Strong morphological effect of Mn₃O₄ nanocrystallites on the catalytic activity of Mn₃O₄ and Au/Mn ₃O₄ in benzene combustion

Gold nanoparticles (3-4 nm) were deposited on Mn₃O₄ nanocrystallites with three distinct morphologies (cubic, hexagonal, and octahedral). The resulting structures were characterized, and their activities for benzene combustion were evaluated. The dominant exposed facets for the three kinds of Mn₃O₄ polyhedrons show the activity order: (103)≈(200)>(101). A similar activity order was derived for the interfaces between the Au and the Mn₃O₄ facet: Au/(200)≈Au/(103) >Au/(101). The metal-support interactions between the Au nanoclusters and specific facets of the Mn₃O₄ polyhedrons lead to a unique interfacial synergism in which the electronic modification of the Au nanoparticles and the morphology of the Mn₃O₄ substrate have a joint effect that is responsible for a significant enhancement in the catalytic activity of the Au/Mn₃O₄ system.