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Abstract: In this paper, Fe2O3–SO4 2−/Nafion® composite membranes were prepared by a solution casting method. The physico-chemical properties of composite membranes were characterized by X-ray diffraction (XRD), SEM–EDX and thermogravimetric analysis (TGA). The water uptake ability, proton conductivity, and methanol permeability of the composite membranes were evaluated and compared with the recast Nafion® membrane. The results showed that the proton conductivity and the water uptake of the composite membranes were slightly higher than that of the recast Nafion® membrane. The composite membrane containing 5 wt.% Fe2O3–SO4 2- showed superior ability to suppress methanol crossover, and it further improved the direct methanol fuel cell (DMFC) performances with both 1 M and 5 M methanol feeding, compared with the recast Nafion® membrane. The preliminary 30 h lifetime test of the DMFC with the composite membrane with 5% Fe2O3–SO4 2 − indicated that the composite membrane is stable working at the real DMFC operating conditions at least during the test. These results suggest the applicability of the composite membranes in DMFCs. [Copyright &y& Elsevier]

Abstract: The effect of hydrous RuO2 (RuO2·xH2O) in anode on the performance of direct methanol fuel cells (DMFCs) was examined by voltammetry, methanol stripping analysis, electrochemical impedance spectroscopy, polarization measurement and chronopotentiometry. The results showed that, compared with the DMFC with conventional structures, the dynamic response and quasi-steady state performance of the RuO2·xH2O-introduced DMFCs were significantly improved. The DMFC with RuO2·xH2O layer (ROL) sandwiched between anode catalyst layer and gas diffusion layer exhibited better quasi-steady state performance than those either with ROL sandwiched between anode catalyst layer and electrolyte membrane or with RuO2·xH2O uniformly distributed in anode catalyst layer. The maximum power density of the DMFC with this novel structure was 16% higher than the DMFC with the conventional structure. Moreover, the dynamic response of this RuO2·xH2O-introduced cell was more stable during 250-hour of operation when compared with that of the conventional cell. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFCs) consisting of multi-layer electrodes provide higher performance than those with the traditional electrode. The new electrode structure includes a hydrophilic thin film and a traditional catalyst layer. A decal transfer method was used to apply the thin film to the Nafion® membrane. Results show that the performance of a cell with the hydrophilic thin film is obviously enhanced. A cell with the optimal thin film electrode structure operating at 1 M CH3OH, 2 atm oxygen and 90 °C yields a current density of 100 mA/cm2 at 0.53 V cell voltage. The peak power density is 120 mW/cm2. The performance stability of a cell in a short-term life operation was also increased when the hydrophilic thin film was employed. [Copyright &y& Elsevier]

Abstract: A carbon supported PtNi/C electrocatalyst synthesized via a polyol process was characterized by XRD, TEM and voltammetry techniques. The XRD analysis showed a decreased lattice constant of Pt for the PtNi/C catalyst compared with the Pt/C, indicating partial PtNi alloy formed. The PtNi/C exhibited enhanced mass activity towards methanol oxidation reaction as well as decreased CO stripping currents in alkaline media compared with the Pt/C. Density functional theory studies revealed the electronic structure modification of Pt by Ni atoms and weakened CO adsorption energy on the Pt3Ni than on the Pt4 clusters, which may account for the increased MOR activity. [ABSTRACT FROM AUTHOR]

Abstract: In this study, Nafion ionomer, as a kind of hyperdispersant, was added to polytetrafluoroethylene (PTFE) water dispersion system to suppress the size of PTFE particles in the ink of microporous layer (MPL). The agglomeration behavior of PTFE in ethanol and MPL were investigated by laser diffraction, dynamic light scattering (DLS) and metallurgical microscopes. The electronic resistance, pore size distribution, gas permeability and surface hydrophobic/hydrophilic properties were also characterized for prepared gas diffusion layers (GDLs). It was shown that PTFE water dispersion system suffered flocculating when dispersed in ethanol and this agglomeration behavior was reduced by employing Nafion ionomer. With the increase in the Nafion ionomer adopted in the MPL, not only the decreased hydrophobic property was shown in the MPL, but the decreased PTFE particle size was also achieved, which results in improved crosslink of carbon and pores themselves as well as the volume loss of pores in micron scale. The increased gas permeability and electronic conductivity of the GDL made the one employing the PTFE dispersion system with 1% Nafion content own its advantages as the cathode diffusion layer for a direct methanol fuel cell (DMFC) under near-ambient conditions. [Copyright &y& Elsevier]

Abstract: Carbon-supported bimetallic Pt m Pb1 (m =1, 2, 3) electrocatalysts with different Pt/Pb atomic ratios were synthesized by a polyol method. The X-ray diffraction results reveal that a PtPb alloy formed in the Pt m Pb1/C electrocatalysts. TEM images show that the PtPb nanoparticles distribute uniformly on the carbon support, and are about 4–5nm in size. The Pt m Pb1/C bimetallic catalysts show superior activities toward methanol electrooxidation reaction (MOR) than the Pt/C in alkaline media. Both CO stripping measurements and density functional theory studies reveal that CO adsorption decreased significantly on the Pt m Pb1/C bimetallic catalysts compared with on pure Pt, which may offer an explanation for the enhanced MOR activity of the Pt m Pb1/C bimetallic catalysts. [Copyright &y& Elsevier]

Abstract: Vulcan XC-72R, Ketjen Black EC 300J and Black Pearls 2000 carbon blacks were used as the additive in Pt black cathode catalyst layer to investigate the effect on direct methanol fuel cell (DMFC) performance. The carbon blacks, Pt black catalyst and catalyst inks were characterized by N2 adsorption and scanning transmission electron microscopy (STEM) with Energy dispersive X-ray (EDX) spectroscopy. The cathode catalyst layers without and with carbon black additive were characterized by scanning electron microscopy, EDX, cyclic voltammetry and current-voltage curve measurements. Compared with Vulcan XC-72R and Black Pearls 2000, Ketjen Black EC 300J was more beneficial to increase the electrochemical surface area and DMFC performance of the cathode catalyst layer. The cathode catalyst layer with Ketjen Black EC 300J additive was kept intimately binding with the Nafion membrane after 360 h stability test of air-breathing DMFC. [ABSTRACT FROM AUTHOR]

Abstract: In present work, a 600h durability test and in situ measurements of water transport were carried out on a single direct methanol fuel cell (DMFC) at atmospheric pressure and 80°C. Effect of water transport on the single cell performance was investigated in detail, which indicated that the accumulated water in the hydrophobic micropores of the cathode gas diffusion layer (GDL) aggravated the cathode flooding, and consequently led to a temporary and reversible degradation of the cell performance. Further investigation revealed that cathode flooding could be alleviated by blowing the cathode with dry air for 150h at open circuit condition and the partially recovered cell performance within the durability could be obtained in consequence. Water analysis combined with the scanning electron microscopy (SEM), contact angle measurement and energy dispersive X-ray (EDX) was used to explore the characteristics of cathode GDL before and after the durability test. Results showed that the variation of the microstructure and hydrophobic properties for both sides of the cathode GDL is probably one of the inherent reasons for the irreversible degradation of the cell performance besides the electro-catalysts deterioration. [Copyright &y& Elsevier]

Abstract: TiO2–SO4 2− solid superacid nanoparticles were fabricated by sol–gel reaction, sulfation and calcination procedure. The TiO2–SO4 2−/Nafion® composite membranes were prepared via solution casting. The physico-chemical properties of solid superacid nanoparticles were investigated by thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The water uptake, proton conductivity, and methanol permeability of composite membranes were evaluated. The proton conductivity of the composite membranes shows slightly lower than that of pure recast Nafion® membrane. The composite membranes with lower TiO2–SO4 2− contents (3, 6%) reduced the methanol crossover, while the membrane with higher contents did not show any ability to decrease the methanol crossover. In direct methanol fuel cell (DMFC) single cell performance test, the composite membrane with 6% TiO2–SO4 2− content achieved similar performance at 1M methanol feed, and a higher performance at 5M methanol feed compared with pure recast Nafion® membrane. [Copyright &y& Elsevier]