Free-Standing Boron-Doped Graphene Hydrogel Buckypaper Fabricated via Zinc-Plate Reduction for High-Performance Supercapacitors

Graphene offers exceptional mechanical flexibility and superior electrical conductivity that are highly desirable for next-generation supercapacitors; however, its intrinsic strong π-π stacking interactions severely hinder energy-storage performance by blocking active redox sites and restricting ion-accessible pathways. To address these limitations, we developed a binder-free, free-standing, boron-doped graphene hydrogel buckypaper with a hierarchical architecture. In this study, a mixed suspension of thermally activated boron-doped expanded graphene (BT-rGO) and graphene oxide (GO) was integrated via a redox reaction using a Zn plate as a substrate, enabling the instantaneous fabrication of a free-standing BT-rGO/Zn-rGO hydrogel buckypaper. The boron-doped graphene framework exhibits enhanced wettability, facilitating efficient electrolyte ion transportation, while the heteroatom-induced uneven charge distribution modulates the local electronegativity and improves electroconductivity throughout the free-standing hydrogel buckypaper network. The electrochemically enhanced E-BT-rGO₃/Zn-rGO₁ hydrogel buckypaper (BT-rGO:GO mass ratio = 3:1) delivers a high specific capacitance of 443.63 F g^-1 at 2 mA cm^-2 and maintains 88% capacitance retention after 10,000 cycles at 50 mA cm^-2. Moreover, a flexible solid-state supercapacitor assembled from the BT-rGO₃/Zn-rGO₁ hydrogel buckypaper achieves an energy density of 16.96 Wh kg^-1 and a power density of 5.21 kW kg^-1, demonstrating its practical applicability for powering LED lightbulbs. Hence, the binder-free strategy creates a mechanically robust, porous framework with fully accessible ion pathways, delivering a purely carbon-based, metal-oxide-free electrode platform with an exceptional electrochemical performance.