Self-assembled three-dimensional macroscopic graphene/MXene-based hydrogel as electrode for supercapacitor

Hydrogels with unique three-dimensional (3D) macroscopic porous architectures are attractive electrode materials for supercapacitors because of their superior electrolyte permeabilities and rapid electron/ion transports. In this letter, a cylindrical-type 3D macroscopic graphene/MXene-based hydrogel (GMH) is prepared by self-assembling laminar-structured graphene oxide (GO) and MXene (Ti3C2) nanosheets via a facile one-step hydrothermal method under the existence of ammonia water and hydrazine hydrate. GO is found to self-converge into a 3D macroscopic porous graphene framework during the hydrothermal process, while Ti3C2 nanosheets are able to prevent the graphene nanosheets from self-restacking. The as-prepared GMH shows a larger specific surface area of 161.1 m2 g-1 and a higher pore volume of 0.5 cm3 g-1 in comparison with the pure graphene hydrogel. A symmetric supercapacitor utilizing GMH as electrodes exhibits high energy densities of 9.3 Wh kg-1 and 5.7 Wh kg-1 at different power densities of 500 W kg-1 and 5000 W kg-1, respectively, as well as an outstanding long-term cycle stability with no loss in capacitance in excess of 10 000 continuous charge-discharge cycles. The strategy of preparation of a 3D macroscopic GMH is expected to realize promising high-performance hydrogel electrodes based on graphene and MXene for electrochemical energy storages.