Reduction in Ethanol Interference of Zirconia-Based Sensor for Selective Detection of Volatile Organic Compounds

Abstract

We have reported the sensing characteristics of an yttria-stabilized zirconia (YSZ)-based gas sensor using NiO sensing-electrode (SE), aiming at selective detection of indoor volatile organic compounds (VOCs) at ppb levels. However, the detection of toluene (a typical VOCs) is strongly affected by the presence of ethanol which is a common interfering gas in indoor environments. To overcome this issue, both an SnO2 catalyst layer and an Al2O3 gas-diffusion barrier layer were applied on the surface and ends of the NiO-SE, respectively. The barrier layer can facilitate effective ethanol oxidation through the SnO2 catalyst layer by hindering direct penetration of ethanol into the NiO-SE layer. As a result, the fabricated sensor was found to be capable of detecting toluene in several tens ppb level, with low interference from high ethanol concentrations. In addition, the sensor showed selective responses toward aromatic VOCs rather than aldehyde. This behavior was confirmed to be due to the facilitated catalytic oxidation of aldehyde in the SnO2 layer. Furthermore, the present sensor exhibited stable sensitivity and selectivity toward 50 ppb toluene after the 13 days operation examined.