EL ELECTRODO DE ORO MODIFICADO CON HIDRÓXIDO DE NÍQUEL ESTUDIADO MEDIANTE LA TÉCNICA DE LA RESISTENCIA SUSUPERFICIAL

R. TUCCERI

Congreso Internacional de Metalurgia y Materiales, 16 Sam-Conamet

Congreso; Congreso Internacional de Metalurgia y Materiales, 16 Sam-Conamet; 2016

Congreso Internacional de Metalurgia y Materiales, 16 Sam-Conamet

Simultaneous cyclic voltammetry (CV) and surface resistance (SR)measurements were employed to study the electrochemical behaviour of the nickelhydroxide-gold modified electrode. To this end, firstly, gold film electrodesof different thicknesses were synthesized, and their CV and SR responses withinthe potential regions corresponding to hydroxide ion adsorption (OHads)and gold oxide (AuO) formationin alkaline medium were analysed. Then, these gold film electrodes weremodified with different nickel hydroxide surface coverages, and their CV and SRresponses were compared with those of bare gold films within the same potentialregions and electrolyte solution. While cyclic voltammetric responses of thebare gold film electrode and the nickel hydroxide-gold film modified electrodeare practically the same within the whole potential range -0.5 V < E < 0.35 V (SCE), SR responses arethe same only within the potential range -0.3 V < E < 0.35 V. Strong differences between the SR responses of thebare gold electrode and the nickel hydroxide-gold modified electrode within thepotential range comprised between -0.5 V and -0.3 V are observed. SR data wereinterpreted in terms of the field effect and size effect theories formulated tostudy adsorption processes at thin metallic films. With regard to the bare goldfilm electrode, the field effect theory allows one to conclude that within the potential region corresponding tohydroxide ion adsorption, 77% of the electron density charge of gold isinvolved in the hydroxide ion?gold interaction. Besides, a linear relationbetween the surface resistance change (DR)and the degree of oxidation (θox) at fixed gold filmthickness (fm) isobtained within the potential region corresponding to gold oxide formation. Inagreement with the size effect theory, the DR/θoxslope exhibits a linear dependence 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),an increase of the surface resistance is observed for the nickel hydroxide-goldmodified electrode, which was attributed to nickel adatoms that directly interactwith the gold film surface. On the basis of the electron conductionscattering model employed to describe the interaction of a metal film surfacewith a foreign atom layer, one can conclude that nickel film growth involves an initial stage in which nickelislands and then, compact structures are formed.