Selectivity Enhancement of YSZ-based VOC Sensor Utilizing SnO_2/NiO-SE via the Application of a Physical Gas-diffusion Barrier

摘要

The sensing characteristics of an yttria-stabilized zirconia (YSZ)-based gas sensor utilizing an SnO_2/NiO(+Al_2O_3) sensing-electrode (SE) were evaluated, with aspirations of selective ppb level detection of indoor volatile organic compounds (VOCs). The fabricated sensor gave a preferential response towards 50 ppb C_7H_8 (toluene), while exhibiting negligible responses towards interfering gases (C_3H_6, H_2, CO, NO_2, C_2H_5OH (ethanol)) at their average atmospheric concentrations. However, it was observed that toluene detection was strongly affected by high concentration ethanol, which can peak to approximately 10 times higher in concentration in indoor environments, owing to the ubiquitous use of alcohol in beverages, cooking and cleaning products. To overcome this limitation, a physical gas-diffusion barrier which was comprised of nano-Al_2O_3 particles was formed on the exposed edges of the NiO-SE, which assisted in the effective oxidation of ethanol in the SnO_2 catalytic layer, by avoiding direct penetration of ethanol into NiO-SE. The developed YSZ-based sensor utilizing an SnO_2/Al_2O_3/NiO(+Al_2O_3)-SE was found to be capable of selectively detecting aromatic VOCs lower than the indoor guideline concentrations, with low interference from high ethanol concentrations.