Electrochemical reduction of O2 and NO on Ni, Pt and Au

The electrochemical reduction of oxygen and nitric oxide was studied using cyclic voltammetry on point electrodes of Ni, Pt and Au in the temperature range 400–600 °C. All the materials were more active towards the reduction of oxygen than towards the reduction of nitric oxide, except Pt at 400 °C. As a general trend it was observed that the activity of the materials towards the reduction of oxygen increases more than the activity of the materials towards the reduction of nitric oxide with increasing temperature. The Ni wire was covered with a layer of NiO. The NiO layer inhibits the reduction of both nitric oxide and oxygen. No sign of the formation of an oxide layer on the platinum and gold wires was observed. Pt was the most active electrode material towards the reduction of nitric oxide. Au showed almost no activity towards the reduction of nitric oxide, but Au was active towards the reduction of oxygen. This implies that the triple-phase boundary (3PB) catalyses the reduction of oxygen but not the reduction of nitric oxide, as Au is a catalytic inactive metal. All the materials were more active towards oxidation than towards reduction that is evolution of oxygen or oxidation of nitric oxide to nitrogen dioxide was more pronounced than the reduction reactions.