Detection of Nitrate/Nitrite Using BDD Electrodes Coated with Metal Nano-Catalysts

The aim of this work is to investigate the mechanisms of nitrate and nitrite ions electroreduction in neutral solution at boron doped diamond (BDD) electrodes modified with metal catalyst nanoparticles. The electrode preparation consists in sputtering a thin metal layer onto polycrystalline BDD by a physical vapor deposition method, followed by a dewetting heat treatment at 700 °C under oxygen-free atmosphere. Such a process leads to a stable population of nanosized metal particles as characterized by scanning electron microscopy (SEM) and cyclic voltammetry. Electro-reduction of NO2− and NO3− was characterized both on a bare BDD electrode and on BDD electrodes decorated with platinum-gold, ruthenium-gold and ruthenium nanoparticles in the range 4 to 25 mM. The amperometric response was enhanced by the presence of the nanoparticles, the most sensitive electrode being Pt-Au/BDD and Ru-Au/BDD for nitrite and nitrate ions, respectively.