Mitigating alcohol inhibition of oxide chemiresistors: bilayer sensors with HZSM-5 zeolite overlayers

Mitigating ethanol inhibition in chemiresistors is essential for accurately detecting target gases in various fields. Conventional approaches to reducing ethanol interference frequently result in a significant deterioration of sensing capabilities, including decreased target gas response, altered selectivity, and sluggish response kinetics. In this study, a coating of acidic proton form ZSM-5 (HZSM-5) overlayer is proposed as a facile and universal strategy for eliminating ethanol inhibition without compromising intrinsic sensing properties. An HZSM-5 overlayer deposited on the oxide sensors exhibits exceptional formaldehyde (HCHO), which poses harmful health impacts to humans even at trace levels, detection properties by effectively eliminating ethanol interference without altering the HCHO response or response time. The exceptional performance of the bilayer sensor is systematically explained by the dehydration of ethanol to less reactive ethylene by the acidic HZSM-5 overlayer. Analysis using NH₃ temperature-programmed desorption (NH₃-TPD), proton transfer reaction quadrupole mass spectrometry (PTR-QMS) as well as in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) are performed to verify the above proposals. Additionally, sensor arrays are employed to enable pattern recognition capable of shielding HCHO, benzene, toluene, and p-xylene from ethanol interferents, thereby facilitating the electronic noses for monitoring indoor air pollutants.