Multiscale modelling of gas sensors response to mixture of CO, CO2 and H2O exposure

International audienceMetal oxides such as tin oxide (SnO 2) are widely used for gas sensing applications, particularly in environmental applications. The change in the resistance of the sensing layer is the detection principle of the gas sensors. The variations of the resistance are due to the charge transfers resulting from the chemical reactions which occur at the surface of the tin dioxide sensitive layer. In this work, a multiscale approach is developed in order to model interactions of SnO 2 with various gases, such as CO and CO 2. Ab initio calculations are systematically used to identify and characterize, at the atomic scale, the chemical reactions occurring at the surface of the sensitive layer of the sensor. Structures and activation energies associated to surface reactions, and charge transfers characteristics of each surface species, are determined. To simulate the sensors behaviour on a wider scale, a mesoscopic model based on the ab initio results and a chemical rate theory technique is developed. This model gives the temporal evolution of the sensors response as a function of external parameters. This methodology, combining ab initio calculations and mesoscopic model, leads to a better understanding of the macroscopic gas sensor behaviour. We identify the SnO 2 reduction by CO, the catalytic oxidation mechanism of CO involving successive reduction and reoxidation of the oxide layer and the tricky detection of CO 2 gas as a function of external parameters like humidity