Hierarchically Porous Carbon Nanosheets from Waste Coffee ...
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Hierarchically Porous Carbon Nanosheets from Waste Coffee Grounds for Supercapacitors Young Soo Yun,1 Min Hong Park,1 Sung Ju Hong,2 Min Eui Lee,1 Yung Woo Park2 and HyoungJoon Jin*,1 1
Department of Polymer Science and Engineering, Inha University, Incheon 402-751, Korea
2
Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (South Korea)
*
Email: [email protected]
1
Figure S1. FE-TEM images at various magnifications of the WCGs exfoliated by ultrasound treatments in N,N-dimethylformamide (DMF).
2
Figure S2. X-ray photoelectron spectroscopy (XPS) C 1s spectrum of the WCGs exfoliated by the ultrasound treatments in N,N-dimethylformamide (DMF). The spectrum showed several distinct peaks related to the C-C bond (284.9 eV), C=O and C-N bonds (287.9 eV), and the OC=O bond (290.7 eV) containing a main C-O and C-S peak centred at 286.7 eV.
3
Figure S3. XPS spectra showing (a) C 1s, (b) O 1s, (c) N 1s, and (d) S 2p of HP-CNSs.
The XPS C 1s spectra of HP-CNSs revealed the presence of the main sp2 carbon structure (284.4 eV) with a sp3 carbon bond (285.3 eV) and C(O)O group (289.1 eV). Two distinct peaks were observed for the oxygen functional groups (a C=O bond centred at 531.5 eV and a C-O bond centred at 533.6 eV) in the XPS O 1s spectra. The chemical configurations of nitrogen and sulphur consisted of two distinct groups of pyridinic N and N-O centred at 398.5 and 402.7, respectively, and C-S and C-SOx centred at 164.3 and 167.7 eV, respectively.
4
Fig. S4. FT-IR spectrum of HP-CNSs.
530 cm-1; C-S=O in-plane defomation vibrations 600 cm-1; N-O2 rocking vibrations 670 cm-1; C-S stretching vibrations 1022 cm-1 and 1061 cm-1; C-O and epoxide 1226 cm-1; pyridine N-oxide N-O stretching vibrations 1371 cm-1; aromatic nitrogen compounds 1580 cm-1, 1631 cm-1; C-C groups 1720 cm-1; C=O group 2853 cm-1, 2921 cm-1; C-H groups 3445 cm-1; O-H group
5
Table S1. Elemental analysis data of HP-CNSs Sample Name
Carbon (wt.%)
Oxygen (wt.%)
Nitrogen (wt.%)
Sulphur (wt.%)
Hydrogen (wt.%)
HP-CNSs
78.2
15.1
4.0
1.7
1.0
6
Table S2. Textural properties of the samples Sample name
Surface area (m2 g-1)
Micropore area (m2 g-1)
Micropore volume (cm3 g-1)
Mesopore volume (cm3 g-1)
MP-CNS-0.5
2036.2
2013.8
0.893
0.091
MP-CNS-1
2110.6
2080.5
0.968
0.148
MP-CNS-2
1903.6
1866.9
1.003
0.217
HP-CNS
1945.7
1845.7
1.146
0.785
7
Figure S5. (a) Cyclic voltammograms of the supercapacitors based on MP-CNS-05 at different scan rates of 10, 20, and 50 mV s−1. (b) Galvanostatic charge/discharge profiles of the supercapacitors based on MP-CNS-05 at current densities of 0.75, 1.00, and 1.50 A g−1.
8
Figure S6. (a) Nitrogen adsorption and desorption isotherm curves of MSP-20 and inset of micropore size distribution. (b) XPS S 2p spectrum of S-MSP-20 and (c) XPS N 1s spectrum of N-MSP-20. (d) Cyclic voltammograms of MSP-20 (Navy), N-MSP-20 (red) and S-MSP-20 (dark cyan) at a scan rate of 20 mV s-1 over a potential range of 0-3 V in 1-butyl-3methylimidazolium tetrafluoroborate/acetonitrile (BMIM BF4/AN) electrolyte.
9
S-MSP-20 was prepared by heating of an elemental sulphur and MSP-20 mixture at 600 °C as a weight ratio of 2:1. A heating rate of 10 °C min-1 and Ar flow rate of 200 ml min-1 were applied. After heating, the resultant (S-MSP-20) was washed using ethanol and stored in a vacuum oven. N-MSP-20 was also prepared by heating of a melamine and MSP-20 mixture at 600 °C as a weight ratio of 2:1. The same heating rate and Ar flow were applied. Then, N-MSP-20 was washed using acetone and ethanol and stored in a vacuum oven.
Fig. S6(a) shows that commercial activated carbon (MSP-20) has a IUPAC type-І microporous structure with a main pore size of about 6 Å. Specific surface area was ~1925 m2 g-1 (Smic: 1910 m2 g-1 and Smeso: 15 m2 g-1), indicating that MSP-20 has the similar textural properties with MPCNSs. After heating with elemental sulphur at 600°C, about 1.7 at.% sulphur was introduced on the surface of MSP-20 as configurations of C-S bonding and C-SOx bonding (Fig. S6(b)). Also, nitrogen heteroatoms were introduced by heating with melamine at 600°C. 4.1 at.% of nitrogen groups such as pyridinic N and pyrrolyic N were found in the XPS N 1s spectrum (Fig. S6(c)). The nitrogen- and sulphur-doped samples (N-MSP-20 and S-MSP-20) showed better electrochemical performances in the rate performances compared with that of the pristine MSP20 (Fig. S6(d)). The cyclovoltammograms of N-MSP-20 and S-MSP-20 exhibit more rectangular-like shapes compared with the pristine MSP-20 sample (Fig. S6(d)). This result can be induced by increases of electrical property or/and wettability with organic electrolytes by the doped heteroaotms. As a result, the nitrogen and sulphur doping on carbon structure enhanced rate performances of the carbon electrodes. And the cyclovoltammogram curves of N-MSP-20
10
and S-MSP-20 are similar to that of MP-CNS-0.5, indicating that HP-CNSs have the superior electrochemical performances compared with the commercialized activated carbons and even sulphur- or nitrogen-doped activated carbons.
11
Figure S7. Nyquist plots of HP-CNS-, MP-CNS-0.5-, MP-CNS-1- and MP-CNS-2-based supercapacitors over the frequency range from 100 kHz to 0.1 Hz.
12
Figure S8. Schematic diagram of the HP-CNS microstructure.
13
Hierarchically Porous Carbon Nanosheets from Waste Coffee Grounds for Supercapacitors Young Soo Yun,1 Min Hong Park,1 Sung Ju Hong,2 Min Eui Lee,1 Yung Woo Park2 and HyoungJoon Jin*,1 1
Department of Polymer Science and Engineering, Inha University, Incheon 402-751, Korea
2
Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (South Korea)
*
Email: [email protected]
1
Figure S1. FE-TEM images at various magnifications of the WCGs exfoliated by ultrasound treatments in N,N-dimethylformamide (DMF).
2
Figure S2. X-ray photoelectron spectroscopy (XPS) C 1s spectrum of the WCGs exfoliated by the ultrasound treatments in N,N-dimethylformamide (DMF). The spectrum showed several distinct peaks related to the C-C bond (284.9 eV), C=O and C-N bonds (287.9 eV), and the OC=O bond (290.7 eV) containing a main C-O and C-S peak centred at 286.7 eV.
3
Figure S3. XPS spectra showing (a) C 1s, (b) O 1s, (c) N 1s, and (d) S 2p of HP-CNSs.
The XPS C 1s spectra of HP-CNSs revealed the presence of the main sp2 carbon structure (284.4 eV) with a sp3 carbon bond (285.3 eV) and C(O)O group (289.1 eV). Two distinct peaks were observed for the oxygen functional groups (a C=O bond centred at 531.5 eV and a C-O bond centred at 533.6 eV) in the XPS O 1s spectra. The chemical configurations of nitrogen and sulphur consisted of two distinct groups of pyridinic N and N-O centred at 398.5 and 402.7, respectively, and C-S and C-SOx centred at 164.3 and 167.7 eV, respectively.
4
Fig. S4. FT-IR spectrum of HP-CNSs.
530 cm-1; C-S=O in-plane defomation vibrations 600 cm-1; N-O2 rocking vibrations 670 cm-1; C-S stretching vibrations 1022 cm-1 and 1061 cm-1; C-O and epoxide 1226 cm-1; pyridine N-oxide N-O stretching vibrations 1371 cm-1; aromatic nitrogen compounds 1580 cm-1, 1631 cm-1; C-C groups 1720 cm-1; C=O group 2853 cm-1, 2921 cm-1; C-H groups 3445 cm-1; O-H group
5
Table S1. Elemental analysis data of HP-CNSs Sample Name
Carbon (wt.%)
Oxygen (wt.%)
Nitrogen (wt.%)
Sulphur (wt.%)
Hydrogen (wt.%)
HP-CNSs
78.2
15.1
4.0
1.7
1.0
6
Table S2. Textural properties of the samples Sample name
Surface area (m2 g-1)
Micropore area (m2 g-1)
Micropore volume (cm3 g-1)
Mesopore volume (cm3 g-1)
MP-CNS-0.5
2036.2
2013.8
0.893
0.091
MP-CNS-1
2110.6
2080.5
0.968
0.148
MP-CNS-2
1903.6
1866.9
1.003
0.217
HP-CNS
1945.7
1845.7
1.146
0.785
7
Figure S5. (a) Cyclic voltammograms of the supercapacitors based on MP-CNS-05 at different scan rates of 10, 20, and 50 mV s−1. (b) Galvanostatic charge/discharge profiles of the supercapacitors based on MP-CNS-05 at current densities of 0.75, 1.00, and 1.50 A g−1.
8
Figure S6. (a) Nitrogen adsorption and desorption isotherm curves of MSP-20 and inset of micropore size distribution. (b) XPS S 2p spectrum of S-MSP-20 and (c) XPS N 1s spectrum of N-MSP-20. (d) Cyclic voltammograms of MSP-20 (Navy), N-MSP-20 (red) and S-MSP-20 (dark cyan) at a scan rate of 20 mV s-1 over a potential range of 0-3 V in 1-butyl-3methylimidazolium tetrafluoroborate/acetonitrile (BMIM BF4/AN) electrolyte.
9
S-MSP-20 was prepared by heating of an elemental sulphur and MSP-20 mixture at 600 °C as a weight ratio of 2:1. A heating rate of 10 °C min-1 and Ar flow rate of 200 ml min-1 were applied. After heating, the resultant (S-MSP-20) was washed using ethanol and stored in a vacuum oven. N-MSP-20 was also prepared by heating of a melamine and MSP-20 mixture at 600 °C as a weight ratio of 2:1. The same heating rate and Ar flow were applied. Then, N-MSP-20 was washed using acetone and ethanol and stored in a vacuum oven.
Fig. S6(a) shows that commercial activated carbon (MSP-20) has a IUPAC type-І microporous structure with a main pore size of about 6 Å. Specific surface area was ~1925 m2 g-1 (Smic: 1910 m2 g-1 and Smeso: 15 m2 g-1), indicating that MSP-20 has the similar textural properties with MPCNSs. After heating with elemental sulphur at 600°C, about 1.7 at.% sulphur was introduced on the surface of MSP-20 as configurations of C-S bonding and C-SOx bonding (Fig. S6(b)). Also, nitrogen heteroatoms were introduced by heating with melamine at 600°C. 4.1 at.% of nitrogen groups such as pyridinic N and pyrrolyic N were found in the XPS N 1s spectrum (Fig. S6(c)). The nitrogen- and sulphur-doped samples (N-MSP-20 and S-MSP-20) showed better electrochemical performances in the rate performances compared with that of the pristine MSP20 (Fig. S6(d)). The cyclovoltammograms of N-MSP-20 and S-MSP-20 exhibit more rectangular-like shapes compared with the pristine MSP-20 sample (Fig. S6(d)). This result can be induced by increases of electrical property or/and wettability with organic electrolytes by the doped heteroaotms. As a result, the nitrogen and sulphur doping on carbon structure enhanced rate performances of the carbon electrodes. And the cyclovoltammogram curves of N-MSP-20
10
and S-MSP-20 are similar to that of MP-CNS-0.5, indicating that HP-CNSs have the superior electrochemical performances compared with the commercialized activated carbons and even sulphur- or nitrogen-doped activated carbons.
11
Figure S7. Nyquist plots of HP-CNS-, MP-CNS-0.5-, MP-CNS-1- and MP-CNS-2-based supercapacitors over the frequency range from 100 kHz to 0.1 Hz.
12
Figure S8. Schematic diagram of the HP-CNS microstructure.
13
