Impact of Aluminum Modification on the Dielectric Properties of Graphene Oxide Membrane: Different Al Source

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The high dielectric constant and low dielectric loss of Graphene oxide (GO) membranes made them good dielectric separator membranes for both dielectric capacitors and planar micro-supercapacitors. A GO membrane, which is GO sheets laminated in the form of “brick-and-mortar” stacking configuration, is an orthotropic material. This means that GO will have different dielectric properties parallel to the GO sheets (in-plane) and perpendicular to the GO sheets (through-plane). Tailoring strategies applied to the membrane will impact its in-plane and through-plane dielectric property differently. Better understanding and ability to tailor the dielectric properties of the GO membrane is crucial for its dielectric applications. The Al3+ has the potential to interact with OFGs of GO sheets on the edge (carboxyl groups), which mainly impacts in-plane properties, or on the basal plane (hydroxyl, carbonyl, and carboxyl groups), which mainly impacts through-plane properties. The uneven interaction of Al3+ with the functional group on the edge and basal plane of GO sheets could lead to different modification effects of the in-plane and through-plane dielectric properties of the GO membrane. It was reported before that Al3+ from different sources will bond with the GO sheet differently, thus it has the potential to impact the through-plane and in-plane dielectric properties of the GO membrane differently. Here, the Al3+-modification to the GO membrane from three different Al source, Al metal foil, chloride salt, and alumina, were applied to tailor the through-plane and in-plane dielectric properties of as-fabricated GO membranes in the frequency range from 0.01 Hz to 105 Hz. Plane-to-plane and edge-to-edge coordination of Al3+ with the functional group on the basal plane or edge of the GO sheets were proposed to understand the different impact of Al3+ on the through-plane and in-plane dielectric properties of the GO membranes. This study provides a facile route to impact the dielectric property of GO membrane through interaction with the oxygenated functional group on the edge and basal plane of the GO sheet, and demonstrate the possibility of designing dielectric GO membrane with controllable dielectric performance.