NO₂ properties that affect its reaction with pristine and Pt-doped SnS₂: a gas sensor study

The reaction of NO₂ with pristine and Pt-doped SnS₂ surfaces is investigated theoretically and compared with the experiment. Transition state theory formalism for gas sensors is adopted to present NO₂ gas sensing. The dissociation temperature at approximately 150 °C is found to be of great importance in NO₂ reactions. The adsorption and transition states of NO₂ with pristine and Pt-doped SnS₂ are calculated. Pt doping includes 0.5, 1, and 1.5% in accordance with available experimental results. The variation of thermodynamic quantities such as Gibbs free energy with Pt concentration and temperature is calculated. Transition state theory parameters that are suitable for the present sensor are determined. The results include the variation in response time with temperature, Pt concentration, and NO₂ concentration. Response and response time as a function of temperature are rarely investigated in theoretical calculations, which is one of the advantages of the present study. Optimum response temperature and Pt concentration are found. The results agree with available experimental results.

Density functional theory at the B3LYP level optimize molecular structures. 6-311G** basis set is used for all elements except Sn and Pt treated using SDD basis set. Gaussian 09 program and its facilities are used to perform present optimizations.