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

Abstract

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 ( E 1/2), the standard apparent rate constant ( rak 0), the transfer coefficient ( α), and the exchange current density ( i 0) 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.