Exploring the Stability of Single-Atom Catalysts Using the DensityFunctional Theory-Based Global Optimization Method: H(2)Formation on VOx/?-Al2O3(100)

Single-atom catalysis is indisputably one of the most trending topicsin heterogeneous catalysis with distinctive performances in many importantchemical reactions. However, surface reconstruction during loading of single-atomtargets and its impact on vital reaction steps have rarely been studied. Herein,taking H2formation, a key step of alkane dehydrogenation, as an example, withgenetic algorithm structure search, we reveal the structure-reactivity relationshipin the H2formation on VOx/gamma-Al2O3(100). We explore a large number of VOx/gamma-Al2O3(100) (x= 0, 1, 2, 3) structures and discover a few reconstructed structureswith low formation energies. Since the pristine gamma-Al2O3(100) support is highlystable, the production of such structures was completely induced by VOxloading.One VO3/gamma-Al2O3(100) structure generates a stable VO4motif by reconstructingthe support surface. Its distinct local chemical environment of vanadium can notonly resist the oxygen removal under reductive conditions but can also offer a low-barrier surface reaction channel to H2formation. Moreover, the hydrogen atom prefers to diffuse into the vanadium site and thencouple with another hydrogen instead of direct coupling if the initial state involves two hydrogen atoms both on oxygen sites.Therefore, the H2formation prefers a surface process that occurs on the vanadium-oxygen pair.