Biocarbon Monoliths as Supercapacitor Electrodes: Influence of Wood Anisotropy on Their Electrical and Electrochemical Properties

Abstract

Biocarbon monoliths were obtained from Eucalyptus grandis and the influence of wood anisotropy on the electrical and electrochemical performance as supercapacitor electrodes was studied. They were produced from wood pieces cut along the transversal and longitudinal direction of the tree trunk, followed by pyrolysis and, for some of them, also by activation with CO 2 . Monoliths with drilled channels were also obtained. All the monoliths were characterized by SEM, nitrogen adsorption/desorption isotherms, electrical conductivity measurements and electrochemical measurements, the latter in 2M aqueous H 2 SO 4 electrolyte. Electrical conductivity and specific capacitance are higher for the transversal carbon monoliths than for the longitudinal ones. The electrical conductivity reaches values up to 27 S cm −1 for the transversal monolith. The specific capacitance reaches values up to 260 F g −1 for the transversal monolith that was activated and drilled. However, the highest volumetric capacitance, of 90 F cm −3 , is found for the longitudinal monolith that was activated and non-drilled. The energy density and power density, both referred to gravimetric and volumetric magnitudes, reach values as high as 36 Wh kg −1 and 12 Wh L −1 , and 2181 W kg −1 and 783 W L −1 , respectively. Comparison with a commercial powder activated carbon is provided.

Composite of hierarchical interpenetrating 3D hollow carbon skeleton from lotus pollen and hexagonal MnO2 nanosheets for high-performance supercapacitors

“…Subsequently, 10 M H 2 SO 4 solution is used as a dehydrant agent to pre-carbonize the pollen grains treated by alcohol (see Fig. [36][37][38] Potassium permanganate penetrates into the inner layer of the surface through holes and grooves on Scheme 1 Schematic illustration of the approach to fabricate hierarchical interpenetrating 3D hollow MnO 2 /C composite 30 the surface of the pollen, and, as a result, reacts with the outside and inside walls. Then, pre-carbonation lotus 65 pollen (PCLP) grains are dipped into KMnO 4 solution.…”

“…9). 27,[72][73][74] The superior electrochemical performance can benefit from the unique hierarchical nanostructure of MnO 2 /C-3 composite: 20 (1)The anisotropic morphology and hollow spherical structure create fast diffusion paths for the electrolyte ion, to enhance ion transmission and facilitate the utilization of electrode; (2) Welldispersed MnO 2 nanosheets can shorten the diffusion path of electrolyte ions and ensure a high electrochemical utilization of MnO 2 ; (3) The porous and carbon skeleton in the composite serves as a support for the deposition of MnO 2 nanosheets; at the same time, it can enhance the overall conductivity of the material and reduce the charge transfer resistance; (4) The unique stable hollow 3D geometric construction may prevent a possible volume 30 change during the charge/discharge procedures and result in outstanding cycling stability. 15 The high energy density in this study are not only comparable to those MnO 2 -based composite supercapacitors, 70, 71 but also higher than most of the biomass-based supercapacitors.…”

“…Active carbon, graphene, carbon nanotubes and others have been used for commercial production. 23 Moreover, hollow porous MnO/C microspheres fabricated via a facile and green 30 bio-template method yielded a specific capacity of 700 mAh/g at 0.1 A/g and gave outstanding cycling stability with 94% capacity retention. At present, the synthesis of carbon materials from organic biomass has attracted strong interest.…”

“…At present, the synthesis of carbon materials from organic biomass has attracted strong interest. 25 Apart from above mentioned materials, fungus, coconut shells, chicken eggshell membranes, fermented rice, wood, cornstalk, yogurt [26][27][28][29][30][31][32] and other biomass materials have been fully utilized for superior supercapacitor electrode materials. Biswal et al recently reported on functional microporous conducting carbon synthesized by dead plant leaves.…”

Preparation of Activated Carbon by KOH Activation from <i>Amygdalus Pedunculata</i> Shell and its Application for Electric Double-layer Capacitor

“…[3][4][5][6] Coconut shell is one of the most typical biomass resources as a raw material of activated carbon and preparation of activated carbon from various abundant biomass has been extensively studied in the environmental viewpoint for contribution to building of sustainable society.…”