Large-area, conductive and flexible reduced graphene oxide (RGO) membrane fabricated by electrophoretic deposition (EPD)

A large-area, conductive, and flexible membrane made from the stabilized aqueous solution of reduced graphene oxide (RGO) is successfully fabricated using an electrophoretic deposition (EPD) method. A low-voltage operation of EPD (∼3 volts) allows a robust consolidation of RGO layers desirably aligned in the in-plane direction through the cohesive electrophoretic squeezing force near the current collector. Transferring the deposited RGO layers to arbitrary substrates or achieving as a free-standing form, two methods of "chemical etching" and "electrochemical etching" are developed to detach the RGO layers from the EPD current collector without damaging the deposited RGO. Further reducing the free-standing RGO membrane by thermal annealing up to 1000 C, a graphite-like architecture is restored (d-spacing at 3.42 Å with C/O ratio at 16.66) and the electrical conductivity increases as high as 5.51 × 10⁵ S/m. The tightly-consolidated and securely-detached RGO membrane allows the free-standing and flexible features and highly conductive characteristics, which are further developed during thermal treatment. Because of the facile scale-up nature of the EPD process and RGO solution, the developed methodology has a considerable potential to be applied to various energy storage devices, flexible conductive coatings, and other electrochemical systems.