Effect of Properties of Hydrophilic Microporous Layer (MPL) on PEFC Performance

For better water management in polymer electrolyte fuel cells (PEFCs), microporous layers (MPLs) are generally used. In this paper, hydrophilic MPLs having various pore volumes and diameters were prepared using a range of carbon materials, and the effect of the MPL on the membrane electrode assembly (MEA) performance was investigated under dry and wet conditions. Under the dry condition (80°C, 30%RH), the MEA employing an MPL with a larger median pore diameter showed higher cell voltage, suggesting that the MPL with a larger pore diameter has better gas diffusivity, leading to better MEA performance. Under the wet condition (80°C, 100%RH), it was confirmed that pore volume of the MPL has a significant impact on the MEA performance and that the hydrophilic MPL with a large pore volume was effective in reducing water flooding in the cathode catalyst layer. When used in an MPL, VGCF-H (carbon fiber with a fiber diameter of 150 nm) gives the largest pore diameter and pore volume. This MEA with a hydrophilic MPL (made of VGCF-H and ionomer) showed the best MEA performance under both dry and wet operating conditions.