Sensing mechanism of SnO2(1Â 1Â 0) surface to H2: Density functional theory calculations

Using density functional theory, we investigate the H2-sensing mechanism of SnO2(1 1 0) surfaces to understand the H2-sensing behaviors of SnO2 surfaces with different reduction degrees and their sensing mechanism at the atomic level. We found that oxygen concentration in the ambient atmosphere greatly affects the H2-sensing mechanism of SnO2 surface. At considerable high oxygen concentrations H2 interacts with oxygen species pre-adsorbed onto SnO2(1 1 0) surface, leading to electron release back to the semiconductor SnO2. When interacting with O2−, H2 gas dissociates with one H atom to form hydroxyl adsorbed onto Sn site and another H atom adsorbed onto the oxygen atom of pre-adsorbed O2−; when interacting with the O−, H2O molecule is formed in the production. At very low oxygen concentration, structural reconstruction is induced by the interaction between H2 and SnO2 sub-reduced surface with removed twofold-coordinated bridging oxygen rows, accompanying electron transfer from H2 to surface without H2O formation. The above-calculated results are consistent with the experimental observation.