Fabrication of superelastic and highly conductive graphene aerogels by precisely "unlocking" the oxygenated groups on graphene oxide sheets

Oxygenated groups in graphene oxide (GO) have significant influences on the physicochemical properties of GO. Accurate identification and manipulation of oxygenated groups should be essential for sheets functionalization and assembly, but remains challenging. Herein a novel design of oxygenated groups on GO via a facile alkali-annealing strategy is reported to rationally "unlock" specific groups and increase covalent bonding density on sheets. The structural evolution of epoxy and enriched in hydroxyl are well monitored and verified. Based on the fact that hydroxyl is widely regarded as active sites for cross-linker polyvinyl alcohol, a well interweaved graphene aerogel (GA) with ordered "layer-strut" bracing architectures is successfully fabricated. The constructed GA possesses an ultralow density of 1.73 mg cm(-3), exceptional resilience with 85% compressive strength recovery even after 1000 cycles, and high conductivity of 17.1 S m(-1), demonstrating the significantly reinforced interplays between adjacent layers. The highest specific conductivity (sigma/rho) of the optimized GA reaches 98.8 S cm(2) g(-1), which is far superior to conventional GA assembled by GO in as-prepared form and exceeding most graphene-based aerogels reported. This new insight into precise engineering oxygenated structures will provide inspirational ideas towards more elaborate graphene-related architectures and a better overall understanding of GO structure. (C) 2020 Elsevier Ltd. All rights reserved.