MICROSTRUCTURE AND RESPONSE BEHAVIOR OF ELECTRODES FOR CO2 GAS SENSORS BASED ON SOLID ELECTROLYTES

The response behaviour of electrodes for solid-electrolyte Nernstian C O2 gas sensors is characterized using the pressure-modulation techniqu e. Porous electrodes are formed on Na2CO3/BaCO3 discs. Response times and their dependence on temperature and O-2, CO2 partial pressures are found to differ widely for various electrode materials, For Ag electr odes, diffusion of silver ions into the carbonate bulk causes a slow r esponse and blocking at both high CO2 and O-2 partial pressures. The r esponse of Au electrodes becomes slower at low O-2 partial pressures d ue to a rate-determining reaction step. Pd and Pt electrodes generally show the fastest response, which is only slightly dependent on gas co mposition and is governed by diffusion.