ELECTROCHEMICAL-BEHAVIOR OF SURFACE-MODIFIED GLASSY-CARBON ELECTRODES OBTAINED BY ELECTROCHEMICAL TREATMENT - ITS EFFECT ON THE OXIDATION OF AROMATIC-AMINES IN AQUEOUS-MEDIA

The fundamental aspects that condition the electrochemical response of glassy carbon (GC) electrodes are the bulk properties and the surface treatment. In previous work we reported an electrochemical treatment in 1 M H2SO4. It consisted of cycling the electrode between -0.50 and 1.86 V (vs. SCE). The same procedure is used in this work. This treatment allowed us to obtain reproducible surfaces, with higher selectivity for the formation of functionalities, and these electrodes behave as essentially film-modified glassy carbon electrodes (MGC). A simple way to obtain well characterized MGC electrodes is described. Also, an investigation of the influence of the GC electrode treatment in the electro-oxidation of N,N-dimethyl-1-naphthylamine (DMN) in acidic aqueous media is reported. DMN undergoes an electrochemical-chemical-electrochemical (ECE) reaction to give its oxidized dimer, TMN2+. At the untreated electrode only TMN is adsorbed, but both reactant and product were found to adsorb at MGC electrodes. The nature of the adsorption process and the characteristics of the electrode in the adsorbed state were studied in detail. The amount of adsorbed DMN was correlated with the degree of activation. The adsorption of TMN follows Frumkin's type of isotherm with a repulsive interaction parameter.