YSZ-based NO2 sensor utilizing hierarchical In2O3 electrode

Mixed-potential type YSZ-based sensor utilizing In2O3 as sensing electrode (SE) was fabricated and examined for detection of NO2 at 700 °C. The hierarchical In2O3 oxide material was synthesized via a facile hydrothermal process, and In2O3 sintered at different temperatures were characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The present study mainly focused on the effect of sintering temperature of SE materials (800 °C, 1000 °C, 1200 °C) on NO2 sensing characteristics. As a result, the sensor attached with In2O3-SE calcined at 1000 °C exhibited the largest sensitivity to NO2, which the response to 100 ppm NO2 was as large as126 mV and excellent long-term stability for 30 days tested at 700 °C. It is noteworthy that the NO2 sensitivities for present device showed a small influence by the change of relative humidity at 700 °C. Additionally, the present devices also displayed good repeatability, the excellent sensitivity and relatively good selectivity in conjunction with various interfering gases before and after 30 days high-temperature-aging of 700 °C. It was speculated that the largest sensing performance for the sensor attached with In2O3-SE sintered at 1000 °C was contributed to the special micro-structure of the SE and the highest electrochemical catalytic activity for cathodic reaction of NO2 at the triple phase boundary (TPB).