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Efficient and Facile Fabrication of Hierarchical Carbon Foams with Abundant Nanoscale Pores for Use in Supercapacitors
Author(s) -
Xiong Wei,
Yang Guijun,
Yang Tae Hyeon,
Liu Shantang,
Jung Yongju
Publication year - 2017
Publication title -
bulletin of the korean chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.237
H-Index - 59
ISSN - 1229-5949
DOI - 10.1002/bkcs.11091
Subject(s) - specific surface area , carbonization , chemical engineering , carbon fibers , materials science , potassium , aqueous solution , mesoporous material , porosity , supercapacitor , cyclic voltammetry , electrochemistry , chemistry , electrode , composite material , organic chemistry , scanning electron microscope , metallurgy , composite number , engineering , catalysis
Hierarchical carbon foams ( HCFs ) with micro‐, meso‐, and macropores were successfully synthesized via a two‐step process: (1) polymerization in oil‐in‐water (O/W) emulsions without any hard templates and (2) carbonization at 850°C. With the aim of both enhancing the stability of the emulsion and forming a micro‐ and mesoporous structure during the carbonization process, potassium citrate was introduced in an aqueous solution of resorcinol and formaldehyde. A series of HCFs were fabricated by changing the mass ratio of potassium citrate to total carbon sources from 0.25 to 1.5. The effect of potassium citrate on the porous structure of HCFs was investigated through nitrogen sorption tests. The prepared HCFs exhibited well‐developed porous structures of micro‐, meso‐ and macropores and high surface areas. The structural characteristics of the HCFs , including pore size distribution, surface area, and porosity, were significantly dependent on the amount of potassium citrate. It was concluded that potassium citrate greatly contributed to the formation of carbon foams with nano‐sized pore structures and high porosity. Interestingly, it was found that when the mass ratio of potassium citrate to total carbon sources was 0.5, the HCFs showed the highest specific surface area (~1360 m 2 /g). Furthermore, the capacitive performances of the HCFs were evaluated in a 6.0 M KOH aqueous solution using typical electrochemical methods such as cyclic voltammetry and galvanostatic charge/discharge tests. The capacitance of the HCFs tended to increase with the increase in surface area. In particular, the HCFs with the highest surface area also exhibited excellent electrochemical properties (high capacitance of 224 F/g at 1.0 A/g, high rate capability of 191 F/g at 10.0 A/g). These features may be attributed to both the resulting interconnected pore structure that is easily accessible to ions and the high surface area. We believe that this synthesis strategy can be easily extended to the preparation of hierarchical porous carbon materials with a desirable pore structure by tuning the organic monomer.