Detection of sub-ppm level of VOCs based on a Pt/YSZ/Pt potentiometric oxygen sensor with reference air

Potentiometric oxygen sensors with Pt|YSZ|Pt structure were applied for detecting several volatile organic compounds (VOCs; acetic acid, methylethylketone, ethanol, benzene, toluene, o- and p-xylene) at sub-ppm levels in the temperature range of 400–500 °C. The electromotive force (EMF) output from the sensors linearly changed with logarithm of VOC concentration, and sufficiently large output was confirmed at sub-ppm levels. Among the examined VOCs, ethanol exhibited the highest sensitivity (−54.1 mV/decade) at 400 °C. However, the sensitivity of ethanol drastically decreased at 500 °C. Thus the sensitivity of all the VOCs examined in this study was tunable with temperature. An increase in temperature decreased the sensitivity but effectively modified the response and recovery times. Analysis of multi-dimensional plots combining the sensor outputs at the different operating temperatures (400, 450 and 500 °C) suggested the possibility to discriminate the different VOCs.