Structural design of gas diffusion layer for proton exchange membrane fuel cell at varying humidification

Abstract Different structural gas diffusion layers (GDLs) have been prepared to improve the performance of proton exchange membrane fuel cells (PEMFCs). Density of microporous layer (MPL), pore structure of MPL and thickness of macroporous substrate (MPS) have been investigated to evaluate the effects on membrane electrode assembly (MEA). From measurements, porosity-graded MPL (MPL-G) on thin MPS reveals the most efficient water management. MPL-G coated on thick MPS (MPL-G-T) shows the lowest contact resistance, highest gas permeability and superior reaction efficiency. Asymmetric MEA has also been assembled by MPL-G for anode and MPL-G-T for cathode, revealing a high adaptability at varying humidification. Significantly, the maximum power density of asymmetric MEA is 1.26 W cm−2 at dry condition of 35%RH (relative humidity) and 1.22 W cm−2 at high humidification of 100%RH. This superior performance is attributed to the efficient balance of gas permeability and water management. Hence, such asymmetric structural MEA is a promising strategy for the optimization of PEMFCs at varying operation.