Development of the Soaking Method for Manufacturing Polymer Electrolyte Fuel Cells with a High-Aspect-Ratio Microstructure

To improve power generation performance of polymer electrolyte fuel cells (PEFCs), it is necessary to decrease the activation overpotential of the oxygen reduction reaction (ORR). We propose a method for manufacturing PEFCs with a high-aspect-ratio microstructure to further increase the triple-phase boundary, where ORR occurs. The cathode surface of a Nafion membrane with a high-aspect-ratio microstructure was soaked in catalyst ink using spraying equipment. After drying, the cross-section observations revealed that the catalyst layer went deep into the microstructure without forming a bridge structure. This was probably because the catalyst ink was impregnated into the microstructure before the solvent evaporated. The impregnation process must be the Cassie-Wenzel transition, and the driving force might be the gravity force of the ink or spray pressure. Power generation tests were conducted on PEFCs with microstructures fabricated using the soaking method, and the cells exhibited better power generation performance than conventional cells.