Structurally defined SnO₂ substrates, nanostructured Au/SnO₂ interfaces, and their distinctive behavior in benzene and methanol oxidation

SnO₂ crystallites of regular morphology [rhombic dodecahedra (r.d-SnO₂), elongated octahedra (e.o-SnO₂), and octahedra (o-SnO₂)], together with low-dimensional rod-clusters (r.c-SnO₂) and plates (p-SnO₂), were controllably synthesized. Based on (HR)TEM, SEM, and SEAD characterizations, the SnO₂ facets were identified as {1 1 1}, {1 1 0}, and {1 0 1}. Au nanoparticles of 2.2–2.4 nm with narrow particle size deviation (±0.6–0.7 nm) were monodispersed on the SnO₂ substrates. Au/SnO₂ interfacial structures with structurally defined oxide substrate and comparable Au particle size and morphology were accomplished. The systems achieved made it possible to study the distinct interfaces in catalytic benzene combustion and methanol oxidation. H₂ TPR, O₂ TPD, and XPS characterizations revealed that the specific Au–SnO₂ interaction has a strong effect on the reactivity of surface and bulk lattice oxygen, the oxidation state of surface Sn atoms, and the sort and relative concentration of surface oxygen adspecies. The Au/SnO₂{1 1 0} and Au/SnO₂{1 0 1} interfaces favor selective oxidation of methanol, whereas Au/SnO₂{1 1 1} enhances total oxidation of both benzene and methanol. These interfacial structures were rather stable in both reactions. Through structural analysis of SnO₂ facets, the evolution of active oxygen species and the possible reaction pathways of benzene combustion have been proposed. The involved reaction pathways are notably influenced by the specific Au/SnO₂ interfacial structure and the nature of the reactant molecule, as well as the reaction temperature. The current study gained insight into the significance of specific Au/SnO₂ facets determining the catalytic activity of benzene and methanol oxidation.