Thin films of amorphous nitrogenated carbon a-CN_x: Electron transfer and surface reactivity

The electrochemical behaviour of thin films of nitrogenated amorphous carbon a-CN_x is similar to that of boron-doped diamond, with a wide potential window in aqueous media. They are elaborated by cathodic sputtering of a graphite target in an Ar-N₂ active plasma for varying nitrogen contents, determined by XPS (0.06 ≤ x ≤ 0.39). Their electrochemical reactivity is sensitive to the surface state. The present study reports on the influence of electrochemical pre treatment on the electronic transfer rate of a fast redox system ferri-ferrocyanide, by focusing on the direction of the potential excursion. On the other hand, the role of both the pH and the potential on the interfacial capacitance in the presence of Na₂SO₄ without redox species is documented. The results show up the sensitivity of the film surface to the electrochemical conditions