Polarization behaviour of nitric acid at rhodized electrodes partially blocked by chemisorbed species

The reduction of nitric acid was studied in 1 mol dm −3 H 2SO 4 at rhodized electrodes partially deactivated by chemisorbed species formed from methanol in order to avoid rate control by transport processes which dominate at low potentials in the overall reaction on a clean electrode. It is demonstrated by cyclic voltammetry and radiotracer study of the adsorption of Cl − ions that chemisorbed molecules formed from methanol 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 blocked electrode are interpreted in terms of mechanisms suggested previously.