Sensor effect theory for the detection of reducing gases

A theory of sensor response to reducing gases in nanostructured semiconducting oxides was developed for the example of SnO2. Donor impurities (oxygen vacancies) provide noticeable electron density in the conduction band. Oxygen atoms, which appear in the adsorption of oxygen on the surface of oxide nanoparticles, are electron traps; they sharply decrease system conductivity. In the adsorption of reducing gases (H-2, CO), oxygen atoms react with them, electrons are released, and conductivity increases; this is the sensor effect. A kinetic scheme corresponding to the picture described above was constructed, and the corresponding equations were solved. As a result, the dependences of sensor sensitivity on temperature, hydrogen pressure, and the mean size of oxide nanoparticles were obtained. The dependences satisfactorily described the literature experimental data.