A New Insight into Cross-Sensitivity to Humidity of SnO2 Sensor.

The efficiency of gas sensors varies enormously from fundamental study to practical application. This big gap comes mainly from the complex and unpredictable effect of atmospheric environment, especially in humidity. Here, the cross-sensitivity to humidity of a SnO2 sensor from local structural and lattice evolutions is studied. The sensing response of ethanol is found to be efficiently activated by adsorbing trace of water but inhibited as humidity increases. By X-ray diffraction, pair distribution function of synchrotron and ab initio calculations, the independent effect of water and ethanol on lattice and local structure are clearly revealed, which elucidate the intricate sensing reactions. The formation of hydrogen bonds and repulsion of ethoxides play key roles in the structural distortions, and also in adsorption energies that are critical to the sensitive behavior. The results show the sensor performance coupled with local structural evolution, which provides a new insight into the controversial effects of humidity on SnO2 sensors.