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...

Pyroprocessing is one of the options for the effective treatment and recycling of spent nuclear fuel (SNF) owing to its economic advantage, environmental safety, and proliferation resistance of the nuclear fuel cycle. [1,2] The head-end process of the pyroprocessing under development at KAERI includes disassembly and oxidative decladding steps, where cladding hull wastes are generated from the fuel rods. The hull wastes are presumably categorized into high-level wastes (HLW) due to traces of SNF residue and fission products that are implemented into the inner surface of the hulls. Thus, the reduction of the amount of HLW will be one of the key issues for the waste management of the pyroprocess.This study demonstrates the electrorefining process, which is able to recover Zr, which is a major component of the hull wastes such as Zircaloy-4 or Zirlo. Electrochemical behaviors of Zr in LiCl-KCl molten salts are examined using cyclic voltammetries and chronoamperometries.An anhydrous LiCl-KCl eutectic (99.99 % purity, Sigma-Aldrich) was used as the electrolyte at 500 °C by adding 4 wt% ZrCl 4 for Zr electrorefining. All the experiments were performed in an Ar-purging glove box, where the oxygen and moisture are controlled below 5 ppm. To examine the electrochemical behavior of Zr, cyclic voltammetries and chronoamperometries were performed using a pure Zr rod as an anode, a tungsten wire cathode, and a Ag/AgCl reference electrode. Subsequently, the Zr anode was replaced with Zircaloy-4 hulls to recover Zr by electrorefining. The Zr deposits were characterized by SEM-EDX, XRD, and ICP-AES. Figure 1 shows cyclic voltammograms of tungsten wire cathodes in LiCl-KCl molten salts at 500 °C. For Zr rod anodes in the absence of ZrCl 4 , the residual current was less than 0.4 mA with no apparent anodic and cathodic reactions associated with salt components within the potential range of -0.2 V to -1.4 V. However, in the presence of 4 wt% ZrCl 4 (red dashed line), several peaks When the Zr rod was replaced with Zircaloy-4 cladding hull samples, additional reduction peaks followed by a shift of the oxidation peaks are revealed owing to the alloying components such as Sn, Fe, and Cr (blue dotted line). To examine the purity of Zr in the recovered Zr deposit, chronoamperometric experiments were performed for 1 hr at a constant potential of -1.15 V, where the reduction of Zr occurs. Assuming that the total amount of Zr ions dissolved from Zircaloy-4 anode was deposited, the number of electrons involved with the electrorefining process can be estimated from the following Faraday equation by measuring the weight difference (Δw) of the Zircaloy-4 hull before and after the deposition.M w is the molecular weight of Zr, and Q is the total charge flown for 1 hr. The calculated n value was found to be 3.99, which reflects the fact that the reduction process may include a two-step reduction of Zr

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