Effects of Structure and Hydrophobic Treatment on Water Transport Behaviour in PEM Fuel Cell Gas Diffusion Layers

Effects of the Surface Structure on the Water Transport Behavior in PEMFC Carbon Fiber Papers

“…They concluded that the 20 wt % PTFE treatment prevents liquid water from filling the pores in the hydrophobic region, thereby facilitating good gas transport through the CFP. In addition to the PTFE treatment, a MPL has been applied on the side of the CFP, which contacts with CL to control the pore structure. , Tabe et al found that the MPL suppresses water accumulation at the interface owing to the smaller pore size and finer contact with the CL, resulting in less water flooding, which is consistent with the results of Owejan et al In recent years, several research studies have demonstrated that the incorporation of one-dimensional substances such as carbon nanotubes (CNTs) in the MPL significantly improved the pore structure of the MPL and water management function of PEMFCs. − The addition of CNTs in the MPL formed hydrophilic large pores, which could enhance the transfer of liquid water from CL to GDL, as more water transfer channels were provided. , In addition, Mao et al prepared porous carbon nanofibers (PCNFs) by the electrospinning method and subsequent heat treatment and then built up to form the MPL. The nanosized pores of PCNF and the larger-sized pores formed by the accumulation of PCNF created a pore-size gradient, which accelerated the discharge of the water product from the system because of the capillary effect.…”

“…We suggest that a small amount of residual water remains attached in the porous CFP and this water reduces the capillary resistance that water needs to overcome to penetrate the CFP. Previous research showed that water saturation in the CFP was considerably decreased after the PTFE treatment and introduction of MPL . After the initial water penetration, the water saturation in pure CFP is higher, and the capillary resistance that water needs to overcome to penetrate the CFP is lower, so the shutoff pressure is lower.…”

“…Since there may be pores larger than 30 μm in CFP, the calculated results are larger than the experimental results but their trends are consistent. In addition, the water flow rates at initial penetration for CFP and PTFE-CFP are 4.65 and 4.35 mg/s, which means that the PTFE treatment makes the flow rate decrease …”

“…The gas diffusion layer (GDL) consisting of carbon fiber papers (CFPs) and the microporous layer (MPL) is a fundamental element of the electrodes in a polymer electrolyte membrane fuel cell (PEMFC) . It provides pathways for the product water removal from the catalyst layer (CL) to the flow channel and plays a crucial role in the water management for PEMFC. , However, excessive amount of liquid water in the GDL blocks the reactant-transporting porous network, hindering oxygen transport to the active sites in the CL and causing mass transport losses. , …”