Retarding Ostwald Ripening to Directly Cast 3D Porous Graphene Oxide Bulks at Open Ambient Conditions

Graphene aerogels (GAs) with attractive properties have shown tremendous potentials in energy- and environment-related applications. Unfortunately, current assembly methods for GAs such as sol-gel and freeze-casting processes must be conducted in enclosed spaces with unconventional conditions, thus being literally inoperative for in situ and continuous productions. Herein, a direct slurry-casting method at open ambient conditions is established to arbitrarily prepare three-dimensional (3D) porous graphene oxide (GO) bulks without macroscopic dimension limits on a wide range of solid surfaces by retarding Ostwald ripening of 3D liquid GO foams when being dried in air. A subsequent fast thermal reduction (FTR) of GO foams leads to the formation of graphene aerogels (denoted as FTR-GAs) with hierarchical closed-cellular graphene structures. The FTR-GAs show outstanding high-temperature thermal insulation (70% decrease for 400 °C), as well as superelasticity (>1000 compression-recovery cycles at 50% strain), ultralow density (10-28 mg cm^-3), large specific surface area (BET, 206.8 m² g^-1), and high conductivity (ca. 100 S m^-1). This work provides a viable method to achieve in situ preparations of high-performance GAs as multifunctional structural materials in aircrafts, high-speed trains, or even buildings for the targets of energy efficiency, comfort, and safety.