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A direct methanol fuel cell (DMFC) is one prominent alternative energy technology. However, there are many problems that prevent the commercialization of DMFC, such as methanol crossover, low power density, and degradation of the membrane. To resolve these issues, functionalized graphene oxide (GO) and calcium hydroxy phosphate (CHP) were incorporated into the Nafion membrane to make a composite membrane. The content of the CHP was varied to determine and further investigation involved spraying the same amount of CHP onto the Nafion membrane to compare with the composite membrane. The fillers were characterized using Fourier-transform infrared spectroscopy and X-ray Powder Diffraction. The ex-situ tests investigated water uptake, solubility, and chemical degradation, while the in-situ tests investigated electrochemical impedance (EIS), methanol permeability, fuel cell performance, and durability. Adding both 1 wt% of CHP and 0.05 wt% functionalized GO into the Nafion membrane, resulting in a 1.86-fold higher durability than that of recast Nafion. In addition, the maximum power density of the composite membrane was 1.34-fold higher (75.41 mW/cm2) than that of the recast Nafion (56.11 mW/cm2) at 1 M methanol and 70 °C. At 2 M methanol and 70 °C, the maximum power density of the composite membrane increased to 80.19 mW/cm2 but then decreased to 46.00 mW/cm2 when the methanol feed increased to 4 M, due to the large amount of methanol crossover. • 1 wt% CHP functionalized 0.05 wt% GO/Nafion was used for DMFC. • The composite membrane was 1.86-fold higher durability than that of recast Nafion. • Power density was 1.34-fold higher than that of Nafion at 1 M methanol and 70 °C. • At 2 M methanol and 70 °C was the optimum condition for DMFC. [ABSTRACT FROM AUTHOR]

Methanol crossover through the proton exchange membranes of a direct methanol fuel cell (DMFC) significantly affects its performance and efficiency. Low methanol permeability and high proton conductivity of the membrane is desired for optimum performance. In this work, a multilayer (ML) membrane configuration prepared by a simple pressing technique is employed with and without the incorporation of sprayed cellulose nanocrystals (CNC) to achieve enhanced membrane properties. Assembled multilayer electrolytes show 19% enhanced maximum power density, while the addition of 1.5 wt% CNC (wt % of total final membrane) further improves the performance, giving a 38% better performance compared to standard Nafion N115. Methanol flux density and electrochemical impedance measurements attribute these improvement to the ~20% enhancement in the proton conductivity for the multilayer membrane which is enhanced further by an 11% reduction in methanol crossover when the cellulose nanocrystals are added. Image 1 • Economical and bio-degradable cellulose nanocrystals (CNC) as barrier material. • Multilayer (ML) membrane as the matrix for CNC with the thickness same as Nafion N115. • 11% reduction in the methanol crossover for ML–CNC–2 compared to N115. • ML–CNC–2 exhibits 38% improved DMFC performance compared to N115. • Lower crossover of ML–CNC–2 leads to possible size reduction of the overall technology. [ABSTRACT FROM AUTHOR]

In this work, composite membranes for a direct methanol fuel cell (DMFC) were prepared using a spraying method to improve cell performance especially at a high methanol concentration. Nafion polymer and mordenite as a filler were used for the composite membrane preparation using a spraying method and a conventional solution casting method and the membranes from the two methods were compared. SEM images showed that a more homogeneous composite membrane could be obtained using the spraying method. The effect of mordenite content was also studied. The membranes were consequently characterized and tested in DMFC operation. The results were compared to those prepared using the solution casting method at 30, 50, and 70 °C with methanol concentrations of 2, 4, and 8 M. It was found that the membrane with 5 wt.% mordenite from the spraying method showed a vast improvement in DMFC performance. When the cell was operated at 70 °C, the maximum power density of 5 wt.% mordenite from the spraying method was higher than that of commercial membrane and 5 wt.% from the solution casting method. Power densities from the 5 wt.% sprayed membrane were higher by around 29%, 40%, and 60% at 2, 4, and 8 M methanol concentration, respectively. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFCs) suffer from performance reduction due to mass transport losses incurred at high current regions. In this work, we report the use of activated carbon (AC), prepared from factory waste-tea, as cathode microporous layer in the membrane electrode assembly (MEA) of a DMFC, alleviating this mass transport effect. This biomass based AC framework, when tested under fuel cell operating conditions provided 0.25 V @ 300 mA cm −2 , enhancing cell performance by 33% over standard electrodes at 70 °C. During uninterrupted durability testing, this electrode displayed exceptional stability in mass transport dominated region, with loss of 15 mV day −1 , compared to 25 mV day −1 loss for the standard. Sample and electrode characterization measurements reveal that pore size distribution/particle size characteristics coupled with hydrophobic nature of the synthesized activated carbon, contributed to the performance improvement. [ABSTRACT FROM AUTHOR]

The effect of alcohol ratio in solution casting of composite membranes is one of the important factors to their good properties for direct methanol fuel cell (DMFC). The investigation was focused on the effect of alcohol ratio (methanol/ethanol mixture) during the fabrication process on the membrane properties, morphology, chemical resistance, water uptake, proton conductivity and methanol permeability. Alcohol mixture with proportion of 0–5 vol ratio was varied in order to prepare the composite membranes. It was found that the alcohol ratio had insignificant effect on the homogeneity of the composite membranes as the layers of polymer rich and mordenite rich were formed. The ratio had insignificant effect on proton conductivity of the composite membranes. Reducing alcohol ratio from five to three, however, led to 80% chemical resistance reduction and 70% higher methanol permeability. Finally, these composite membranes with five volume ratio of alcohol were used in membrane electrode assembly and tested in a DMFC compared to recast Nafion membrane. The composite membranes gave a maximum power density of 11.5 mW cm−2 at 343.15 K, which was 58% higher than that of recast membrane. • Effect of solvent in solution cast method for composite membrane fabrication was studied. • Amount of solvent in fabrication did not affect filler dispersion. • The higher amount of alcohol in membrane fabrication leads to higher DMFC performance. [ABSTRACT FROM AUTHOR]