Improvement in Response/Recovery Characteristics of Mixed-Potential-Type Zirconia-Based CO Sensor Using ZnCr_2O_4 Added with Au Particles-Sensing Electrode

摘要

The response/recovery characteristics to CO for a mixed-potential-type yttria-stabilized zirconia (YSZ)-based sensor using a ZnCr_2O_4 and Au nanoparticles composite sensing electrode (ZnCr_2O_4 (+nano-Au)-SE) were improved by tuning the size of the added Au particles. Among SEs tested, the sensor using ZnCr_2O_4 (+subμ-Au)-SE, which is ZnCr_2O_4-SE added with submicrometer-sized Au particles, exhibited faster response to 800 ppm CO than that of ZnCr_2O_4 (+nano-Au)-SE at 550°C under the wet condition. From the results of polarization curve measurements, the addition of Au nanoparticles into the ZnCr_2O_4-SE layer was found to decrease the catalytic activity to the cathodic reaction of O_2, responsible for the slow response/recovery characteristics. After investigating the additive amount of subμ-Au particles aiming at the enhancement of the CO response, it can be concluded that an appropriate additive amount is 5 wt.%. The 90% response/recovery times of the present sensor were significantly improved, and they were less than 30 s.