Proton Conductivity and Gas Barrier Properties of Graphene Oxide for PEMFC Membranes

Abstract

Treatment of graphite by the modified Hummers method results in exfoliation of the graphene layers and the introduction of oxygen-containing surface functional groups.1 The resulting graphene oxide offers interesting possibilities for a wide range of applications in areas as diverse as e.g. humidity sensing,2 molecular sieving,3 gas barriers,4 dielectrics,5 and fuel cells.6,7 Polymer electrolyte membrane fuel cells (PEMFCs) are seen as a sustainable energy source for the future. So far the most commonly used membrane in PEMFCs is Nafion, due to its high mechanical and chemical stability as well as its high proton conductivity. However Nafion is expensive, has limited performance at temperatures > 100°C,8 and has only moderate gas barrier properties (leading to fuel crossover in very thin membranes). Graphene oxide membrane fuel cells (GOMFCs) have displayed reasonable power densities at room temperature,7and with some improvements could act as an electrolyte in low temperature fuel cells. Here, the proton conductivity, fuel cell performance, fuel crossover of graphene oxide paper with different oxygen content, surface morphology, and surface functional groups are investigated by impedance spectroscopy, membrane electrode assembly testing, and gas permeation measurements. The manufacturing techniques for production of graphene oxide membranes and the optimal thickness of membranes are also discussed.