Room temperature potentiometric sensor for hydrogen sulfide and sulfur dioxide based on a Zn-doped Na3Zr2Si2PO12 electrolyte

In this study, four sodium superionic conductors Na 3 Zr 2-x Zn x Si 2 PO 12 (x=0, 0.1, 0.2, 0.3) were used as solid electrolytes for planar mixed-potential gas sensors (Zn0, Zn1, Zn2, and Zn3 sensors) to detect hydrogen sulfide (H 2 S) and sulfur dioxide (SO 2 ). The total conductivity of the Na 3 Zr 2-x Zn x Si 2 PO 12 electrolyte first increased and then decreased with increasing Zn 2+ doping. When doped with 0.2   mol of Zn 2+ , the electrolyte exhibited the highest total conductivity of 6.37 × 10 -5 S·cm -1 at 25°C, which was 14.2 times higher than that of the undoped electrolyte. At 25°C, the response of the Zn2 sensor to 10 ppm H 2 S was -237.8   mV, which was 6.9, 2.1, and 5.8 times that of the Zn0, Zn1, and Zn3 sensors, respectively. A high response of -58.6   mV was obtained by the Zn2 sensor at 25°C for 0.5 ppm H 2 S. In addition, the sensitivity to H 2 S at 25°C was -150.9   mV/decade. In comparison with reported mixed-potential H 2 S sensors, the Zn2 sensor demonstrated significantly higher response and sensitivity at room temperature. Moreover, the Zn2 sensor responded to 10 ppm SO 2 and H 2 S almost equally at 25°C. The gas sensing behavior was discussed in terms of the variation of sodium ionic conductivity, Na 3 PO 4 phase proportion, and ZnS formation under H 2 S or SO 2 atmosphere. Additionally, taking the detection of H 2 S-contaminated environments as an example, a gas leakage detection and alarm platform based on the Zn2 sensor was designed. This study provides insights into designing and developing high-performance mixed-potential gas sensors for H 2 S and SO 2 at room temperature.