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Abstract: A graphitic mesoporous carbon (denoted as GMC) was synthesized using resorcinol and formaldehyde as carbon precursors and iron nitrate as a graphitization catalyst. The GMC was characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM), and nitrogen adsorption. The results show that the GMC has a mesoporous structure and a high surface area of 403 m2 g−1, and particularly, a well-defined graphitic framework. Using the GMC as the support, a PtRu/GMC was synthesized to act as an electrocatalyst for the methanol oxidation reaction (MOR). A counterpart with Vulcan® XC-72 (denoted as XC) as the support was prepared for comparison. TEM images show that PtRu nanoparticles are distributed uniformly on the carbon supports for both electrocatalysts. The electrochemical activity of the PtRu/GMC toward the MOR is slightly higher than that of the PtRu/XC in both half cell and single cell measurements. The 1500h stability test of a single cell suggests that the PtRu/GMC is excellent stable. [Copyright &y& Elsevier]

Abstract: Carbon-supported bimetallic PdAg catalysts with Pd/Ag atomic ratios varying from 4/1 to 1/2 were prepared by an impregnation–reduction method. The impregnated black mixture was treated in H2/N2 atmosphere at a temperature varying from 180 to 500°C. The obtained Pd x Ag y /C catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV) and chronoamperometry (CA). XRD results show that the lattice constant of Pd is dilated, suggesting the formation of PdAg alloy. The lattice constant of Pd for the Pd x Ag y /C-500 (reduced at 500°C by H2) increases linearly and the average metal particle size decreases slightly from 6.8 to 5.1nm with increasing Ag fractions from 20% to 67% in the PdAg composition. For Pd x Ag y /C catalysts with a certain specific Pd/Ag atomic ratio, e.g., Pd2Ag1/C, the dilated lattice constant of Pd is independent of the reducing temperature, indicating the alloy degree for the Pd2Ag1/C-t catalysts is comparable. The average metal particle size for the Pd2Ag1/C-t catalysts increases from 3.4 to 5.2nm with H2 reduction temperature increasing from 180 to 500°C. The potentiodynamic measurements on ethanol electrooxidation reaction (EOR) show that the catalytic activities for the Pd x Ag y /C-t catalysts toward the EOR are improved by alloying Pd with Ag. At typical potential of a working fuel cell, e.g., −0.4V vs. Hg/HgO, the EOR current density presents a volcano shape as a function of the Ag fractions in PdAg with the maximum occurs at the Pd/Ag atomic ratios between 2/1 and 3/1. The CA tests show that the Pd x Ag y /C-500 catalysts perform high stability than that of Pd/C-500. The improved EOR activity for the Pd x Ag y /C-t catalysts, compared with whether Pd/C or Ag/C catalyst, may possibly be attributed to the formation of PdAg alloy and the fitted particle size. [Copyright &y& Elsevier]