Oxygen Evolution Reactions on Nickel, Nickel Oxide Electrodes using Galvanostatic Methods

Abstract

<p>An electrochemical cell has been designed for use for water electrolysis in 30 w/o KOH solution at 80˚C. Various electrode holders and coatings are tested using Ni, NiO as oxygen electrode. A teflon holder in which the electrode press-fits is found to give adequate protection to the electrode.</p> <p>Epofix resin, when mixed in the ratio of 8 parts epoxy to 1 part hardner, applied to the back face of an electrode, is found to restrict electrode reaction to only the surface of interest. This hardner is stable in 30 w/o KOH solution at 80˚C. Current-potential measurements obtained for polished polycrystalline nickel are found consistent with those reported in the literature. The measured electrode potentials on polished nickel are similar to that of electrode which was thermally pre-oxidised in air. This is thought to be due to the fact that the polished nickel surface is rapidly covered with a layer of oxide as soon as oxygen evolution begins.</p> <p>Dual Tafel regions are observed for each electrode, and the higher slope at the high current densities are thought to be due to oxide formation at these current densities but the absence of hysteresis loops are taken as an indication that the oxide may not be stable with polarisation.</p>