Influence of cathode opening size and wetting properties of diffusion layers on the performance of air-breathing PEMFCs |
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| Affiliation: | 1. Energy Conversion R&D Center, Central Academy of Dongfang Electric Corporation, Chengdu 611731, China;2. School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 610023, China;1. Key Lab of RF Circuits and Systems of Ministry of Education, Microelectronics CAD Center, Hangzhou Dianzi University, Hangzhou 310018, China;2. MEMS Center, Harbin Institute of Technology, Harbin 150001, China;1. Key Laboratory of Ministry of Education in the Field of Road and Transport Engineering, Tongji University, Shanghai 201804, China;2. Clean Energy Automotive Engineering Center, 4800 Caoan Road, Tongji University, Shanghai 201804, China;3. School of Automotive Studies, 4800 Caoan Road, Tongji University, Shanghai 201804, China;1. Eco-materials and Renewable Energy Research Center, Department of Materials Science and Engineering, Department of Physics and National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, China;2. Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China;3. Kunshan Innovation Institute of Nanjing University, Kunshan, 215347, China;1. EPSRC “Frontier Engineering” Centre for Nature Inspired Engineering & Department of Chemical Engineering, University College London, London WC1E 7JE, United Kingdom;2. Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London WC1E 7JE, United Kingdom;3. National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom |
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| Abstract: | Air-breathing PEMFCs consist of an open cathodic side to allow an entirely passive supply of oxygen by diffusion. Furthermore, a large fraction of the produced water is removed by evaporation from the open cathode. Gas diffusion layers (GDLs) and the opening size of the cathode have a crucial influence on the performance of an air-breathing PEMFC. In order to assure an unobstructed supply of oxygen the water has to be removed efficiently and condensation in the GDL has to be avoided. On the other hand good humidification of the membrane has to be achieved to obtain high protonic conductivity.In this paper the influence of varying cathodic opening sizes (33%, 50% and 80% opening ratios) and of GDLs with different wetting properties are analysed. GDLs with hydrophobic and hydrophilic properties are prepared by coating of untreated GDLs (Toray® carbon paper TGP-H-120, thickness of 350 μm). The air-breathing PEMFC test samples are realised using printed circuit board (PCB) technology.The cell samples were characterised over the entire potential range (0–0.95 V) by extensive measurements of the current density, the temperature and the cell impedance at 1 kHz. Additionally, measurements of the water balance were carried out at distinct operation points.The best cell performance was achieved with the largest opening ratio (80%) and an untreated GDL. At the maximum power point, this cell sample achieved a power density of 100 mW cm−2 at a moderate cell temperature of 43 °C. Furthermore, it could be shown that GDLs with hydrophilic or intense hydrophobic properties do not improve the performance of an air-breathing PEMFC.Based on the extensive characterisations, two design rules for air-breathing PEMFCs could be formulated.Firstly, it is crucial to maximise the cathode opening as far as an appropriate compression pressure of the cell assembly and therewith low contact resistance can be assured. Secondly, it is advantageous to use an untreated, slightly hydrophobic GDL. |
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