ELECTROCATALYTIC REDUCTION OF NITRIC-ACID AT RHODIZED ELECTRODES AND ITS INHIBITION BY CHLORIDE-IONS

The electrocatalytic reduction of nitric acid was studied at rhodized electrodes with low (10-25) roughness factor values in 1 mol dm(-3) H2 SO4 supporting electrolyte, A simple logarithmic current vs. potential relationship was found for the cases where the role of transport proc esses could be neglected. Consequently, a simple charge transfer react ion could be considered as rate determining step. The inhibition of th e reduction process by the adsorption of chloride ions was studied and it was shown that the potential and concentration dependent adsorptio n of Cl- species triggers potential oscillations under galvanostatic c onditions. Similar oscillatory behaviour was observed under open circu it conditions in a hydrogen atmosphere, ie the oscillation of the mixe d potential of two coupled reactions, the reduction of nitrate and oxi dation of molecular hydrogen, takes place.