MnO₂ Nanowire/Biomass-Derived Carbon from Hemp Stem for High-Performance\nSupercapacitors

Abstract

Hierarchical\n3D nanostructures based on waste biomass are being\noffered as promising materials for energy storage due to their processabilities,\nmultifunctionalities, environmental benignities, and low cost. Here\nwe report a facile, inexpensive, and scalable strategy for the fabrication\nof hierarchical porous 3D structure as electrode materials for supercapacitors\nbased on MnO₂ nanowires and hemp-derived activated carbon\n(HC). Vertical MnO₂ wires are uniformly deposited onto\nthe surface of HC using a one-step hydrothermal method to produce\nhierarchical porous structures with conductive interconnected 3D networks.\nHC acts as a near-ideal 3D current collector and anchors electroactive\nmaterials, and this confers a specific capacitance of 340 F g^–1 at 1 A g^–1 with a high rate capability\n(88% retention) of the 3D MnO₂/HC composite because of\nits open-pore system, which facilitates ion and electron transports\nand synergistic contribution of two energy-storage materials. Moreover,\nasymmetric supercapacitors fabricated using 3D HC as the anode and\n3D MnO₂/HC as the cathode are able to store 33.3 Wh kg^–1 of energy and have a power delivery of 14.8 kW kg^–1.