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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: 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]