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Porosity development of templated porous carbons dried by vacuum as carbon electrodes for electric double-layer capacitors
(2023-03-15)
Kraiwattanawong, Kriangsak
Resorcinol and formaldehyde (RF) resin serves as the carbon precursor for porous carbons and carbon/carbon composites possessing a high specific surface area (SSA). This work presents the porosity improvement by the elimination of cotton fibers (CF) from CF/RF composite hydrogels subsequently exchanged by tertiary butyl alcohol (TBA), dried by vacuum, and carbonized. This route contributes the templated porous carbons (TPC) with an asymmetric structure comprising micropores, mesopores, and macropores. At 0.25 of the CF/RF weight ratio, TPC dried by vacuum apparatus has SSA of 2,102 m2 g−1, whereas TPC dried by evaporation only offers SSA of 663 m2 g−1. Using the vacuum acts as pseudo-freeze drying during TBA removal, forming sponge-like carbon and allowing ultra-high SSA. The electrochemical properties of vacuumed TPCs were analyzed, showing that TPC at 0.25 of the CF/RF weight ratio possessed 626 F g−1 more than TPC at 0.00 of the CF/RF weight ratio which had 392 F g−1 at 200 mA g−1.
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Macropore-assisted electrolyte transfer inside binder-free templated carbon xerogels as carbon electrode for electric double layer capacitors
(2020-05-05)
Kraiwattanawong, Kriangsak
Capacitive performance of electric double layer capacitors is influenced by specific surface area, while pore structure also promotes electrolyte transfer inside a carbon electrode. Organic electrolytes require macropores, whereas aqueous electrolytes operate best using mesopores for electrolyte transfer. Templated carbon xerogels (TCXs) were prepared from resorcinol and formaldehyde with cotton fibers as a hard template containing macropores, mesopores and micropores as the carbon electrode. Results suggested that macropores (>50 nm) were contiguously created and connected with mesopore diameters (2–50 nm), leading to convenient ion transport inside the TCXs. Vacuum drying formed sponge-like carbon xerogels that permitted electrolyte transfer. Despite the insignificant change of porous properties, TCXs possessing sponge-like carbon xerogels showed increased capacitance values from 137 F/g to 317 F/g at 200 mA/g in a three-electrode system as a result of macropore-assisted electrolyte transfer in aqueous electrolytes.
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Capacitive performance of binder-free carbon/carbon composite cryogels
(2013-01-01)
Kraiwattanawong, Kriangsak
;
Sano, Noriaki
;
Tamon, Hajime
A carbon/carbon (C/C) composite cryogel was prepared by pouring a resorcinol-formaldehyde (RF) sol into vials containing cotton fibers, followed by solvent exchange with t-butanol, freeze drying and pyrolysis under inert atmosphere. The porous properties of C/C composites were analyzed by nitrogen adsorption, and their mesopore texture was observed by a scanning electron microscope. The capacitive performance of C/C composites was also analyzed by galvanostatic charge/discharge method and cyclic voltammetry. The results demonstrate that the capacitance can be increased with the increase of amount of cotton fibers added to C/C composites, because the broader micropore size distribution and the carbon tunnels of C/C composites promote the charge propagation inside the pore structure. The suitable pore texture and the carbon tunnels can play the crucial role relevant to the high surface area in order to obtain the high capacitance value. © 2012 Elsevier Inc. All rights reserved.

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