Proton exchange membrane water electrolyser (PEMWE) technology can be used to produce hydrogen from renewable energy sources; the technology is therefore a promising component in future national power and transportation fuel systems. The main challenges faced by the technology include prohibitive materials costs, maximising efficiency and ensuring suitable longevity. Therefore, research is needed to understand the internal operation of the systems so that cell design can be optimised to obtain maximum performance and longevity. PEMWE is a low temperature electrolysis system that consists of cell components such as end plates, current collectors, bipolar plates, gas diffusion layers (GDLs) and membrane electrode assemblies (MEAs). Cell performance is strongly reliant on the materials and designs of each of the components. Three cell designs were used to study different aspects of PEMWE operation: commercial cell, optically transparent cell and combined optical and current mapping cell. Polarisation measurements performed on a commercially available lab-scale test cell at ambient conditions illustrated an increase in mass transport limitations with increasing water flow rate which was confirmed using electrochemical impedance spectroscopy (EIS) measurements. A transparent cell was constructed to allow optical access to the flow channels. Measurements made on the cell showed a transition from bubbly to slug flow that affects mass transport limitations and consequently the electrochemical performance. Thermal imaging measurements supported a mass and energy balance of the system. Finally, a combined transparent and current mapping cell was constructed using PCB technology that indicated higher current densities closer to the exit of the channel. Optical measurements showed that this increase in current was associated with larger bubbles and a transition to slug flow which led to enhanced mass transport of water to the electrode surface. A model developed for the system showed that the cell potential is dominated by the anode activation overpotential. Experimental data obtained at similar conditions with the commercially available lab-scale test cell agreed well with the model and the fitted parameters were in close proximity with values published in literature.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:626553 |
| Date | January 2014 |
| Creators | Dedigama, I. U. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1426127/ |
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