DEMS-CYCLIC VOLTAMMETRY INVESTIGATION OF THE ELECTROCHEMISTRY OF NITROGEN-COMPOUNDS IN 0.5M POTASSIUM HYDROXIDE

The electro-oxidation and -reduction of 0.05 M ammonia, 0.01 M hydroxy lamine, 0.01 M sodium nitrite and 0.05 M sodium nitrate in 0.5 M KOH a t Pt-black electrodes has been investigated using a combination of cyc lic voltammetry with on-line MS analysis of volatile products (DEMS). All compounds investigated in this study form adsorbates with very sim ilar properties. These adsorbates can be reduced to ammonia and oxidis ed to nitrogen. Ammonia is adsorbed anodically, while nitrite and nitr ate are adsorbed cathodically. In contrast to the adsorbates of the ot her compounds, adsorbed nitrite can also be reduced to nitrogen oxides in addition to ammonia. The combination of cyclic voltammetry and on- line MS proves that the adsorbates do not consist solely of triple bon ded nitrogen. Ammonia and hydroxylamine also form nitrogen oxides in b ulk oxidation processes. For the first time, a reaction mechanism whic h takes into account the interconversion of nitrogen compounds and ads orbate processes is discussed.