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Metal nanoparticles (NPs) have been extensively investigated owing to their unique properties attributing to their high surface/bulk ratio and finite number of atoms. However, the thermodynamic instability of NPs, which originates from their finite size, limits their practical applications. Hence, carbon-supported Pt NPs are synthesized onto carbon-containing liquid substrates via direct one-step sputtering. In order to successfully produce uniform Pt NPs via sputtering using various ionic liquids as non-volatile liquid substrates, special conditions are required, and the relationship between ionic liquids and particle surfaces should be investigated. It has been reported that anions and carbon supports of ionic liquids significantly affect the dispersion and synthesis of Pt NPs. In this study, we proposed a mechanism underlying the chemical bonding between anions and carbon supports and verified it using X-ray photoelectron spectroscopy and infrared spectroscopy.

Despite the advantage of chemical vapor deposition (CVD) for realization of large area epitaxial growth of graphene on transition metal catalysts, both etching and transfer process of CVD-grown graphene sheets still remain a big challenge. Here we demonstrate the formation of multilayer graphene (MLG) sheets tailored from C60 thin films on the top of Si/Ni substrate without etching and transfer steps based on Ni films. This self-assembled process separates the MLG sheets from the conductive Ni catalyst, embarking a possibility for direct characterizations of MLG sheets. The fine-tuned C60 films (30 nm) are transformed into approximately 17 MLG sheets, thus making it large-area MLG sheets for a variety of direct applications.

An anode electrode with the carbon buffer layer is fabricated to increase the performance of direct methanol fuel cell (DMFC). The carbon buffer layer is located in the middle of the anode catalyst layers, consists of porous carbon and Nafion ionomer. Since the porous and relatively hydrophilic carbon buffer layer absorbs methanol, the flux of the methanol solution in the anode electrode can be controlled. And methanol crossover is decreased by the effect of the carbon buffer layer. Consequently, methanol can be oxidized more efficiently and the performance of DMFC increases. Therefore, the membrane electrode assembly (MEA) with the carbon buffer layer on the anode electrode exhibits higher open circuit voltage (OCV) and maximum power density compared to those of conventional MEA. Especially with 3.0 M methanol solution, the maximum power density is increased by ∼60%.

Pd-based nanoparticles, such as 40 wt.% carbon-supported Pd50Pt50, Pd75Pt25, Pd90Pt10 and Pd95Pt5, for anode electrocatalyst on polymer electrolyte membrane fuel cells (PEMFCs) were synthesized by the borohydride reduction method. PdPt metal particles with a narrow size distribution were dispersed uniformly on a carbon support. The membrane electrode assembly (MEA) with Pd95Pt5/C as the anode catalyst exhibited comparable single-cell performance to that of commercial Pt/C at 0.7 V. Although the Pt loading of the anode with Pd95Pt5/C was as low as 0.02 mg cm−2, the specific power (power to mass of Pt in the MEA) of Pd95Pt5/C was higher than that of Pt/C at 0.7 V. Furthermore, the single-cell performance with Pd50Pt50/C and Pd75Pt25/C as the anode catalyst at 0.4 V was approximately 95% that of the MEA with the Pt/C catalyst. This indicated that a Pd-based catalyst that has an extremely small amount of Pt (only 5 or 50 at.%) can be replaced as an anode electrocatalyst in PEMFC.

To understand the difference in degradation characteristics between carbon-supported platinum (Pt/C) and platinum–nickel alloy (Pt1Ni1/C) cathode catalysts in membrane electrode assemblies (MEAs) of a polymer electrolyte membrane fuel cell (PEMFC), constant current operation of MEA in a single cell was conducted for 1100 h. A significant change in cell potential for the Pt1Ni1/C MEA was observed throughout the test. High-resolution transmission electron microscopy showed that sintering and detachment of metal particles in the Pt1Ni1/C catalyst occurred more sparingly than in the Pt/C catalyst. Instead, X-ray photoelectron spectroscopy element mapping revealed dissolution of Ni atoms in the Pt1Ni1 catalysts even when the Pt1Ni1/C catalyst used in the MEA was well synthesized.

A methanol-tolerant cathode electrode composed of heterogeneous composites was developed to overcome CO poisoning and large O2 mass transfer overpotential generated by methanol crossover as well as the limitation of a single alloy catalyst with methanol-tolerance in direct methanol fuel cells (DMFCs). Two additives, PtRu black and PTFE particles, were well distributed in the Pt/C matrix of the cathode electrode, and had significant effects upon open circuit voltage (OCV) and performance. A small amount of PtRu black protected the Pt surface during the oxygen reduction reaction (ORR) by decreasing CO poisoning. In addition, hydrophobic PTFE particles reduced the O2 mass transfer overpotential induced by water and permeated methanol in the cathode. Despite only 0.5 mg cm−2 of metal catalysts in the cathode, the membrane electrode assembly (MEA) with 3 M methanol showed high performance (0.117 W cm−2), which was larger than that of the traditional MEA (0.067 W cm−2).

Water management is one of the most important factors for improving the performance in polymer electrolyte membrane fuel cells (PEMFCs). The micro-porous layers (MPLs) in the membrane-electrode assembly provide proper pores and paths for mass transport, thereby allowing for the control of the water balance. In this study, a copolymer containing hydrophilic functional groups is introduced into the binder materials of the MPL instead of a highly hydrophobic binder. When 10 wt.% of the binder is incorporated in the MPL on the cathode side, the best performance is exhibited and the ohmic resistance is decreased. Although the charge transfer resistance at low potential is higher than that of the hydrophobic treated MPL, due to the flooding effects, the charge transfer resistance at high potential becomes smaller. This indicates that excess liquid absorption from the catalyst layer to the hydrophilic MPL occurs more strongly than in the case of the hydrophobic MPL. This may bring about an increase in the accessibility of oxygen to the active sites, because the excess liquid near the catalyst agglomerates is expelled as fast as possible. Consequently, the hydrophilicity control in the MPL has a positive effect on the water management in PEMFCs.

In this work, a surface modified Nafion 212 membrane was fabricated by plasma etching in order to enhance the performance of a membrane electrode assembly (MEA) in a polymer electrolyte membrane fuel cell. Single-cell performance of MEA at 0.7 V was increased by about 19% with membrane that was etched for 10 min compared to that with untreated Nafion 212 membrane. The MEA with membrane etched for 20 min exhibited a current density of 1700 mA cm−2 at 0.35 V, which was 8% higher than that of MEA with untreated membrane (1580 mA cm−2). The performances of MEAs containing etched membranes were affected by complex factors such as the thickness and surface morphology of the membrane related to etching time. The structural changes and electrochemical properties of the MEAs with etched membranes were characterized by field emission scanning electron microscopy, Fourier transform-infrared spectrometry, electrochemical impedance spectroscopy, and cyclic voltammetry.

A catalyst-coated membrane (CCM) as used in the membrane electrode assembly (MEA) of a polymer electrolyte membrane fuel cell is treated by dilute sulfuric acid solution (0.5 M) at boiling temperature for 1 h. This treatment improves the single-cell performance of the CCM without further addition of Pt catalyst. The changed microstructure and electrochemical properties of the catalyst layer are investigated by field emission scanning electron microscopy with energy dispersive X-ray, mercury intrusion porosimetry, waterdrop contact angle measurement, Fourier transform-infrared spectrometry in attenuated total reflection mode, electrochemical impedance spectroscopy, and cyclic voltammetry. The results indicate that this pretreatment enhances MEA performance by changing the microstructure of the catalyst layer and thus changing the degree of hydration, and by modifying the Pt surface, thus enhancing the oxygen reduction reaction.