrease of the Tafel slope in case of Ni and (ii) an equally significant increase in the exchange-current density in the case of Co.