The direct methanol fuel cell (DMFC) performance has been improved via two approaches. The first approach reduces methanol crossover in the membrane electrode assemblies (MEAs) by incorporating a methanol barrier layer onto an anode electrode of the MEA. The second approach increases the triple phase boundaries via the modified morphology of catalyst layers in the MEA. Methanol barrier layers containing a composite layer of Nafion/mordenite (MOR), Nafion/zeolite Y (ZY), Nafion/montmorillonite (MMT) or Nafion/titanate (TN) were distributed onto the anode of an MEA. The performance of these MEAs were tested in a single cell DMFC for temperatures between 30-80 °C and methanol concentrations of 1 M-4 M and compared with a standard MEA to identify changes in power output. At 2 M methanol concentration and 80 °C, the MEAs featuring with Nafion/0.50 wt% MMT and Nafion/0.50 wt% TN delivered higher power densities, 19.76% and 26.60%, respectively, than that of standard MEA. The catalyst morphology has been adjusted by the dilution of catalyst ink to prevent an agglomeration of catalyst particles, resulting in the increased triple phase boundaries which are the phases for electrochemical reactions and for the transportation of electron and proton products. The new-standard MEA presented the best improvement in power density of 81.15% over the conventional counterpart at 80 °C and 2 M methanol concentration. This modified procedure was further utilised for MEAs fabrication. Further investigation has been carried out by the selected Nafion/MMT layer. The MMT loading of 0.25 wt%-1.00 wt% were incorporated onto the barrier layer where the Nafion/0.25 wt% MMT layer illustrated the best performance. This MEA attributed the highest power density of 69.14 mW cm⁻² which is 2.76% higher than 67.23 mW cm⁻² of the new-standard MEA at 80 °C and 2 M methanol concentration. The best improvement in power density, 27.09%, was obtained at low temperature and low methanol concentration of 30 °C and 1 M. The power density was 25.30 mW cm⁻² when compare to 19.91 mW cm⁻² of the new-standard MEA. These results suggest that the methanol barrier layer and the modified morphology of catalyst layer accomplish the aim of improving DMFC performance.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:686788 |
| Date | January 2016 |
| Creators | Chailuecha, Chatkaew |
| Contributors | Holmes, Stuart |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/methanol-barrier-layer(2c347cde-c81d-4024-90b0-a62e1bf94918).html |
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