POLARIZATION BEHAVIOR OF NITRIC-ACID AT RHODIZED ELECTRODES PARTIALLYBLOCKED BY CHEMISORBED SPECIES

The reduction of nitric acid was studied in 1 mol dm(-3) H2SO4 at rhod ized electrodes partially deactivated by chemisorbed species formed fr om methanol in order to avoid rate control by transport processes whic h dominate at low potentials in the overall reaction on a clean electr ode. It is demonstrated by cyclic voltammetry and radiotracer study of the adsorption of Cl- ions that chemisorbed molecules formed from met hanol are ideal blocking agents as no change in their coverage occurs in the potential range where the reduction of nitric acid takes place. The observed kinetic relationship and the appearance of a minimum (a maximum in the reduction rate) on the polarization curve at the blocke d electrode are interpreted in terms of mechanisms suggested previousl y. Copyright (C) 1996 Elsevier Science Ltd