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Carbon-supported Ir3Sn/C and Ir/C catalysts were simply prepared with NaBH4 as a reducing agent under the protection of ethylene glycol at room temperature. TEM and X-ray diffraction (XRD) data showed that the catalysts with small particle size exhibited the typical characteristic of a crystalline Ir fcc structure. Their electrocatalytic activities in comparison with Pt/C and Pt3Sn/C catalysts also prepared by the NaBH4 reduction process were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) techniques. The results indicated that Ir-based catalysts showed superior electrocatalytic activity towards ethanol oxidation to Pt/C and Pt3Sn/C catalysts, mainly in the low potential region. During single-cell tests at 90°C, better performances of Ir-based catalysts as anodes were obtained compared to that of Pt/C catalyst. The comparable overall performance of Ir3Sn/C to Pt3Sn/C makes it a promising alternative choice of anode catalyst for direct ethanol fuel cells. [Copyright &y& Elsevier]

Abstract: Potential-scan tests were conducted to evaluate the stability of a PtRu/C electrocatalyst at anode potentials in a direct methanol fuel cell (DMFC). The results show that, under normal operating conditions, the anode potential in a DMFC is benign for the PtRu/C electrocatalyst. But in the case of deep discharge or short circuit, the anode potential value may exceed 0.6V versus DHE, which is harmful to the PtRu/C electrocatalyst. The dissolution of catalyst components results in an enhanced ohmic resistance and a lowered catalytic activity for methanol electro-oxidation. [Copyright &y& Elsevier]

A series of 40 wt.% Pt/C electrocatalysts were prepared by a modified polyol process and an improved aqueous impregnation method with different impregnation time. The characterization results of TEM and XRD identically reveal that the size and distribution of Pt nanoparticles on carbon are controllable by modifying impregnation time in both routes. High dispersion of Pt nanoparticles on carbon is achieved by both methods with 15 min impregnation, while aggregation of Pt nanoparticles takes place with prolonging the impregnation time to 36 h, especially in the aqueous impregnation procedure. UV–vis spectroscopy measurements verified that the redox reaction between PtCl62- and formaldehyde could take place at a slow rate under ambient conditions via a two-step reaction path, where PtCl42- serves as an intermediate. On the other hand, PtCl62- anion can be directly reduced to Pt0 above 333 K in the modified polyol process through an autocatalytic pathway. The short-time-impregnated 40 wt.% Pt/C as cathode electrocatalysts in direct methanol fuel cell performs better than that of long-time-impregnated electrocatalysts. Experimental evidence provides clues for fundamental understanding of elementary steps of the redox reactions, which helps guiding the design and preparation of highly dispersed Pt catalyst with high metal loadings for fuel cells. [Copyright &y& Elsevier]