Tunable properties and composition of ZnO films supported on metal surfaces

Abstract

Oxide overlayers covering metal supports find applications in sensors, catalysis, microelectronics, and optical devices. For example, depending on the choice of metal support, ZnO films may serve as sensors for hydrogen or ethanol and exhibit catalytic activity in CO oxidation or methanol synthesis, which is catalyzed in the chemical industry by intensely studied Cu–ZnO catalysts. Here, we apply density functional (DFT) calculations to characterize the properties of periodic ZnO monolayers supported on close-packed surfaces of various metals (Mo, Ru, Pd, Pt, Cu, Ag, Au, Sn, and Pb) under oxidative, ambient, and hydrogenation conditions. Thermodynamic analysis revealed high stability of the films on most metals, except highly reactive Mo and insufficiently reactive Sn and Pb. Metal–oxide interactions are found to have a significant and locally uneven effect on the electronic structure of ZnO. Compared to pristine ZnO, the supported ZnO films show a higher propensity for H adsorption and O vacancy formation, whose energies may be tuned by more than 1 eV depending on the choice of metal support. As a result, under hydrogenation conditions supported ZnO films are calculated to adsorb significant quantities of H or develop O vacancies, unlike pristine ZnO. The calculations reveal how the composition, stability and reactivity of ZnO films are affected by the metal support and provide guidelines for the rational design of ZnO–metal interfaces.