Graphene Coating of Nafion Membranes for Enhanced Fuel Cell Performance
Jasper Ruhkopf, Ulrich Plachetka, Michael Moeller, Oliver Pasdag, Ivan Radev, Volker Peinecke, Marco Hepp, Christian Wiktor, Martin R. Lohe, Xinliang Feng, Benjamin Butz, Max C. Lemme
Abstract
High Resolution Image Download MS PowerPoint Slide Electrochemically exfoliated graphene (e-G) thin films on Nafion membranes exhibit a selective barrier effect against undesirable fuel crossover. This approach combines the high proton conductivity of state-of-the-art Nafion and the ability of e-G layers to effectively block the transport of methanol and hydrogen. Nafion membranes are coated with aqueous dispersions of e-G on the anode side, making use of a facile and scalable spray process. Scanning transmission electron microscopy and electron energy-loss spectroscopy confirm the formation of a dense percolated graphene flake network, which acts as a diffusion barrier. The maximum power density in direct methanol fuel cell (DMFC) operation with e-G-coated Nafion N115 is 3.9 times higher than that of the Nafion N115 reference (39 vs 10 mW cm –2 @0.3 V) at a 5M methanol feed concentration. This suggests the application of e-G-coated Nafion membranes for portable DMFCs, where the use of highly concentrated methanol is desirable.