Zinc oxide-based direct thermoelectric gas sensor for the detection of volatile organic compounds in air

Using thermoelectricity as a platform for sensor design and fabrication commercially and historically precedes its power generation aspect, but recent advancements in science and engineering of materials have failed to elevate this platform as the researchers mainly pursue higher figure of merit (zT) materials. It has been shown that thermoelectricity in polycrystalline semiconductors is partly related to the grain boundary effects, and the profound contribution of grain boundaries to the Seebeck voltage (SV) generation has been demonstrated. It immediately follows that all grain boundary-related effects should be detectable via SV measurement, as well. Here, we report the variations of the SV generated at the presence of a constant temperature gradient along a ZnO pellet with respect to the concentration of the various volatile organic compounds (VOCs) in the surrounding atmosphere. The presence of VOCs reversibly reduces the SV generated along the sample. Similar to the case of chemoresistivity, the recorded chemo-thermoelectric responses obey the power law; providing another reason for the common origin of these two apparently distinct phenomena.