Influence of the sensing and reference electrodes relative size on the sensing properties of Li3PO4-based potentiometric CO2 sensors

Abstract

A potentiometric CO2 gas sensor was developed using thermal evaporated Li3PO4 as the electrolyte and sensing material. Thin-film Au metal electrodes were obtained by using the magnetron sputtering deposition method, and influence of the relative size ratio between sensing and reference electrodes on the characteristics of the sensor was investigated. Results showed that sensor sensitivity error is within ±5% in case of reference electrode equal to or larger than the sensing electrode, but the sensor sensitivity deteriorates from the theoretical value in case of reference electrode smaller than the sensing electrode. Oversized electrode is the factor that results in the deviation of output EMF value in high CO2 concentration, and the ideal width ratio of sensing electrode and reference electrode is 1:2, that is 400μm for sensing electrode and 800μm for reference electrode. The reference electrode area and width ratio of sensing and reference electrode are both considered to be influence factors of the response and recovery time.