Improved sensing performances of NO2 sensors based on YSZ and porous sensing electrode prepared by MnCr2O4 admixed with phenol-formaldehyderesin microspheres

The phenol-formaldehyde (PF) resin microspheres were firstly used as the template in the sensing electrode (SE) preparation process of sensors based on Y 2 O 3 stabilized ZrO 2 (YSZ). The PF resin microspheres were synthesized by a facile hydrothermal method. The high char yield and the few morphological changes of PF resin microspheres before and after sintering at 900 °C indicated the perfect thermal stability at high temperature. The sensors using MnCr 2 O 4 admixed with various contents PF microspheres (0 wt%, 5 wt%, 10 wt%, and 20 wt%) were fabricated and their sensing performances on NO 2 gas were also investigated. The sensor with sensing electrode prepared by MnCr 2 O 4 with 10 wt% PF showed the best NO 2 sensing performance with a response of 110.8 mV to 100 ppm NO 2 as well as the higher sensitivity (87.4 mV/decade) with the NO 2 concentration ranging from 10 to 500 ppm at 550 °C. According to the mixed-potential mechanism, the porous electrode is good for gas penetration, so the gas can easily reach the MnCr 2 O 4 /YSZ/gas triple phase boundary (TPB) to participate in the electrochemical reactions. Additionally, the sensor exhibited excellent selectivity and repeatability, which indicated its potential application in the NO 2 detection.