Speaker
Description
High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) operate at 120-200°C, avoiding water flooding, tolerating CO, and improving reaction kinetics. The gas diffusion layer (GDL), which consist of the microporous layer (MPL) and carbon paper/cloth, is crucial for mass transport, heat transfer, and electricity conduction. The presence of the MPL can enhance electrochemical surface area (ECSE) and prevented phosphoric acid leaching toward the channel. Those aspects are important to enhance the performance and durability. In this work, the role of MPL in enhancing HT-PEMFC performance, with a focus on MPL structure, is investigated. The MPL with various polytetrafluoroethylene (PTFE) compositions (5, 10, and 20%) and thickness (10 to 50 µm are prepared in-house employing ultrasonic spray technology. The commercial carbon paper (GDS310, CeTech, Taiwan) is sprayed with MPL followed by 1 mg Pt cm -2, while the anode is commercial carbon paper (GDL 340, CeTech, Taiwan) sprayed with 0.5 mg Pt cm -2. HT-PEMFC is operated at 180oC, with stoichiometric ratios of 1.2 and 2 for hydrogen and air, respectively. The results indicate that, for lower binder composition, increasing MPL thickness can enhance HT-PEMFC performance. However, this trend does not hold for higher binder composition. The optimal MPL structure in this study is 50 µm in thickness with 5% PTFE. The cell voltage is 0.6 V at 0.324 A cm -2, while maximum power density peaks at 0.3864 W cm -2. When the MPL thickness is constant, the performance decreases with increasing binder composition: a decrease of 22% at 10% PTFE and 26% at 20% PTFE. The EIS test confirms that the ohmic resistance is 2.7% and 9.7% higher at 5% PTFE compared to 10% and 20% PTFE, respectively, at a thickness of 50 µm. However, further observation is needed for 10% and 20% PTFE cases to obtain comprehensive results.
