Nitrite oxidation on RuO2 electrodes

An electrochemical kinetic investigation of nitrite oxidation to nitrate on RuO2 is discussed. The process is studied by cyclic voltammetry, steady-state measurements and potential step measurements. The overall oxidation reaction is a two-electron process where the first step involves a reversible charge transfer: NO2− ⇔ NO2 + e− The one-electron oxidation of nitrite yields adsorbed NO2 which is further oxidized to adsorbed (NO2)+ and subsequently desorbed via a chemical reaction. In the general case, fit of experimental data is obtained with adsorption described by a Temkin isotherm unless the electrode is pre-treated at a cathodic potential where the (NO2)ads is removed. This treatment lowers the degree of coverage by intermediates but not the nature of the slow step.