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

The profound contribution of grain boundaries to the Seebeck voltage generation in the polycrystalline semi- conductors 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.

Automated summary

The study reveals the significant contribution of grain boundaries to the generation of Seebeck voltage in polycrystalline semiconductors, leading to the discovery of the chemithermoelectric (CTE) effect. It is found that the magnitude of CTE effect is linearly related to the intergranular potential barrier height, which can be reversibly modified by exposing the samples to H2S-contaminated air. This effect is utilized for the fabrication of a CTE-based H2S sensor, which requires no electrical power source and provides safer monitoring than traditional chemiresistive sensors.