Compact and planar type rapid response ppb-level SO2 sensor based on stabilized zirconia and SrMoO4 sensing electrode

The planar yttria-stabilized zirconia (YSZ) solid electrolyte based mixed potential type gas sensing devices attached with molybdate MMoO4 (M: Ni, Co, Zn, Mn and Sr) sensing electrodes (SEs) were designed and fabricated, attempting to sensitively and rapidly monitor ppb-level SO2. The sensor using SrMoO4-SE possessed the highest potential response signal of -37.5 mV to 500 ppb SO2 at 550 degrees C. More importantly, the low detection limit of 20 ppb SO2 and fast response time of 37 s to 200 ppb SO2 were presented for the device utilizing SrMoO4-SE at 550 degrees C. The linear dependence between response value and the SO2 concentration logarithm in the range of 0.02-1 ppm was observed, which the sensitivity (slop) was -29 mV/decade. Furthermore, the sensor also showed excellent selectivity, reproducibility and high temperature stability of 7 days to SO2 at 550 degrees C. The mixed potential sensing mechanism was discussed and further verified based on the measurement of polarization curves.