Atmospheric Dependence of Thermoelectric Generation in SnO₂ Thin Films with Different Intergranular Potential Barriers Utilized for Self-Powered H₂S Sensor Fabrication

Abstract

The profound contribution of grain boundaries to the Seebeck voltage generation in the polycrystalline semiconductors has recently been stated. Considering the direct link between the chemiresistive sensitivity and intergranular energy barrier, the “chemithermoelectric” (CTE) effect follows as the interrelating effect. Here, we compare the magnitude of the CTE effects in SnO2 thin films with different intergranular potential barriers and show that the Seebeck coefficient and CTE magnitude are both linearly related to the experimentally determined charge conduction barrier height. It is shown that exposing the samples to the H2S-contaminated air at elevated temperatures reversibly modifies the barrier height and, hence, the Seebeck voltage generated along the sample at the presence of a constant temperature gradient. The demonstrated effect is utilized for the fabrication of the first CTE-based H2S sensor. Safety regulations regarding this highly hazardous gas are tight and the presented device provides safer monitoring of the surrounds than its chemiresistive counterpart; natural aging brings its output closer to the alarming level preventing silent failure. Powered by a temperature gradient, the device detects the presence of sub-parts per million H2S concentrations in air requiring no electrical power source for operation.

Nanometer-Thick ZnO/SnO2 Heterostructures Grown on Alumina for H2S Sensing

“…The gas response of the sensor in pure SnO 2 can be originated from the homojunction barrier of the intergranular barrier in SnO 2 . 20 In the air atmosphere, the adsorption of oxygen molecules in the form of O 2 – , O – , and O 2– generates an electron depletion layer at the surface, resulting in a decrease in conductivity. 4 Upon exposure to the target gas, the reaction between H 2 S molecules and oxygen preadsorbed species on the surface of SnO 2 can return electrons to the conduction band.…”

“…The gas-sensing mechanism of ZnO/SnO 2 heterostructures could be described by the surface depletion and grain boundary mechanism. The gas response of the sensor in pure SnO 2 can be originated from the homojunction barrier of the intergranular barrier in SnO 2 . In the air atmosphere, the adsorption of oxygen molecules in the form of O 2 – , O – , and O 2– generates an electron depletion layer at the surface, resulting in a decrease in conductivity .…”

“…For gas sensing, there are also many applications for medical and safety purposes as well as environmental monitoring requiring robust, compact, and high-performance H 2 S gas sensors. , It is well-known that polluted air contains dangerous gases, for example, O 3 , CO 2 , CH a , and CO, where H 2 S gas is corrosive and flammable with an infamous rotten egg smell. , Exposure to even low concentrations of H 2 S over a long period of time can cause negative effects on human health such as irritation of the nose, eyes, throat, and respiratory system. , In addition, identifying H 2 S in exhaled breath contributes to the detection of symptoms of a variety of oral diseases such as halitosis …”

“…11,19 Exposure to even low concentrations of H 2 S over a long period of time can cause negative effects on human health such as irritation of the nose, eyes, throat, and respiratory system. 18,20 In addition, identifying H 2 S in exhaled breath contributes to the detection of symptoms of a variety of oral diseases such as halitosis. 21 Nanostructured metal oxides with different morphologies have been utilized for a wide range of applications.…”

Flexible solar and thermal energy conversion devices: Organic photovoltaics (OPVs), organic thermoelectric generators (OTEGs) and hybrid PV-TEG systems

“…Recently, wearable electronics with multi-functional features that can fit the human body curvatures have attracted much attention due to the booming fields of Internet of Things (IoT) and sensor networking [39][40][41]. Wearable devices should be small, lightweight, flexible, and portable [42].…”