Solution-Based Evolution and Enhanced Methanol Oxidation Activity of Monodisperse Platinum–Copper Nanocubes This work was partially supported by the NSF (DMR-0731382 & CHM-0616436), DOE (DE-FG02-07ER86296), and the Research Foundation of SUNY. We thank Dr. Jibao He and Dr. Amar Kumbhar for their assistance with the TEM studies. (2009)

Platinum nanoparticles (Pt NPs) have been extensively studied because of their unique catalytic properties in various significant applications. It has been shown that the catalytic activity of Pt NPs is highly dependent on the surface atomic arrangements of the particles. For example, previous studies on oxygen reduction in adsorbing acidic solutions show that Pt {100} planes are more active than Pt {111} planes, and the current density measured on Pt nanocubes is higher than that of truncated cubic Pt nanocrystals (NCs). Pt nanocubes have therefore received more attention as electrocatalysts than other morphologies such as multipods and one-dimensional nanostructures. To further reduce the overall use of expensive Pt and afford the potential of poisoning resistance, platinumbased bimetallic NCs such as Pt–Ni, Pt–Co, and Pt– Cu have attracted increasing interest. Moreover, recent reports indicate that electrocatalytic activities of some platinum-containing bimetallic NCs are superior to those of pure Pt metal. Therefore, the synthesis of platinumcontaining nanocubes and the examination of their electrocatalytic performance is a highly worthwhile and significant step. However, to the best of our knowledge, there have been very few reports on the preparation of platinum-containing bimetallic nanocubes and the investigation of their electrocatalytic behavior to date. Herein, we report a convenient and effective colloidal method for the synthesis of high-quality Pt– Cu nanocubes and their electrocatalytic activity towards methanol oxidation. The influences of several important experimental parameters on the final product development were also explored through systematic studies on the growth of Pt–Cu nanocubes. The Pt–Cu nanocubes were prepared by simultaneous reduction of a 1:1 molar ratio of platinum(II) acetylacetonate ([Pd(acac)2]) and copper(II) acetylacetonate ([Cu(acac)2]) by 1,2-tetradecanediol (TDD) in 1-octadecene (ODE) as solvent, which also contained tetraoctylammonium bromide (TOAB), oleylamine (OLA), and a trace amount of 1dodecanethiol (DDT). A typical transmission electron microscopic (TEM) image shows that the overall morphology of the sample consists of (8.0 1.0) nm (side length) Pt–Cu nanocubes, which are formed in greater than 90% selectivity (Figure 1a). The nanocube composition has been extensively investigated by using various techniques including inductively coupled plasma mass spectrometry (ICP-MS) and energydispersive X-ray spectroscopy equipped on a TEM (EDSTEM), and the consistent results obtained suggest that the Pt/Cu molar ratio is 3:2. ATEM diffraction pattern of the Pt– Cu nanocubes (Figure 1b) indicates a high crystallinity of these NCs and a {200}-enhanced diffraction (see below). The high-resolution TEM (HRTEM) image of a single Pt–Cu nanocube (Figure 1c) shows clear lattice fringes with an interfringe distance of approximately 1.90 , which corre-