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

Abstract

Abstract Graphene hydrogel (GH) has been widely explored as electrode material for supercapacitors due to its three-dimensional 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/GH composite, 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 μWh 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.