Meso-and macroporous materials synthesized via various routes [1] are important because of their potential applications as devices, [2] catalysts, [3] quantum-electronic technologies, [4] acoustic [5] and electrical insulators, [6] and optics. [7] Much attention has been focused on the synthesis of nanostructured carbons using arc-discharge, [8] chemical vapor deposition, [9] or template-synthesis techniques.[10] These materials have been studied for their applications as adsorbents, [11] catalyst supports, [12] hydrogen-storage materials, [13] and electrode materials. [14,15] Recently, interest has increased in the fuel-cell applications of nanostructured carbons. However, even though it is relatively easy to synthesize nanostructured carbons, it is not easy to impregnate precious-metal nanoparticles into them while maintaining some degree of control of particle size and shape.Here we describe a novel procedure to synthesize a new mesoporous platinum±carbon nanocomposite. This method is based on the pyrolysis of carbon and platinum precursors in silica mesopores such as SBA-15 in order to take advantage of the excellent size-and shape-control achievable in the synthesis of nanodispersions. It has been reported previously that pyrolysis of an organometallic Pt compound at high temperature results in Pt clusters being buried in the carbon that is not exposed to the environment.[16] However, with the method reported here we have synthesized Pt nanoclusters studded in the microporous nanowalls of ordered mesoporous carbon. We found that this material is composed of regularly interconnected PtC nanocomposite arrays, as shown in Figure 1, and can be successfully used as a methanol-tolerant cathode material in direct-methanol fuel cells (DMFC). ªMethanol crossoverº through an electrolyte membrane from anode to cathode is a major problem that limits the performance of a DMFC.[17] During DMFC operation, the anode performance increases with increasing methanol concentration, but the methanol crossover rate also increases, causing degradation of the cathode performance. [18] Although the development of methanol-tolerant oxygen-reduction electrocatalysts, [19] such as transition-metal sulfides and Ru 1.92 Mo 0.08 -SeO 4 , is a promising approach, a platinum electrocatalyst is generally used because of its high stability under acidic and high overpotential conditions. The small-angle X-ray diffraction (XRD) pattern of the assynthesized PtC nanocomposite shows three well-resolved peaks (Fig. 2a) that can be indexed as (100), (110), and (200) reflections associated with hexagonal symmetry. The pore size distribution obtained from Ar-desorption experiments (Fig. 2b) exhibits a narrow peak at 3.5 nm. The scanning electron microscopy (SEM, Fig. 2a, inset) and transmission electron microscopy (TEM, Figs. 3a,b) images reveal that the PtC nanocomposite consists of well-ordered hexagonally arrayed bundles approximately 1 lm long. The composite nanorods are 7 nm in diameter (Fig. 3b); this parameter can be controlled by va...
