Characterization and Improvement of Surface Conductive, Graphene Membrane Electrodes Produced by Phase Inversion atop Prelayered Graphene Nanosheets

Surface conductive, graphene membrane electrodes (grMEs) can be highly effective for electrochemical applications that combine molecular separation and current collection. However, it is important to understand the relationships between fabrication procedures, nanosheet arrangements, and conductivity. Here, we present a series of improvements on graphene nanosheet transfer including demonstrating a >10x increase in membrane area with comparable sheet resistance (79 Ω/sq) as smaller (11 cm2) samples, controlling the loading of graphene nanosheets, and identifying two flexible polymer membranes viable as transfer media: Celgard 3501 (coated-polypropylene) and microporous ECTFE (ethylene-chlorotrifluoroethylene). These changes produced a range of sheet resistances from 128 to 16 Ω/sq, with total graphene loading producing the most significant decreases in sheet resistance. Additionally, we present a methodology for analyzing the arrangement of the graphene nanosheet layer in the composite membrane by comparing X-ray diffraction (XRD) patterns to those reported in the literature. Even though these grMEs have only a micrometer(s)-scale graphene nanosheet layer, we conclude that their arrangement varied predictably depending on the transfer media and vacuum deposition force applied. Interestingly, different overall amounts of deposited graphene nanosheets generated different XRD correlations with the conductivity, likely the result of the anisotropy between the in-plane and vertical conductivities of stacked nanosheets. Finally, we also report the effect of the membrane polymer in these composite grMEs on the liquid and gas mass transfer under diffusion-dominated conditions to illustrate the potential application of grMEs for an abiotic glucose fuel cell device.