NANO LETTERS
Synthesis of Platinum Nanowire Networks Using a Soft Template
Yujiang Song,*, Robert M. Garcia,, Rachel M. Dorin,, Haorong Wang,, Yan Qiu,, Eric N. Coker, William A. Steen, James E. Miller, and John A. Shelnutt*,,§
AdVanced Materials Laboratory, Sandia National Laboratories, Albuquerque, New Mexico 87106, Department of Chemical and Nuclear Engineering, UniVersity of New Mexico, Albuquerque, New Mexico 87131, and Department of Chemistry, UniVersity of Georgia, Athens, Georgia
Received August 3, 2007; Revised Manuscript Received October 23, 2007
2007 Vol. 7, No. 12 3650-3655
ABSTRACT
Platinum nanowire networks have been synthesized by chemical reduction of a platinum complex using sodium borohydride in the presence of a soft template formed by cetyltrimethylammonium bromide in a two-phase water-chloroform system. The interconnected polycrystalline nanowires possess the highest surface area (53 ± 1 m2/g) and electroactive surface area (32.4 ± 3.6 m2/g) reported for unsupported platinum nanomaterials; the high surface area results from the small average diameter of the nanowires (2.2 nm) and the 210 nm pores determined by nitrogen adsorption measurements. Synthetic control over the network was achieved simply by varying the stirring rate and reagent concentrations, in some cases leading to other types of nanostructures including wormlike platinum nanoparticles. Similarly, substitution of a palladium complex for platinum gives palladium nanowire networks. A mechanism of formation of the metal nanowire networks is proposed based on confined metal growth within a soft template consisting of a network of swollen inverse wormlike micelles.
Nanostructured platinum is important in many technical applications, including as an electrocatalyst in proton exchange membrane fuel cells1,2 and as catalysts in many reactions including solar water-splitting devices.3,4 However, the high cost and limited supply of platinum in these applications remain a challenge that demands its efficient commercial usage. The manipulation of the size and shape of platinum materials at the nanoscale can contribute to lowering Pt usage and achieving the necessary cost reduction.5-8 Previous efforts to produce platinum in various shapes have produced Pt nanowires,9,10 tetrahedra, and octahedra11 using the polyol method. Cubic, cuboctahedral, and porous Pt nanoparticles have been synthesized using a capping polymer combined with differing reduction conditions.12-14 Pt nanotubes15 and mesoporous Pt films16,17 were obtained by chemical and electrochemical reduction of Pt salts confined within the aqueous environment of the lyotropic liquid crystalline phases of surfactants. In addition, Pt multipods have been synthesized by an induced anisotropic growth in organic solvents,18 and very recently monodispersed Pt nanocubes have been obtained by decomposing a Pt precursor with pressurized hydrogen.19 Finally, using

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