La chromites and Au/oxide composites as HC sensitive electrode materials for mixed potential solid-state sensors

摘要

New electrode materials for the in situ measurement of low HC-concentrations in exhaust gases or air quality control were tested on solid electrolyte sensors in different diluted combustible gases. The electrodes show stable responses in lean and rich mixtures as well. The potential response correlates with the catalytic activity. Highest sensitivities were found for composite electrodes made of Au/Nb_2O_5 in toluene. Oxygen stoichiometry measurements show that this oxide responds very fast to changing oxygen partial pressures indicating that the surface has high defect densities. The sensitivity of the investigated materials to the different combustible gases differs steeply and highly selective HC-sensors could be developed by the combination of different electrodes in one sensor. It is possible to construct gas symmetrical solid electrolyte sensors with mixed potential behaviour using perovskites and composites as measuring electrodes and Pt as reference electrodes in exhaust gases where rich conditions can occur. Ag reference electrodes are suited for sensor applications of air quality control with lean conditions and stable oxygen partial pressures.