PREPARATION OF ELECTRODEPOSITED THIN-FILMS OF NICKEL IRON-ALLOYS ON MILD-STEEL FOR ALKALINE WATER ELECTROLYSIS .1. STUDIES ON OXYGEN EVOLUTION

Thin films of electrodeposited nickel - iron alloys containing 15.6 - 38.5 % Fe were obtained on mild steel at 30-degrees-C. The films were uniform, porous and p-type semiconducting. Cyclic voltammograms showed the formation of a single quasireversible redox couple, Ni(III)/Ni(II ), on each film electrode in the anodic region (0-0.6 V) in IM KOH. Ox ygen evolution studies demonstrated a substantial increase in the elec trocatalytic activity of Ni in the presence of 17.9 % Fe additive. The Tafel slopes were 40 +/- 5 mV decade-1. The reaction order with respe ct to OH- ion concentration was observed to be approximately 2. The re sults suggest that the oxygen evolution reaction occurs on the oxidize d Ni(III) sites on the electrode surface with a mechanism involving an electrochemical adsorption of OH- ions in a fast step and their subse quent electrochemical desorption in the slow step.