Alternately layered Au/Fe3O4 with porous structure—a self-assembled nanoarchitecture for catalysis materials

Nanoporous gold fabricated by the dealloying of binary Au alloys has a three-dimensional network of fine ligaments on the nano-scale, which is a novel unsupported gold catalyst with exceptional catalytic activity for CO oxidation. Here we report a new nanoporous structure—a composite formed by alternately layered Au/Fe3O4/Au with layer spacing ∼200 nm and with porous structure (the pore size is below 20 nm). The Au/Fe3O4/Au revealed much higher catalytic performance for CO oxidation than the previously reported conventional Au/Fe2O3 catalyst, where the porous Au and porous Fe3O4 were responsible for the high activity and high thermal stability, respectively. The porous structure is formed via a self-assembly process by the dealloying of Al in a NaOH aqueous solution for a conventionally melting Al-Au-Fe alloy precursor with an alternately layered Al2Au/Al2Fe/Al2Au structure. We show here, that a fine composite nanoporous structure could be intentionally designed on the basis of the metallurgically tailored microstructure of the precursor alloy.

[1]  M. Bäumer,et al.  Nanoporous Gold Catalysts for Selective Gas-Phase Oxidative Coupling of Methanol at Low Temperature , 2010, Science.

[2]  J. C. Fister,et al.  The Mechanism of Dealloying of Copper Solid Solutions and Intermetallic Phases , 1984 .

[3]  C. Wagner,et al.  Electrolytic Dissolution of Binary Alloys Containing a Noble Metal , 1967 .

[4]  A. J. Forty.  Corrosion micromorphology of noble metal alloys and depletion gilding , 1979, Nature.

[5]  H. Gasteiger,et al.  Kinetics of the Selective Low-Temperature Oxidation of CO in H2-Rich Gas over Au/α-Fe2O3 , 1999 .

[6]  M. Bäumer,et al.  Gold catalysts: nanoporous gold foams. , 2006, Angewandte Chemie.

[7]  Martin Muhler,et al.  CO Oxidation over Supported Gold Catalysts—“Inert” and “Active” Support Materials and Their Role for the Oxygen Supply during Reaction , 2001 .

[8]  Takeshi Fujita,et al.  Three-dimensional morphology of nanoporous gold , 2008 .

[9]  M. Bäumer,et al.  Nanoporous Au: An Unsupported Pure Gold Catalyst? , 2008 .

[10]  Q. Pankhurst,et al.  Microstructural comparison of calcined and uncalcined gold/iron-oxide catalysts for low-temperature CO oxidation , 2002 .

[11]  Xiaohong Xu,et al.  Low temperature CO oxidation over unsupported nanoporous gold. , 2007, Journal of the American Chemical Society.

[12]  Y. Katsuya,et al.  A new large radius imaging plate camera for high-resolution and high-throughput synchrotron x-ray powder diffraction by multiexposure method. , 2008, The Review of scientific instruments.

[13]  B. Hillebrands,et al.  Anisotropy of magneto-optical spectra in ultrathin Fe/Au/Fe bilayers , 2002 .

[14]  Bernard Delmon,et al.  Low-Temperature Oxidation of CO over Gold Supported on TiO2, α-Fe2O3, and Co3O4 , 1993 .

[15]  Shouheng Sun,et al.  Colloidal deposition synthesis of supported gold nanocatalysts based on Au-Fe3O4 dumbbell nanoparticles. , 2008, Chemical communications.

[16]  Y. Yamauchi,et al.  Rational design of mesoporous metals and related nanomaterials by a soft-template approach. , 2008, Chemistry, an Asian journal.

[17]  A. Tsai,et al.  CO Oxidation Over a Fine Porous Gold Catalyst Fabricated by Selective Leaching from an Ordered AuCu3 Intermetallic Compound , 2008 .

[18]  M. Stratmann,et al.  Materials science: A pore view of corrosion , 2001, Nature.

[19]  A. Karma,et al.  Evolution of nanoporosity in dealloying , 2001, Nature.

[20]  H. Nakajima,et al.  Artificial fabrication of an L10‐type ordered FeAu alloy by alternate monatomic deposition , 1995 .