Graphene Quantum Dots Pinned on Nanosheets‐Assembled NiCo‐LDH Hollow Micro‐Tunnels: Toward High‐Performance Pouch‐Type Supercapacitor via the Regulated Electron Localization

Abstract A combined delicate micro‐/nano‐architecture and corresponding surface modification at the nanometer level can co‐tailor the physicochemical properties to realize an advanced supercapacitor electrode material. Herein, nanosheets‐assembled nickel‐cobalt‐layered double hydroxide (NiCo‐LDH) hollow micro‐tunnels strongly coupled with higher‐Fermi‐level graphene quantum dots (GQDs) are reported. The unique hollow structure endows the electrolyte accessible to more electroactive sites, while 2D nanosheets have excellent surface chemistry, which favors rapid ion/electron transfer, synergistically resulting in more super‐capacitive activities. The experimental and density functional theory calculations recognize that such a precise decoration generally tunes the charge density distribution at the near‐surface due to the Fermi‐level difference of two components, thus regulating the electron localization, while decorating with conductive GQDs co‐improves the charge mobility, affording superior capacitive response and electrode integrity. The as‐acquired GQDs@LDH‐2 electrode yields excellent capacitance reaching ≈1628 F g −1 at 1 A g −1 and durable cycling longevity (86.2% capacitive retention after 8000 cycles). When coupled with reduced graphene oxide‐based negative electrode, the hybrid device unveils an impressive energy/power density (46 Wh kg −1 / 7440 W kg −1 ); moreover, a flexible pouch‐type supercapacitor can be constructed based on this hybrid system, which holds high mechanical properties and stable energy and power output at various situations, showcasing superb application prospects.