Preferred surface orientation for CO oxidation on SnO₂ surfaces

In the present study, we perform a comparative study on the oxidation mechanism of CO gas molecules on SnO₂ (110), (101), and (100) surfaces. The optimized adsorption configurations show that the adsorption of CO molecules could occur similarly on the three SnO₂ surfaces via two adsorption modes, physisorption of CO on the Sn_5c site that is considered as the first step for CO oxidation, followed by CO chemisorption on the O_2c site resulting in the formation of CO₂ species. Based on the calculated adsorption energies and CO molecule diffusion on SnO₂ surfaces, CO molecule adsorption on the (101) surface exhibits the highest adsorption energy and the lowest reaction barrier for CO oxidation compared to the widely considered (110) surface or the (100) surface. These findings are expected to have a major impact on improving sensing properties toward toxic gas by means of surface-orientation engineering.