A phosphate-based proton conducting solid electrolyte hydrocarbon gas sensor

A potentiometric sensor based on a proton conducting sodium phosphate solid electrolyte was utilized in conjunction with a hydrogenation catalyst to detect methane at 600 °C. By using a two-compartment cell with gold electrodes and H2 gas, it was established that the solid electrolyte behaves as a proton conducting material, exhibiting Nernstian behavior. For sensing methane, Pt/CeO2 was painted onto one of the gold electrodes. Two cell designs, including a two-chamber cell with a reference gas, as well as a planar cell without a reference gas were examined for methane sensing. Pt/CeO2 prepared with colloidal Pt tested on the planar cell showed superior sensitivity to methane. A mixed potential behavior, arising from the combined effect of electrochemical reactions of methane and its oxidation products is proposed to give rise to the methane response.