An electrochemical study of the nickel hydroxide-gold modified electrode employing the surface resistance technique

R. TUCCERI

JOURNAL OF ELECTROANALYTICAL CHEMISTRY - (Print)

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2016 vol. 774 p. 95 - 101

1572-6657

Simultaneous cyclic voltammetry (CV) and surfaceresistance (SR) measurements were employed to study the electrochemicalbehaviour of the nickel hydroxide-gold modified electrode. To this end,firstly, gold film electrodes of different thicknesses were synthesized, andtheir CV and SR responses within the potential regions corresponding tohydroxide ion adsorption (OHads) and gold oxide (AuO) formation in alkaline mediumwere analysed. Then, these gold film electrodes were modified with differentnickel hydroxide surface coverages, and their CV and SR responses were comparedwith those of bare gold films within the same potential regions and electrolytesolution. While cyclic voltammetric responses of the bare gold film electrodeand the nickel hydroxide-gold film modified electrode are practically the same withinthe whole potential range -0.5 V < E< 0.35 V (SCE), SR responses are the same only within the potential range-0.3 V < E < 0.35 V. Strongdifferences between the SR responses of the bare gold electrode and the nickelhydroxide-gold modified electrode within the potential range comprised between -0.5V and -0.3 V are observed. SR data were interpreted in terms of the fieldeffect and size effect theories formulated to study adsorption processes atthin metallic films. With regard to the bare gold film electrode, the fieldeffect theory allows one to conclude that within the potential region corresponding to hydroxide ion adsorption,77% of the electron density charge of gold is involved in the hydroxide ion?goldinteraction. Besides, a linear relation between the surface resistance change (DR) and the degree of oxidation (θox)at fixed gold film thickness (fm) is obtained within the potential region corresponding to gold oxideformation. In agreement with the size effect theory, the DR/θox slope exhibits a lineardependence on fm-2. The same SRresponses for the nickel hydroxide-gold modified electrode and the bare goldelectrode within the potential range ?0.3 V < E < 0.35 V indicate that thenickel hydroxide layer does not directly interact with the gold film surface. However,after the reduction of OHads and AuO layers, at potential values more negative than -0.3 V (SCE), anincrease of the surface resistance is observed for the nickel hydroxide-goldmodified electrode, which was attributed to nickel adatoms that directlyinteract with the gold film surface. On the basis of the electronconduction scattering model employed to describe the interaction of a metalfilm surface with a foreign atom layer, one can conclude that nickel film growth involves an initialstage in which nickel islands and then, compact structures are formed.