Seeking a Structure–Function Relationship for γ‑Al₂O₃ Surfaces

The surface of γ-Al₂O₃ is perhaps the most exploited surface in chemistry. It is used as a catalyst and as a catalyst support. Its porosity is often evoked as the key quality of this material. However, an atomic-level understanding of this system has yet to be achieved, in most part because of the plethora of microscopic realizations of this surface. The atomic-level understanding of γ-Al₂O₃ surfaces is arguably essential to predict and explain how catalytic and catalytic support properties arise. In this work we aim to characterize the influence of various surface formations that we induce in several surface models (e.g., dehydrated, partially hydroxylated, and terminated with aluminum atoms) by carrying out pseudopotential DFT simulations. By computing surface electronic density of states, OH/H₂O/H₂ binding energy, and work functions, we extract a picture of the effects that varying surface coverages, surface adsorbents, and the surrounding environment have on stability, morphology, and position of the Fermi level (via the work function). We show that surface morphological variations can induce significant changes in work function and surface dipole, particularly in regards to the surface oxidation level. Our results offer a new perspective on the surface morphology of γ-Al₂O₃ aimed at understanding structure–electronic properties relationships, e.g., by shedding light on a nonadditive/synergistic effect for water adsorption on γ-Al₂O₃.