Narrow Results

A hierarchical carbon material containing nanopores (micropores and mesopores) and micrometric sized capillaries (macropores) is produced using a combination of hard and soft templates. The hard template is a polypropylene (PP) cloth which decomposes during pyrolysis leaving a macroporous structure. The soft template is a cationic polyelectrolyte which stabilizes the resorcinol/formaldehyde (RF) resin porous structure during drying to give a nanoporous RF resin. The method produces a nanocomposite of the porous RF resin with an imbibed PP cloth. The composite is then pyrolyzed in a inert gas atmosphere to render a carbon material having macropores as well as micro/mesopores. The material exhibits both a large surface area (S_BET = 742 ± 2 m²/g) due to nanopores and goof fluid permeability due to micrometric sized pores. The macropores can be oriented during fabrication. The nanoporous surface can be used to support metal nanoparticles for fuel cell while the macropores allow easy flux of gas and liquids through the monolithic material.

In this work, slurry spraying is evaluated as a deposition method of thin electrolytes for solid oxide fuel cells. This method is cost effective, uncomplicated and have several advantages in respect to widely used screen printing method. Influence of deposition parameters: slurry concentration, spraying pressure are discussed. Anode supported cells are produced with three different electrolyte thicknesses: 5, 10 and 20 μm showing flexibility of the developed method. Prepared fuel cells achieve satisfactory power densities of almost 1 W cm^-2 at 800°C. As evidenced by impedance spectroscopy, performance of cells is determined by the polarization resistance. Cross sections of cells show that all electrolyte layers are of high quality. Slurry spraying is a feasible method for fabrication of functional cells and can be easily scaled for large quantity production.

Catalysts are a key component of polymer electrolyte membrane fuel cells (PEMFCs). In this work, nitrogen-doped three-dimensional graphene-supported platinum (Pt-3DNG) catalysts are successfully prepared and characterized. SEM and TEM images show the Pt nanoparticles are uniformly dispersed in the sheets of nitrogen-doped 3DNG. Compared with that of the commercial Pt/C catalysts, Pt-3DNG show much better oxygen reduction reaction (ORR) activity and cycling stability, and the reduction in limit current density after 1000 cycles is only about 1.6% for the Pt-3DNG catalysts, whereas 7.2% for the commercial Pt/C catalysts. The single cell using Pt-3DNG catalysts in both the anode and the cathode show a higher peak power density (21.47mW cm${}^{-2})$ than that using commercial Pt/C catalysts (20.17mW cm${}^{-2})$ under the same conditions. These properties make this type of catalyst suitable for the application in PEMFCs.

In order to develop non-noble metal-based electrocatalysts for glucose oxidation, the Ni-doped, urchin-like Bi₂S₃ particles were prepared by a solvothermal method using the solvent of ethylene glycol/H₂O. The obtained products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The background signal from capacitance current is relatively low and the electrocatalytic oxidation current of glucose relatively high due to the urchin-like nanostructure of Bi₂S₃ particles and high surface area where the presence of Bi also improves the electrocatalytic performance of Ni${}^{II}$/Ni${}^{III}$ shift.