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 similar to 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.