Amperometric NO gas sensor in the presence of diffusion barrier: selectivity, mass transfer of NO and effect of temperature

Using various PTFE films as diffusion barriers, the mass transfer of nitric oxide and the selectivity in the amperometric NO gas sensor is studied in this paper. The sensitivities of nitric oxide gas sensor are found to be 1.53, 1.56, 1.48 and 1.46 muA ppm(-1) by using PTFE films with pore sizes of 0.2, 1.0, 5.0 and 10.0 mum as diffusion barriers, respectively, for gas flow rate greater than 160 ml min(-1). The diffusion coefficients of nitric oxide in PTFE diffusion barrier with pore size of 0.2, 1.0, 5.0 and 10.0 mum are found to be 8.57 x 10(-6), 1.00 x 10(-5), 1.33 x 10(-5) and 1.45 x 10(-5) cm(2) s(-1), respectively. The mixing of Knudsen and bulk diffusions is found in the diffusion barrier with 1.0, 5.0 and 10.0 mum pore size and the diffusion of nitric oxide in 0.2 mum pore size of diffusion barrier is mainly contributed by Knudsen diffusion. The sensing current of NO gas sensor is significantly affected by the presence of NO2 and SO2. On the other hand, the interference from the humidity, O-2 and CO in the NO gas sensor is insignificant. (C) 2002 Elsevier Science B.V. All rights reserved.