Multivalent Cation Cross-Linking Suppresses Highly Energetic Graphene Oxide’s Flammability

Graphene oxide (GO), a common intermediate for making graphene-like materials from graphite, was recently found to possess an explosive fire hazard that can jeopardize the GO’s large-scale production and wide applications. This work reports a simple and facile method to cross-link the GO with Al³⁺ cations, in one step, into a freestanding flexible membrane. This inorganic membrane resists in-air burning on an open flame, at which non-cross-linked GO was burnt out within ∼5 s. All characterization data suggested that the in situ “epoxy ring-opening” reactions on the GO surface facilitated the cross-linking, which elucidated a new mechanism for the generalized inorganic polymerization. With the much improved thermal and water stabilities, the cross-linked GO film can help to advance high-temperature fuel cells, electronic packaging, etc. as one of the long-sought inorganic polymers known to date.