Carbonated MOF-based graphene hydrogel for hierarchical all-carbon supercapacitors with ultra-high areal and volumetric energy density

Graphene hydrogel (GH) has been widely explored as electrode material for supercapacitors due to its threedimensional porous network structure. However, poor conductivity and low capacitance activity have limited practical application. Herein, we design and fabricate a hierarchical all-carbon GH-based electrode material decorated with MOF-derived porous carbon (cZIF-8) and highly N-doped graphene quantum dots. In this N-GQD@cZIF-8/GHcomposite, GH constructs an interconnected porous structure which benefits rapid electron/ion transport, and cZIF-8 provides a large specific surface area and enhances electrical conductivity, while N-GQDs contribute pseudo-capacitance and improve the wettability. The supercapacitor based on N-GQD@cZIF-8/GH shows a high areal capacitance (617.1 mF cm(-2)) and areal energy density (85.7 mu Wh cm(-2)) at 1 mA cm(-2). It also has good rate capability (81.5% at 20 mA cm(-2)) and excellent cycling stability (93.1% after 10,000 cycles). Moreover, the assembled all-solid-state flexible supercapacitor can deliver a high energy density of 18.1 mWh cm(-3) at high power density of 4907.3 mW cm(-3). This rational-designed all-carbon electrode opens up opportunities in the fabrication of next-generation wearable electronic equipments.