Superhydrophobic flow channel surface and its impact on PEM fuel cell performance

Water management is a critical issue in polymer electrolyte membrane fuel cells (PEMFCs), and it is normally achieved through the modification of surface wettability condition for the cell components. In this study, superhydrophobic surface-coating materials were developed and the gas flow channel surfaces were modified for superhydrophobic surface property with small sliding angles (SAs). The coated surface characteristics were measured, including static contact angle (CA), SA and CA hysteresis as well as surface geometrical properties. The flow characteristics through such surface-coated channels were measured, and comparison was made with hydrophilic channels and channels coated with poly(tetrafluoroethylene), a commonly used surface-coating agent in PEMFCs. It was found that the presently modified superhydrophobic flow channels yield the lowest resistance to the two-phase flow; and both the mechanical and thermal stabilities of the attained superhydrophobicity for the coated surfaces were also investigated. It was demonstrated experimentally that such coated flow channels result in improved PEMFC performance due to improved water management.