Highly ordered graphene oxide paper laminated with a Nafion membrane for direct methanol fuel cells

• A GO-laminated Nafion membrane for DMFC is originally proposed.
• The parallel orientation of the GO paper can effectively block methanol crossover.
• The novel membrane shows its superiority in DMFC at higher methanol feed concentrations.

This study presents graphene oxide (GO)-laminated Nafion 115 as a proton exchange membrane for a direct methanol fuel cell (DMFC). Compared to a GO-dispersed polymer composite membrane, a GO-laminated proton-conducting membrane is advantageous for DMFC operating at higher methanol feed concentrations. The novel laminate membrane consists of highly ordered GO paper with parallel orientation prepared by using a vacuum filtration method. This dual-layer membrane is fabricated by laminating the Nafion 115 membrane with a highly orientated GO paper through transfer printing followed by hot-pressing. Scanning electron microcopy (SEM) shows that the GO paper measuring approximately 1.0 μm thick (i.e., corresponding to 1.5 wt%) adhered well to the base membrane. The methanol permeability of the GO-laminated membrane is approximately 70% lower than that of Nafion 115 at an expense of a 22% decrease in proton conductivity. The proposed membrane has a 40% higher selectivity (i.e. ratio of proton conductivity to methanol permeability) than Nafion 115. The GO-laminated Nafion membrane is far superior to the pristine Nafion membrane in DMFC performance when operating at an 8 M methanol feed concentration.