A rule for operation temperature selection of a conductometric VOC gas sensor based on ZnO nanotetrapods

Abstract

The performance of conductometric gas sensors depends critically on the operation temperature. However, it remains unclear how the characteristics of gas may require a shift in the operation temperature to achieve the best detection performance. In this work, we studied the effects of temperatures on the selectivity and response of a ZnO nanotetrapod (NTP)-based sensor using four common volatile organic compounds (VOCs). Our experiments revealed that the optimal detection temperatures for formaldehyde and acetone are the lowest and highest, respectively, among formaldehyde, ethanol, methanol and acetone. Selectivity shifts from formaldehyde to ethanol before and after 260 ℃. More interestingly, temperatures for optimizing the response magnitude and selectivity to formaldehyde are different: 260 ℃ and 100 ℃. A theoretical explanation is proposed that is primarily associated with chemical bonds and electrons involved in gas redox reactions. Ultimately, we proposed a temperature selection rule based on the molecular structure of the target gas to compromise between selectivity and response magnitude. For maximizing the response magnitude, the gas with a larger molecular structure requires a higher temperature. For optimizing the selectivity, low temperatures favor selectivity to smaller molecules with fewer and weaker bonds. This work might facilitate multifunctional gas sensor development.