However, the effects of the crack size and the areal fraction of cracks on device performance have not been studied, and reproduction of the same crack morphology is not easy in the case of MEAs with randomly distributed cracks. This simple and facile method does not require any post-treatment after stretching the MEA, and the cracks on the electrode effectively act as macropores to improve mass transport. Our recent study showed that cracks generated on the cathode (formed by stretching the MEA) simultaneously enhanced mass transport and reduced membrane resistance 10. These methods require chemical or thermal post-treatments, which are complex and time consuming. Another method to improve water transport is to introduce pore-forming agents, such as carbonate or polystyrene particles, which are removed after the catalyst layer is sprayed onto the electrolyte membrane 18, 19, 20. However, the inserted hydrophobic polymers adhere to the carbon support and catalyst surface without selectivity, which decreases the electrochemically active surface area of the catalyst layer. First, hydrophobic polymer nanoparticles, such as polytetrafluoroethylene, were mixed with a catalyst ink and inserted into the cathode catalyst layer during the MEA fabrication process 15, 16, 17. Many attempts have been made to effectively remove the water generated by the electrochemical reaction at the cathode. Hence, the produced water must be appropriately removed to maintain the pathway for the reactant oxygen gas. In relation to water transport, water molecules that are generated by the oxygen reduction reaction block the catalyst surface and pores in the cathode catalyst layer, reducing device performance. To obtain high device performance, ohmic loss should be reduced by using a thinned electrolyte membrane 8, 9, 10 and water transport at the cathode of the membrane electrode assembly (MEA) should be enhanced 11, 12, 13, 14. Although many technological advances have been achieved in the research field of PEMFCs, some practical issues still hinder their commercialization. ![]() ![]() Polymer electrolyte membrane fuel cells (PEMFCs) have received significant attention over the past several decades as future clean energy devices because they do not emit pollutants and they provide high energy conversion efficiencies 1, 2, 3, 4, 5, 6, 7.
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