Electrochemical Growth of Surface Oxides on Nickel. Part 1: Formation of α-Ni(OH)2 in Relation to the Polarization Potential, Polarization Time, and Temperature

Abstract

Electro-oxidation of Ni(poly) in 0.5 M aqueous KOH solution at various polarization potentials (E p ) up to 0.5 V vs. reversible hydrogen electrode, for polarization times (t p ) up to 2 h, and at 285≤T≤318 K leads to the formation of a thin layer of α-Ni(OH) 2 . Interfacial capacitance measurements show that the Ni(poly) electrode covered with a layer of α-Ni(OH) 2 can be completely reduced back to its metallic state by applying a negativegoing potential scan with a lower potential limit of −0.2 V. An increase of E p , t p , and/or T results in an increase of the thickness of the α-Ni(OH) 2 layer, which, however, never exceeds two monolayers. The electrochemical formation of α-Ni(OH) 2 follows a direct logarithmic growth kinetic law. The results reported in this contribution and their interpretation imply that other oxide growth theories, such as the Langmuir-type adsorption, the point defect model, the electron tunneling, or the nucleation-and-growth model, are not applicable to the growth of α-Ni(OH) 2 . The potentiostatic growth of α-Ni(OH) 2 on Ni(poly) is successfully treated by applying the interfacial place-exchange mechanism and the associated kinetic law.

Enhancement of Ethanol Oxidation Reaction on Pt (PtSn)-Activated Nickel Foam Through In situ Formation of Nickel Oxy-Hydroxide Layer

“…These findings are in very good agreement with those presented by Barbosa et al [5], Motheo et al [17] and by Kim and Park [18]. It should be stressed however that comprehensive studies of Ni oxide growth and characterization were published in important papers by van Drunen et al [22] and by Alsabet et al [39][40][41].…”

An Oxalate Method for Measuring the Surface Area of Nickel Electrodes

“…It has been suggested that the electrochemically formed α-Ni(OH) 2 surface component has a limiting thickness of two layers. 19 The adsorbed oxalate layer may therefore have a similar thickness of about two layers or less. Conventional IR reflectance measurements are incapable of detecting such thin surface components.…”

Nickel hydroxides and related materials: a review of their structures, synthesis and properties

“…Ni(OH) 2 also forms electrochemically on Ni electrodes in alkaline media, which has importance for the development of Ni-based electrocatalysts [23,105,179,[184][185][186][187]. Consequently, the surface electrochemistry has been extensively studied using atomic force microscopy [188], ellipsometry [181,[189][190][191], IR spectroscopy [192], Raman spectroscopy [166,193,194], UV-Vis spectroscopy [192,195], voltammetry [179,185,[196][197][198][199][200][201], X-ray scattering [176], XPS [179,202] and gravimetry with an electrochemical quartz crystal microbalance [203,204]. During a forward voltammetric sweep, a surface bilayer of α-Ni(OH) 2 underlaid by NiO x forms initially [179].…”

“…The voltammetric peak at approximately 0.3 V versus RHE has been used to estimate the surface area of nickel electrodes [197]. The method approximates that the peak corresponds to the formation of a monolayer consisting entirely of α-Ni(OH) 2 .…”