Facile Gram-Scale Synthesis of Size-Tunable MgO Nanosheets Enclosed by (111) Surface with Remarkable Stability and Uniform Host Sites for Atom Dispersion

MgO has long been utilized as a catalyst/support with Lewis base properties in the chemical industry, but its synthesis with exposed (111) surfaces has received relatively little attention compared to those of (110) and (100) surfaces. The unique adsorption energy of this surface for adsorbates also remains elusive. Herein, we present a simple and scalable method for the production of MgO nanosheets exposing the (111) surface (denoted as MgO(111) NSs). This is achieved through the topotactic conversion of Mg(OH)2 NSs at elevated temperatures in an air environment. By adjusting the precursor ratio and the strength of the base, we successfully prepared Mg(OH)2 NSs consisting of approximately 6 atomic layers with lateral sizes ranging from 80 nm to 1 μm in a single step. Subsequent thermal dehydration yields MgO(111) NSs with a preserved dimension. Using Ru as the adsorbate, we found that the remarkable stability and uniformity of its atomic dispersion on the (111) surface can be attributed to the strong structural coordination provided by three oxygen atoms. In contrast, the metal–support interaction on the (110) and (100) surfaces proved to be insufficient to overcome the cohesive energy between Ru atoms, resulting in the formation of Ru clusters. Beyond Ru, this study holds great potential in guiding the rational selection of surfaces to achieve a uniform atomic dispersion of other elements.