Orderly sandwich-shaped graphene oxide/Nafion composite membranes for direct methanol fuel cells

A novel type of graphene oxide (GO)/Nafion composite membrane is fabricated and used as a proton exchange membrane for direct methanol fuel cells (DMFCs) in this article. The membranes are prepared by depositing GO nanosheets on the surface of recast Nafion ® 117 via a layer-by-layer (LbL) procedure using 1, 4-phenyldiamine hydrochloride (PDHC) as the cross-linker. This approach prevents the GO nanosheets from dissolving in water and imparts the composite membranes a good stability. The methanol permeability of the composite membranes is lower than that of recast Nafion ® 117 measured under the same conditions. The composite membrane with 80-layered GO nanosheets exhibits a value of 6.7×10 −8   cm 2   s −1 at 30   °C, which is two orders of magnitude lower than that of recast Nafion ® 117. In addition, the relative selectivity of the composite membranes is 5 times higher than that of recast Nafion ® 117. The endurance time of the composite membranes in Fenton׳s reagent is 10 times longer than that of Nafion. Single cell evaluation using the composite membrane with 50-layered GO showed an open circuit voltage (OCV) of 0.67   V. A maximum power density of 64.38   mW   cm −2 at a current density of 200   mA   cm −2 can be achieved at 60   °C.