Anodic oxide films at nickel electrodes in alkaline solutions—I. Kinetics of growth of the β-Ni(OH)2 phase

✍ Scribed by J.F. Wolf; L-S.R. Yeh; A. Damjanovic

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 684 KB
• Volume: 26
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(81)85030-x

✦ Synopsis

The growth kinetics of thin anodic oxide films at nickel electrodes are examined in 0.1 N KOH solutions at room temperature under potentiodynamic and galvanostatic conditions. At electrodes that have been mechanically polished and cathodically reduced, growth ofthe lower oxidation state phase, fi-Ni(OH),, follows, under both experimental conditions, the formalism of the Cabrera-Mott model of high fieldassisted formation of thin oxide films. At lo-' Acrr-', the field within the oxide phase is 8.5 x lo6 V/cm. The field decreases 1.3 x 106 V/cm for each ten-fold decrease of current density. The potential at which b-Ni(OH)2 begins to grow, V, = -0.39 V US she, is identified as the reversible potential of the phase. It is, however, 270mV positive than the reversible potential listed in literature for Ni(OH), formation in solutions of the same pH. It is suggested that the observed reversible potential refers to the B-Ni(OH), phase. The exchange current density for the oxide film growth is 2.3 x lO-lo Acm-'. Comparison of the kineticsat Pt and Ni electrodes indicates that the activation energy for the growth of the b-Ni(OH), phase is 21 kcal/mole. Anodic oxidation of Ni electrodes in alkaline solutions under galvanostatic[ f,2], potentiodynamic[3-71 and potentiostaticC2, 81 conditions leads initially to the formation of a Ni(OH), film [l-9] of about 10 atomic