Nickel‐Based Alloys as Electrocatalysts for Oxygen Evolution from Alkaline Solutions

Abstract

The oxygen evolution reaction on the alloys of Ni with Ir, Ru, or W and on Ni‐Ti intermetallic compounds was studied in at 80°C using steady‐state potentiostatic and slow potentiodynamic (at 0.1 mV/sec) methods. Since this reaction always takes place on film‐covered surfaces, the nature of oxide films formed on these alloys was investigated using cyclic voltammetry. The peaks for the formation and reduction of oxygen‐containing layers appearing on the pure metals are not always found on these alloys. Oxygen overpotentials at an apparent current density of 20 mA/cm2, on the alloys of 50Ni‐50Ir and 75Ni‐25Ru (in atomic percent, a/o) and the intermetallic compound were less than on Ni by about 40, 30, and 20 mV, respectively. On long‐term polarization at potentials in the oxygen evolution region, the oxygen‐containing films on Ni‐Ir and Ni‐Ru alloys are predominantly composed of nickel oxide and independent of the bulk composition of the alloys themselves. This accounts for the absence of any direct dependence of electrocatalytic activities for oxygen evolution on their electronic properties. The effects of relative activities of the individual components in the alloys are however detectable on the oxide formation reactions on the surfaces of freshly prepared electrodes.