Metal–Support Interactions in Metal/Oxide and Inverse Oxide/Metal Catalysts: A Case Study Using Cu/ZnO and ZnO/Cu Model Catalysts

Metal–metal oxide interfaces comprise the most common type of “active sites” in heterogeneous catalysis. The activity of interface sites originates from geometry, namely, certain facets and their corresponding electronic structures, as well as charge transfer between the oxide support and metal particles and the binding modes that stabilize reaction intermediates. In most instances, the metal is dispersed on an oxide support in the form of particles ranging from a few nanometers to tens of nanometers in size. There are also inverse metal oxide/metal catalysts in which the oxide is dispersed on the metal surface. Herein, we employ DFT calculations using extended nanowire models representing metal particles as well as their inverse configuration. Through this, we address similarities and differences between the two types of metal–metal oxide interfaces, especially regarding their electronic properties and corresponding stabilization of important reaction intermediates. We use the well-studied Cu/ZnO catalyst and the corresponding CO/CO2 hydrogenation to CH3OH as an example.