The sensing mechanism of Pt-doped SnO2 surface toward CO: A first-principle study

• The formation of oxygen vacancy is facilitated by Pt doping.
• The adsorption of CO is enhanced by Pt doping.
• The oxidation of CO by the lattice O ion of Pt6c/SnO2 takes place easily.
• The oxidation of CO by oxygen species in the oxygen vacancy takes place easily.

The oxidation process of CO on the Pt-doped SnO2 is studied using first-principles method based on the density functional theory. It is found that the Pt dopant prefers to substitute the 6-fold tin site and induces new electronic states near the Fermi energy, which will lower the electrical resistance of SnO2. The enhanced sensitivity can be attributed to both the chemical and electrical factors. In view of chemical factors, the presence of Pt facilitates the formation of oxygen vacancy and improves the oxygen ion activity, which will promote the CO oxidation. Besides, the adsorption of CO can be promoted by Pt doping, which favor the oxidation of CO. With respect to the electrical factors, compared with the undoped surface, the Pt-doped SnO2 surface get more electrons from the adsorbed CO, which plays roles in increasing the sensor's sensitivity. In addition, the recycle process of the Pt6c/SnO2 surface is investigated.