An Investigation of Some Electrocatalytic Processes Occurring at Low Potentials at a Nickel Electrode in Base

Abstract

It was observed that nickel in base is not a very effective electrocatalyst for the oxidation of organic species, such as methanol and its derivatives, at low potentials. With regard to the oxidation of reactive inorganic species used in electroless nickel plating baths, the behavior of nickel is rather similar to that of gold in that two mediator species appear to be involved. Anionic species such as hypophosphite and the hydroxytrihydroborate anion commence oxidation well below 0 V(RHE), the reaction being mediated by an interfacial cationic Ni(I) hydrous oxide species. Neutral molecules such as hydrazine commence oxidation just above 0 V, the reaction being mediated by an interfacial Ni(II) hydrous oxide species. Severe deactivation of the surface for a particular reaction occurs when the interfacial species undergoes a chemical change, e.g., when Ni(I) alters to Ni(II) or the hydrous Ni(II) species alters to a less-hydrated deposit of Ni(OH)2. As pointed out recently in connection with similar work carried out with cobalt in base, the present approach provides a logical basis for understanding the behavior of reductants used in electroless plating baths.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2015-02-20 to IP

EQCM studies on oxidation of metallic nickel electrode in basic solutions

“…b-Ni(OH) 2 phase transformation, takes place [1,13,38,39] resulting in irreversible changes in the shape of CV and EQCM curves [2,3,13,16,38,39,68]. As a result, the electrode is covered with a layer of oxidised Ni(II) compounds, most probably b-Ni(OH) 2 , that could not be reduced back to metallic nickel.…”

Study of Underlying Premonolayer Oxidation of Nickel Electrode in Basic Solution Related to the Catalytic Oxidation of Hypophosphite on Nickel

“…However, its voltammetric response hasn't been explored due to the shielding effect of the current of hydrogen evolution reaction (HER). 17 In this paper, AC voltammetry was employed to investigate the premonolayer redox reactions of nickel electrode in basic solution to interpret the catalytic oxidation of hypophosphite on nickel for the first time. Furthermore, X-ray photoelectron spectroscopy (XPS) was used to illustrate the premonolayer oxidation of nickel electrode.…”

“…26,28,29 As the result of the presence of NaH 2 PO 2 , hypophosphite oxidation peaks both on positive (peak a III ) and negative (peak a IV ) sweeps appear in low potential region. 11,[15][16][17] Figs. 1b and 1c show the in-phase fundamental harmonic and second harmonic of AC voltammetry obtained with nickel electrode in 1.0 M NaOH.…”

“…17 The IHOAM model considers that the premonolayer oxidation of metal electrode at low potential induces the catalytic oxidation of reductant if the two reactions begin at the same potential. Premonolayer oxidation has already been characterized, 18,19 especially by AC voltammetry which could amplify the responses of reversible processes and reduce the influences of irreversible processes.…”

“…Premonolayer oxidation has already been characterized, 18,19 especially by AC voltammetry which could amplify the responses of reversible processes and reduce the influences of irreversible processes. [20][21][22][23] The IHOAM model of electrocatalysis has been applied to many metal electrodes such as nickel, 17 gold, 20 silver 24 and copper. 21 Ni(I) premonolayer hydrous oxide is assumed to be generated during premonolayer oxidation and catalyze the oxidation of hypophosphite.…”