Abstract : In the present work, the reaction mechanism of nitrate reduction at copper electrode was explored in NaClO4 neutral solution and compared to the results obtained in acidic and alkaline media. Cyclic voltammetry was mainly employed and revealed three separate waves when nitrate ions are introduced into the neutral solution. Rotating disk electrode measurements were carried out and the effect of the potential scan rate was studied in order to further explore the reaction mechanism. The numbers of electrons associated with the reduction peaks were found to be 2, 6 and 8 suggesting nitrate reduction to nitrite, hydroxylamine and ammonia, respectively. Exhaustive electrolyses were performed yielding NO2-, NH2OH and/or NH3 depending on the applied potential. Differential electrochemical mass spectroscopy was also used for the detection of gaseous products. Only N2O was found to be produced at -1.2V/ECS. Some experiments were carried out to shed some light on the origin of the progressive decrease of the cathodic current observed when a one compartment electrochemical cell is used. This deactivation could be attributed to the copper electrode poisoning by adsorbed NO which is produced at the counter electrode due to ammonia oxidation by hydroxyl radicals. Finally, Electrochemical Impedance Spectroscopy (EIS) measurements were performed in the presence of nitrate ions. Nyquist plots revealed an inductive loop which constitutes the signature of an adsorbed intermediate involved in the reduction process. EIS experiments using rotating disk electrode allowed us an accurate determination of nitrate diffusion coefficient at 25°C, subsequently used to determine the number of electrons involved at each step of the nitrate reduction.