Atomic-level Insights into Selective Adsorption of H2 and CO on SnO2/CoO Heterojunctions

Chemical resistive gas sensors prove that the interface effect of p-n heterojunction can afford a convinced gas selectivity. However, the effects of heterojunction on the sensor selectivity are still blurred and indistinct. In this study, based on the lattice mismatch theory and the adhesion function, SnO2(100)/CoO(110) and CoO(110)/SnO2(100) nanomaterials are structured to insight their sensing properties for H2 and CO gases at nanoscale by first principles. The adsorption energy, adsorption distance, and the d-band center reveal the stability of H2 and CO on the heterojunctions. Interestingly, the density of states reflects that the heterojunctions show an n-type response to CO and a p-type response to H2. When H2 and CO are adsorbed on CoO(110)/SnO2(100)-O2, there is a strong bond between CO and O2, while the chemical bond between H2 and O2 is weak according to electron density. Consequently, heterojunctions have a high selectivity to CO over H2. This work provides meaningful theoretical insight into the selective adsorption of reducing gases by heterojunctions.