Electrocatalytic oxidation of nitric oxide at TiO2–Au nanocomposite film electrodes

Structured films of TiO2 (anatase) nanoparticles (ca. 6 nm diameter) and gold nanoparticles (nominal 20 nm diameter) are formed via a layer-by-layer deposition procedure. TiO2 nanoparticles are deposited with a Nafion polyelectrolyte binder followed by calcination to give a mesoporous thin film electrode. Gold nanoparticles are incorporated into this film employing a poly(diallyldimethylammonium chloride) polyelectrolyte binder followed by calcination to give a stable mesoporous TiO2–gold nanocomposite. This methodology allows well-defined and structured films to be formed which are re-usable after a 500 °C heat treatment in air.Electrochemical experiments are performed in aqueous KCl and buffer solutions and for the oxidation of nitric oxide, NO, and nitrite in phosphate buffer solution. It is shown that the NO oxidation occurs as a highly effective electrocatalytically amplified process at the surface of the gold nanocomposite probably with co-evolution of oxygen, O2. In contrast, the oxidation of nitrite to nitrate occurs at the same potential but without oxygen evolution. A mechanistic scheme for the amplified NO detection process is proposed.