Mixed-potential type NO sensor using stabilized zirconia and MoO3–In2O3 nanocomposites

Abstract Highly sensitive mixed-potential-type NO2 sensors based on yttria-stabilized zirconia (YSZ) electrolyte and In2O3–MoO3 nanocomposite electrode were fabricated. The In2O3 doped with 2%, 5%, 10% MoO3 and pure In2O3 were synthesized by sol–gel method, and these materials were applied to sensing electrode (SE). The effects of doping amount of MoO3 on NO2-sensing properties were investigated. It was found that the sensor using In2O3 sensing electrode doped with 5 wt% MoO3 exhibited larger sensitivity to NO2 in the range of 10–200 ppm than the other sensors using In2O3 doped with 0%, 2% and 10% MoO3. The sensor using In2O3 sensing electrode doped with 5% MoO3 showed high sensitivity (59 mV/decade), good stable and repeatable performance at elevated temperature. The electric potential difference (ΔV) of the sensor varies almost linearly with the NO2 concentrations in the examined range of 10–200 ppm. Moreover, it is noteworthy that the influence of relative humidity on NO2 sensitivities at 500 °C is little. Combined with the XRD analysis, XPS analysis, ICP analysis of the sensing materials and modified-polarization curves of the sensors, it could be speculated that the MoO3, doped to the In2O3 sensing electrode, plays a significant role in sensing performance, and a possible mechanism for the improvement of NO2-sensing properties was proposed here.