Effect of electrode variable contact angle on the performance and transport characteristics of passive direct methanol fuel cells

• A comprehensive multiphase model for passive DMFC is developed.
• Variable contact angle effect of electrode due fabrication is studied.
• Increasing contact angle along flow direction of methanol reduces crossover.
• DL/MPL and MPL/CL interfacial transport resistance is critical.
• Results shed light on development of novel electrode with variable contact angle.

In this study, a multiphase passive direct methanol fuel cell (DMFC) model is developed to study the effect of micro porous layer (MPL) insertion, and the variable contact angle effects due to the different fabrication processes of diffusion layer (DL) and MPL are also investigated in details. It is found that with the contact angle increasing along the flow direction of methanol in anode DL (ADL), the liquid always needs to flow from a more hydrophilic region to a more hydrophobic region, leading to less methanol crossover. A higher ADL contact angle generally leads to more methanol crossover, although it increases the flow resistance at the inlet, the mass transport resistance at the DL/MPL interface is reduced, and the capillary driven flow is also enhanced inside the DL. However, since MPL is often a very thin layer compared with GDL, it could act as a mass transfer barrier mainly because of the contact angle differences across the MPL/DL and MPL/CL interfaces, which is the dominating factor determining the MPL function. The results also shed the light on the development of novel electrode with variable contact angle based on different fabrication processes.