A Novel Aqueous Asymmetric Supercapacitor based on Pyrene-4,5,9,10-Tetraone Functionalized Graphene as the Cathode and Annealed Ti 3 C 2 T x MXene as the Anode.

Asymmetric supercapacitors (ASCs), employing two dissimilar electrode materials with a large redox peak position difference as cathode and anode, have been designed to further broaden the voltage window and improve the energy density of supercapacitors. Organic molecule based electrodes can be constructed by combining redox-active organic molecules with conductive carbon-based materials such as graphene. Herein, pyrene-4,5,9,10-tetraone (PYT), a redox-active molecule with four carbonyl groups, exhibits a four-electron transfer process and can potentially deliver a high capacity. PYT is noncovalently combined with two different kinds of graphene (Graphenea [GN] and LayerOne [LO]) at different mass ratios. The PYT-functionalized GN electrode (PYT/GN 4-5) possesses a high capacity of 711 F g -1 at 1 A g -1 in 1 M H 2 SO 4 . To match with the PYT/GN 4-5 cathode, an annealed-Ti 3 C 2 T x (A-Ti 3 C 2 T x ) MXene anode with a pseudocapacitive character is prepared by pyrolysis of pure Ti 3 C 2 T x . The assembled PYT/GN 4-5//A-Ti 3 C 2 T x ASC delivers an outstanding energy density of 18.4 Wh kg -1 at a power density of 700 W kg -1 . The PYT-functionalized graphene holds great potential for high-performance energy storage devices.