Biomass-Derived Sponge-like Carbonaceous Hydrogels and Aerogels for Supercapacitors

Abstract

As a newly developed material, carbon gels have been receiving considerable attention due to their multifunctional properties. Herein, we present a facile, green, and template-free route toward sponge-like carbonaceous hydrogels and aerogels by using crude biomass, watermelon as the carbon source. The obtained three-dimensional (3D) flexible carbonaceous gels are made of both carbonaceous nanofibers and nanospheres. The porous carbonaceous gels (CGs) are highly chemically active and show excellent mechanical flexibility which enable them to be a good scaffold for the synthesis of 3D composite materials. We synthesized the carbonaceous gel-based composite materials by incorporating Fe3O4 nanoparticles into the networks of the carbonaceous gels. The Fe3O4/CGs composites further transform into magnetite carbon aerogels (MCAs) by calcination. The MCAs keep the porous structure of the original CGs, which allows the sustained and stable transport of both electrolyte ions and electrons to the electrode surface, leading to excellent electrochemical performance. The MCAs exhibit an excellent capacitance of 333.1 F·g(-1) at a current density of 1 A·g(-1) within a potential window of -1.0 to 0 V in 6 M KOH solution. Meanwhile, the MCAs also show outstanding cycling stability with 96% of the capacitance retention after 1000 cycles of charge/discharge. These findings open up the use of low-cost elastic carbon gels for the synthesis of other 3D composite materials and show the possibility for the application in energy storage.

Paper‐Based Electrodes for Flexible Energy Storage Devices

“…Different structures such as carbon film,76, 250 carbon foam,154, 251 carbon aerogel,26, 252 carbon hydrogel,253, 254 carbon paper,255, 256 and carbon cloth,80, 91 have been developed. Various morphologies like nanodots,257 nanotubes,49 nanoribbon,258 nanofiber,228 nanosheets,109 have also been explored to improve their performances.…”

Biomass-derived renewable carbon materials for electrochemical energy storage

“…Additionally, by coupling with chemical activation, the specific surface area and surface chemistry of the final carbon products could be further improved and modified by adding special oxidizing agent. Various carbon materials with high specific surface areas and modified functional groups have been produced from biomass precursors for supercapacitors, such as cellulose, potato starch and eucalyptus wood saw dust [111], hemicellulose [112], paper pulp mill sludge [113], D-glucosamine [114], fungi [70], fungus [115], bamboo waste [116], microalgae [117], watermelon [118] and hemp [119]. For example, Sevilla et al produced microporous carbons from the microalgae by a HTC process accompanied with a post-KOH activation treatment (Figure 7(a)).…”

The enhancement of electrochemical capacitance of biomass-carbon by pyrolysis of extracted nanofibers

“…Among the various types of carbon-based electrode material such as activated carbons, graphene and carbon nanotubes, porous carbons derived from biomass are particularly promising due to the abundance, low cost and the hierarchical structures of the raw materials [2,3]. High electrochemical capacitances have been achieved with carbons derived from a variety of biomass such as lotus, watermelon, leaves, and hemp fibers [4][5][6][7][8][9][10]. However, most of the work converted crude biomass directly into carbon; there are large variations in the capacitances for biomass-derived carbons in…”