Organic/inorganic hybrid proton conductive membrane and related membrane electrode assembly for fuel cell application
| Autor: | Chien, Hung-Chung, 簡宏仲 |
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| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 102 In this study, we focus on the modification of carbon materials and their application on fuel cells. 1. Highly hydrated Nafion/activated carbon hybrids The incorporation of highly porous activated carbon (AC) to Nafion membranes confers unprecedented levels of water uptake (4 times higher for 10 wt% AC compared to neat Nafion) at a minimal dimensional swelling and results in dramatic enhancements in ionic conductivity at low relative humidity. This behavior reveals the development of a robust network of water nanochannels formed by the carbon pores and the polymeric ionic domains which is structurally stabilized by the rigid Nafion backbone and the non-deformable AC particles. 2. Characteristics of high-water-uptake activated carbon/Nafion hybrid membranes for proton exchange membrane fuel cells A cost-effective and high-throughput method for producing high-water-uptake membranes is developed by combining high-porosity and superior-surface-area activated carbon with Nafion. The resultant activated carbon/Nafion hybrid composite exhibits high water uptake and an improved proton conductivity, which can be exploited in a proton exchange membrane fuel cell (PEMFC). This hybrid membrane displays a superior performance to that of the commercial Nafion 211 when used in fuel-cell measurements. Electrochemical impedance spectroscopy (EIS) is used to simulate the changes in resistance during the operation of the fuel cells and conclusively explains the improved performance of the composite membranes. 3. Sulfonated graphene oxide/Nafion composite membranes for high-performance direct methanol fuel cells 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 behavior 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). The regular backbone of the composite membrane shows a higher storage modulus, increased -relaxation (transition temperature), and improved tolerance to pressure during membrane electrode assembly (MEA). The small angle X-ray spectra indicate the shrinkage of the ionic clusters in the composite membranes, which thus reduce methanol crossover. The hybrid membranes applied to DMFCs demonstrate performances superior to that of the commercial Nafion115 in 1 M and 5 M methanol solutions. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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