First-principles calculations on the resistance and electronic properties of H adsorption on a CoO-SnO heterojunction surface.

Compared with pure metal oxides, heterojunctions greatly change the response to gas by the synergistic effect of the interface. In this work, density functional theory was used to reveal the adsorption performance of H on the heterojunction under oxygen conditions. First, we determined the most reasonable heterojunction structure based on the adhesion work. According to the adsorption energy, the presence of SnO100)(I)/CoO(110)(II) made the adsorption of H more stable. The DOS results showed that the resistance of the heterojunction increased with H adsorption, following the same trend as that of CoO(110) with H adsorption, although that of the heterojunction increased more. The electron density and electron density difference indicated that the heterojunction improved the reaction between H and oxygen ions on CoO(110). However, the resistance of CoO(110)(II)/SnO(100)(II) increased after H adsorption, contrary to the resistance change of SnO(100). Besides, the bonding energy between H and the adsorption site became worse. The above results demonstrated that the presence of the heterojunction could indeed change the response trend and the adsorption behavior of H. Interestingly, the adsorption sites and effects of H were different when two metal oxides were used as the substrate of the heterojunction, respectively.