Synthesized carbon-supported Pt nanoparticles (10 wt% Pt/C) and their commercial counterpart (40 wt% Pt-Etek/C) have been used to study the electrochemical reduction of NOx- ions at different concentrations in alkaline and acid pH. A comparative study between nanostructured and massif platinum was evaluated. Cycling Voltammetry (CV), Rotating Disc Electrode (RDE) and Differential Mass Spectrometry (DEMS) were used for this purpose. Stationary current-potential curves indicate that the adsorption-desorption phenomena take place in two different regions of potential: the electrochemical reduction of NOx- ions for potentials ranging from -0.60 to -0.95 V/SCE, and the hydrogen evolution reaction (HER) at potential lower than -0.95 V/SCE. These results confirmed that the reduction of NOx- ions follows the order Pt/C > Pt-Etek/C > Pt-massif. DEMS demonstrated the formation of nitrogen species such as N2, NO, N2O and NO2.