Catalyst-induced gas-sensing selectivity in ZnO nanoribbons: Ab-initio investigation at room temperature

The functionalization of ZnO nano-ribbons (ZnO-NRs) to yield gas-sensing selectivity is theoretically investigated. Transition metals (e.g., Pt, Pd, Fe, Ag, Au) are used as catalyst adatoms on ZnO-NRs and tested against their propensity to selectivity sense pollutant gases such as: H₂, H₂S and CO₂. The computational method, based on a combination of density-functional theory (DFT) with non-equilibrium Green's function (NEGF) formalism, is used to probe both the adsorption and the transport properties, essential in the study of the gas-sensing response. The results show that both Pt and Pd have poor selectivity toward any gas at room temperature (RT). This is consistent with experimental reports that selectivity can be achieved only at high temperatures (e.g., T ≈ 400 °C in case of Pt catalyst). On the other hand, the selectivity towards H₂S can be achieved using either Ag or Au and towards CO₂ using Fe, at RT. These latter results are further corroborated with experimental evidence.