hierarchical porous carbon with high nitrogen content derived...

Vol.:(0123456789)1 3

Journal of Materials Science: Materials in Electronics (2018) 29:7707–7717 https://doi.org/10.1007/s10854-018-8766-0

Hierarchical porous carbon with high nitrogen content derived from plant waste (pomelo peel) for supercapacitor

Guangsheng Fu1 · Qiang Li1 · Jianglin Ye2 · JunJian Han1 · Jiaqi Wang1 · Lei Zhai3 · Yanwu Zhu2

Received: 29 December 2017 / Accepted: 13 February 2018 / Published online: 23 February 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018

AbstractThe plant waste pomelo peels are used as carbon precursors to fabricate nitrogen-doped hierarchical porous carbon. The sample PC600 is fabricated at mild calcination temperature of 600 °C, which has nitrogen content of as high as 4.47% and hierarchical pores with a BET surface area of 1104 m2 g−1. The symmetric supercapacitor based on PC600//PC600 electrodes exhibits excellent electrochemical performance benefiting from both the electric double-layer capacitance and pseudocapaci-tance of PC600. In 1 M H2SO4 electrolyte, this supercapacitor delivers gravimetric capacitance of 208.7 F g−1, volumetric capacitance of 219.3 F cm−3, and energy density of 7.3 Wh kg−1 at a current density of 1 A g−1. Furthermore, the extraordi-nary energy density of 21.6 Wh kg−1 at 1 A g−1 and 17.1 Wh kg−1 at 20 A g−1 are obtained in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte. The suitable calcination process can make the contents of nitrogen atoms and pores structures in PC600 to achieve an optimal combination, leading to improved electrochemical performance.

1 Introduction

Much research efforts have been devoted to renewable energy as fossil fuels have caused more and more serious environmental problems. Therefore, the energy storage devices with high energy density, fast charge/discharge speed, long cycling stability and good temperature charac-teristics are urgently needed to store the electricity gener-ated from renewable energy resources such as solar energy and wind energy [1, 2]. Supercapacitor, an electrochemi-cal energy storage device, has attracted significant research interests in recent years to improve its energy density mainly through exploring electrode materials with new components and/or structures [3–5]. Activated carbon (AC) is the widely

used electrode material in the commercial supercapacitors, typically because of its low cost, great chemical stability, and high specific surface area [6]. However, the commonly recognized shortcoming of the traditional AC is its relatively low energy density and poor electrical conductivity [2].

Various methods have been investigated to generate appropriate structures in the AC to improve its electro-chemical properties. For example, the ACs containing interconnected micro-, meso-, and macro-pores were pro-duced where hierarchical porous structures can effectively enhance their electrochemical performance [7–9]. In these ACs, the micro/mesopores can provide high specific surface areas with large active sites for the storage of electrolyte ions to increase the electric double-layer capacitance (EDLC). The meso/macropores can minimize the diffusion resistance and distance of electrolyte ions to the electrochemical active sites on the electrode/electrolyte interface [7]. In addition, doping heteroatoms, especially nitrogen, into the lattice of AC can also increase its specific capacitance. The function of doped-hetoratoms is two folds, enhancing the electrical conductivity and wettability of the AC, and providing extra pseudocapacitance through the redox reactions between het-eroatoms and electrolyte ions [10].

Nitrogen-doped hierarchical porous activated carbons (NHPACs) have been produced through several approaches. Porous templates have been widely used to construct hierar-chical pores in ACs [11, 12], and nitrogen are traditionally

* Qiang Li [email protected]

* Yanwu Zhu [email protected]

1 School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, Anhui, China

2 Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, Anhui, China

3 NanoScience Technology Center and Department of Chemistry, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA

http://crossmark.crossref.org/dialog/?doi=10.1007/s10854-018-8766-0&domain=pdf

7708 Journal of Materials Science: Materials in Electronics (2018) 29:7707–7717

1 3

doped into ACs by the pyrolysis of nitrogen-rich polymers under inert atmosphere, or the heat treatment of ACs in ammonia [13–15]. However, these methods are always expensive, time-consuming and non-renewable [16]. In the efforts of producing NHPACs, plant wastes have attracted much attention as promising candidates (Table 1). Plant wastes are easily available, cheap and renewable. Above all, they usually contain well-defined porous structures and nitrogen given by nature. Table 1 shows that, except PC600 (NHPAC from this work), high temperature (i.e. 700° and above) is required for carbonization and/or activation to pro-duce NHPACs from plant wastes. However, the high temper-ature calcination process would cause the loss of nitrogen in the plant wastes precursors. Usually, the elevated calcination temperature decreases the nitrogen content and increases the carbon content in the obtained NHPACs [17]. Furthermore, high temperature in the carbonization and/or activation pro-cess would also affect the pore structure and pore size dis-tribution of the derived ACs [18]. Therefore, it is necessary to optimize the carbonization and/or activation process for different plant wastes precursors to obtain NHPACs with better electrochemical performance.

Here we report the fabrication of NHPAC (PC600) from pomelo peels via optimized calcination at 600 °C which is lower than the temperature of reported calcination process of plant wastes (Table 1). Pomelo has a thick, sponge-like and nitrogen-enriched peel, therefore the low-cost pomelo peels are an appropriate carbon precursor to fabricate NHPACs for supercapacitors [26–29]. However, the maxi-mum nitrogen content of reported NHPACs derived from pomelo peels is as low as 2.85% [26]. In this work, the opti-mized carbonization followed by KOH activation at 600 °C

generated NHPAC (PC600) with nitrogen content as high as 4.47% (Tables 1, 3). Symmetric supercapacitor was built by using PC600//PC600 electrodes, and it display excel-lent electrochemical performance in 1 M H2SO4 electrolyte with a specific capacitance of 208.7 F g−1 and 219.3 F cm−3 at current density of 1 A g−1. This supercapacitor has an energy density of 7.25 Wh kg−1 at 1 A g−1, and cycling stability of 96.2% capacitance retention after 10,000 cycles at 5 A g−1. Moreover, it also delivers high energy density of 21.6 Wh kg−1 at 1 A g−1 and 17.1 Wh kg−1 at 20 A g−1 in an EMIMBF4 electrolyte.

2 Experimental

Schematic illustration of the experimental process was shown in Fig. 1.

2.1 Preparation of NHPACs

The pomelo peel (PP) was cut into pieces with a volume about 1 cm3. The peels were washed with acetone and immersed in DI water for 30 min. After rinsed several times, the PP was placed in vacuum oven at 110 °C for 24 h. The dried PP (about 1 g) was crushed in a mortar till no obvi-ous chunks were visible. The dried PP was carbonized in a tube furnace under nitrogen atmosphere with a flowing rate of 5 cc min−1 and a heating rate of 10 °C min−1. When the furnace reached setting temperature, it was kept for 2 h then cooled naturally to room temperature. For comparison, the

Table 1 Comparison of PC600 with the reported carbons from plant wastes

a Carbonization temperatureb KOH or ZnCl2 activation temperaturec Nitrogen contentd Calcination atmosphere

Precursor TCa (°C) TAb (°C) Nc (At.%) Ad Ref.

Willow catkins 750 \ 1.82 Ar [19]Corn husk \ 800 0.64 N2 [20]Agricultural waste \ 800 2.5 N2 [21]Tree fluff 300 800 1.5 Ar [22]Tobacco rods 200 800 1.4 N2 [10]Elm samara \ 700 0.8 Ar [23]Frutescens 700 \ 1.7 N2 [18]Waste tea-leaves \ 700 3.0 N2 [24]Poplar catkins \ 800 0.4 N2 [25]Pomelo peels 400 800 2.85 N2 [26]PC600 600 600 4.47 N2 This work

Fig. 1 Schematic illustration of the nitrogen-doped hierarchical porous carbon derived from pomelo peel for supercapacitor applica-tions

7709Journal of Materials Science: Materials in Electronics (2018) 29:7707–7717

1 3

PP was carbonized at 400, 500, 600 and 700 °C in the same manner.

The carbonized PP (about 0.2 g) was mixed with KOH with mass ratio of 1:4 (carbonized PP:KOH). The mixture was dispersed in DI water, and dried at 60 °C. The dried mixture was calcinated in a tube furnace following the same procedure as the carbonization process. The activated sam-ples were washed firstly with a dilute HCl aqueous solution and DI water until the pH value in the filtered wastewater reached neutral. The mixture was then dried in a vacuum oven at 60 °C for 12 h. The obtained NHPACs were denoted as PC400, PC500, PC600 and PC700 according to treating temperatures. Taking PC600 for example, PC is the abbre-viation of PP derived Carbon, 600 means the carbonization followed by KOH activation of PP both at 600 °C.

2.2 Characterization method

The surface morphologies of the samples were examined by scanning electron microscopy (SEM, SU8020).Their microstructures were studied using high-resolution trans-mission electron microscopy (HRTEM, JEOL 2010). X-ray diffraction spectroscopy (XRD, D/max-TTR III, Cu Kα radiation with a scan rate of 5° min−1 from 10° to 80°) was used to examine the structures of samples. Raman spec-tra were obtained on an HR Evolution (HORIBA JOBIN YVON) with 532 nm laser. X-ray photoelectron spectros-copy (XPS) studies were performed on a spectrometer (Per-kin-Elmer, ESCALAB 250). The pore size distribution of the samples were calculated via a density functional theory (DFT) method by using the data obtained through Brunauer-Emmett-Teller (BET) methods via N2 adsorption–desorption (autosorb iQ) at 77 K.

2.3 Electrochemical measurements

Electrochemical measurements of the NHPAC samples were performed using a symmetrical two-electrode supercapacitor system. Cyclic voltammetry (CV), galvanostatic charge–dis-charge (GCD) and electrochemical impedance spectroscopy (EIS, frequency range from 100 kHz to 0.01 Hz with A.C. perturbation of 10 mV) of the fabricated supercapacitors were tested in 1 M H2SO4 and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) using a CHI660E (Chenhua Instruments Co. Ltd., Shanghai) electrochemical worksta-tion. The active material, acetylene black and PTFE were mixed thoroughly at a mass ratio of 80:15:5 and then rolled into a sheet with a thickness of ~ 40 µm. Round discs with a diameter of 9 mm were punched out from the sheet and put in a vacuum oven at 110 °C for 48 h. Two discs were used as electrodes to assemble a symmetrical supercapacitor for electrochemical measurements. According to the GCD results, the gravimetric capacitance (Ccp, F g−1), volumetric

capacitance (Cv, F cm−3), energy density (E, Wh kg−1) and power density (P, W kg−1) of the samples were calculated by the following equations [30],

where I is the discharge current, m is the total mass and Vm is the total volume for two electrodes, ΔV is the voltage change (IR drop was excluded), Δt is the discharge time.

3 Results and discussion

3.1 Characterization

X-ray diffraction spectra and Raman spectra clearly reveal the structure of the sample. XRD spectra of the samples (Fig. 2a) show that all samples have a weak and broad dif-fraction peak at near 23° (2θ), corresponding to the (002) graphite planes, indicating that all samples mainly contain amorphous carbon. Therefore, the activation treatments at temperature from 400 to 700 °C are not enough to change the graphitic planes of the activated carbon. The Raman spectra of the samples (Fig. 2b) shows that the D-bands locate at near 1350 cm−1 and G-bands locate at about 1580 cm−1 [31]. D-band represents the disordered carbon while G-band represents the in-plane stretching vibration of the sp2-hybridized carbon. The ratio of the D-band to G-band (ID/IG) of the samples (PC400, PC500, PC600 and PC700) increases from 0.89 to 1.02 (Table 2), which indi-cates the increase of imperfect structures in the NHPACs associated with the increased calcination temperature from 400 to 700 °C [32].

Surface morphologies of the dried pomelo peel (PP) and samples were examined by SEM. Figure 3a, b are the low and high magnification SEM images of the dried PP, respec-tively. The close stacking of dry PP layered structure can be clearly observed (Fig. 3b). The surface morphologies have changed significantly after the dry PP was carbonized fol-lowed by KOH activation. The SEM images with different magnification of PC600 are shown in Fig. 3c–e. Compared to Fig. 3a, c shows larger amount of smaller and irregular particles resulted from the high temperature calcination pro-cess. The interconnected holes and channels can be found

(1)Ccp =4IΔt

mΔV

(2)Cv =Ccp × m

Vm

(3)E = 1∕8 × Ccp ΔV2

(4)P = E∕Δt


1 3

in some of these PC600 particles (Fig. 3d, e) attributed to the KOH activation. These holes and channels are expected to facilitate the transport of electrolyte ions during charge/discharge process by working as electrolyte reservoir. Fur-thermore, the fine microstructure of PC600 was examined by HRTEM (Fig. 3f). The presence of a small number of crystalline carbon domains supports the XRD results show-ing that the majority of carbon in NHPACs is amorphous.

Pore structure distribution of the samples is characterized by nitrogen adsorption desorption isotherm test. As shown in Fig. 4a, PC600 shows a conjugate curve of type-I and type-IV [33, 34]. The large slope at low relative pressure (p/p0 < 0.1) indicates the existence of abundant micropores, and the hysteresis loop at medium relative pressure range (p/p0 = 0.2–0.9) demonstrates the presence of large number of mesopores [35, 36]. Figure 4b shows the pore size distribu-tion of PC600 where the diameter of micropores is concen-trated near 1 nm. The distribution of mesopores is relatively large with three peaks locating at 3.2, 4.1 and 12 nm. Spe-cific surface area (SSA) and total pore volume of PC600 were calculated to be 1104 m2 g−1 and 0.51 cm3 g−1 by the BET method, both keeping highest among the samples

(Table 2). Combined with SEM results, the hierarchical porous structures of PC600 would facilitate the transport and storage of electrolyte ions. Therefore, although the SSA of PC600 is not very high, it also delivers excellent electro-chemical performance.

Figure 4c is the XPS survey specta of PC600, showing a strong C 1s peak (~ 284.8 eV), an O 1s peak (~ 533 eV), and a weak N 1s peak (~ 400.5 eV). The contents of C, O and N were 84.07%, 11.47 and 4.47%, respectively. Four functional groups, graphite or elemental carbon (C–C/C=C, 284.5–285.5 eV), phenol groups (C–O, 286.6 eV) and car-boxyl or ester groups (O–C=O, 288.8 eV) are identified in C 1s spectrum (Fig. 4d) [37]. O 1s spectrum (Fig. 4e) shows three functional groups, carbonyl groups (C=O, 531.7 eV), phenol groups (C–OH, 533.2 eV) and carboxyl groups (COOH, 534.2 eV). The peaks of N 1s at 399.2, 400.4 and 401.3 eV in Fig. 4f represent pyrrolic N, quatermary N and pyridine nitrogen oxides, respectively [38, 39]. The Atomic concentrations of C, N and O elements of all samples from XPS results were listed in Table 2, showing that the nitrogen content of the samples decreases with increased calcination temperature. Particularly, the nitrogen content decreases

Fig. 2 The XRD (a) and Raman (b) spectra of all samples

Table 2 Structure parameters and capacitances of the samples

a Atomic concentrations (at.%)b Specific surface area (m2 g−1)c Total pore volume (cm3 g−1)d Ratio of the D-band to G-bande Specific capacitance (Cg, F g−1) and volumetric capacitance (Cv, F cm−3) in 1 M H2SO4 at 1 A g−1

f Cg and Cv in EMIMBF4 at 1 A g−1

Samples Ca Na Oa SSAb Vtc ID/IG

d Cge Cv

e Cgf Cv

f

PC400 75.28 4.68 20.04 803 0.39 0.89 134.7 126.6 / /PC500 83.49 4.51 12.00 1011 0.48 0.90 190 184.3 63.1 60.0PC600 84.07 4.47 11.47 1104 0.51 1.00 208.9 219.3 108.1 109.2PC700 84.16 2.69 13.15 873 0.41 1.02 140.2 129.0 77.5 72.1


1 3

rapidly from 4.47% (PC600) to 2.69% (PC700) when the calcination temperature increases from 600 to 700 °C while the carbon content increases only 0.09%. This result shows that treating temperature has profound effect on the nitrogen content of NHPACs produced from plant wastes. The nitro-gen functional groups can enhance the wettability and elec-trical conductivity of the samples, and the faradaic reactions between these functional groups and electrolyte ions would provide extra pseudocapacitance [40, 41]. In addition, the EDLC of samples would be affected by their carbon content and pores structures. Therefore, a suitable carbonization and activation process can make the contents of nitrogen atoms and pores structures in NHPACs to achieve an optimal com-bination, leading to improved electrochemical performance.

3.2 Electrochemical measurement

The electrochemical performances of the samples were all tested in a two-electrodes symmetrical supercapacitors sys-tem. Figure 5 depicts the results of electrochemical measure-ment of all samples in 1 M H2SO4 with voltage range from 0 to 1 V. Figure 5a shows the cyclic voltammetry (CV) curves of all samples at scan rate of 0.1 V s−1. It is obvious that the CV curves become more rectangular with increased treat-ing temperature. In other words, the pseudocapacitances of the samples decreases accompanied by increased electrical double-layer capacitances (EDLCs) when the treating tem-perature increases. The CV curve of PC600 has the largest

area (i.e. the highest capacitance) among the samples, which indicates the optimal equilibrium ratio of EDLC and pseu-docapacitance of PC600. Figure 5b shows the galvanostatic charge/discharge (GCD) curves of the samples at current density of 1 A g−1 which also indicates that PC600 has the best capacitance performance.

The CV curves of PC600 at scan rates from 0.01 to 0.2 V s−1 are shown in Fig. 5c. The imperfect rectangles with observable Faradaic humps suggest the co-existence of redox reaction and electrical double-layer performance. The GCD curves of PC600 at current densities ranging from 1 to 20 A g−1 are almost symmetric with very small IR drop (Fig. 5d). Figure 5e is the Nyquist plots of the samples. PC700 has the most vertical Nyquist plot, confirming its best electrical double-layer capacitance, which is consist-ent with the CV measurements. As shown in the inset of Fig. 5e (high frequency region), PC600 has the smallest equivalent series resistance (ESR) of 1.2 Ω (intercept with real axis). Moreover, the shortest region of the plot with a slope about 45° indicates that PC600 also has smallest Warburg resistance, suggesting the low diffusion resistance and short diffusion path of electrolyte ions within PC600 during charge/discharge process [10]. The volumetric and gravimetric capacitances of the samples at different current densities were alculated according to the GCD curves as shown in Fig. 5f. It is obvious that PC600 has the highest capacitance at all current densities. At 1 A g−1, PC600 has a volumetric capacitance of 219.3 F cm−3 and a gravimetric

Fig. 3 SEM images of dried pomelo peel (a, b) and PC600 (c–e). f HRTEM image of PC600


1 3

capacitance of 208.7 F g−1. PC600 has a specific capacitance of 175.2 F cm−3 and 166.9 F g−1 at 20 A g−1, showing an outstanding rate capability (80%).

A higher voltage window can improve the energy density of supercapacitor. Therefore, the electrochemical perfor-mances of PC500, PC600 and PC700 in two-electrode sym-metrical supercapacitors were also evaluated in BMIMBF4 with voltage range from 0 to 2.4 V, as shown in Fig. 6. Both CV curves at 0.1 V s−1 (Fig. 6a) and GCD curves at 1 A g−1 (Fig. 6b) indicate that PC600 has the best electrochemical

performance in BMIMBF4 electrolyte. Figure 6c shows the CV curves of PC600 at scan rates from 0.01 to 0.2 V s−1, and Fig. 6d shows its GCD curves at current densities from 1 to 20 A g−1. The nearly vertical Nyquist plot of PC600 (Fig. 6e) indicates the excellent capacitive performance of PC600 in BMIMBF4 [42]. Compared with the ESRs in 1 M H2SO4, ESRs in BMIMBF4 increased a little bit, but still as low as about 2 Ω (the inset of Fig. 6e), indicating the good conduc-tivity of the samples. Figure 6f shows the relationship of the volumetric and gravimetric capacitances of the samples

Fig. 4 BET and XPS measurements of PC600. a N2 adsorption and desorption isotherms. b Pore size distribution by DFT method. c XPS full spectrumspectra. d C 1s region. e O 1s region. f N 1s region


1 3

with different current densities calculated from their GCD curves. PC600 keeps the highest capacitance in BMIMBF4 with 109.2 F cm−3 and 108.1 F g−1 at 1 A g−1. The spe-cific capacitance of PC600 decreases to 86.1 F cm−3 and 85.2 F g−1 when the current density increases to 20 A g−1, showing 78.8% capacitance retention which is just 1.2% lower than that in 1 M H2SO4. As shown in Table 3, PC600 has a higher volumetric capacitance than the reported carbon

materials produced from biomasses in two-electrodes sys-tem, such as olive pits [43, 44], soybean residue [45], jujube pit [46] and seaweed [47], and also higher than some carbon materials tested in three-electrode systems, e.g. pomelo peel [26] and Lignin [48].

The symmetrical supercapacitor based on PC600 was charge–discharged for 10,000 cycles at 5 A g−1 in 1 M H2SO4 to test its cycling stability, and maintained 96.2% of

Fig. 5 Electrochemical performance of the samples under symmetri-cal supercapacitor system in 1 M H2SO4. a CV curves at scan rate of 0.1 V s−1. b GCD curves at 1 A g−1. c CV curves of PC600 at scan

rates from 0.01 to 0.2 V s−1. d GCD curves of PC600 at current den-sities from 1 to 20 A g−1. e Nyquist plots (the inset is high frequence region). f (1) Volumetric capacitance and (2) gravimetric capacitance


1 3

its original capacitance (Fig. 7a). No visible change for the GCD curves (the inset in Fig. 7a) was observed in the start-ing six cycles and the last six cycles, indicating the excellent cycling stability of PC600. Figure 7b presents the Ragone plots of PC600 in 1M H2SO4 and in BMIMBF4, and also the energy-power characteristics of some other biomass based ACs. PC600 has an energy density of 7.25 Wh kg−1 at a power density of 260.8 W kg−1 (current density at 1 A g−1).

Furthermore, its energy density remains 5.8 Wh kg−1 when power density increases to 5110.6 Wk kg−1 (20 A g−1) in 1 M H2SO4 (voltage range of 0–1 V). When tested in BMIMBF4 (voltage range of 0–2.4 V), PC600 delivers an energy density of 21.6 Wh kg−1 at power density of 675.4 Wk g−1 (1 A g−1). It is obvious that PC600 has a com-petitive performance with the ACs from some biomasses, such as corn husk [20], tree fluff [22], frutescens [18], waste

Fig. 6 Electrochemical performance of PC500, PC600 and PC700 under symmetrical supercapacitor system in EMIMBF4. a CV curves at scan rate of 0.1 V s−1. b GCD curves at 1 A g−1. c CV curves of PC600 at scan rates from 0.01 to 0.2 V s−1. d GCD curves of PC600

at current densities from 1 to 20 A g−1. e Nyquist plots (the inset is high frequence region). f (1) Volumetric capacitance and (2) gravi-metric capacitance


1 3

tea leaves [24], poplar catkins [25], jujube pit [45], and soy-bean residue [46]. However, the AC derived from tobacco rods delivers very high energy density of 31.3 Wh kg−1 (at 0.5 A g−1) [10].

4 Conclusions

In summary, we have fabricated nitrogen-doped hierar-chical porous activated carbon from low-cost pomelo peels via a carbonization followed by a KOH activation at 600 °C. The symmetric supercapacitor of PC600//PC600 electrodes exhibits excellent electrochemical performance

with a gravimetric capacitance of 208.7 F g−1, a volumet-ric capacitance of 219.3 F cm−3, and an energy density of 7.25 Wh kg−1 at a current density of 1 A g−1 in 1 M H2SO4 electrolyte. Its specific capacity retention is 96.2% after 10,000 cycles at 5 A g−1, showing a great cycling stability. Moreover, this supercapacitor delivers extraordinary energy density of 21.6 Wh kg−1 at 1 A g−1 and still 17.1 Wh kg−1 at 20 A g−1 in EMIMBF4 electrolyte.

Acknowledgements Authors appreciate financial support from the China Government 1000 Plan Talent Program, China MOE NCET Program, Natural Science Foundation of China (51322204), Special-ized Research Fund for the Doctoral Program of Higher Education (No. 20120111120009) and Fundamental Research Funds for the Central

Table 3 Comparison of PC600 with the reported biomass-derived carbons

a Calcination temperatureb Current densityc Electrolyted Volumetric capacitancee Gravimetric capacitancef Two or three electrodes testing system

Precursor Ta (°C) Cb (A g−1) Ec Vd (F cm−3) Ge (F g−1) Sf Ref.

Olive pits 700 0.5 6 M KOH 140 260 2E [43]Olive pits 700 5 mVs−1 EMI-TFSI (99%) 80 179 2E [44]Frutescens 700 0.5 6 M KOH 287 270 3E [18]Soybean residue 800 0.2 1 M H2SO4 150 258 2E [45]Jujube pit 800 0.5 6 M KOH 62.4 260 2E [46]Fungus 800 0.5 6 M KOH 360 374 3E [49]Seaweed 600 0.05 1 M H2SO4 208 264 2E [47]Lignin 900 0.1 6 M KOH 97.1 208.4 3E [48]Glucose 800 0.2 2 M KOH 335 386 3E [50]pomelo peel 800 0.2 6 M KOH 171 342 3E [26]PC600 600 1 1 M H2SO4 219.3 208.7 2E This work

600 1 BMIMBF4 109.2 108.1 2E

Fig. 7 a Cycling stability of PC600 in 1 M H2SO4 at 5 A g−1, the inset is the GCD curves of start six cycles and last six cycles. b Ragone plots of PC600 and some reported ACs


1 3

Universities (WK2060140014, WK2060140017, 2013HGXJ0199, J2014HGXJ0092).

References

1. M. Winter, R.J. Brodd, What are batteries, fuel cells, and super-capacitors? Chem. Rev. 104, 4245–4270 (2004)

2. P. Simon, Y. Gogotsi, Materials for electrochemical capacitors. Nat. Mater. 7, 845–854 (2008)

3. G. Wang, L. Zhang, J.J. Zhang, A review of electrode materials for electrochemical supercapacitors. Chem. Soc. Rev. 41, 797–828 (2012)

4. Z.N. Yu, M. McInnis, J. Calderon, S. Seal, L. Zhai, J. Thomas, Functionalized graphene aerogel composites for high-performance asymmetric supercapacitors. Nano Energy. 11, 611–620 (2015)

5. R.R. Salunkhe, Y.V. Kaneti, Y. Yamauchi, Metal-organic frame-work-derived nanoporous metal oxides toward supercapacitor applications: progress and prospects. ACS Nano 11, 5293–5308 (2017)

6. P. Simon, Y. Gogotsi, Capacitive energy storage in nanostruc-tured carbon-electrolyte systems. Acc. Chem. Res. 46, 1094–1103 (2013)

7. Y.C. Liu, B.B. Huang, X.X. Lin, Z.L. Xie, Biomass-derived hier-archical porous carbons: boosting the energy density of super-capacitors via an ionothermal approach. J. Mater. Chem. A. 5, 13009–13018 (2017)

8. J. Xu, Z.Q. Tan, W.C. Zeng, G.X. Chen, S.L. Wu, Y. Zhao, K. Ni, Z.C. Tao, M. Ikram, H.X. Ji, Y.W. Zhu, A hierarchical car-bon derived from sponge-templated activation of graphene oxide for high-performance supercapacitor electrodes. Adv. Mater. 28, 5222–5228 (2016)

9. X. Du, L. Wang, W. Zhao, Y. Wang, T. Qi, C.M. Li, Preparation of hierarchical porous carbon from waste printed circuit boards for high performance electric double-layer capacitors. J. Power Sources 323, 166–173 (2016)

10. Y.Q. Zhao, M. Lu, P.Y. Tao, Y.J. Zhang, X.T. Gong, Z. Yang, G.Q. Zhang, H.L. Li, Hierarchically porous and heteroatom doped carbon derived from tobacco rods for supercapacitors. J. Power Sources 307, 391–400 (2016)

11. Z. Wang, A. Stein, Morphology control of carbon, silica, and car-bon/silica nanocomposites: from 3D ordered macro-/mesoporous monoliths to shaped mesoporous particles. Chem. Mater. 20, 1029–1040 (2008)

12. H. Nishihara, T. Kyotani, Energy storage: templated nanocarbons for energy storage. Adv. Mater. 24, 4473–4498 (2012)

13. C.O. Ania, V. Khomenko, E.R. Pinero, J.B. Parra, F. Beguin, The large electrochemical capacitance of microporous doped carbon obtained by using a zeolite template. Adv. Funct. Mater. 17, 1828–1836 (2007)

14. Y.J. Kim, Y. Abe, T. Yanaglura, K.C. Park, M. Shimizu, T. Iwa-zaki, S. Nakagawa, M. Endo, M.S. Dresselhaus, Easy prepara-tion of nitrogen-enriched carbon materials from peptides of silk fibroins and their use to produce a high volumetric energy density in supercapacitors. Carbon. 45, 2116–2125 (2007)

15. K. Jurewicz, K. Babel, R. Pietrzak, S. Delpeux, H. Wachowska, Capacitance properties of multi-walled carbon nanotubes modi-fied by activation and ammoxidation. Carbon. 44, 2368–2375 (2006)

16. S. Dutta, A. Bhaumik, C.W. Wu, Hierarchically porous carbon derived from polymers and biomass: effect of interconnected pores on energy applications. Energy Environ. Sci. 7, 3574–3592 (2014)

17. F. Gao, J.Y. Qu, Z.B. Zhao, Z.Y. Wang, J.S. Qiu, Nitrogen-doped activated carbon derived from prawn shells for high-performance supercapacitors. Electrochim. Acta. 190, 1134–1141 (2016)

18. B. Liu, Y.J. Liu, H.B. Chen, M. Yang, H.M. Li, Oxygen and nitrogen co-doped porous carbon nanosheets derived from Perilla frutescens for high volumetric performance supercapacitors. J. Power Sources 341, 309–317 (2017)

19. Y.W. Ma, J. Zhao, L.R. Zhang, Y. Zhao, Q.L. Fan, X.A. Li, Z. Hu, W. Huang, The production of carbon microtubes by the carboni-zation of catkins and their use in the oxygen reduction reaction. Carbon 49, 5292–5297 (2011)

20. S.J. Song, F.W. Ma, G. Wu, D. Ma, W.D. Geng, J.F. Wan, Facile self-templating large scale preparation of biomass-derived 3D hierarchical porous carbon for advanced supercapacitors. J. Mater. Chem. A 3, 18154–18162 (2015)

21. R.C. Claudia, S. Christoph, P. Stefano, B. Andrea, Microporous carbonaceous materials prepared from biowaste for supercapacitor application. Electrochim. Acta 206, 452–457 (2016)

22. Y.Q. Zhang, X. Liu, S.L. Wang, S.X. Dou, L. Li, Interconnected honeycomb-like porous carbon derived from plane tree fluff for high performance supercapacitors. J. Mater. Chem. A 4, 10869–10877 (2016)

23. C. Chen, D.F. Yu, G.Y. Zhao, B.S. Du, W. Tang, L. Sun, Y. Sun, F. Besenbacher, M. Yu, Three-dimensional scaffolding framework of porous carbon nanosheets derived from plant wastes for high-performance supercapacitors. Nano Energy 27, 377–389 (2016)

24. G.F. Ma, J.D. Li, K.J. Sun, H. Peng, E.K. Feng, Z.Q. Lei, Tea-leaves based nitrogen-doped porous carbons for high-performance supercapacitors electrode. J. Solid State Electrochem. 21, 525–535 (2017)

25. S.Y. Gao, X.G. Li, L.Y. Li, X.J. Wei, A versatile biomass derived carbon material for oxygen reduction reaction, supercapacitors and oil/water separation. Nano Energy. 33, 334–342 (2017)

26. Q.H. Liang, L. Ye, Z.H. Huang, Q. Xu, Y. Bai, F.Y. Kang, Q.H. Yang, A honeycomb-like porous carbon derived from pomelo peel for use in high-performance supercapacitors. Nanoscale 6, 13831–13837 (2014)

27. C. Peng, J.W. Lang, S. Xu, X.L. Wang, Oxygen-enriched activated carbons from pomelo peel in high energy density supercapacitors. RSC Adv. 4, 54662–54667 (2014)

28. Y.Y. Wang, B.H. Hou, H.Y. Lu, C.L. Lu, X.L. Wu, Hierarchi-cally porous N-doped carbon nanosheets derived from grapefruit peels for high-performance supercapacitors. ChemistrySelect 1, 1441–1446 (2016)

29. J. Li, W.L. Liu, D. Xiao, X.H. Wang, Oxygen-rich hierarchical porous carbon made from pomelo peel fiber as electrode material for supercapacitor. Appl. Surf. Sci. 416, 918–924 (2017)

30. Y.W. Zhu, S. Murali, M.D. Stoller, K.J. Ganesh, W. Cai, P.J. Fer-reira, A. Pirkle, R.M. Wallace, K.A. Cychosz, M. Thommes, D. Su, E.A. Stach, Carbon-based supercapacitors produced by activa-tion of grapheme. Science. 332, 1537–1541 (2011)

31. Z.S. Li, J.H. Che, B.L. Li, W. Luo, Z.S. Liu, D.H. Li, Preparation of carbon nanospheres/Fe3O4 composites and their supercapacitor performances. J. Mater. Sci.: Mater. Electron. 28, 17388–17396 (2017)

32. P.S. Yang, L. Ma, M.Y. Gan, Y. Lei, X.L. Zhang, M. Jin, G. Fu, Preparation and application of PANI/N-doped porous carbon under the protection of ZnO for supercapacitor electrode. J. Mater. Sci.: Mater. Electron. 28, 7333–7342 (2017)

33. Z. Fan, D. Qi, Y. Xiao, J. Yan, T. Wei, One-step synthesis of biomass-derived porous carbon foam for high performance super-capacitors. Mater. Lett. 101, 29–32 (2013)

34. J. Han, J.H. Kwon, J.W. Lee, J.H. Lee, K.C. Roh, An effective approach to preparing partially graphitic activated carbon derived from structurally separated pitch pine biomass. Carbon 118, 431–437 (2017)


1 3

35. I.A. Tan, A.L. Ahmad, B.H. Hameed, Adsorption isotherms, kinetics, thermodynamics and desorption studies of 2,4,6-trichlo-rophenol on oil palm empty fruit bunch-based activated carbon. J. Hazard. Mater. 164, 473–482 (2009)

36. X.L. Su, M.Y. Cheng, L. Fu, J.H. Yang, X.C. Zheng, X.X. Guan, Superior supercapacitive performance of hollow activated carbon nanomesh with hierarchical structure derived from poplar catkins. J. Power Sources. 362, 27–38 (2017)

37. W. Wang, W.Y. Liu, Y.X. Zeng, Y. Han, M.H. Yu, X.H. Lu, Y.X. Tong, A novel exfoliation strategy to signifi cantly boost the energy storage capability of commercial carbon cloth. Adv. Mater. 27, 3572–3578 (2015)

38. Y.Z. Ma, Y. Guo, C. Zhou, C.Y. Wang, Biomass-derived dendritic-like porous carbon aerogels for supercapacitors. Electrochim. Acta 210, 897–904 (2016)

39. Y.F. Song, J. Yang, K. Wang, S. Haller, Y.G. Wang, C.X. Wang, Y.Y. Xia, In-situ synthesis of graphene/nitrogen-doped ordered mesoporous carbon nanosheet for supercapacitor application. Carbon 96, 955–964 (2016)

40. A. Jain, C.H. Xu, S. Jayaraman, R. Balasubramanian, J.Y. Lee, M.P. Srinivasan, Mesoporous activated carbons with enhanced porosity by optimal hydrothermal pre-treatment of biomass for supercapacitor applications. Microporous Mesoporous Mater. 218, 55–61 (2015)

41. L. Zhao, L.Z. Fan, M.Q. Zhou, H. Guan, S.Y. Qiao, M. Antoni-etti, M.M. Titirici, Nitrogen-containing hydrothermal carbons with superior performance in supercapacitors. Adv. Mater. 22, 5202–5206 (2010)

42. A.B. Fuertes, M. Sevilla, High-surface area carbons from renew-able sources with a bimodal micro-mesoporosity for high-per-formanceionic liquid-based supercapacitors. Carbon. 94, 41–52 (2015)

43. E. Redondo, J.C. González, E. Goikolea, J. Ségalini, R. Mysyk, Effect of pore texture on performance of activated carbon super-capacitor electrodes derived from olive pits. Electrochim. Acta 160, 178–184 (2015)

44. E. Redondo, W.Y. Tsai, B. Daffos, P.L. Taberna, P. Simon, E. Goikolea, R. Mysyk, Outstanding room-temperature capacitance of biomass-derived microporous carbons in ionic liquid electro-lyte. Electrochem. Commun. 79, 5–8 (2017)

45. G.A. Ferrero, A.B. Fuertes, M. Sevilla, From soybean residue to advanced supercapacitors. Sci. Rep. 5, 16618 (2015)

46. K.L. Sun, S.S. Yu, Z.L. Hu, Z.H. Li, G.T. Lei, Q.Z. Xiao, Y.H. Ding, Oxygen-containing hierarchically porous carbon materials derived from wild jujube pit for high-performance supercapacitor. Electrochim. Acta. 231, 417–428 (2017)

47. E. Raymundo-Pinero, M. Cadek, F. Beguin, Tuning carbon mate-rials for supercapacitors by direct pyrolysis of seaweeds. Adv. Funct. Mater. 19, 1032–1039 (2009)

48. H. Li, D. Yuan, C.H. Tang, S.X. Wang, J.T. Sun, Z.B. Li, T. Tang, F.K. Wang, H. Gong, C.B. He, Lignin-derived interconnected hierarchical porous carbon monolith with large areal/volumetric capacitances for supercapacitor. Carbon. 100, 151–157 (2016)

49. C.L. Long, X. Chen, L.L. Jiang, L.J. Zhi, Z.J. Fan, Porous layer-stacking carbon derived from in-built template in biomass for high volumetric performance supercapacitors. Nano Energy 12, 141–151 (2015)

50. D.Y. Guo, X.A. Chen, Z.P. Fang, Y.F. He, C. Zheng, Z. Yang, K.Q. Yang, Y. Chen, S.M. Huang, Hydrangea-like multi-scale carbon hollow submicron spheres with hierarchical pores for high performance supercapacitor electrodes. Electrochim. Acta 176, 207–214 (2015)

hierarchical porous carbon with high nitrogen content derived...

Documents