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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]

In this work, a 3D-printed reactor was designed to enable natural graphite flakes to be used for electrochemical exfoliation to quickly obtain graphene oxide. Graphite foil as a typical raw material of electrochemical exfoliation was also exfoliated for comparison. Under the same conditions (10 V, 1 mol L-1 ammonium sulphate solution as electrolyte), the graphene products obtained by one-step electrochemical exfoliation using natural graphite flakes based on the reactor, have a significantly higher degree of oxidation than products obtained using graphite foil (the oxygen content is increased by 50.2%). In addition, the degree of oxidation can be further increased by increasing the electrolyte concentration or reaction time. This design achieves one-step exfoliation using natural graphite flakes to obtain graphene oxide with tunable oxygen content in short time without using any strong oxidants or strong acids. The as-prepared electrochemically exfoliated graphene oxide (EGO) was used to prepare polybenzimidazole (PBI)/graphene oxide (GO) composite membranes for high-temperature polymer electrolyte membrane fuel cells (HTPEMFC). The 0.5%, 1% and 2% EGO loadings in the PBI membrane increased the peak power density by 13.8%, 24.4% and 29.2%, respectively. Image 1 • The use of natural graphite flakes as raw materials for electrochemical exfoliation. • No oxidant and acid used to obtain graphene oxide. • A novel reactor design achieves the above goals. • Electrochemically exfoliated graphene oxide enhances the performance of PBI membrane. [ABSTRACT FROM AUTHOR]