A kinetic study for electrooxidation of NO gas at a Pt/membrane electrode-application to amperometric NO sensor

The electrochemical oxidation of nitric oxide (NO) gas at a Pt/membrane electrode has been studied. The Pt/Nafion® electrode was prepared by the impregnation–reduction (I–R) chemical plating method and was tested over the NO concentration range from 0 to 500 ppm. It is assumed that the electrooxidation of NO gas at the electrode can be considered as an irreversible process, from which a transcendental equation describing the I–E relationship can be derived. The derived I–E relationship fits the experimental data reasonably well. Several electrochemical parameters for the reaction, including the half-wave potential (E1/2), the standard apparent rate constant (rak0), the transfer coefficient (α), and the exchange current density (i0) can be extracted from the experimental data. Under the kinetic controlled regime, with the potential in the range of 0.7–0.9 V (versus Ag/AgCl/sat. KCl), the kinetic model predicts the electrooxidative behavior of NO at a Pt/Nafion® electrode over a wide concentration range of 100–500 ppm. An amperometric NO gas sensor based on a Pt/Nafion® electrode has been fabricated and tested over the NO concentration range from 0 to 500 ppm at 1.15 V (versus Ag/AgCl/sat. KCl) and a flow rate of 200 ml per min.