N-doped reduced graphene oxide aerogel coated on carboxyl-modified carbon fiber paper for high-performance ionic-liquid supercapacitors

Accepted Manuscript N-doped reduced graphene oxide aerogel coated on carboxyl-modified carbon fiber paper for high-performance ionic-liquid supercapacitors Pawin Iamprasertkun, Atiweena Krittayavathananon, Montree Sawangphruk PII:

S0008-6223(15)30558-3

DOI:

10.1016/j.carbon.2015.12.092

Reference:

CARBON 10618

To appear in:

Carbon

Received Date: 1 November 2015 Revised Date:

17 December 2015

Accepted Date: 28 December 2015

Please cite this article as: P. Iamprasertkun, A. Krittayavathananon, M. Sawangphruk, N-doped reduced graphene oxide aerogel coated on carboxyl-modified carbon fiber paper for high-performance ionic-liquid supercapacitors, Carbon (2016), doi: 10.1016/j.carbon.2015.12.092. 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 proof before it is published in its final 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.

1

ACCEPTED MANUSCRIPT 1

N-doped Reduced Graphene Oxide Aerogel Coated on Carboxyl-modified Carbon

2

Fiber Paper for High-performance Ionic-liquid Supercapacitors

3

Pawin Iamprasertkuna, Atiweena Krittayavathananonb, and Montree Sawangphruka,b,*

RI PT

4 5

6

a

7

Its Applications in Chemical Food and Agricultural Industries, and NANOTEC-KU-Centre of

8

Excellence on Nanoscale Materials Design for Green Nanotechnology, Kasetsart University,

9

Bangkok 10900, Thailand

11

SC

b

M AN U

10

Department of Chemical Engineering, Center for Advanced Studies in Nanotechnology and

Department of Chemical and Biomolecular Engineering, School of Energy Science and

Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21210, Thailand

TE D

12

*Corresponding author. Tel: +66(0)33-01-4251 Fax: +66(0)33-01-4445. E-mail address:

14

[email protected] (M. Sawangphruk).

15

EP

13

Abstract

17

Nitrogen-doped reduced graphene oxide aerogel (N-rGO aerogel) with high porosity and

18

ionic conductivity were synthesized by a hydrothermal reduction of graphene oxide with

19

hydrazine and following freezing-dry method. N-rGO aerogel was spray-coated on carboxyl-

20

modified carbon fiber paper with a hydrophilic surface and used as the supercapacitor

21

electrode. Not only can the N-rGO aerogel electrode accelerate the diffusion of the electrolyte

22

but also it can store electronic charge via a surface redox reaction due to the N-containing

23

groups. Among the electrolytes studied, the ionic liquid-based supercapacitor of the N-rGO

AC C

16

2

ACCEPTED MANUSCRIPT

aerogel provides a wide working potential of ca. 4.0 V and rather high specific capacitance of

25

764.53 F/g at 1 A/g with a capacity retention of 86% over 3000 charge-discharge cycles as

26

well as maximum specific power and energy of 6525.56 W/kg and 245.00 Wh/kg,

27

respectively. The device prototype fabricated in a single coin cell shape (CR2016) can supply

28

electricity to red LED over 17 min.

RI PT

24

29

1. Introduction

SC

30

Supercapacitors are energy storage devices, which have high power density (500-

32

10,000 W/kg), good reversible charge-discharge performance, and long cycle life (>500,000

33

cycles)[1] due to their charge storage mechanisms based on electrochemical double layer

34

capacitance (EDLC) and pseudocapacitance[2-4]. Both mechanisms mainly occur at the

35

surfaces of the supercapacitor electrodes. Whilst, the battery counterparts store electronic

36

charges inside the crystalline bulk materials used as the battery electrodes. The

37

supercapacitors are employed together with the batteries or fuel cells in hybrid electric

38

vehicles (HEVs) and self-sufficiently used in emergency backup power sources and public

39

transportation vehicles[5]. However, the supercapacitors store low specific energy (typically

40

5–10 Wh/kg) when compared with the batteries (∼20–170 Wh/kg) limiting their applications

41

in high specific energy devices such as mobile phones[6].

TE D

EP

AC C

42

M AN U

31

To enhance the specific energy of the supercapacitors, the materials with high specific

43

surface area, high electronic and ionic conductivities, and high porosity are needed. In the

44

past decade, graphene has been widely investigated as the electrode material of the

45

supercapacitors due to its high theoretical surface area of 2,630 m2/g[7], electrical

46

conductivity of 2x103 S/cm[8], and specific capacitance of 550 F/g[9]. Graphene stores

47

charges via EDLC; thus, the graphene-based supercapacitors have higher specific power and

3

ACCEPTED MANUSCRIPT 48

capacity retention when compared with the pseudocapacitors chemically storing an electronic

49

charge via a surface redox reaction on the electrode surfaces of metal oxides and conducting

50

polymers[10]. Although a single graphene sheet has many outstanding theoretical values, the

52

restacked form of graphene sheets has poor empirical properties. This is because the van der

53

Waals attractive force among the adjacent graphene sheets draws them together forming the

54

restacked structure exhibiting low surface area and poor charge storage capacity. The

55

restacked graphene is then not ideal to be used as the supercapacitor electrode[11]. Recently,

56

graphene aerogel with open pore structure was synthesized and used as the supercapacitor

57

electrodes[12-18]. Though the graphene aerogel has light weight, porosity, and specific

58

surface area leading to high charge storage capacity[12], its specific capacitance is still under

59

the theoretical value of a single layer of graphene sheet.

M AN U

SC

RI PT

51

In order to enhance the charge storage performance of the graphene aerogel, diluted

61

nitrogen content was more recently doped to 3D graphene[19, 20] and reduced graphene

62

oxide[21] (N-rGO) aerogel structures[22]. The N-rGO aerogel was previously produced by

63

the pyrolysis of poly (methyl methacrylate)–graphene oxide (PMMA-GO) composite in a

64

mixed nitrogen and ammonia gas[22]. In this work, N-rGO aerogel was produced by using a

65

hydrothermal reduction process of GO with hydrazine and following freezing-dry method.

66

The N-rGO aerogel was spray-coated on carboxyl-modified carbon fiber paper[23, 24] and

67

used as the electrode of the ionic liquid–based supercapacitor. To the best of our knowledge,

68

the ionic liquid supercapacitor of the N-rGO aerogel has not yet been reported. For

69

comparison, the supercapacitors of N-rGO nanosheet were in addition fabricated and tested in

70

a number of electrolytes.

AC C

EP

TE D

60

71

The as-fabricated ionic liquid supercapacitor in a single coin shape (CR2016) in this

72

work can provide a high specific capacitance of 764.53 F/g at 1 A/g, which is over a

4

ACCEPTED MANUSCRIPT 73

theoretical value of a single graphene sheet as well as maximum specific power and energy

74

of 6525.56 W/kg and 245.00 Wh/kg, respectively. The device prototype can supply electricity

75

to red light emitting diode (LED) over 17 min.

77

2. Experimental

78

2.1 Chemicals and materials

RI PT

76

Graphite powder (20-40 µm, Sigma Aldrich), sulfuric acid (98%, QRec), hydrogen

80

peroxide (30%, Merck), potassium permanganate (99%, Ajax Finechem), sodium nitrate

81

(99.5%, QRec), sodium hydroxide (99.5%, QRec), sodium sulphate (99.5%, QRec),

82

hydrazine hydrate (80%, Merck), 1-butyl-1-methylpyrrolidinium dicyanamide, [BMP][DCA]

83

(≥97.0%, Sigma Aldrich), tetraethylammonium tetra-fluoroborate (≥99.0%, Sigma Aldrich)

84

and acetonitrile (99.9%, Honeywell) were of analytical reagent grade. Water was purified by

85

using the Milli-Q system (>18 MΩ cm, Millipore).

M AN U

TE D

87

2.2 Preparation of graphene oxide

EP

86

SC

79

GO was synthesized by using a Hummers method[25] with our modification as

89

follows[26-28]. Briefly, graphite powder (2.0 g) and NaNO3 (3.0 g) were added to a

90

concentrated H2SO4 (200 ml) while stirring at 100 rpm in an ice bath for 1 h. KMnO4 (16.0 g)

91

was slowly added to the mixture at 25 °C and kept stirring (100 rpm) for 24 h. Then, Milli-Q

92

water was slowly added to the suspension and 30 % H2O2 (60 ml) was slowly added to the

93

diluted suspension and kept stirring (100 rpm) for 24 h. For the purification, the mixture was

94

filtered through polyester fiber (Carpenter Co.). The filtrate was centrifuged at 6000 rpm for

95

15 min and the remaining solid material (GO) was then washed in succession with 200 ml of

96

water. This process was repeated for 3 times. The final product GO was collected by

AC C

88

5

ACCEPTED MANUSCRIPT 97

centrifugal and vacuum dried at 60 °C.

98

2.3 Preparation of N-doped reduced graphene oxide aerogel The N-rGO material was synthesized via the hydrothermal reduction of GO with

100

hydrazine and following freezing-dry method. Briefly, 2 mg/mL suspension of GO in water

101

was prepared by the ultrasonication of GO (200 mg) in water (100 mL) for 2 h.

102

Consequently, 0.5 M hydrazine hydrate was added to the GO suspension. The mixture

103

solution was transferred to Teflon-lined autoclave and maintained at 160 °C for 3 h. Then, the

104

autoclave was naturally cooled down to room temperature and the as-prepared N-rGO

105

hydrogel was harvested by vacuum filtration. Finally, the as-filtrated N-rGO hydrogel was

106

aged in Milli-Q water at room temperature for 72 h for which the water was changed every

107

24 h to wash out the residual reducing agent. The final product aerogel was then chilled at

108

0˚C for 24 h and then freeze-dried for 72 h.

110

SC

M AN U

TE D

109

RI PT

99

2.4 Morphological and structural characterizations The morphology of the as-synthesized materials was characterized by field-emission

112

scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM).

113

Nitrogen adsorption/desorption isotherm was measured by a Brunauer-Emmett-Teller (BET)

114

method. The structural characterization was analyzed by Raman spectroscopy and X-ray

115

diffraction (XRD). The functional groups were analyzed by Fourier transform infrared

116

spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS).

AC C

EP

111

117

118 119

2.5 Supercapacitor fabrication and electrochemical evaluation N-rGO material powder (2 mg) was dispersed and sonicated in n-methyl-2-

6

ACCEPTED MANUSCRIPT

pyrrolidone (2 ml) with a solid content of 1 mg/ml. The dispersion was then sprayed on the

121

carboxyl-modified carbon fiber paper (c-CFP)[23, 24] by an airbrush (Paasche Airbrush

122

Company, USA) with 0.3 mm brush nozzle and eventually dried at 50˚C for 24 h[29, 30].

123

Polyethylene (PE) and hydrolyzed PE films with a thickness of 25 µm were used as the

124

separators of organic- and non-organic-based supercapacitors, respectively. The weight

125

content of N-rGO material on the circle substrate with a diameter of 1.98 cm determined

126

using a 5-digit analytical balance (Mettler Toledo, New Classic MF MS205DUX) is 1 mg.

127

[BMP][DCA] was used as an ionic liquid. 0.5 M tetraethyl ammonium tetra-fluoroborate in

128

acetonitrile (TEABF4/AN) was used as the organic electrolyte. 1 M H2SO4, 1 M NaOH, 0.5

129

M Na2SO4 were used as the aqueous electrolytes. The separators were soaked in the

130

electrolytes for 10 min before used.

M AN U

SC

RI PT

120

Electrochemical property of the as-fabricated supercapacitors were evaluated by

132

cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical

133

impedance spectroscopy (EIS) using a Metrohm AUTOLAB potentiostat (PGSTAT 302N)

134

made in Netherlands running NOVA software (version 1.10.3). The symmetric

135

supercapacitor was assembled of two N-rGO aerogel electrodes with a geometrical coin cell

136

(CR2016 size).

EP

AC C

137

TE D

131

138

3. Results and discussion

139

3.1 Morphological and structural characterizations

140

An FE-SEM image in Fig.1a shows the morphology of N-rGO nanosheet exhibiting a

141

few layers of rGO sheets overlapping each other. When compared with the FE-SEM image of

142

N-rGO aerogel in Fig. 1c, the surface of N-rGO sheets is much smoother than that of N-rGO

143

aerogel. Also, the N-rGO nanosheet tend to be restacked forming the thicker sheets. As the

7

ACCEPTED MANUSCRIPT

result, the N-rGO aerogel produced by the hydrothermal reduction with hydrazine hydrate

145

and following freeze-drying method exhibits ultrahigh porosity, which can enhance the

146

electrolyte diffusion[23, 24, 30]. The interconnected macropores with a diameter of ca. 0.5-3

147

µm are also found in N-rGO aerogel in Fig 1c. TEM images of N-rGO nanosheet and aerogel

148

are shown in Fig. 1b and d, respectively. The N-rGO sheets with rather sooth surfaces are

149

nearly transparent indicating a few layers of rGO sheets (Fig. 1b). Whilst, the N-rGO aerogel

150

sheets consist of many wrinkles, which are from their framework structures (see Fig.1d).

151

Their electron diffraction patterns of N-rGO nanosheet and aerogel (inset images in Fig. 1b

152

and d, respectively) show symmetrical hexagonal spots of the crystalline rGO structure

153

indicating that the pristine GO was reduced to rGO[31, 32].

AC C

EP

TE D

M AN U

SC

RI PT

144

154 155

Fig. 1. (a) FE-SEM images of N-rGO nanosheet (b) TEM images of N-rGO nanosheet (c)

156

FE-SEM images of N-rGO aerogel and (d) TEM images of N-rGO aerogel.

8

ACCEPTED MANUSCRIPT

The as-prepared materials were further characterized by XRD, RAMAN, FTIR, and

158

N2 gas adsorption/desorption. After the reduction process of GO with hydrazine, the XRD

159

peak at 2θ of about 10.0° (see Fig. S2a of the supporting information), which is a

160

characteristic peak of GO, completely disappears. The XRD patterns of both N-rGO

161

nanosheet and aerogel have two broad peaks located at 24.5° and 43.0° corresponding to the

162

(002) and (100) reflections, respectively, which refer to graphene peak pattern[20].

RI PT

157

SC

The RAMAN spectra in Fig. 2a display two distinct bands at 1350 cm-1 and 1595 cm-

163 164

1

165

represents the amount of disordered carbon in as-synthesized materials, while the intensity of

166

G band represents the amount of sp2 hybridization indicating the degree of graphitization. In

167

order to determine ratio of disordered and ordered content on rGO sheet, ID/IG values of GO,

168

N-rGO nanosheet and N-rGO aerogel are 1.17, 1.14 and 0.81. It can be seen that the ID/IG

169

proportion of N-rGO aerogel has the lowest value, which is in good agreement with previous

170

work[19]. In addition, the percentages of amorphous carbon on GO, N-rGO nanosheet and N-

171

rGO aerogel were calculated from area under the peak around 1550 cm-1 divided by the total

172

area, which are 22.40, 17.07 and 12.84, respectively.

EP

TE D

M AN U

, which refer to D and G bands, respectively. Normally, the intensity of the D band

The reduction of GO can be further confirmed by FTIR spectra as shown in Fig. S2b.

174

The FTIR spectrum of pristine GO displays obvious peaks at ∼3360, 1722, 1612, 1226,

175

1057 cm−1, which attribute to the vibrations of O–H, C=O, C=C, C-OH, C-O, respectively.

176

After the reduction process, all these characteristic peaks are diminished for the spectra of N-

177

rGO nanosheet and aerogel samples.

AC C

173

178

The porous structure of the samples was also studied using N2 adsorption/desorption

179

measurement (see Fig. 2b). According to IUPAC classification, the N-rGO aerogel is

180

classified as a type-IV isotherm material with a hysteresis loop type 2 due to the

9

ACCEPTED MANUSCRIPT

interconnected pore networks. The N-rGO nanosheet has the similar pore form of pristine

182

GO, which is a slit-shaped mesopores (H3 type hysteresis loop). The BET surface areas of

183

agglomerated GO, N-rGO nanosheet, and N-rGO aerogel are ca. 40, 124, 294 m2/g,

184

respectively. Note that the materials with hydrophilic and sticky properties due to oxygen and

185

nitrogen-containing groups are stable in the agglomerated form leading to low surface area

186

based on the gas adsorption method. The materials therefore need ultrasonication for 30 min

187

before use in the electrode fabrication process.

188

TE D

M AN U

SC

RI PT

181

Fig. 2. (a) RAMAN spectra and (b) N2-adsorption/desorption isotherms of GO, N-rGO

190

nanosheet, and N-rGO aerogel.

EP

189

Diluted nitrogen contents and the organic functional groups on the surface of N-rGO

192

aerogel were characterized by XPS. As shown in a wide scan XPS in Fig. 3a, N-rGO aerogel

193

has a predominant C1s peak at 284.4 eV, a minor O1s peak at 532.4 eV, and a N1s peak at

194

399.4 eV, without any other elements impurities found on the surface of the as-synthesized

195

material. Based on the peak area calculation, it reveals that the atomic contents of C, O, and

196

N are 91.38, 2.52, 6.10 %, respectively. The narrow-scan C1s spectrum as shown in Fig. 3b

197

can be deconvoluted into four bonding types at 285.0 eV, 285.3 eV, 286.7 eV and 288.8 eV

198

corresponding to the C-C, C-N, C-O, C=O, respectively[33]. The N1s spectra as shown in

AC C

191

10

ACCEPTED MANUSCRIPT

Fig. 3c display four peaks at 399.2, 400.4, 401.8 and 405.0 eV relating to the pyridinic-N,

200

pyrrolic-N, graphitic-N, and oxidized N, respectively[34]. It can be estimated that the the

201

pyridinic-N, pyrrolic-N, graphitic-N, and oxidized N contain 23.82, 45.54, 11.61 and 19.03

202

%, respectively. As statement previously, the presence of the pyridinic-N, pyrrolic-N in rGO

203

sheets can provide lone pair electrons and improve the charge mobility in carbon matrix[35].

204

The graphitic-N is the nitrogen atom bonding to a benzene ring of the graphitic sheet[36],

205

which plays an important role in connecting rGO framework[34]. The O1s spectra as shown

206

in Fig. 3d display three peaks at 531.0, 532.3 and 533.7 eV, attributing to O=C-OH, C=O and

207

C-OH configurations, respectively. Note, the XPS spectra of N-rGO nanosheet also carried

208

out is shown in Fig. S3 for which there is no significant difference with those of N-rGO

209

aerogel.

AC C

EP

TE D

M AN U

SC

RI PT

199

210

11

ACCEPTED MANUSCRIPT 211

Fig. 3. (a) Wide-scan XPS spectrum and narrow scan XPS spectra of (b) C1s, (c) N1s, and

212

(d) O1s of N-rGO aerogel.

213

3.2 Electrochemical evaluation

RI PT

214

The CR2016 coin-cell supercapacitors of all as-prepared materials were eventually

216

fabricated and electrochemically evaluated by cyclic voltammetry (CV), galvanostatic

217

charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) methods. The

218

CV curves of N-rGO nanosheet and aerogel supercapacitors were evaluated in BMP-DCA

219

ionic liquid electrolyte at a scan rate of 10 mV/s showing a wide working potential up to 4V

220

(see Fig. 4a). There are broad redox peaks observed in the CV curves of the supercapacitors

221

indicating that the N-rGO materials behave as the pseudocapacitive materials stemming from

222

the N-containing functional groups[37, 38]. Note, the control experiment using uncoated c-

223

CFP substrate as the electrode of the ionic liquid-based supercapacitor was carried out for

224

which the device can store little ionic liquid charges (see Fig. 4b). To further finely tune the

225

charge storage performance of N-rGO aerogel, different electrolytes were used. The CV

226

curves of the supercapacitors using 1.0 M H2SO4, 1.0 M NaOH, 0.5 M Na2SO4, 0.5 M

227

TEABF4/AN, [BMP][DCA] as the electrolytes tested at their working potential limits at a

228

scan rate of 10 mV/s are also shown in Fig. 4a. The [BMP][DCA] ionic liquid electrolyte

229

shows much larger capacitive current than the aqueous and organic electrolytes for a range of

230

scan rates (see Fig. 4b).

AC C

EP

TE D

M AN U

SC

215

231

In addition to CV, GCD was also carried to evaluate the performance of the as-

232

fabricated supercapacitors (see Fig. 4c). The BMP-DCA based supercapacitor of N-rGO

233

aerogel with the specific capacitances of 764.53, 744.95, 718.71, and 673.66 F/g at the

12

ACCEPTED MANUSCRIPT

applied specific currents of 1, 2, 3, and 4 A/g, respectively (see Fig. 4d and the calculation

235

details in the supporting information). It is necessary to note here that the iR drop of the ionic

236

liquid-based supercapacitor is in principle higher than that of aqueous- and organic-based

237

supercapacitors. The N-rGO aerogel device also shows about 38% higher capacitive current

238

than N-rGO nanosheet at an applied specific current (1 A/g) (see Fig. 4d) due to its higher

239

surface area and porosity. The capacitances here are much high than those of the

240

supercapacitors using other electrolytes in this work and much higher than 197 F/g at a

241

current density of 0.2 A/g of the KOH/PVA solid-based supercapacitor of N-doped

242

graphene[19]. Note, the cut-off potential is rather crucial since the decomposition of the

243

electrolytes may occur at high operating potentials.

AC C

EP

TE D

M AN U

SC

RI PT

234

244

13

ACCEPTED MANUSCRIPT

Fig. 4. (a) CV curves of N-rGO nanosheet and N-rGO aerogel supercapacitors at 10 mV/s in

246

different electrolytes, (b) the specific capacitance vs. scan rates of the supercapacitors, (c)

247

GCD curves of N-rGO nanosheet and N-rGO aerogel supercapacitors at 1 A/g in different

248

electrolytes, and (d) the specific capacitances vs. applied specific current of the

249

supercapacitors.

RI PT

245

In addition, the EIS of the as-fabricated supercapacitors was also carried out using a

251

sinusoidal signal of 10 mV over the frequency range from 100 kHz to 1 mHz. The Nyquist

252

plots of the N-rGO nanosheet and aerogel supercapacitors in [BMP][DCA] ionic liquid

253

electrolyte are shown in Fig. 5a. The characteristic of the Nyquist plots in Fig. 6a is close to

254

that of an ideal supercapacitor, which has a vertical line in parallel with the Y-axis especially

255

at low frequency. At high frequency (the bottom left-hand corner of the Nyquist plot), the

256

electronic charge transfer resistances stemming from the surface redox reaction of the N-rGO

257

are about 17.38 Ω and 11.44 Ω for N-rGO nanosheet and N-rGO aerogel, respectively. The

258

internal resistance (Rs) was an interception on X-axis, which is about 1.7 Ω and 8.1 Ω for N-

259

rGO aerogel and N-rGO nanosheet, respectively. The specific capacitances vs. the applied

260

frequencies are shown in Fig. 5b. The results are in good agreement with CV and GCD

261

results.

M AN U

TE D

EP

AC C

262

SC

250

Eventually, the stability or cycle life of the as-fabricated supercapacitors was

263

evaluated by GCD over 3000 cycles. The capacity retention values of N-rGO nanosheet and

264

N-rGO aerogel supercapacitors in [BMP][DCA] ionic liquid electrolyte are 85.6% and 66.1

265

%, respectively (see Fig. 5c). The Ragone plot of the as-fabricated supercapacitors was also

266

calculated and shown in Fig. 5d. The supercapacitor device of N-rGO aerogel has about 2.5-

267

fold higher energy and 2.6-fold higher power density than those of N-rGO nanosheet. The

268

[BMP]-[DCA] ionic liquid electrolyte provides the highest specific energy of 245.00 Wh/kg

14

ACCEPTED MANUSCRIPT

at a specific power of 1481.04 W/kg, which is higher than those of other devices fabricated in

270

this work and other previous work. To demonstrate the practical use of the as-fabricated

271

supercapacitor, it was used to supply electricity to the red LED with a fully discharged time

272

of 17.53 min (see an inset image in Fig.5c and movies s1 in the supporting information).

EP

TE D

M AN U

SC

RI PT

269

AC C

273 274

Fig. 5. (a) Nyquist plots and (b) the specific capacitance vs. frequency of the N-rGO

275

nanosheet and N-rGO aerogel supercapacitors in [BMP][DCA] ionic liquid electrolyte as

276

well as (c) capacitance retention of as-fabricated devices over 3000 cycles and (d) Ragone

277

plots of the as-fabricated devices compared with some previous report[19, 39, 40] .

278

279

4. Summary

15

ACCEPTED MANUSCRIPT

N-rGO aerogel was synthesized by a hydrothermal reduction of GO with hydrazine

281

and following freeze-drying method. The coin-cell supercapacitors of N-rGO aerogel were

282

fabricated using different electrolytes i.e. H2SO4, NaOH, Na2SO4, TEABF4/AN, and

283

[BMP][DCA]. The [BMP][DCA] ionic liquid electrolyte-based supercapacitor of the N-rGO

284

aerogel provides a wide working potential up to 4.0 V, high specific capacitance of 764.53

285

F/g at 1 A/g, and a capacity retention of 86% over 3000 charge-discharge cycles as well as

286

maximum specific power and energy of 6525.56 W/kg and 245.00 Wh/kg, respectively. High

287

performance of the device is due to ultra-high porosity of 3D structure, wide window

288

potential of ionic liquid electrolyte, high ionic conductivity of N-rGO framework, and

289

pseudocapacitive capacitance of N-containing functional groups.

M AN U

SC

RI PT

280

290 291

Acknowledgments

This work was financially supported by the Thailand Research Fund and

293

Vidyasirimedhi Institute of Science and Technology (RSA5880043). Supports from the

294

Frontier Research Centre at VISTEC and the graduate school Kasetsart University are also

295

acknowledged.

EP

296

TE D

292

References

298

[1]

299

Power Sources 2006;157(1):11-27.

300

[2]

301

Convers Manage 2010;51(12):2901-12.

302

[3]

303

2008;7(11):845-54.

AC C

297

Pandolfo AG, Hollenkamp AF. Carbon properties and their role in supercapacitors. J

Sharma P, Bhatti TS. A review on electrochemical double-layer capacitors. Energ

Simon P, Gogotsi Y. Materials for electrochemical capacitors. Nat Mater

16

ACCEPTED MANUSCRIPT 304

[4]

Kötz R, Carlen M. Principles and applications of electrochemical capacitors.

305

Electrochim Acta 2000;45(15-16):2483-98.

306

[5]

307

and Conversion. Handbook of Clean Energy Systems: John Wiley & Sons, Ltd 2015.

308

[6]

309

Ultrahigh Energy Density. Nano Lett 2010;10(12):4863-8.

310

[7]

311

Two-dimensional gas of massless Dirac fermions in graphene. Nature 2005;438(7065):197-

312

200.

313

[8]

314

with High Electrical Conductivity and Good Thermal Stability by Hydrogen Arc Discharge

315

Exfoliation. ACS Nano 2009;3(2):411-7.

316

[9]

317

Lett 2008;8(10):3498-502.

318

[10]

319

Nanowire Arrays on Graphene Oxide Sheets with Synergistic Effect for Energy Storage.

320

ACS Nano 2010;4(9):5019-26.

321

[11]

322

high-performance flexible all-solid-state supercapacitors. J Mater ChemA 2014;2(28):10895-

323

903.

324

[12]

325

aerogels toward supercapacitors. Electrochim Acta 2015;173(0):1-6.

326

[13]

327

performance of graphene aerogel with a superhigh C/O molar ratio. J Mater Chem

328

2012;22(43):23186-93.

RI PT

Kim BK, Sy S, Yu A, Zhang J. Electrochemical Supercapacitors for Energy Storage

Liu C, Yu Z, Neff D, Zhamu A, Jang BZ. Graphene-Based Supercapacitor with an

M AN U

SC

Novoselov KS, Geim AK, Morozov SV, Jiang D, Katsnelson MI, Grigorieva IV, et al.

Wu Z-S, Ren W, Gao L, Zhao J, Chen Z, Liu B, et al. Synthesis of Graphene Sheets

TE D

Stoller MD, Park S, Zhu Y, An J, Ruoff RS. Graphene-Based Ultracapacitors. Nano

EP

Xu J, Wang K, Zu S-Z, Han B-H, Wei Z. Hierarchical Nanocomposites of Polyaniline

AC C

Ju H-F, Song W-L, Fan L-Z. Rational design of graphene/porous carbon aerogels for

Liu T, Song W-L, Fan L-Z. Alcohol-dependent environments for fabricating graphene

Wu X, Zhou J, Xing W, Wang G, Cui H, Zhuo S, et al. High-rate capacitive

17

ACCEPTED MANUSCRIPT 329

[14]

Lee YJ, Park HW, Hong UG, Song IK. Characterization and electrochemical

330

performance of Graphene-containing carbon Aerogel for Supercapacitor. J Nanosci

331

Nanotechnol 2013;13(12):7944-9.

332

[15]

333

aerogel composites for high-performance asymmetric supercapacitors. Nano Energy

334

2015;11:611-20.

335

[16]

336

foam as a binder-free supercapacitor electrode. ACS Appl Mater Interfaces 2013;5(15):7122-

337

9.

338

[17]

339

large surface area for flexible all-solid-state supercapacitors. Electrochim Acta 2015;165:92-

340

7.

341

[18]

342

graphene aerogels and their effect on supercapacitor performance. Nanoscale

343

2015;7(10):4386-93.

344

[19]

345

self-doped hierarchical porous carbon aerogels derived from chitosan for high performance

346

supercapacitors. Nano Energy 2015;15:9-23.

347

[20]

348

aerogels as efficient supercapacitor electrodes and gas adsorbents. ACS Appl Mater

349

Interfaces 2015;7(3):1431-8.

350

[21]

351

graphene family – A recommended nomenclature for two-dimensional carbon materials.

352

Carbon 2013;65:1-6.

RI PT

Yu Z, McInnis M, Calderon J, Seal S, Zhai L, Thomas J. Functionalized graphene

M AN U

SC

Ye S, Feng J, Wu P. Deposition of three-dimensional graphene aerogel on nickel

Chen TT, Song WL, Fan LZ. Engineering graphene aerogels with porous carbon of

TE D

Jung SM, Mafra DL, Lin CT, Jung HY, Kong J. Controlled porous structures of

AC C

EP

Hao P, Zhao Z, Leng Y, Tian J, Sang Y, Boughton RI, et al. Graphene-based nitrogen

Sui ZY, Meng YN, Xiao PW, Zhao ZQ, Wei ZX, Han BH. Nitrogen-doped graphene

Bianco A, Cheng H-M, Enoki T, Gogotsi Y, Hurt RH, Koratkar N, et al. All in the

18

ACCEPTED MANUSCRIPT 353

[22]

Pham VH, Nguyen-Phan TD, Jang J, Tuyet Vu TD, Lee YJ, Song IK, et al. Nitrogen-

354

doped mesoporous reduced graphene oxide for high-performance supercapacitors. RSC Adv

355

2014;4(43):22455-62.

356

[23]

357

et al. High-performance supercapacitor of electrodeposited porous 3D polyaniline nanorods

358

on functionalized carbon fiber paper: Effects of hydrophobic and hydrophilic surfaces of

359

conductive carbon paper substrates. Mater Today Commun 2015;4:176-85.

360

[24]

361

Suksomboon M, et al. High-Performance Supercapacitor of Functionalized Carbon Fiber

362

Paper with High Surface Ionic and Bulk Electronic Conductivity: Effect of Organic

363

Functional Groups. Electrochim Acta 2015;176:504-13.

364

[25]

365

1958;80(6):1339-.

366

[26]

367

nanoparticles decorated on reduced graphene oxide rotating disk electrodes toward

368

ultrasensitive hydrazine detection: Effects of particle size and hydrodynamic diffusion. Anal

369

Chem 2014;86(24):12272-8.

370

[27]

371

Limtrakul J. High-performance supercapacitor of manganese oxide/reduced graphene oxide

372

nanocomposite coated on flexible carbon fiber paper. Carbon 2013;60:109-16.

373

[28]

374

antifungal activity of reduced graphene oxide nanosheets. Carbon 2012;50(14):5156-61.

375

[29]

376

Sanguansak Y, et al. High-performance supercapacitors based on silver nanoparticle-

SC

RI PT

Kaewsongpol T, Sawangphruk M, Chiochan P, Suksomboon M, Suktha P, Srimuk P,

M AN U

Suktha P, Chiochan P, Iamprasertkun P, Wutthiprom J, Phattharasupakun N,

TE D

Hummers WS, Offeman RE. Preparation of Graphitic Oxide. J Am Chem Soc

EP

Krittayavathananon A, Srimuk P, Luanwuthi S, Sawangphruk M. Palladium

AC C

Sawangphruk M, Srimuk P, Chiochan P, Krittayavathananon A, Luanwuthi S,

Sawangphruk M, Srimuk P, Chiochan P, Sangsri T, Siwayaprahm P. Synthesis and

Sawangphruk M, Suksomboon M, Kongsupornsak K, Khuntilo J, Srimuk P,

19

ACCEPTED MANUSCRIPT 377

polyaniline- graphene nanocomposites coated on flexible carbon fiber paper. J Mater Chem A

378

2013;1(34):9630-6.

379

[30]

380

supercapacitor of reduced graphene oxide-metal organic framework composite coated on

381

carbon fiber paper. Electrochim Acta 2015;157:69-77.

382

[31]

383

aerogel via magnesiothermic reduction of graphene oxide assemblies. Nano Res

384

2015;8(5):1710-7.

385

[32]

386

Rotational Stacking Faults in Few Layer Graphene. Nano Lett 2009;9(1):102-6.

387

[33]

388

graphene surfactant. Chem Commun 2012;48(62):7732-4.

389

[34]

390

Robust 3D Porous N-Doped Graphene. Adv Mater 2015;27(35):5171-5.

391

[35]

392

doped graphene-carbon nanotube hybrid paper for high-performance supercapacitors. RSC

393

Adv 2015;5(12):9228-36.

394

[36]

395

Graphene for High-Performance Ultracapacitors and the Importance of Nitrogen-Doped Sites

396

at Basal Planes. Nano Lett 2011;11(6):2472-7.

397

[37]

398

Sulfur in Co-Doped Graphene and Synergetic Effect in Supercapacitor. Sci Rep

399

2015;5:9591.

RI PT

Srimuk P, Luanwuthi S, Krittayavathananon A, Sawangphruk M. Solid-type

SC

Tang H, Gao P, Bao Z, Zhou B, Shen J, Mei Y, et al. Conductive resilient graphene

M AN U

Warner JH, Rümmeli MH, Gemming T, Büchner B, Briggs GAD. Direct Imaging of

Some S, Kim Y, Hwang E, Yoo H, Lee H. Binol salt as a completely removable

TE D

Qin Y, Yuan J, Li J, Chen D, Kong Y, Chu F, et al. Crosslinking Graphene Oxide into

EP

Fan W, Miao Y-E, Huang Y, Tjiu WW, Liu T. Flexible free-standing 3D porous N-

AC C

Jeong HM, Lee JW, Shin WH, Choi YJ, Shin HJ, Kang JK, et al. Nitrogen-Doped

Wang T, Wang L-X, Wu D-L, Xia W, Jia D-Z. Interaction between Nitrogen and

20

ACCEPTED MANUSCRIPT 400

[38]

Sahu V, Grover S, Tulachan B, Sharma M, Srivastava G, Roy M, et al. Heavily

401

nitrogen doped, graphene supercapacitor from silk cocoon. Electrochim Acta 2015;160:244-

402

53.

403

[39]

404

Dioxide/Manganese Carbonate/Reduced Graphene Oxide Aerogel for Asymmetric

405

Supercapacitors. Electrochim Acta 2015;164:154-62.

406

[40]

407

aerogels with enhanced capacitance in aqueous and ionic liquid electrolytes. J Power Sources

408

2015;278:751-9.

RI PT

Liu Y, He D, Wu H, Duan J, Zhang Y. Hydrothermal Self-assembly of Manganese

M AN U

SC

Shao Q, Tang J, Lin Y, Li J, Qin F, Yuan J, et al. Carbon nanotube spaced graphene

AC C

EP

TE D

409