ELECTROCHEMICAL-BEHAVIOR OF SURFACE-MODIFIED GLASSY-CARBON ELECTRODESOBTAINED 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 treatm ent allowed us to obtain reproducible surfaces, with higher selectivit y for the formation of functionalities, and these electrodes behave as essentially film-modified glassy carbon electrodes (MGC). A simple wa y to obtain well characterized MGC electrodes is described. Also, an i nvestigation of the influence of the GC electrode treatment in the ele ctro-oxidation of N,N-dimethyl-1-naphthylamine (DMN) in acidic aqueous media is reported. DMN undergoes an electrochemical-chemical-electroc hemical (ECE) reaction to give its oxidized dimer, TMN2+. At the untre ated electrode only TMN is adsorbed, but both reactant and product wer e found to adsorb at MGC electrodes. The nature of the adsorption proc ess and the characteristics of the electrode in the adsorbed state wer e studied in detail. The amount of adsorbed DMN was correlated with th e degree of activation. The adsorption of TMN follows Frumkin's type o f isotherm with a repulsive interaction parameter.