NICKEL COATINGS - DEPOSITION ON AN IRON SUBSTRATE AND O2-EVOLUTION IN40 WT-PERCENT KOH

Nickel was electrodeposited on an iron substrate in aqueous solutions at pH 9.8 and 23-degrees-C containing nickel sulphate, ammonium citrat e and ammonium hydroxide. The oxygen evolution reaction (OER) has been investigated on those electrodes in 40 wt.% KOH after 30 min of prean odization under a current density of 1 A cm-2. The improvement of the electrocatalytic activity at 80-degrees-C with the nickel loading is d ue to the increase of the exchange current density with the amount of reducible species. The temperature of the electrolyte (40 wt.% KOH) st rongly influences the electrocatalytic activity and the relative amoun t of accumulated reducible species formed during preanodization.