STUDY OF THE FACTORS AFFECTING MASS-TRANSPORT IN ELECTROCHEMICAL GAS SENSORS

The effect of various diffusion barriers on the mass transport control led current for an amperometric gas sensor with a porous membrane is c onsidered, A general equation is derived which relates the total curre nt to the diffusion parameters for each barrier, By varying the thickn ess of one barrier at a-time, keeping all the other parameters constan t, the relative roles of each of the barriers can be determined, This is done for CO and H2S sensors and in both bases it is shown that more than 70% of the transport control is provided by the electrolyte film in the porous electrode/membrane. This conclusion is supported by obs ervations of the temperature dependence of the sensor currents. It is concluded that, in order to obtain more consistent and reproducible re sults from porous membrane covered amperometric gas sensors, a more co ntrollable method of electrode manufacture and assembly would be desir able.