A Discovery of Strong Metal–Support Bonding in Nanoengineered Au–Fe₃O₄ Dumbbell-like Nanoparticles by in Situ Transmission Electron Microscopy

Abstract

The strength of metal-support bonding in heterogeneous catalysts determines their thermal stability, therefore, a tremendous amount of effort has been expended to understand metal-support interactions. Herein, we report the discovery of an anomalous "strong metal-support bonding" between gold nanoparticles and "nano-engineered" FeO substrates by in situ microscopy. During in situ vacuum annealing of Au-FeO dumbbell-like nanoparticles, synthesized by the epitaxial growth of nano-FeO on Au nanoparticles, the gold nanoparticles transform into the gold thin films and wet the surface of nano-FeO, as the surface reduction of nano-FeO proceeds. This phenomenon results from a unique coupling of the size-and shape-dependent high surface reducibility of nano-FeO and the extremely strong adhesion between Au and the reduced FeO. This strong metal-support bonding reveals the significance of controlling the metal oxide support size and morphology for optimizing metal-support bonding and ultimately for the development of improved catalysts and functional nanostructures.

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“…For example, Han C.W. et al [88] has obtained Fe 3 O 4 -Au core-shell nanoparticles by in situ vacuum annealing of dumbbell-like Au-Fe 3 O 4 nanoparticles obtained by epitaxial growth of magnetite on Au nanoparticles. The process was undertaken using a transmission electron microscope and recorded.…”

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“…Recently, intraparticle atom movements have been followed using in situ TEM techniques. [329][330][331][332] However, in this case, the condition that led to the real-time atom movement, i.e. simple heating, is not relevant to the catalytic setting.…”