- Email: [email protected]
Size-controllable templates for the synthesis of porous carbon with tunable pore configurations
Author’s Accepted Manuscript Size-controllable templates for the synthesis of porous carbon with tunable pore configurations Fei Sun, Jihui Gao, Xin Liu, Yuqi Yang, Shaohua Wu www.elsevier.com
PII: DOI: Reference:
S0167-577X(16)30387-1 http://dx.doi.org/10.1016/j.matlet.2016.03.062 MLBLUE20513
To appear in: Materials Letters Received date: 15 November 2015 Revised date: 15 February 2016 Accepted date: 12 March 2016 Cite this article as: Fei Sun, Jihui Gao, Xin Liu, Yuqi Yang and Shaohua Wu, Size-controllable templates for the synthesis of porous carbon with tunable pore configurations, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.03.062 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Size-controllable templates for the synthesis of porous carbon with tunable pore configurations Fei Sun, Jihui Gao*, Xin Liu, Yuqi Yang, Shaohua Wu School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China. *Corresponding author. Tel: +86-13796032371. Email: [email protected] (Jihui Gao)
ABSTRACT Microporous carbon (MPC) and hierarchically porous carbon (HPC) were precisely designed by a colloidal process using the same carbon source and pore template. Tetraethyl orthosilicate (TEOS) hydrolysis and condensation reaction under acid condition yields the MPC featuring a highly microporous structure with BET surface area of 2068 m2 g-1 and pore volume of 0.99 cm3 g-1 while the reaction under alkaline condition makes the resulting carbon with hierarchically porous structure (HPC), giving a surface area of 1051 m2 g-1 and pore volume of 0.8 cm3 g-1. MPC is also proved to be a promising candidate for supercapacitors with a high capacitance of 287 F g-1 at 0.5 A g-1 and 152 F g-1 at 50 A g-1. Keywords: Carbon materials; Colloidal processing; Energy storage and conversion 1. Introduction Porous carbon materials are still the most preferable electrode materials for electrochemical double-layer capacitors (EDLCs) due to the large surface area, good electronic conductivity, chemical inertness and environmental friendliness [1]. Based on the EDLCs mechanism, namely, ion diffusion and adsorption at electrode-electrolyte interfaces inside nanopores, pore configuration (e.g. microporous carbon, mesoporous carbon and hierarchical porous carbon) 1
poses great impacts on the capacitive performance of carbon materials. Of the concern to provide high capacitance, micropores perform better than mesopores [2] because the stored electrical energy will be theoretically proportional to the surface area of the electrode. Besides, mesoporous or hierarchical porous carbons have been suggested to provide high ion diffusion efficiency through large pores and lead to improved rate performance [3]. As known, nano-sized silica particles from tetraethyl orthosilicate (TEOS) hydrolysis and condensation process have been demonstrated effective as pore template for the synthesis of porous carbon materials [4-5]. Controlling the conditions of TEOS hydrolysis and condensation process, including catalyst, PH value and solvents could endow the resulting silica particles with various aggregation state and sizes [6]. Herein, microporous carbon (MPC) and hierarchically porous carbon (HPC) were precisely designed using the same carbon source (phenolic resin) and pore template (TEOS). By simply tunning the PH values of precursor solution under acid and basic conditions, SiO2 colloidal crystals with different sizes can be obtained and leave the carbon products with microporous structure and hierarchically porous structure after carbonization and washing. The as-synthesized MPC was also demonstrated to exhibit excellent supercapacitive performance with a high capacitance of 287 F g-1 at 0.5A g-1 and still maintaining 152 F g-1 at high rate of 50 A g-1. 2. Materials and methods 2.1 sample preparation As illustrated in Fig. 1, simply controlling the PH values of precursor solution results in the porous carbons with tunable pore structure. For the synthesis of microporous carbon (MPC), 0.61g of phenol was firstly added to a round-bottom flask and was melted at 40 °C. Afterwards, 10mL deionized water, 10mL formalin aqueous solution (37 wt%) and 1mol L-1 NaOH solution
2
were sequentially added for PH value to 9. The reaction mixture was stirred and refluxed at 80°C for 1h. Then, 10 mL ethanol and 0.1 mol L-1HCl solution were added into above reaction system for PH value decreasing to 3. After cooling down, 2.1 g of TEOS was added with vigorous stirring for 30 min. Subsequent drying the solution gave the solid precursor which further experienced a carbonization (8°C min-1 to 900°C under N2 for 3h) and washing process (10wt% HF and water) to yield the MPC sample. The synthesis of hierarchically porous carbon (HPC) follows the same procedure as MPC except for keeping the PH value of precursor solution at 9. 2.2. Characterization The morphology and microstructure of prepared samples was analyzed using scanning electron microscopy (JSM- 7401F) and transmission electron microscopy (TEM, JEOL-2010) with an acceleration voltage of 120 kV. The pore structure characteristics were determined by N2 adsorption at -196°C using ASAP 2020 volumetric sorption analyzer. BET surface area was calculated from the isotherm using the Brunauer-Emmett-Teller equation. Pore size distribution was calculated based on nonlocal density functional theory (NLDFT) method on the basis of the adsorption branch. X-ray photoelectron spectroscopy (XPS) analysis was performed on a PHI 5700 ESCA system using AlKa X-ray at 14 kV and 6 mA. 2.3. Preparation of electrode and electrochemical measurement A three-electrode configuration, using 6M KOH as the electrolyte, was constructed to evaluate the supercapacitive performance of the prepared samples. The working electrodes were prepared by mixing the active materials with conducting carbon black and binder poly-tetrafluoroethylene (PTFE) with the ratio of 8:1:1. Nickel-foam was used as current collector. The active material on each electrode was ~1.0 mg. Pt slice and a saturated calomel electrode (SCE) were used as the counter electrode and reference electrode, respectively. Cyclic voltammetry curves and
3
galvanostatic charge-discharge curves were teste on VMP3 Electrochemical Workstation (Biologic). Specific capacitances (Cs, F g-1) of materials were calculated based on the following formula: Cs = I△t/(m△V), where I is discharge current, △t is discharge time, m is the mass of active material and△V represents voltage window (excluding the IR drop). 3. Results and discussion The TEM images of obtained microporous carbon (MPC) and hierarchically porous carbon (HPC) are presented in Fig. 1. Both MPC and HPC show amorphous structure with different scale nanopores embedding in the carbon framework. Specifically, MPC shows a smooth and compact surface morphology consisting of abundant internal micropores while HPC features a hierarchical porous structure containing some mesopores with diameter around 10 nm. The SEM images also reveal the small pores of MPC and large-dimension pores of HPC (Fig. S1).
Fig. 1. Schematic illustration of the synthesis process of microporous carbon (MPC) and hierarchically porous carbon (HPC).
4
N2 adsorption-desorption isotherms further reveal the pore configuration and corresponding pore parameter of MPC and HPC, as illustrated in Fig. 2 and Table S1. When TEOS hydrolysis and condensation process take place in an acid condition (PH=3 in our work), the resultant MPC features a typical I type isotherms, suggesting the dominant microporous structure [7] which yields a BET surface area of 2068 m2 g-1 and total pore volume of 0.99 cm3 g-1. The pore size distribution was centered at ~1 nm and ~2 nm which are favorable for most electrolyte ions penetration (Fig. 2b). The microporous structure of MPC is derived from the relatively small silica particles which are attributed to the slow cross-link and growth rate of silica clusters in acid condition. In contrast, when TEOS adding into a basic condition (PH=9 in our work), in addition to the growth of small-sized silica colloids from the hydrolysis of TEOS by a Stöber growth process, the basic condition could promote the secondary nucleation of existing silica seeds which enables the resulting silica particles with relatively large sizes [8]. Accordingly, the resulting HPC sample exhibits a combined I/IV type isotherms with a small hysteresis loop within the relative pressure P/P0 of 0.4-0.8 indicating the coexistence of micro- and meso-pores (Fig. 2a) [9]. Pore size distribution of HPC also suggests the hierarchical pore structure with enlarged and expanded pore sizes around 1.5nm, 3nm and 10nm (Fig. 2b). X-ray photoelectron spectroscopy (XPS) measurements were conducted to elucidate the chemical composition in HPC and MPC (Fig S2 and Table S1). As expected, only C1s and O1s signals can be observed and the F contents of MPC and HPC from XPS analysis are only 0.04% and 0.06%, respectively, which demonstrate the negligible residual of F element in porous carbon.
5
Fig. 2 (a) Nitrogen adsorption isotherms of MPC and HPC; (b) Pore size distributions of MPC and HPC
Fig. 3. Electrochemical performances of HPC and MPC.(a) Representative cyclic voltammograms at scan rates of 20 mV s-1 and 200 mV s-1;(b) Charge-discharge profiles under different current densities; (c)
Gravimetric capacitances at different charge-discharge current densities; (d) Cycling stabilities at 5 A g-1.
6
In short, microporous carbon (MPC) and hierarchically porous carbon (HPC) were successfully synthesized based on TEOS hydrolysis and condensation process. Given the above-described pore structures, MPC and HPC were investigated as electrode materials for supercapacitors in a three-electrode system with 6M KOH as electrolyte. The electrochemical performances are presented in
Fig. 3 and Fig. S3. Both cyclic voltammetry (CV) curves show quasirectangular
shapes at the scan rate of 20 mV s−1. With increasing the scan rate to 200 mV s−1, MPC and HPC still keeps a rather good rectangular-like CV curve, indicating the good rate performances (Fig. 3a) [10]. The galvanostatic charge-discharge curves for HPC and MPC at low rate and high rate are shown in Fig. 3b. At 0.5 A g-1, HPC shows a specific capacitance of 220 F g-1 and MPC exhibits a much higher capacitance of 287 F g-1. Even at a high rate of 50 A g-1, HPC and MPC still keep good linear capacitive behaviors with a rather limited voltage (IR) drop < 0.2 V, which give an gravimetric capacitance of 70 F g-1 for HPC and 152 F g-1 for MPC, respectively. For all the tested current densities in the range of 0.5-50 A g-1, MPC presents the obvious higher gravimetric capacitance than the HPC (Fig. 3c). Considering the almost same chemical compositions of HPC and MPC, the difference of specific capacitances between the two samples must originate from their different pore structures. Compared with HPC with a relatively low surface area (1051 m2g-1), MPC possesses highly microporous structure with high surface area (2068 m2g-1), enabling the high capacitance. Furthermore, both MPC and HPC exhibit excellent cycling stability of > 95% capacitance retention for 10000 cycles (Fig. 3d). 4. Conclusion In summary, we have developed a simple and convenient method by mixing phenol polymerization system and TEOS hydrolysis system to prepare porous carbons. Simply controlling the PH values of the precursor solution endows the resulting carbons with tunable
7
pore structures. Microporous carbon (MPC) and hierarchically porous carbon (HPC) were successfully synthesized and tested as supercapacitore electrode material. MPC with high surface area and pore volume demonstrates excellent supercapacitive performances, delivering 287 F g-1 at 0.5 A g-1 and still 152 F g-1 at high current density of 50 A g-1. Our synthesis strategy could also be extended to prepare other porous carbon materials with various carbon sources.
Acknowledgements This research was financially supported by the National Natural Science Foundation-Shenhua Group, ‘‘Coal Joint Fund’’ (Grant No. 51134015) and National Natural Science Foundation of China (Grant No. 51376054). References [1] G. Wang, L. Zhang, J. Zhang, Chem. Soc. Rev., 41 (2012)797-828. [2]Y.P. Zhai, Y.Q. Dou, D. Y. Zhao, P. F. Fulvio, R. T. Mayes, S. Dai, Adv. Mater. 23 (2011) 4828-4850. [3] Y. F. Zhang, C. X. Zhang, G. X. Huang, B. L. Xing, Y. L. Duan, Mater. Lett. 159 (2015) 377-380. [4] J. Lee, J. Kim,T. Hyeon, Adv. Mater. 18 (2006) 2073-2094. [5] J. X. Wang, S. S. Feng, Y. F. Song, W. Li,W. J. Gao, A. A. Elzatahry, et al.,Catalysis Today 243 (2015) 199-208. [6] C.J. Brinker, Journal of Non-Crystalline Solids. 100 (1988) 31-50. [7]J.E. Hampsey , Q.Y.Hu , L.Rice , J. B. Pang , Z.W.Wu , Y.F. Lu, Chem. Commun., (2005) 3606-3608. [8] K.S. Chou, C. C. Chen, Ceramics International 34 (2008) 1623-1627. [9] A.B. Chen, T. T. Xing, R. J. Wang, Y. L. Li, Y. T. Li, Mater. Lett. 157 (2015) 30-33. [10] J. Zhao, H. W. Lai, Z. Y. Lyu, Y. F. Jiang, K. Xie, X. Z. Wang, et al., Adv. Mater. 27 (2015) 35413545.
8
Figure captions: Fig. 1 Schematic illustration of synthesis process of microporous carbon (MPC) and hierarchically porous carbon (HPC) Fig. 2 (a) Nitrogen adsorption isotherms of MPC and HPC; (b) Pore size distributions of MPC and HPC. Fig. 3 Electrochemical performances of HPC and MPC.(a) Representative cyclic voltammograms at scan rates of 20 mV s-1 and 200 mV s-1;(b) Charge-discharge profiles under different current densities; (c) Gravimetric capacitances at different charge-discharge current densities; (d) Cycling stabilities at 5 A g-1.
Research Highlights: ● Microporous carbon (MPC) and hierarchically porous carbon (HPC) were designed. ● Controlling the PH values endows resulting carbons with tunable pore structures. ● MPC shows microporous structure with high surface area of 2068 m2g-1. ● MPC is promising for supercapacitors with a high capacitance of 287 F g-1.
9
PII: DOI: Reference:
S0167-577X(16)30387-1 http://dx.doi.org/10.1016/j.matlet.2016.03.062 MLBLUE20513
To appear in: Materials Letters Received date: 15 November 2015 Revised date: 15 February 2016 Accepted date: 12 March 2016 Cite this article as: Fei Sun, Jihui Gao, Xin Liu, Yuqi Yang and Shaohua Wu, Size-controllable templates for the synthesis of porous carbon with tunable pore configurations, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.03.062 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Size-controllable templates for the synthesis of porous carbon with tunable pore configurations Fei Sun, Jihui Gao*, Xin Liu, Yuqi Yang, Shaohua Wu School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China. *Corresponding author. Tel: +86-13796032371. Email: [email protected] (Jihui Gao)
ABSTRACT Microporous carbon (MPC) and hierarchically porous carbon (HPC) were precisely designed by a colloidal process using the same carbon source and pore template. Tetraethyl orthosilicate (TEOS) hydrolysis and condensation reaction under acid condition yields the MPC featuring a highly microporous structure with BET surface area of 2068 m2 g-1 and pore volume of 0.99 cm3 g-1 while the reaction under alkaline condition makes the resulting carbon with hierarchically porous structure (HPC), giving a surface area of 1051 m2 g-1 and pore volume of 0.8 cm3 g-1. MPC is also proved to be a promising candidate for supercapacitors with a high capacitance of 287 F g-1 at 0.5 A g-1 and 152 F g-1 at 50 A g-1. Keywords: Carbon materials; Colloidal processing; Energy storage and conversion 1. Introduction Porous carbon materials are still the most preferable electrode materials for electrochemical double-layer capacitors (EDLCs) due to the large surface area, good electronic conductivity, chemical inertness and environmental friendliness [1]. Based on the EDLCs mechanism, namely, ion diffusion and adsorption at electrode-electrolyte interfaces inside nanopores, pore configuration (e.g. microporous carbon, mesoporous carbon and hierarchical porous carbon) 1
poses great impacts on the capacitive performance of carbon materials. Of the concern to provide high capacitance, micropores perform better than mesopores [2] because the stored electrical energy will be theoretically proportional to the surface area of the electrode. Besides, mesoporous or hierarchical porous carbons have been suggested to provide high ion diffusion efficiency through large pores and lead to improved rate performance [3]. As known, nano-sized silica particles from tetraethyl orthosilicate (TEOS) hydrolysis and condensation process have been demonstrated effective as pore template for the synthesis of porous carbon materials [4-5]. Controlling the conditions of TEOS hydrolysis and condensation process, including catalyst, PH value and solvents could endow the resulting silica particles with various aggregation state and sizes [6]. Herein, microporous carbon (MPC) and hierarchically porous carbon (HPC) were precisely designed using the same carbon source (phenolic resin) and pore template (TEOS). By simply tunning the PH values of precursor solution under acid and basic conditions, SiO2 colloidal crystals with different sizes can be obtained and leave the carbon products with microporous structure and hierarchically porous structure after carbonization and washing. The as-synthesized MPC was also demonstrated to exhibit excellent supercapacitive performance with a high capacitance of 287 F g-1 at 0.5A g-1 and still maintaining 152 F g-1 at high rate of 50 A g-1. 2. Materials and methods 2.1 sample preparation As illustrated in Fig. 1, simply controlling the PH values of precursor solution results in the porous carbons with tunable pore structure. For the synthesis of microporous carbon (MPC), 0.61g of phenol was firstly added to a round-bottom flask and was melted at 40 °C. Afterwards, 10mL deionized water, 10mL formalin aqueous solution (37 wt%) and 1mol L-1 NaOH solution
2
were sequentially added for PH value to 9. The reaction mixture was stirred and refluxed at 80°C for 1h. Then, 10 mL ethanol and 0.1 mol L-1HCl solution were added into above reaction system for PH value decreasing to 3. After cooling down, 2.1 g of TEOS was added with vigorous stirring for 30 min. Subsequent drying the solution gave the solid precursor which further experienced a carbonization (8°C min-1 to 900°C under N2 for 3h) and washing process (10wt% HF and water) to yield the MPC sample. The synthesis of hierarchically porous carbon (HPC) follows the same procedure as MPC except for keeping the PH value of precursor solution at 9. 2.2. Characterization The morphology and microstructure of prepared samples was analyzed using scanning electron microscopy (JSM- 7401F) and transmission electron microscopy (TEM, JEOL-2010) with an acceleration voltage of 120 kV. The pore structure characteristics were determined by N2 adsorption at -196°C using ASAP 2020 volumetric sorption analyzer. BET surface area was calculated from the isotherm using the Brunauer-Emmett-Teller equation. Pore size distribution was calculated based on nonlocal density functional theory (NLDFT) method on the basis of the adsorption branch. X-ray photoelectron spectroscopy (XPS) analysis was performed on a PHI 5700 ESCA system using AlKa X-ray at 14 kV and 6 mA. 2.3. Preparation of electrode and electrochemical measurement A three-electrode configuration, using 6M KOH as the electrolyte, was constructed to evaluate the supercapacitive performance of the prepared samples. The working electrodes were prepared by mixing the active materials with conducting carbon black and binder poly-tetrafluoroethylene (PTFE) with the ratio of 8:1:1. Nickel-foam was used as current collector. The active material on each electrode was ~1.0 mg. Pt slice and a saturated calomel electrode (SCE) were used as the counter electrode and reference electrode, respectively. Cyclic voltammetry curves and
3
galvanostatic charge-discharge curves were teste on VMP3 Electrochemical Workstation (Biologic). Specific capacitances (Cs, F g-1) of materials were calculated based on the following formula: Cs = I△t/(m△V), where I is discharge current, △t is discharge time, m is the mass of active material and△V represents voltage window (excluding the IR drop). 3. Results and discussion The TEM images of obtained microporous carbon (MPC) and hierarchically porous carbon (HPC) are presented in Fig. 1. Both MPC and HPC show amorphous structure with different scale nanopores embedding in the carbon framework. Specifically, MPC shows a smooth and compact surface morphology consisting of abundant internal micropores while HPC features a hierarchical porous structure containing some mesopores with diameter around 10 nm. The SEM images also reveal the small pores of MPC and large-dimension pores of HPC (Fig. S1).
Fig. 1. Schematic illustration of the synthesis process of microporous carbon (MPC) and hierarchically porous carbon (HPC).
4
N2 adsorption-desorption isotherms further reveal the pore configuration and corresponding pore parameter of MPC and HPC, as illustrated in Fig. 2 and Table S1. When TEOS hydrolysis and condensation process take place in an acid condition (PH=3 in our work), the resultant MPC features a typical I type isotherms, suggesting the dominant microporous structure [7] which yields a BET surface area of 2068 m2 g-1 and total pore volume of 0.99 cm3 g-1. The pore size distribution was centered at ~1 nm and ~2 nm which are favorable for most electrolyte ions penetration (Fig. 2b). The microporous structure of MPC is derived from the relatively small silica particles which are attributed to the slow cross-link and growth rate of silica clusters in acid condition. In contrast, when TEOS adding into a basic condition (PH=9 in our work), in addition to the growth of small-sized silica colloids from the hydrolysis of TEOS by a Stöber growth process, the basic condition could promote the secondary nucleation of existing silica seeds which enables the resulting silica particles with relatively large sizes [8]. Accordingly, the resulting HPC sample exhibits a combined I/IV type isotherms with a small hysteresis loop within the relative pressure P/P0 of 0.4-0.8 indicating the coexistence of micro- and meso-pores (Fig. 2a) [9]. Pore size distribution of HPC also suggests the hierarchical pore structure with enlarged and expanded pore sizes around 1.5nm, 3nm and 10nm (Fig. 2b). X-ray photoelectron spectroscopy (XPS) measurements were conducted to elucidate the chemical composition in HPC and MPC (Fig S2 and Table S1). As expected, only C1s and O1s signals can be observed and the F contents of MPC and HPC from XPS analysis are only 0.04% and 0.06%, respectively, which demonstrate the negligible residual of F element in porous carbon.
5
Fig. 2 (a) Nitrogen adsorption isotherms of MPC and HPC; (b) Pore size distributions of MPC and HPC
Fig. 3. Electrochemical performances of HPC and MPC.(a) Representative cyclic voltammograms at scan rates of 20 mV s-1 and 200 mV s-1;(b) Charge-discharge profiles under different current densities; (c)
Gravimetric capacitances at different charge-discharge current densities; (d) Cycling stabilities at 5 A g-1.
6
In short, microporous carbon (MPC) and hierarchically porous carbon (HPC) were successfully synthesized based on TEOS hydrolysis and condensation process. Given the above-described pore structures, MPC and HPC were investigated as electrode materials for supercapacitors in a three-electrode system with 6M KOH as electrolyte. The electrochemical performances are presented in
Fig. 3 and Fig. S3. Both cyclic voltammetry (CV) curves show quasirectangular
shapes at the scan rate of 20 mV s−1. With increasing the scan rate to 200 mV s−1, MPC and HPC still keeps a rather good rectangular-like CV curve, indicating the good rate performances (Fig. 3a) [10]. The galvanostatic charge-discharge curves for HPC and MPC at low rate and high rate are shown in Fig. 3b. At 0.5 A g-1, HPC shows a specific capacitance of 220 F g-1 and MPC exhibits a much higher capacitance of 287 F g-1. Even at a high rate of 50 A g-1, HPC and MPC still keep good linear capacitive behaviors with a rather limited voltage (IR) drop < 0.2 V, which give an gravimetric capacitance of 70 F g-1 for HPC and 152 F g-1 for MPC, respectively. For all the tested current densities in the range of 0.5-50 A g-1, MPC presents the obvious higher gravimetric capacitance than the HPC (Fig. 3c). Considering the almost same chemical compositions of HPC and MPC, the difference of specific capacitances between the two samples must originate from their different pore structures. Compared with HPC with a relatively low surface area (1051 m2g-1), MPC possesses highly microporous structure with high surface area (2068 m2g-1), enabling the high capacitance. Furthermore, both MPC and HPC exhibit excellent cycling stability of > 95% capacitance retention for 10000 cycles (Fig. 3d). 4. Conclusion In summary, we have developed a simple and convenient method by mixing phenol polymerization system and TEOS hydrolysis system to prepare porous carbons. Simply controlling the PH values of the precursor solution endows the resulting carbons with tunable
7
pore structures. Microporous carbon (MPC) and hierarchically porous carbon (HPC) were successfully synthesized and tested as supercapacitore electrode material. MPC with high surface area and pore volume demonstrates excellent supercapacitive performances, delivering 287 F g-1 at 0.5 A g-1 and still 152 F g-1 at high current density of 50 A g-1. Our synthesis strategy could also be extended to prepare other porous carbon materials with various carbon sources.
Acknowledgements This research was financially supported by the National Natural Science Foundation-Shenhua Group, ‘‘Coal Joint Fund’’ (Grant No. 51134015) and National Natural Science Foundation of China (Grant No. 51376054). References [1] G. Wang, L. Zhang, J. Zhang, Chem. Soc. Rev., 41 (2012)797-828. [2]Y.P. Zhai, Y.Q. Dou, D. Y. Zhao, P. F. Fulvio, R. T. Mayes, S. Dai, Adv. Mater. 23 (2011) 4828-4850. [3] Y. F. Zhang, C. X. Zhang, G. X. Huang, B. L. Xing, Y. L. Duan, Mater. Lett. 159 (2015) 377-380. [4] J. Lee, J. Kim,T. Hyeon, Adv. Mater. 18 (2006) 2073-2094. [5] J. X. Wang, S. S. Feng, Y. F. Song, W. Li,W. J. Gao, A. A. Elzatahry, et al.,Catalysis Today 243 (2015) 199-208. [6] C.J. Brinker, Journal of Non-Crystalline Solids. 100 (1988) 31-50. [7]J.E. Hampsey , Q.Y.Hu , L.Rice , J. B. Pang , Z.W.Wu , Y.F. Lu, Chem. Commun., (2005) 3606-3608. [8] K.S. Chou, C. C. Chen, Ceramics International 34 (2008) 1623-1627. [9] A.B. Chen, T. T. Xing, R. J. Wang, Y. L. Li, Y. T. Li, Mater. Lett. 157 (2015) 30-33. [10] J. Zhao, H. W. Lai, Z. Y. Lyu, Y. F. Jiang, K. Xie, X. Z. Wang, et al., Adv. Mater. 27 (2015) 35413545.
8
Figure captions: Fig. 1 Schematic illustration of synthesis process of microporous carbon (MPC) and hierarchically porous carbon (HPC) Fig. 2 (a) Nitrogen adsorption isotherms of MPC and HPC; (b) Pore size distributions of MPC and HPC. Fig. 3 Electrochemical performances of HPC and MPC.(a) Representative cyclic voltammograms at scan rates of 20 mV s-1 and 200 mV s-1;(b) Charge-discharge profiles under different current densities; (c) Gravimetric capacitances at different charge-discharge current densities; (d) Cycling stabilities at 5 A g-1.
Research Highlights: ● Microporous carbon (MPC) and hierarchically porous carbon (HPC) were designed. ● Controlling the PH values endows resulting carbons with tunable pore structures. ● MPC shows microporous structure with high surface area of 2068 m2g-1. ● MPC is promising for supercapacitors with a high capacitance of 287 F g-1.
9