Efficient ppt-Level H₂S Gas Sensor Based on YSZ and α-Fe₂O₃ Nanofoam Sensing Electrode

Herein, porous α-Fe₂O₃ nanofoam was successfully synthesized and used as a sensing electrode to fabricate a yttria-stabilized zirconia (YSZ) mixed-potential hydrogen sulfide (H₂S) sensor for real-time monitoring of hazardous H₂S gas. The sintering temperature was adjusted to modify the microstructure of the sensing electrode material and its electrochemical reaction intensity to H₂S, enhancing the sensor's performance. Among the tested materials, α-Fe₂O₃ nanofoam sintered at 800 °C exhibited the highest electrochemical catalytic activity toward H₂S in electrochemical tests, suggesting its suitability as a sensing electrode material for YSZ-based H₂S sensors. The sensor incorporating α-Fe₂O₃ nanofoam sintered at 800 °C achieved the highest response of -273 mV to 10 ppm of H₂S at 625 °C. Moreover, this sensor exhibited a low detection limit of 100 ppt and, within the H₂S concentration range of 0.5-10 ppm, a high sensitivity of -180.3 mV/decade, outperforming other reported YSZ-based H₂S sensors. Furthermore, this fabricated sensor exhibited excellent repeatability, selectivity, and long-term stability, indicating its potential for industrial safety early warnings and precise environmental monitoring. This study provides a valuable reference for designing porous sensing electrode materials and enhancing the sensing performance of mixed-potential gas sensor.