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Supporting Information
Rapid single-step synthesis of porous carbon from an agricultural waste
for energy storage application
Weimin Chena,b, Xin Wanga,b, Chaozheng Liua,b, Min Luoa,b, Pei Yanga,b, and Xiaoyan Zhoua,b*
aCollege of Materials Science and Engineering, Nanjing Forestry University, Nanjing
210037, China;
bJiangsu Engineering Research Center of Fast-growing Trees and Agri-fiber Materials,
Nanjing 210037, China;
*Corresponding author: Tel.: +86 25 8542 8506; Fax: +86 25 85428518; E-mail:
[email protected]; Postal address: No. 159, Longpan Road, Nanjing, Jiangsu
Province, China, 210037
Keywords: Wheat straw; Char; Microwave; Porous carbon; Supercapacitor.
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Figures
Fig. S1. Diagram of the prepared supercapacitor.
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Fig. S2. Temperature profiles of the reactor as a function of microwave heating duration.
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Fig. S3. Pore structure of CPC: (a) N2 adsorption-desorption isotherms, (b) pore size distribution by DFT
method.
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Fig. S4. TEM images: (a) PC-10 and (b) PC-20.
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Fig. S5. Surface chemical properties of PCs: (a) O-containing chemical groups in carbon framework, and
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(b) O1s spectra.
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Fig. S6. The low-resulotion spectra of the compared PC prepared in a tubular furnace with the folloing
conditions: a mass ratio (wheat straw: wheat straw-derived char: KOH) of 1:1:6, a heating rate of 10 °C
min−1 to 630 °C and held for 1h, as well as by single-step contact heating.
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Fig. S7. CV profiles of (a) PC-10 and (b) PC-20.
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Fig. S8. Capacitive performances of the electrode based on wheat straw char-derived porous carbon in 6
mol L-1 KOH electrolyte using three-electrode configuration: (a) CV profiles, (b) rate capability, insert:
GCD curve at 0.5 A g-1, (c) Nyquist plots.
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Fig. S9. CV profiles at operational potential ranges, and tested at a scan rate of 50 mV s−1.
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Tables
Table S1. Proximate and elemental compositions of wheat straw and its derived char.
Content (%)
Wheat straw Wheat straw-derived char
Proximate compositiona
Moistureb 8.2 5.3
Volatilesc 62.1 19.8
Fixed carbond 23.4 58.3
Ashe 6.3 16.6
Elemental compositionf
C 43.7 67.2
H 5.8 0.9
O 37.1 8.4
N 0.9 0.7
Sh 0 0
a Dry basis,
b, c Determined using a thermogravimetric analyzer (STA449C, Netzsch),
d Determined by difference,
e Determined after calcination in a tubular furnace at 800 °C for 1h,
f Dry ash-free basis and Determined using an elemental analyzer (2400 , PerkinElmer),Ⅱ
h Not detectable,
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Table S2. Estimation for production costa.
Item Estimated cost for single-step synthesis
Microwave heating for PC-50 Conventional contact heatingb
Raw material
Waste wheat straw 0.5 CNY kg−1
Wheat-straw-derived charc 1.1 CNY kg−1
Transportation 0.1 CNY kg−1
Cost (0.5 kg * 0.5 CNY kg−1 + 0.5 kg * 1.1 CNY
kg−1) + 1 kg * 0.1 CNY kg−1 = 0.9 CNY
0.5 kg * 1 CNY kg−1 + 1 kg *
0.1 CNY kg−1 =0.6 CNY
Electrical consumption
Yield amount 26 wt% Yield * (0.5 kg wheat straw + 0.5
kg char) = 0.26 kg
15 wt% Yield * 1 kg wheat
straw = 0.15 kg
Batch 15 (1 kg/0.07 kg batch−1=14.3) 1d
Electricity 0.8 CNY (kW h)−1
Output power 0.8 kW 4.0 kW
Heating consumption 15 batch * 0.8 kW * (5/60) h = 1.00 kW h 1 batch * 4.0 kW * (137.5/60) h
≈ 9.17 kW h
Cost 1.00 kW h * 0.8 CNY (kW h)−1 = 0.8 CNY 9.17 kW h * 0.8 CNY (kW h)−1
= 7.3 CNY
Total cost (0.9 CNY + 0.8 CNY)/0.26 kg ≈ 6.54 CNY
kg−1
(0.6 CNY + 7.3 CNY)/0.15 kg ≈
52.67 CNY kg−1
a The same items between these two approach such as chemical activating agent were not included,
b A typical production procedure was used in conventional contact heating: wheat straw was heated from
room temperature to 800 °C and held for 1h at a heating rate of 10 °C min−1,
c For large-scale production, commercial wheat-straw-derived char can be used directly, since it only
acted as microwave absorber during microwave irradiation,
d The conventional contact heating can use a much larger reactor than that of microwave heating, since
there is a long holding duration to ensure sufficient activation.
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