| Summary: | 博士 === 國立交通大學 === 應用化學系碩博士班 === 101 === Abstract (in English)
In this study, we focus on the modification of materials and their application on fuel cells.
1. Poly(ethylene glycol) modified activated carbon for high performance proton exchange membrane fuel cells
A high water retention membrane is developed by co-assembling poly(ethylene glycol) (PEG) grafted activated carbon (AC-PEG) with Nafion. The AC-PEG is prepared via a sol-gel process. The use of PEG as a transporting medium in AC-PEG shows a largely improved water retention ability, a higher proton conductivity and a reduced swelling ratio, making it well suited for proton exchange membrane fuel cells (PEMFCs). Further, the composite membranes show improved mechanical properties at high temperature, thus ensuring the structural stability of membranes during the fuel cell operation. Compositional optimized AC-PEG/Nafion composite membrane (15 wt% compared to Nafion) demonstrates a better performance than the commercially available counterpart, Nafion 212, in fuel cell measurements. To identify the key factor of the improved performance, current interrupt technique is used to quantitatively verify the changes of resistance under different relative humidity environment.
2. Sulfonated graphene oxide/Nafion composite membranes with low methanol permeability
An easy and effective method for producing low methanol-crossover membranes is developed by dispersing sulfonated graphene oxide (SGO) into a Nafion matrix. A SGO/Nafion mixture with low SGO content exhibits unique viscosity behaviour and allows for better SGO dispersion within the Nafion. After film casting, the composite membranes show lower methanol and water uptakes, a reduced swelling ratio, improved proton conductivity in low relative humidity, and extremely high methanol selectivity, which can be implemented in direct methanol fuel cells (DMFCs).
3. Novel Bilayer Composite Membrane for Passive Direct Methanol Fuel Cells with Pure Methanol
The bilayer composite membrane composed of the sulfonated graphene oxide (SGO)/Nafion and sulfonated activated carbon (SAC)/Nafion composite membrane is designed and prepared by repeatedly bar-coating. With the carefully chosen of solvent, the bilayer composite membrane has shown identical thickness on SEM observation. The SGO/Nafion side has a low methanol permeability ascribed to the unique selectivity of the SGO. Moreover, the SAC side has good water retention which can facilitate the back diffusion water produced by the cathode. The unique design of composite membranes confers low methanol crossover and high proton conductivity at the same time. The bilayer composite membrane shows better power density than Nafion 212 and Nafion 115 and the performance monitored for 24h to ensure the stable power density and the durability of the membrane.
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