First-principles study of NOx and SO2 adsorption onto SnO2(110) and SnO2 nanoparticles

Abstract

An ab initio study of the adsorption of NOx and SO2 onto SnO2(110) surfaces is presented and related to gas-sensing applications. Using first-principles calculations (DFT-GGA approximation) the most relevant NO and NO2 adsorptions are analyzed by estimating their adsorption energies and charge transfers. The resulting values are compared with experimental desorption temperatures for NO and NO2. The adsorption of the poisoning agent SO2 is also analyzed. Optimum SnO2 working temperatures for minimum SO2 poisoning in NO2 sensing applications are discussed from the perspective of adsorption. In all cases, we observe that the surface reduction state has noticeable consequences on adsorption strength. We also present an ab initio thermodynamics study to analyze the stability of several surface reduction configurations with respect to the ambient oxygen partial pressure and the temperature of the material. Finally, the interaction of NO2 with spherical SnO2 nanoparticles smaller than 2nm is considered.