Enhanced transport properties of graphene‐based, thin Nafion® membrane for polymer electrolyte membrane fuel cells

Summary A polymer electrolyte membrane fuel cell (PEMFC) is one of the promising renewable energy conversion systems; however, its performance is considerably limited by the sluggish transport properties and/or reaction kinetics of the catalyst layers, especially at a high current density. In this study, graphene‐based, thin Nafion® membranes are prepared using 0 to 4 wt% of graphene nanoflakes, and the effects of the graphene are examined for enhanced transport properties. The electrical conductivity and dielectric constant are drastically enhanced to 0.4 mS/cm and 26 at 4 wt% of graphene nanoflakes, respectively, while the thermal conductivity linearly increases to 3 W/m‐K. The proton conductivity also significantly increases with the aid of graphene nanoflakes at >2 wt% of graphene nanoflakes, and the enhancement doubles compared with those of the carbon‐black (CB)‐based and carbon nanotube (CNT)‐based, thin Nafion® membranes, perhaps due to unique graphene structures. Additionally, the quasi‐steady‐state water contact angle increases from 113° to ~130° with the addition of graphene nanoflakes, showing that a hydrophobic‐like water wetting change may be related to the significant proton conductivity enhancement. This work provides an optimal material design guideline for the transport‐enhanced cathode catalyst layer using graphene‐based materials for polymer electrolyte membrane fuel cell applications.