Improving response performance of impedimetric NO2 sensor using NiO-YSZ mixed conductor porous layer

The mixed conductor porous layer was prepared by introducing the electronic conductor NiO into the oxygen ion conductor YSZ for the impedimetric NO2 sensor. By changing the ratio of YSZ/NiO in the porous layer, the morphology and electron-ion conduction properties of the mixed conductor porous layer were tuned to obtain the high-performance sensing electrode/electrolyte/gas three-phase boundary (TPB) and improve the response characteristics of the sensor. The results show that the number of pores in the porous layer decreases with increasing NiO doping, while the average pore size shows an opposite trend. The results of AC impedance and NO2-TPD measurement show that the introduction of NiO in the YSZ porous layer significantly improves the electrochemical activity of the sensor at TPB and the NO2 adsorption capacity, which in turn improves the sensitivity of the sensor. The sensor based on the YSZ:NiO= 1:0.5 (mass ratio) porous layer exhibits the highest Θ (ΔΘ = 19.13° for 300 ppm) and |Z| (S|Z|=0.35 for 300 ppm) response value. The sensor also has good anti-interference ability. The changes of ΔΘ caused by CH4, CO2, H2, NO and NH3 are 0.6%, 1.6%, − 2.6%, 3.3% and − 2.4%, and the Δ|Z| are 2.5%, 3.2%, − 2.7%, 5.6% and 1.2%. Meanwhile, the humidity has almost no effect on the |Z| and Θ response.