A Discovery of Strong Metal-Support Bonding in Nanoengineered Au-Fe<sub>3</sub>O<sub>4</sub> Dumbbell-like Nanoparticles by in Situ Transmission Electron Microscopy.

Han, Chang Wan; Choksi, Tej; Milligan, Cory; Majumdar, Paulami; Manto, Michael; Cui, Yanran; Sang, Xiahan; Unocic, Raymond R et al. · Nano Lett · 2017

basic_science · Level V

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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" Fe<sub>3</sub>O<sub>4</sub> substrates by in situ microscopy. During in situ vacuum annealing of Au-Fe<sub>3</sub>O<sub>4</sub> dumbbell-like nanoparticles, synthesized by the epitaxial growth of nano-Fe<sub>3</sub>O<sub>4</sub> on Au nanoparticles, the gold nanoparticles transform into the gold thin films and wet the surface of nano-Fe<sub>3</sub>O<sub>4</sub>, as the surface reduction of nano-Fe<sub>3</sub>O<sub>4</sub> proceeds. This phenomenon results from a unique coupling of the size-and shape-dependent high surface reducibility of nano-Fe<sub>3</sub>O<sub>4</sub> and the extremely strong adhesion between Au and the reduced Fe<sub>3</sub>O<sub>4</sub>. 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.