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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]

Pt–Fe/C catalysts were prepared by a modified polyol synthesis method in an ethylene glycol (EG) solution, and then were heat-treated under H2/Ar (10 vol.%) at moderate temperature (300 °C, Pt–Fe/C300) or high temperature (900 °C, Pt–Fe/C900). As comparison, Pt–Fe/C alloy catalyst was prepared by a two-step method (Pt–Fe/C900B). X-ray diffraction (XRD) and transmission electron microscopy (TEM) images show that particles size of the catalyst increases with the increase of treatment temperatures. Pt–Fe/C300 catalyst has a mean particle size of 2.8 nm (XRD), 3.6 nm (TEM) and some Pt–Fe alloy was partly formed in this sample. Pt–Fe/C900B catalyst has the biggest particle size of 6.2 nm (XRD) and the best Pt–Fe alloy form. Cyclicvoltammetry (CV) shows that Pt–Fe/C300 has larger electrochemical surface area than other Pt–Fe/C and the highest utilization ratio of 76% among these Pt-based catalysts. Rotating disk electrode (RDE) cathodic curves show that Pt–Fe/C300 has the highest oxygen reduction reaction (ORR) mass activity (MA) and specific activity (SA), as compared with Pt/C catalyst in 1.0 M HClO4. However, Pt–Fe/C catalyst does not appears to be a more active catalyst than Pt/C for ORR in 1.0 M HClO4 + 0.1 M CH3OH. Pt–Fe/C300 exhibits higher ORR activity and better performance than other Pt–Fe/C or Pt/C catalysts when employed for cathode in direct methanol single cell test, the enhancement of the cell performance is logically attributed to its higher ORR activity, which is probably attributed to more Pt0 species existing and Fe ion corrosion from the catalyst. [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]