The main goal of this project was to improve the performance of Direct methanol fuel cell (DMFC) by reducing methanol crossover without affecting the proton conductivity. This was investigated by modifying a Nafion membrane. The modification involved incorporating novel materials within a Nafion (polymer) such as ionic liquid (IL), type of (1-ethyl-3-methylimidazolium bis (trifluoromethyl sulfonyl) imide, which is referred to as [EMIM][NTf2]; and inorganic material diatomaceous earth (DE), in order to reduce methanol crossover. The DE was treated and functionalised with silane coupling agent type 3-mercapto propyl trimethoxy-silane (MPTS) in order to enhance the bonding between the organic-inorganic substances which are Nafion and DE. The optimum operating conditions were found by testing the DMFC under different cell temperatures 50â-80â, various methanol concentrations, and various methanol flowrate. Membranes with a thickness of 80μm were fabricated from Nafion-DE-IL. The membranes are abbreviated with NIL (Nafion and IL Pure substances), NDE (Nafion and Diatom pure substances), NDEfil (Nafion and Diatom that functionalised with IL), NDEscaIL (Nafion and Diatom that functionalised with silane coupling agent in presence of IL) and NDEIL (Nafion IL and Diatom pure substances). The prepared membranes, NDE, NDEfil and NDEscaIL, showed higher (45-80%) power density than the commercial Nafion 117 (CN117) at all operating temperatures and methanol concentrations. The addition of DE with 0.5wt% (wt% of the total final membrane) all three membranes and 45wt% of IL in the NDEscaIL membrane leads to the power density increases with a percentage % was 4-89% for 1M represented at the operational temperatures in range of (50â-80â) with 10â interval. The membranes above also showed the same rising trend in power density for 2M and 4M methanol concentrations. While the membranes NIL and NDEIL showed fluctuation in power density compared to the commercial Nafion CN117 at mentioned operational temperatures and methanol concentrations. The membranes (NDE, NDEfil and NDEscaIL) showed higher conductivity than the CN117 with a maximum of around 22% and a minimum of about 1%. The same membranes showed a lower methanol permeability percentage in range from 1% (minimum)-67% than CN117 at operational temperatures in different methanol concentrations (1M,2M,4M). Also, the membranes are shown a good durability performance compared to the CN117, in which the drop in the voltage was higher in case of CN117, as the ~60% loss in voltage in the case of CN117 higher than in case of the Nafion-DE-IL composite membranes. Adding the DE to the Nafion matrix provided the produced membranes with a favourable morphology structure as the DE enhanced the pores size and porosity distribution within the membrane structure. The DE worked on enhances the membrane's physical properties by increasing the porosity and pore distribution because 85% of DE is made up of microscopic, interlinked pores and this feature will maintain the water content inside the membrane which is favourable to enhance the conductivity properties and the same time protect the membrane from quick dehydration. Regarding the IL [EMIM][NTf2], adding the IL has improved the thermal properties of the membranes by increasing the decomposition temperature of the fabricated membranes due to that [EMIM][NTf2] has high-temperature decomposition >360â. Sustaining the performance of the fabricated membranes under high temperatures is an advantage that allows these membranes to be tested in higher temperature FCs like a hydrogen fuel cell that works at temperatures >100â.
Date of Award | 1 Aug 2023 |
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Original language | English |
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Awarding Institution | - The University of Manchester
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Supervisor | Stuart Holmes (Supervisor) & Philip Martin (Supervisor) |
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- Ionic liquid
- Direct methanol fuel cells
- Diatomaceous earth
- Nafion
- Fuel cells
Novel Materials to Enhance the Performance of Direct Methanol Fuel Cells Using Ionic Liquids and Diatomaceous Earth.
Hassan-Naji, R. (Author). 1 Aug 2023
Student thesis: Phd