We report for the first time a novel electrochemical treatment applied to a glassy carbon electrode (GCE) during p-nitrophenol (PNP) oxidation and dedicated to the limitation of electrode passivation by nitrophenol compounds oxidation. We propose an electrochemical process of direct phenol oxidation by starting the electrolysis at a very low potential, −1.2 V/SCE, in order to generate a soluble monomer, p-aminophenol, on the electrode surface. Then, p-aminophenol elaborated on the electrode surface in the place of oligomers, gives benzoquinone as a by-product and no film formation was observed. Furthermore, the presence of a p-NiTSPc (film of nickel tetrasulfonated phtalocyanine) coating permitted to increase two times the electrode sensitivity without passivation, too.