Large scale synthetic method for free standing graphene film and graphene sponges

Here we present a simple method to prepare large-scale graphene sponges and free-standing graphene films using a speed vacuum concentrator. During a centrifugal evaporation process, suspended graphene oxide (GO) sheets in an aqueous solution have been assembled to generate network-linked GO sponges or a series of multilayer GO films depending on the temperature of a centrifugal vacuum chamber. While sponge-like bulk GO materials (GO sponges) have been produced at 40°C, uniform free-standing GO films which size were up to 9 cm² were generated at 80°C. Ihe thickness of GO films can be controlled from 200 nm to 1 μm based on the concentration of the GO colloidal suspension and evaporation temperature. The synthesized GO films exhibit high flexibility with a smooth surface and condensed density. Reduced GO sponges and films have been produced through a thermal annealing process at 800°C with H₂/Ar flow. Scanning electron microscope (SEM), High resolution transmission electron microscope (HRTEM) and x-ray photoelectron spectroscope (XPS) were employed to charaterize the reduced GO sponges and films.