ACS Publications. Most Trusted. Most Cited. Most Read
My Activity
CONTENT TYPES

Figure 1Loading Img

Electrochemical Properties of Biobased Carbon Aerogels Decorated with Graphene Dots Synthesized from Biochar

  • Bony Thomas
    Bony Thomas
    Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    More by Bony Thomas
  • Gejo George
    Gejo George
    Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    More by Gejo George
  • Anton Landström
    Anton Landström
    Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
  • Isabella Concina
    Isabella Concina
    Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
  • Shiyu Geng
    Shiyu Geng
    Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    More by Shiyu Geng
  • Alberto Vomiero
    Alberto Vomiero
    Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172 Venezia Mestre, Italy
  • Mohini Sain
    Mohini Sain
    Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    Department of Mechanical & Industrial Engineering (MIE), University of Toronto, Toronto, Ontario M5S 3G8, Canada
    More by Mohini Sain
  • , and 
  • Kristiina Oksman*
    Kristiina Oksman
    Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    Department of Mechanical & Industrial Engineering (MIE), University of Toronto, Toronto, Ontario M5S 3G8, Canada
    *Email: [email protected]. Tel: +46 70 358 5371.
Cite this: ACS Appl. Electron. Mater. 2021, 3, 11, 4699–4710
Publication Date (Web):October 20, 2021
https://doi.org/10.1021/acsaelm.1c00487

Copyright © 2021 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY 4.0.
  • Open Access

Article Views

3017

Altmetric

-

Citations

LEARN ABOUT THESE METRICS
PDF (10 MB)
Supporting Info (1)»

Abstract

Carbon aerogels prepared from low-cost renewable resources are promising electrode materials for future energy storage applications. However, their electrochemical properties must be significantly improved to match the commercially used high-carbon petroleum products. This paper presents a facile method for the green synthesis of carbon aerogels (CAs) from lignocellulosic materials and graphene dots (GDs) from commercially available biochar. The produced carbon aerogels exhibited a hierarchical porous structure, which facilitates energy storage by forming an electrical double-layer capacitance. Surprisingly, the electrochemical analyses of the GD-doped carbon aerogels revealed that in comparison to pristine carbon aerogels, the surface doping of GDs enhanced the electrochemical performance of carbon aerogels, which can be attributed to the combined effect from both double-layer capacitance and pseudocapacitance. Herein, we designed and demonstrated the efficacy of a supercapacitor device using our green carbon electrode as a sustainable option. These green carbon aerogels have opened a window for their practical use in designing sustainable energy storage devices.

This publication is licensed under

CC-BY 4.0.
  • cc licence
  • by licence

Introduction

ARTICLE SECTIONS
Jump To

The deteriorating global environment and critical energy issues have led to the search for new energy materials/devices with excellent storage and power/energy density, which has been a hot topic in the past few years. (1−3) Supercapacitors are energy storage devices that consist of electrochemical double-layer capacitors (EDLCs) and pseudocapacitors. (4) Fast and reversible redox reactions according to the charge storage mechanism are the basis of pseudocapacitors. (4) Pseudocapacitors are associated with high theoretical capacitance values. However, their disadvantages include a short cycle life, low energy density (as a result of low conductivity), a relatively low reaction rate for the redox mechanism, and more importantly, the redox reactions lead to the structural collapse of the material. (5) In electrode materials featuring very high surface areas, the performance of EDLCs depends mainly on the double layer to support the physical adsorption/desorption of ions. On the other hand, advantages such as a long cycle lifetime, superior power density, fast charge/discharge rate, and excellent retention rate due to electrostatic interactions are associated with ideal EDLCs. Therefore, research on EDLCs has been gaining momentum over the past few years. (6) The key to improving the performance of EDLCs is to develop an active material (electrode) possessing a good specific capacity. In the past decade, carbonaceous substances have emerged as potential electrode materials for EDLCs owing to their good conductivity and low-cost production routes. (7−9)
Several studies have reported the use of high-capacitance electrodes composed of different carbon materials such as activated carbon, carbon nanodots, and graphene-based carbon materials. (7,10,11) As an alternative to the conventional resources for the aforementioned carbon materials, lignin is increasingly used for the preparation of carbon-based supercapacitor electrodes due to its high thermal stability, easy availability, low cost, and high carbon yield. (12) Lignin is a byproduct from paper and pulp industries throughout the world. Millions of tons of lignin are produced annually for use in low-value applications. (13) As a potential resource for high-value carbon materials, lignin-based carbon aerogels (CAs) have proven to achieve a hierarchical pore structure, high porosity, low density, and interconnected structure with the use of the proper processing routes, which are essential for a good supercapacitor electrode material. (14,15) Different types of lignins such as Kraft lignin (KL) (14,15) and soda lignin (15) have been used for the preparation of freestanding, binder-free carbon aerogel electrodes. The preparation involved the carbonization of freeze-dried lignin/cellulose nanofibers (CNF) aerogels, which were ice-templated to generate an anisotropic microstructure. Kraft lignin-based carbon aerogels achieved a high capacitance of 163.4 F g–1 at 0.1 A g–1 current density, and an energy density of 5.67 Wh kg–1 was achieved at a power density of 50 W kg–1. (15) However, their electrochemical performances could be improved using different approaches such as activation techniques to increase the surface area or the doping of aerogels using carbon nanomaterials, which would increase both the electrical double-layer capacitance and the pseudocapacitance (PC).
Among the different types of carbon nanomaterials, graphene-based materials are the most promising for supercapacitor applications due to their extraordinarily high surface area and superior electrical conductivity. (2,17) It has been reported that if the entire surface area of single-layer graphene were successfully utilized, it would result in an EDLC capacitance of 550 F g–1 with an energy density of 19 Wh kg–1. (16,17) However, the charge transfer in graphene-based materials can only take place when the graphene system forms a dense cross-linked network, which reduces the surface area. As a result, in most practical cases, graphene-based electrodes have a low surface area that is accessible to electrolyte ions. Hence, one of the main challenges in graphene-based supercapacitors is to increase the energy storage density because, in reality, they have a much lower EDLC capacitance than the expected theoretical value. (17,18) The latest graphene-based nanomaterials to be developed are graphene quantum dots (GQDs). GQDs are characterized by an atomically thin graphitic plane with sp2-hybridized carbon and dimensions of less than 100 nm. GQDs show remarkable properties such as good dispersibility in common solvents, abundant active sites (due to a large number of functional groups and defects), bandgap opening owing to quantum confinement, comparable size to biomolecules, and excellent optical properties. (19) These advantageous properties of GQDs facilitate their use in numerous applications. (20−22) In addition, the nanoscale size of the graphene in GQDs aids in creating numerous surface defects and edge states on a pure graphene plane. (23) As a result, GQDs have confined energy bandgaps along with delocalized charge carriers, leading to additional properties such as a high surface area and the ability to transport both ions and electrons/holes. (24) Compared to other graphene-based nanomaterials, GQDs with the abovementioned morphology enables ion transport, leading to easier access and the diffusion of ions. (1,26) Size-dependent quantum confinement and edge electronic states determine the π–π conjugated electronic state of the GQDs. Thus, explicit properties of GQDs can be tailored by tuning the size and, consequently, the energy states. The aforementioned attractive properties of GQDs make them ideal candidates as EDLC electrode materials possessing acceptable capacitance and storage capability. (1,25) The top-down and bottom-up approaches are the two synthetic methodologies used to produce GQDs. The decomposition, oxidation, or exfoliation of economical and readily available carbon materials (e.g., graphite, carbon nanotubes, graphene oxides, fullerenes) is the basis of the top-down approach, which generally involves the use of strong acids such as KClO3, HNO3, and H2SO4 for the hydrolyzation. (26,27) The bottom-up approach, on the other hand, involves the synthesis of GQDs from small aromatic structures. This approach has the advantage of controllable properties of the final product, but the disadvantages are a low yield and complex preparation routes. Compared to the bottom-up methods, the top-down approach can control the size distribution of GQDs under facile reaction conditions. (26,28) Interestingly, biomass waste such as rice husks, waste peels, food waste, and biomass derivatives have recently emerged as attractive precursors for GQD production due to their renewable, economical, and sustainable characteristics. (29)
Although many studies have been conducted on the preparation of biomass-based GQDs, few studies have analyzed their electrochemical properties. To the best of our knowledge, the present work introduces the novel use of biomass-derived graphene dots (GDs) as a functional additive for improving the electrochemical performance of green carbon aerogels derived from lignocellulosic materials. Thus, this study can be considered as a significant step toward future energy storage by introducing a completely biomass-based, self-standing, binder-free, and high-performance carbon electrode for supercapacitor applications.

Experimental Section

ARTICLE SECTIONS
Jump To

Materials

The biochar (brand name Biohiili) used in the present work was supplied by RPK Hiili Oy (Mikkeli, Finland). This type of carbon has a carbon content of ∼97% and is most commonly used as a soil conditioner. The biochar was prepared by the pyrolysis of Finnish hardwood at a temperature of 350 °C. Sulfuric acid (95–98%, ACS Reagent, CAS No: 7664-93-9) and nitric acid (70%, ACS Reagent, CAS No: 7697-37-2) were purchased from Merck KGaA (Darmstadt, Germany). Distilled water was used for all experimental procedures. Kraft lignin (CAS No: 8068-05-1) with a low sulfonate content (Mw of ∼10 000) was purchased from Sigma-Aldrich (St. Louis, MO), whereas cellulose nanofibers (mechanically fibrillated) from birch hardwood with an approximate diameter of 15 nm were prepared based on the work reported by Berglund et al. (30)

Preparation of Carbon Aerogels

The first step in the preparation of carbon aerogels (CAs) is the preparation of a lignin/CNF suspension for producing lignin/CNF precursor aerogels. Kraft lignin (KL) and an aqueous suspension of mechanically fibrillated cellulose nanofibers (1 wt %) were mechanically mixed at a ratio of 60:40, respectively, to obtain a lignin/CNF suspension having a final solid content of 2.4 wt %. The obtained lignin/CNF suspension was kept in a refrigerator at 4 °C for 12 h before proceeding to the ice-templating process. Ice-templating was performed by carefully adding the lignin/CNF suspension to a cylindrical Teflon mold mounted on the top end of a copper rod. The bottom part of the copper rod was immersed in a liquid nitrogen bath. The top end of the copper rod was connected to a heating element that maintained a cooling rate of 10 °C min–1 during the ice-templating process. The temperature difference between the ends of the copper rod helped to achieve unidirectional freezing of the suspension from the bottom to the top. After the ice-templating process, the frozen samples were transferred to a freezer (−20 °C) for 2 h. The final step in the preparation of the lignin/CNF aerogels was freeze-drying, which was performed in an Alpha 1-2 LDplus freeze dryer (Martin Christ GmbH, Osterode, Germany), where the fully frozen samples were subjected to a pressure of 1.00 mbar for 72 h and the shelf temperature was maintained at 30 °C. The obtained lignin/CNF aerogel was carbonized in a Nabertherm RHTC-230/15 horizontal tube furnace (Nabertherm GmbH, Lilienthal, Germany) under a nitrogen (N2) atmosphere to prepare the Kraft lignin-based carbon aerogel, denoted as KLCA60, where KL stands for Kraft lignin, CA stands for carbon aerogel, and 60 indicates the percentage of lignin present in the lignin/CNF precursor aerogels. For the carbonization process, the lignin/CNF aerogel was heated from room temperature to 100 °C at a rate of 5 °C min–1 and was maintained at 100 °C for 1 h. After removing the moisture, the temperature was increased from 100 to 400 °C at a rate of 5 °C min–1 and was then isothermally maintained at 400 °C for 1 h. Further heating was carried out from 400 to 1000 °C at a rate of 5 °C min–1, followed by isothermal holding at 1000 °C for 1 h to complete the carbonization process. The preparation steps for KLCA60 are schematically shown in Figure 1a.

Figure 1

Figure 1. Schematic representation of the preparation steps for GD-doped carbon aerogel. (a) Preparation of carbon aerogel from lignin/CNF suspension. (b) Synthesis of GDs from biochar using oxidative acid treatment involving 3:1 concentration of H2SO4/HNO3; the reaction mixture was refluxed for 6 h at 90 °C. (c) Surface doping of prepared carbon aerogels using GDs synthesized from biochar.

Preparation of Graphene Dots (GDs) from Wood Biochar

For the synthesis of GDs, in a representative reaction, 2 g of the biochar was taken in a 100 mL round-bottomed flask and then mixed with an acid mixture of H2SO4 and HNO3 (3:1 ratio) based on a previously reported work. (31) This mixture was then heated to 90 °C and kept under reflux for 6 h. A schematic representation of the reaction process is presented in Figure 1b.
Upon completion of the reaction process, the reaction mixture was diluted with 100 mL of distilled water. This diluted dispersion was initially filtered under vacuum using a 1.6 μm pore size Whatman glass microfiber filter (Whatman International Ltd., Maidstone, U.K.) to remove the large unreacted biochar particles. The obtained clear dispersion was filtered through a 0.2 μm pore size poly(tetrafluoroethylene) (PTFE) syringe filter (Sartorius Stedim Biotech GmbH, Göttingen, Germany) to remove the unreacted carbon and other particles that were larger than 200 nm. GDs were present in the brown filtrate obtained after the double filtration. However, owing to the strong oxidative acid treatment, the filtrate was acidic in nature and required purification to neutralize the dispersion. A dialysis membrane was used for the purification process, which took up to 48–72 h. The obtained neutralized solution was kept in an air oven at 100 °C for 24 h to obtain the dried GDs. The yield was found to be 10–12% in comparison with the initial quantity of biochar, which was in accordance with previous results, where GDs were synthesized from biochar/biomass. (31)

Preparation of Graphene Dots Surface-Doped Carbon Aerogels

To incorporate the GDs into the prepared KLCA60 (Kraft lignin-based carbon aerogel produced by carbonizing the lignin/CNF aerogel with 60% lignin), an aqueous dispersion of the GDs was prepared, and the aerogel was dipped into it. After several tests, it was optimized that KLCA60 (weight ∼ 0.12 g) can absorb 4.3 mL of the aqueous GD dispersion. After absorption of GD dispersion, the dipped sample was kept in an air oven at 80 °C for 24 h to remove the moisture. The dried sample was then heated in a tube furnace at 180 °C for 1 h under a nitrogen atmosphere to induce the attachment of the GDs on the surfaces of KLCA60. The temperature was limited to 180 °C because at higher temperatures, the GDs tend to lose carboxyl groups through decomposition.

UV–Visible and Photoluminescence (PL) Spectroscopy

A Cary 5000 UV–vis spectrophotometer (Agilent Technologies, Santa Clara, CA) and an FLS980 PL spectrofluorometer (Edinburgh Instruments, Edinburgh, U.K.) were used for UV–visible and photoluminescence (PL) spectroscopy. The samples were analyzed by dispersing the GDs (0.01 wt %) in distilled water and then recording the spectra. In the PL spectroscopy, the effect of the excitation wavelength on the spectra was analyzed by recording the emission spectra at different excitation wavelengths from 350 to 510 nm. The absolute fluorescence quantum yield was measured using an integrating sphere, with water as the reference. The presence of GDs in the carbon aerogels after decoration was confirmed by solid-state PL spectroscopy using the same instrument.

Raman Spectroscopy

The Raman spectra of the biochar and GDs were recorded by placing the material in a holder on a Bruker SENTERRA Raman microscope (Bruker Corporation, Billerica, MA). The spectra were recorded over a Raman shift of 50–4500 cm–1 using a 532 nm laser with a laser power of 2 mW and a magnification of 20×.

X-ray Diffractometry (XRD)

The XRD patterns of the GD powder and the carbon aerogels were analyzed by recording the X-ray diffraction using Cu Kα radiation and a machine equipped with a PIXcel3D detector and a graphite monochromator. A Panalytical Empyrean X-ray diffractometer (Malvern, U.K.) was used for the analysis by 2θ scanning from 10 to 50°. The instrument was operated at a voltage of 45 kV and a current of 40 mA.

Thermogravimetric Analysis (TA)

A TGA Q500 analyzer (TA Instruments, New Castle, DE) was used to analyze the thermal properties of both the precursor biochar and the GDs. A nitrogen atmosphere was used during the analysis in a temperature range of 25–900 °C at a heating rate of 10 °C min–1. The thermal properties of the Kraft lignin and cellulose nanofibers were analyzed from room temperature to 1000 °C at a heating rate of 10 °C min–1 under a nitrogen atmosphere.

Fourier Transform Infrared Spectroscopy

The sample was mixed with dry KBr (after drying at 80 °C in a vacuum oven for 3 h) and then formed into pellets. A Vertex 80v spectrometer (Bruker, Ettlingen, Germany) was used to record the spectra in the medium IR spectral range.

Atomic Force Microscopy (AFM)

Samples were prepared by drop-casting a drop of 0.01 wt % aqueous GD dispersion onto a mica plate (freshly cleaved) and drying it at 80 °C under vacuum in an oven for a few minutes to avoid agglomeration of the particles. The tapping mode on a Nanoscope Multimode system (Veeco Metrology, Santa Barbara, CA) was utilized for the AFM analysis of the topography of the GDs. The cantilever used was antimony-doped silicon (NCHV-A, Bruker) with a tip radius of 8 nm and a spring constant of 42 N m–1. Gwyddion software (open source) was used to analyze the obtained AFM images. The final images presented are after the subtraction of the mean plane and the removal of the polynomial background.

Transmission Electron Microscopy (TEM)

A 0.015 wt % aqueous GD dispersion was used to prepare the sample for TEM analysis (JEM-2200FS, Jeol, Tokyo, Japan). A single drop of dispersion was drop-cast onto a carbon grid and then dried. Prior to drop-casting, the dispersion was bath sonicated for 5 min.

Brunauer–Emmett–Teller (BET) Surface Area Analysis

The surface areas of the GD-incorporated carbon aerogels were measured using a BET instrument (Gemini VII, Micromeritics Instrument Corp., Norcross, GA). The samples were first degassed under nitrogen at 180 °C for 3 h, after which the surface area was measured at relative pressures (P/P0) between 0 and 1 using an equilibration time of 10 s and an evacuation rate of 50 mm Hg min–1.

Field Emission Scanning Electron Microscopy (FE-SEM)

The structure and morphology of the carbon aerogels and the effect of the GD incorporation were studied using a high-resolution FE-SEM (Magellan 400 XHR SEM, FEI Company, Hillsboro, OR). Samples were prepared by carefully peeling the outer surface with tape so that the microstructure of the carbon aerogels would be retained for a detailed analysis. Images from both the cross section and longitudinal section were recorded. Elemental analysis using the SEM–energy-dispersive X-ray spectroscopy (EDX) data of the carbon aerogels was conducted using a scanning electron microscope (JSM-IT300, Jeol, Tokyo, Japan) equipped with a silicon drift detector (Oxford X-MaxN, 50 mm2, Oxford Instruments, Abingdon, U.K.).

Electrochemical Measurements

Electrochemical analysis was performed using a Princeton VersaStat 3 electrochemical workstation (Ametek Scientific Instruments, Wokingham, U.K.). A typical two-electrode system in a symmetric configuration with 6 M KOH as the electrolyte was employed for the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The current collectors were composed of the Inconel 600 superalloy, and the separator was Whatman filter paper (Grade 1, GE Healthcare, Machelen, Belgium). In a typical experiment, the mass of one CA electrode was ∼2.5 mg, with an area and thickness of ∼20 mm2 and 2 mm, respectively. The electrodes were freestanding, and no binders were used during the electrode preparation. A frequency range of 0.01 Hz to 100 kHz coupled with a sinusoidal signal of 10 mV was employed for the EIS measurements. The galvanostatic charge–discharge (GCD) curves were then utilized to determine the specific gravimetric capacitance (C) of the samples according to the following equation
(1)
where I is the discharging current, ΔV is the scanned potential window during the study, Δt is the time taken for the full discharge, and m is the mass of the electrode material used for the study. The power (Pd) and energy (Ed) densities were calculated using the following equations
(2)
(3)
Cyclic stability was analyzed using a three-electrode measurement system (Pine Research Instrumentation, Durham, NC) equipped with Princeton Applied Research VersaSTAT 3 potentiostat/galvanostat. The counter and reference electrodes used were platinum and Ag/AgCl electrodes, respectively. Briefly, 1 M H2SO4 was used as the electrolyte.

Results and Discussion

ARTICLE SECTIONS
Jump To

In the present work, carbon aerogels prepared from lignocellulosic precursors by ice-templating and freeze-drying followed by carbonization were incorporated with GDs, which can be used as supercapacitor electrodes. UV–vis and PL spectroscopies were employed to study the optical properties of the as-prepared GDs. The UV–vis absorption spectra of the GDs are shown in Figure 2a. The spectrum clearly reveals that the GDs have a strong absorption in the UV region. The characteristic absorption spectrum showing a shoulder at ∼260 nm is due to the graphitic structure of the material. (26,32) The presence of aromatic sp2 domains in the system leads to π–π* transition, which may also cause strong absorption below 300 nm. (31)Figure S1a is a photograph of an aqueous solution of GDs when exposed to daylight and a 365 nm UV lamp. In daylight, a dilute aqueous solution of GDs is light brown, clear, and transparent but exhibits blue fluorescence under excitation by a 365 nm UV light.

Figure 2

Figure 2. (a) UV–visible spectrum. (b) Photoluminescence (PL) spectra at different excitation wavelengths, showing the optical properties of the produced GDs in an aqueous medium (0.01 wt %). (c) Atomic force microscopic image of GDs. (d) TEM image showing graphene particles with an ordered carbon structure and a size range of 5–15 nm.

To further understand the optical properties of the prepared GDs, a detailed PL spectroscopic analysis of the sample was performed using different excitation wavelengths. Figure 2b shows the PL emission spectra of the GDs with excitation wavelengths ranging from 350 to 510 nm. PL spectra showing the dependence upon the excitation wavelengths are characteristic of most luminescent GDs. (32,33) The large number of different emissive sites/functional groups on GDs and the optical selection of differently sized GDs are the major contributors to excitation-dependent features, as in the present case. (32,34) The PL quantum yield was found to be 1% for the produced GDs, with water as the reference material. The presence of acidic and salt impurities resulting from the neutralization process, as well as the lower carbon quality of the starting material compared to other starting materials such as graphene oxide and graphite, (31) could be the reason for the relatively lower quantum yield.
Morphological and structural characterizations of the prepared GDs were performed using TEM and AFM analyses. An AFM image of the GD particles is shown in Figure 2c. The topographic heights of the quantum dots were found to be between 1 and 3 nm (Figure S1b), which indicates the presence of 2–6 graphene sheets/layers in the particles. (35) Almost 85% of the GDs have a height profile between 1 and 3 nm, further evidencing a uniform size distribution (Figure S1b,c). TEM images of the GDs are depicted in Figure 2d, which clearly reveal that the produced GDs range in size (diameter) from 5 to 15 nm. However, extensive surface interaction of the GDs due to the presence of a large number of −COOH and −OH groups on the particle surface led to interparticle hydrogen bonding and π–π stacking. (31) This is the reason for the widespread superlattice formation, as apparent from the TEM images. The TEM images of the GDs also reveal the presence of a clearly noticeable lattice structure with a lattice spacing of 0.24 nm, which can be attributed to the (1120) plane of graphene. (36)
The presence of a high concentration of −OH groups in the prepared GDs was confirmed by the occurrence of a peak at approximately 3277 cm–1 in the FTIR spectra (Figure 3a). In addition to the −OH peak, the Fourier transform infrared (FTIR) spectra also confirmed the presence of −C═O groups attributed to the peak at ∼1738 cm–1 and the C–O–C stretching vibration at 1280 cm–1. (37) The FTIR spectra also revealed the characteristic bands of an aromatic compound (peak at 1642 cm–1 is due to the skeletal vibration of aromatic rings). The good dispersibility in an aqueous medium for the produced GDs can be attributed to the presence of the aforementioned functional groups on the surface.

Figure 3

Figure 3. (a) FTIR spectrum of GDs exhibiting numerous surface functional groups. (b) Thermogravimetric analysis of GDs compared to the biochar precursor showing a higher weight loss of GDs owing to the decomposition of carboxylic acid groups. (c) Thermogravimetric analysis of KL and CNF. (d) Raman spectra of biochar precursor, GDs prepared from biochar, and carbon aerogel KLCA60. (e) X-ray diffractometry of the GDs and KLCA60.

Figure 3b,c shows the thermograms of the biochar, prepared GDs, Kraft lignin (KL), and cellulose nanofibers (CNF). The biochar precursor lost only ∼20% of its weight after the completion of the temperature cycle. There were slight mass losses before 100 °C and at ∼600 °C, which can be attributed to the evolution of moisture and the decomposition of residual lignin fractions, respectively. (38) Nevertheless, the higher thermal stability of the biochar is due to the aromatic functionalities. (39,40) The GDs exhibited a weight loss of ∼50% at 600 °C, which was due to the removal of the carboxylic acid groups present at the edges of the quantum dot structure. (41) Vázquez-Nakagawa et al. (41) reported that the skeletal structure of GDs tends to decompose at temperatures between 700 and 900 °C. KL and CNF showed char residues of 45 and 24%, respectively, after thermal treatment at 1000 °C. This indicates the sacrificial templating of CNF during the carbonization process that contributed to the formation of hierarchical porous carbon aerogels (CAs). (15)Figure 3d shows the Raman spectra of the biochar, GDs, and KLCA60 over the spectral range of 900–3500 cm–1. The Raman spectra show distinctive graphitic features, such as the D band (∼1310–1335 cm–1), which is the result of defects in the carbon structure, along with the G band (∼1600 cm–1), which is due to the C–C deformations (in-plane). (42) The presence of a well-defined intense G band demonstrates that the GDs are highly crystalline, with an integrated graphitic nature. The prevalence of functional groups and vacancies leads to the presence of defect D bands in the spectra. The ID/IG ratio for the GDs in the present work was 0.89, denoting the high graphitic content of the material. Figure 3e shows the X-ray diffractogram of GDs showing a peak at 2θ = 23.4°, which is different from the characteristic diffraction peak of graphene at 2θ = 26.3° that corresponds to the (002) plane of carbon materials. This shift in the peak position can be attributed to the change in size, the numerous edge effects, and the presence of functional groups, leading to the partial destruction of the carbon atom network. KLCA60 showed broad peaks located at 2θ = 21 and 2θ = 44°, as shown in Figure 3e, which represent the (002) and (101) planes of the partially graphitized carbon structures.

Effect of GDs When Incorporated into Carbon Aerogel Based Supercapacitor Electrodes

The morphology of the GD-incorporated carbon aerogels was studied using FE-SEM, and the images are shown in Figure 4. KLCA60 displayed anisotropic macroporous structures arising as a result of the ice-templating process that assisted in the fast mass or electrolyte ion transfer in the longitudinal direction and hence is advantageous for several applications, including supercapacitor electrodes, thermal insulation, and carbon dioxide adsorption. (14) In this study, carbon aerogels without GDs were produced as references (Figure 4a–d) for comparison with the GD-incorporated samples. The FE-SEM images of the carbon aerogel samples also revealed the presence of small particles on the surface of the material, which was characterized using localized EDX spectra (Figure S2). The EDX spectrum of these samples indicated that at several places, the sodium concentration was much higher on the surface, suggesting that the particles may be sodium salts (sodium sulfate or carbonate). These salts formed as a result of the migration of sodium ions from the core of the cell walls to the surface during the carbonization process. (14) However, the introduction of GDs into the carbon aerogel system led to some interesting observations. The FE-SEM images of the GD-incorporated carbon aerogels revealed the absence or relatively low quantity of the aforementioned sodium salts. EDX analysis also revealed a reduced sodium content in the GD-incorporated aerogels (Figure S2). This can be attributed to two reasons: (a) the high surface area of the GDs due to their nanodimensions allowed them to envelope the salt particles by forming a layer, and (b) the carboxyl groups present on the GDs, as evidenced by FTIR, reacted with the salt particles and hence they were not visible under FE-SEM. The removal of these sodium salts exposed the previously closed meso- and micropores, which improved the properties of the carbon aerogels, as demonstrated by the results from surface area analysis shown in Figure 5b and Table 1.

Figure 4

Figure 4. Microstructure of the prepared materials. (a) and (e) Longitudinal views of KLCA60 and GD-doped KLCA60; magnified images of the longitudinal sections showing the surface texture of both are shown in (b) and (f). Cross-sectional views of KLCA60 and GD-doped KLCA60 are shown in (c) and (g), and the respective high magnification images are shown in (d) and (h).

Figure 5

Figure 5. (a) Solid-state photoluminescence (PL) spectrum of KLCA60 doped with GDs at 315 nm excitation wavelength. (b) Nitrogen adsorption isotherms of KLCA60 and GD-incorporated KLCA60.

Table 1. BET Specific Surface Area, Contribution of Specific Surface Area by Micropores, Pore Volumes, and Average Pore Diameters Obtained from Brunauer–Emmett–Teller (BET) Surface Area Analysis of KLCA60 and KLCA60 with GDs
sampleBET surface area (m2 g–1)micropore area (m2 g–1)pore volume (cm3 g–1)avg. pore diam. (nm)
KLCA604362230.2542.33
KLCA60 with GDs5034360.2221.77
The presence of GDs on the surface of KLCA60 was confirmed using solid-state PL spectroscopy at an excitation wavelength of 315 nm, as shown in Figure 5a. The emission peak observed at 550 nm in the PL spectrum indicates the effective doping of KLCA60 with GDs. Raman spectroscopy and XRD were ineffective for confirming the doping of GDs because both KLCA60 and GDs showed characteristic peaks that were overlapping and indistinguishable. The exposure of meso- and micropores of the GD-incorporated carbon aerogels was further corroborated by the Brunauer–Emmett–Teller (BET) surface area analysis of the samples, and the results are summarized in Table 1.
Figure 5b shows the N2 adsorption isotherms of both the carbon aerogels and the GD-incorporated carbon aerogels. The GD-incorporated carbon aerogels exhibited a higher surface area of 503 m2 g–1 compared to those without GDs (436 m2 g–1), which is in accordance with the FE-SEM results. It was observed that with the incorporation of GDs into KLCA60, the micropore area was remarkably enhanced, which confirms the opening of previously closed micropores, as discussed earlier. In addition, the aggregation of GDs can result in the conversion of existing mesopores in KLCA60 to numerous micropores. This is further evidenced by the reduction in the pore volume (0.222 cm3 g–1 compared to 0.254 cm3 g–1 for KLCA60) and average pore diameter (1.77 nm compared to 2.33 nm in KLCA60) for the GD-doped KLCA60.
The effect of the incorporation of GDs on the electrochemical properties of the carbon aerogels as the electrodes in supercapacitors was evaluated. A two-electrode setup was utilized for the electrochemical analysis with 6 M KOH as the electrolyte, and the supercapacitor assembly is schematically represented in Figure S3a. Prior to testing, all of the electrodes were dipped in a 6 M KOH solution for 3 h. The cyclic voltammetry (CV) curves for both the carbon aerogels and GD-incorporated carbon aerogels are shown in Figure 6a,b, respectively. The CV curves of the carbon aerogel show nearly rectangular shapes, indicating good capacitive capability connected with low contact resistance, leading to the efficient transport of ions. However, an interesting observation regarding the CV curves of GD-incorporated carbon aerogels is the presence of a pseudocapacitance and a quasi-rectangular shape for the curves. The CV curves of the GD-incorporated carbon aerogels show a pair of redox peaks at the voltages of 0.62 and 0.85 V, respectively, as a result of the pseudocapacitance originating from the electrochemical reactions taking place at the GD active sites (edges and functional groups). (43) The GD-incorporated carbon aerogels show marginally larger areas under the CV curve and hence a higher specific capacitance compared to the pristine carbon aerogels (Table S1). The enhanced capacitance of the GD-loaded carbon aerogels was also exhibited in the galvanostatic charge–discharge (GCD) curves of the two sets of samples. The GCD profiles of pristine carbon aerogels and GD-incorporated carbon aerogels at varying current densities (0.1–1 A g–1) are shown in Figure 6c,d, and the capacitance values at different current densities for KLCA60 and GD-doped KLCA60 are shown in Figure 7a,b. Analogous to the CV results, it can be seen that the GD-doped carbon aerogels displayed higher discharging times at all current densities, indicating that the GD-doped samples have a higher specific capacitance than the pristine samples due to the increased surface area as well as the pseudocapacitance. The capacitance of the carbon aerogels increased from 157.1 to 180.4 F g–1 at 0.1 A g–1 current density upon the incorporation of GDs, thereby further proving the positive effect of the GD into carbon aerogels. Undoubtedly, the CV and GCD results (Table S2) indicate that the introduction of GDs into CAs enhances the electrochemical performance of the parent material by the synergistic effect of the increased surface area (by the opening of pores closed by salt deposition) along with the pseudocapacitance, as a result of numerous functional groups and edges. This means that the GD-doped KLCA60 exhibits the characteristics of both electrical double-layer capacitance (EDLC) and pseudocapacitance (PC). To distinguish the respective contributions from EDLC and PC, capacitance differentiation was carried out according to the Trasatti analysis (44) (Figure 7c,d), and the detailed calculations are summarized in the Supporting Information. According to the Trasatti analysis, (44) for GD-doped KLCA60, the total capacitance contributions from EDLC and PC were 57 and 43%, respectively (Figure 7d).

Figure 6

Figure 6. (a) and (b) CV curves of supercapacitors composed of KLCA60 and GD-doped KLCA60 at different scan rates. (c) and (d) GCD curves of KLCA60 and GD-doped KLCA60 at different current densities.

Figure 7

Figure 7. Results from the electrochemical analysis. (a) Specific capacitances for KLCA60 at different current densities and (b) specific capacitances of GD-doped KLCA60 at different current densities obtained from GCD analysis. Capacitance contribution calculation using Trasatti method: (c) plot of the reciprocal of the gravimetric capacitance (C–1) against the square root of the scan rate (ν0.5). (d) Plot of C against the reciprocal of the square root of the scan rate (ν–0.5). (e) Nyquist plots obtained from EIS measurements and (f) Ragone plots of the carbon aerogels and GD-incorporated carbon aerogels.

Electrochemical impedance spectroscopy (EIS) was employed to further investigate the electrochemical behavior of the CAs, and the Nyquist plots are displayed in Figure 7e (the inset shows an enlarged view of the high-frequency region). The charge-transfer resistance at the interface between the electrode and the electrolyte can be estimated from the diameter of the semicircle in the Nyquist plots (inset shown in Figure 7e) in the high-frequency region, which is obtained from the x-intercepts in the Nyquist plot. (45) For the GD-doped KLCA60, the charge-transfer resistance was measured as 18 Ω compared to 19 Ω for KLCA60, which indicates a low internal resistance and a relatively higher conductivity, which favors their application in supercapacitors. The carbon aerogels had an equivalent series resistance (ESR) value of <1 Ω; however, for the GD-incorporated carbon aerogel, the value increased owing to the higher contact resistance between the electrode and current collector. The presence of the inclined vertical line in the Nyquist plot of the pristine carbon aerogel represents effortless ion transfer in the electrodes, which indicates ideal double-layer capacitive behavior in these materials. However, in the GD-incorporated sample, a near 45° region can be observed in the intermediate frequency region, indicating the presence of Warburg impedance in the GD-incorporated material. An equivalent circuit has been modeled by fitting the EIS spectra using ZView software and is represented in Figure S3b. The model shows good agreement with the experimental EIS data, as clearly observed in Figure S3c,d. Corresponding parameters have been listed in Table S3. The Ragone plots presented in Figure 7f show that the GD-doped carbon aerogels exhibit energy densities of 6.3 and 3.8 Wh kg–1 at power densities of 50 and 500 W kg–1, respectively, compared to 5.5 and 3.3 Wh kg–1 energy densities at power densities of 50 and 500 W kg–1, respectively, for the pristine carbon aerogels. Cyclic stability analysis at 3 A g–1 up to 3000 charge–discharge cycles (Figure S4) indicated that the GD-incorporated carbon aerogels retained 92% of their initial capacitance, demonstrating the high stability of these materials as supercapacitor electrodes. Thus, the GD-doped aerogels exhibit pure capacitive behavior that is closely associated with better ion diffusion in the interior parts of the electrodes rather than the ideal double-layer capacitive behavior. (1,46)
The improvement in the electrochemical properties of the carbon aerogels upon the introduction of GDs can be explained as follows. Upon incorporation, the GDs remained distributed on the surface of the carbon aerogels, which consequently caused the removal of salt particles that otherwise tended to obstruct the pores in the carbon aerogels. The doping of GDs on the aerogels also led to an increased surface area for the material as a whole. Upon closely examining the properties of KLCA60 and GD-doped KLCA60, it was clear that the energy storage mechanism in KLCA60 was purely based on the electrical double-layer capacitance (EDLC), whereas, in the GD-doped KLCA60, the capacitance was contributed by both the EDLC and pseudocapacitance. Hence, it can be concluded that the doping of nanosized GDs on carbon aerogels leads to a reduction in the capacitance contribution from the double-layer capacitance, but on the other hand, the GDs contribute remarkably toward pseudocapacitance, and hence, the total specific capacitance of the GD-doped KLCA60 is higher than that of the pristine KLCA60.

Conclusions

ARTICLE SECTIONS
Jump To

Novel GDs ranging in size from 5 to 15 nm were successfully synthesized from bio-derived carbon by oxidative acid treatment involving sulfuric and nitric acids. The synthesized biomass-based GDs were incorporated into carbon aerogels to fabricate supercapacitor electrodes and were subjected to electrochemical analysis. The specific capacitance of the GD-doped carbon aerogels was 180.4 F g–1 compared to 157.1 F g–1 for pristine carbon aerogels. The GD-doped carbon aerogels exhibited energy densities of 6.3 and 3.8 Wh kg–1 at power densities of 50 and 500 W kg–1, respectively, which are higher than those of the pristine carbon aerogels. The present work thus proves the concept of using waste-derived biocarbon to design high-quality functional carbon nanomaterials. Furthermore, such novel green functional materials can be exploited as functional additives to improve the electrochemical properties of lignin-based carbon aerogels.

Supporting Information

ARTICLE SECTIONS
Jump To

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsaelm.1c00487.

  • (a) GD dispersion in normal light and 365 nm UV light; (b) height profile of GDs from AFM; (c) size distribution histogram of GDs based on AFM image (Figure S1); results from elemental analysis, EDX spectra of (a) pristine KLCA60 and (b) GD-doped KLCA60 (Figure S2); electrochemical parameters of carbon aerogels and GD-doped carbon aerogels based on cyclic voltammetry (CV) curves (Table S1); electrochemical properties of carbon aerogels and GDs-incorporated carbon aerogels based on galvanostatic charge–discharge (GCD) curves (Table S2); (a) schematic representation of supercapacitor (SC) assembly; (b) equivalent circuit for electrode interface fitted using ZView software showing equivalent series resistance (RESR), double-layer capacitance (CEDL), charge-transfer resistance (RCT), constant phase element (CPE) representing pseudocapacitance along with faradaic resistance (RF); (c) experimental and fitted Nyquist plots; and (d) experimental and fitted |Z| vs frequency plots for the supercapacitor demonstrating good fitting of equivalent circuit with SC (Figure S3); EIS parameters obtained after fitting the equivalent circuit using ZView (Table S3); capacitance retention for the GD-doped KLCA60 electrode after 3000 cycles in the cyclic stability measurements using three-electrode system at 3 A g–1; inset showing the charge–discharge cycles for 2990–3000 cycles; Trasatti method (Figure S4) (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

ARTICLE SECTIONS
Jump To

  • Corresponding Author
    • Kristiina Oksman - Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, SwedenDepartment of Mechanical & Industrial Engineering (MIE), University of Toronto, Toronto, Ontario M5S 3G8, CanadaOrcidhttps://orcid.org/0000-0003-4762-2854 Email: [email protected]
  • Authors
    • Bony Thomas - Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    • Gejo George - Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    • Anton Landström - Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden
    • Isabella Concina - Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, SwedenOrcidhttps://orcid.org/0000-0003-1785-7177
    • Shiyu Geng - Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, SwedenOrcidhttps://orcid.org/0000-0003-1776-2725
    • Alberto Vomiero - Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, SwedenDepartment of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Via Torino 155, 30172 Venezia Mestre, ItalyOrcidhttps://orcid.org/0000-0003-2935-1165
    • Mohini Sain - Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, SwedenDepartment of Mechanical & Industrial Engineering (MIE), University of Toronto, Toronto, Ontario M5S 3G8, CanadaOrcidhttps://orcid.org/0000-0003-0808-271X
  • Author Contributions

    B.T.: Conceptualization, data curation, formal analysis, investigation, methodology, validation, visualization, writing─original draft, writing─review & editing. G.G.: Data curation, formal analysis, investigation, methodology, validation, writing─original draft, writing─review & editing. A.L.: Investigation, writing─review & editing. I.C.: Investigation, writing─review & editing. S.G.: Conceptualization, formal analysis, investigation, supervision, writing─review & editing. A.V.: Investigation, writing─review & editing. M.S.: Resources, supervision, writing─review & editing. K.O.: Conceptualization, funding acquisition, project administration, resources, supervision, writing─review & editing.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

ARTICLE SECTIONS
Jump To

The authors are grateful for the funding provided by the Bio4Energy National Strategic Research Program (Project name: Carbonization of biomass to high-quality renewable carbon materials for CO2 capture and energy storage). The authors are also thankful for the Grelectronics Project financed by Business Finland, Vetenskapsrådet VR for financing (Carbon Lignin 2017-04240), and the Kempe Foundation for financing the research infrastructure at LTU. Dr. Rasoul Esmaeely and the University of Oulu Nanocenter are acknowledged for the TEM analysis.

References

ARTICLE SECTIONS
Jump To

This article references 46 other publications.

  1. 1
    Zhang, S.; Sui, L.; Dong, H.; He, W.; Dong, L.; Yu, L. High-Performance Supercapacitor of Graphene Quantum Dots with Uniform Sizes. ACS Appl. Mater. Interfaces 2018, 10, 1298312991,  DOI: 10.1021/acsami.8b00323
  2. 2
    Tan, Z.; Chen, G.; Zhu, Y. Carbon-Based Supercapacitors Produced by the Activation of Graphene Nanocarbons. Nanocarbons Adv. Energy Storage 2015, 16, 211225,  DOI: 10.1126/science.1200770
  3. 3
    Baños, R.; Manzano-Agugliaro, F.; Montoya, F. G.; Gil, C.; Alcayde, A.; Gómez, J. Optimization Methods Applied to Renewable and Sustainable Energy: A Review. Renewable Sustainable Energy Rev. 2011, 15, 17531766,  DOI: 10.1016/j.rser.2010.12.008
  4. 4
    Lee, K.; Lee, H.; Shin, Y.; Yoon, Y.; Kim, D.; Lee, H. Highly Transparent and Flexible Supercapacitors Using Graphene-Graphene Quantum Dots Chelate. Nano Energy 2016, 26, 746754,  DOI: 10.1016/j.nanoen.2016.06.030
  5. 5
    Abdullah, M. A.; Muttaqi, K. M.; Agalgaonkar, A. P. Sustainable Energy System Design with Distributed Renewable Resources Considering Economic, Environmental and Uncertainty Aspects. Renewable Energy 2015, 78, 165172,  DOI: 10.1016/j.renene.2014.12.044
  6. 6
    Wang, J.; Ding, B.; Xu, Y.; Shen, L.; Dou, H.; Zhang, X. Crumpled Nitrogen-Doped Graphene for Supercapacitors with High Gravimetric and Volumetric Performances. ACS Appl. Mater. Interfaces 2015, 7, 2228422291,  DOI: 10.1021/acsami.5b05428
  7. 7
    Ganganboina, A. B.; Dutta Chowdhury, A.; Doong, R. A. New Avenue for Appendage of Graphene Quantum Dots on Halloysite Nanotubes as Anode Materials for High Performance Supercapacitors. ACS Sustainable Chem. Eng. 2017, 5, 49304940,  DOI: 10.1021/acssuschemeng.7b00329
  8. 8
    Zhu, Y.; Ji, X.; Pan, C.; Sun, Q.; Song, W.; Fang, L.; Chen, Q.; Banks, C. E. A Carbon Quantum Dot Decorated RuO 2 Network: Outstanding Supercapacitances under Ultrafast Charge and Discharge. Energy Environ. Sci. 2013, 6, 36653675,  DOI: 10.1039/c3ee41776j
  9. 9
    Jian, X.; Li, J. G.; Yang, H. M.; Cao, L. L.; Zhang, E. H.; Liang, Z. H. Carbon Quantum Dots Reinforced Polypyrrole Nanowire via Electrostatic Self-Assembly Strategy for High-Performance Supercapacitors. Carbon 2017, 114, 533543,  DOI: 10.1016/j.carbon.2016.12.033
  10. 10
    Ahmed, S.; Ahmed, A.; Rafat, M. Supercapacitor Performance of Activated Carbon Derived from Rotten Carrot in Aqueous, Organic and Ionic Liquid Based Electrolytes. J. Saudi Chem. Soc. 2018, 22, 9931002,  DOI: 10.1016/j.jscs.2018.03.002
  11. 11
    Genc, R.; Alas, M. O.; Harputlu, E.; Repp, S.; Kremer, N.; Castellano, M.; Colak, S. G.; Ocakoglu, K.; Erdem, E. High-Capacitance Hybrid Supercapacitor Based on Multi-Colored Fluorescent Carbon-Dots. Sci. Rep. 2017, 7, 11222  DOI: 10.1038/s41598-017-11347-1
  12. 12
    Kai, D.; Tan, M. J.; Chee, P. L.; Chua, Y. K.; Yap, Y. L.; Loh, X. J. Towards Lignin-Based Functional Materials in a Sustainable World. Green Chem. 2016, 18, 11751200,  DOI: 10.1039/C5GC02616D
  13. 13
    Bajwa, D. S.; Pourhashem, G.; Ullah, A. H.; Bajwa, S. G. A Concise Review of Current Lignin Production, Applications, Products and Their Environment Impact. Ind. Crops Prod. 2019, 139, 111526  DOI: 10.1016/j.indcrop.2019.111526
  14. 14
    Geng, S.; Wei, J.; Jonasson, S.; Hedlund, J.; Oksman, K. Multifunctional Carbon Aerogels with Hierarchical Anisotropic Structure Derived from Lignin and Cellulose Nanofibers for CO2 Capture and Energy Storage. ACS Appl. Mater. Interfaces 2020, 12, 74327441,  DOI: 10.1021/acsami.9b19955
  15. 15
    Thomas, B.; Geng, S.; Sain, M.; Oksman, K. Hetero-Porous, High-Surface Area Green Carbon Aerogels for the next-Generation Energy Storage Applications. Nanomaterials 2021, 11, 653  DOI: 10.3390/nano11030653
  16. 16
    Liu, C.; Yu, Z.; Neff, D.; Zhamu, A.; Jang, B. Z. Graphene-Based Supercapacitor with an Ultrahigh Energy Density. Nano Lett. 2010, 10, 48634868,  DOI: 10.1021/nl102661q
  17. 17
    Li, Z.; Qin, P.; Wang, L.; Yang, C.; Li, Y.; Chen, Z.; Pan, D.; Wu, M. Amine-Enriched Graphene Quantum Dots for High-Pseudocapacitance Supercapacitors. Electrochim. Acta 2016, 208, 260266,  DOI: 10.1016/j.electacta.2016.05.030
  18. 18
    Yoo, J. J.; Balakrishnan, K.; Huang, J.; Meunier, V.; Sumpter, B. G.; Srivastava, A.; Conway, M.; Mohana Reddy, A. L.; Yu, J.; Vajtai, R.; Ajayan, P. M. Ultrathin Planar Graphene Supercapacitors. Nano Lett. 2011, 11, 14231427,  DOI: 10.1021/nl200225j
  19. 19
    Abbas, A.; Mariana, L. T.; Phan, A. N. Biomass-Waste Derived Graphene Quantum Dots and Their Applications. Carbon 2018, 140, 7799,  DOI: 10.1016/j.carbon.2018.08.016
  20. 20
    Yan, Y.; Gong, J.; Chen, J.; Zeng, Z.; Huang, W.; Pu, K.; Liu, J.; Chen, P. Recent Advances on Graphene Quantum Dots: From Chemistry and Physics to Applications. Adv. Mater. 2019, 31, 1808283  DOI: 10.1002/adma.201808283
  21. 21
    Li, Y.; Wu, F.; Jin, X.; Xu, H.; Liu, X.; Shi, G. Preparation and Electrochemical Properties of Graphene Quantum Dots/Biomass Activated Carbon Electrodes. Inorg. Chem. Commun. 2020, 112, 107718  DOI: 10.1016/j.inoche.2019.107718
  22. 22
    Li, L.; Wu, G.; Yang, G.; Peng, J.; Zhao, J.; Zhu, J. J. Focusing on Luminescent Graphene Quantum Dots: Current Status and Future Perspectives. Nanoscale 2013, 5, 40154039,  DOI: 10.1039/c3nr33849e
  23. 23
    Gong, X.; Hu, Q.; Chin Paau, M.; Zhang, Y.; Zhang, L.; Shuang, S.; Dong, C.; Choi, M. M. F. High-Performance Liquid Chromatographic and Mass Spectrometric Analysis of Fluorescent Carbon Nanodots. Talanta 2014, 129, 529538,  DOI: 10.1016/j.talanta.2014.04.008
  24. 24
    Fringes, S.; Volk, C.; Terrés, B.; Dauber, J.; Engels, S.; Trellenkamp, S.; Stampfer, C. Tunable Capacitive Inter-Dot Coupling in a Bilayer Graphene Double Quantum Dot. Phys. Status Solidi C 2012, 9, 169174,  DOI: 10.1002/pssc.201100340
  25. 25
    Feng, J.; Dong, H.; Yu, L.; Dong, L. The Optical and Electronic Properties of Graphene Quantum Dots with Oxygen-Containing Groups: A Density Functional Theory Study. J. Mater. Chem. C 2017, 5, 59845993,  DOI: 10.1039/C7TC00631D
  26. 26
    Zhu, C.; Yang, S.; Wang, G.; Mo, R.; He, P.; Sun, J.; Di, Z.; Kang, Z.; Yuan, N.; Ding, J.; Ding, G.; Xie, X. A New Mild, Clean and Highly Efficient Method for the Preparation of Graphene Quantum Dots without by-Products. J. Mater. Chem. B 2015, 3, 68716876,  DOI: 10.1039/c5tb01093d
  27. 27
    Zong, J.; Zhu, Y.; Yang, X.; Shen, J.; Li, C. Synthesis of Photoluminescent Carbogenic Dots Using Mesoporous Silica Spheres as Nanoreactors. Chem. Commun. 2011, 47, 764766,  DOI: 10.1039/c0cc03092a
  28. 28
    Wang, L.; Wang, Y.; Xu, T.; Liao, H.; Yao, C.; Liu, Y.; Li, Z.; Chen, Z.; Pan, D.; Sun, L.; Wu, M. Gram-Scale Synthesis of Single-Crystalline Graphene Quantum Dots with Superior Optical Properties. Nat. Commun. 2014, 5, 5357  DOI: 10.1038/ncomms6357
  29. 29
    Ding, Z.; Li, F.; Wen, J.; Wang, X.; Sun, R. Gram-Scale Synthesis of Single-Crystalline Graphene Quantum Dots Derived from Lignin Biomass. Green Chem. 2018, 20, 13831390,  DOI: 10.1039/c7gc03218h
  30. 30
    Berglund, L.; Anugwom, I.; Hedenström, M.; Aitomäki, Y.; Mikkola, J. P.; Oksman, K. Switchable Ionic Liquids Enable Efficient Nanofibrillation of Wood Pulp. Cellulose 2017, 24, 32653279,  DOI: 10.1007/s10570-017-1354-2
  31. 31
    Suryawanshi, A.; Biswal, M.; Mhamane, D.; Gokhale, R.; Patil, S.; Guin, D.; Ogale, S. Large Scale Synthesis of Graphene Quantum Dots (GQDs) from Waste Biomass and Their Use as an Efficient and Selective Photoluminescence on-off-on Probe for Ag+ions. Nanoscale 2014, 6, 1166411670,  DOI: 10.1039/c4nr02494j
  32. 32
    Ran, C.; Wang, M.; Gao, W.; Yang, Z.; Shao, J.; Deng, J.; Song, X. A General Route to Enhance the Fluorescence of Graphene Quantum Dots by Ag Nanoparticles. RSC Adv. 2014, 4, 2177221776,  DOI: 10.1039/c4ra03542a
  33. 33
    Gan, Z. X.; Xiong, S. J.; Wu, X. L.; He, C. Y.; Shen, J. C.; Chu, P. K. Mn2+-Bonded Reduced Graphene Oxide with Strong Radiative Recombination in Broad Visible Range Caused by Resonant Energy Transfer. Nano Lett. 2011, 11, 39513956,  DOI: 10.1021/nl202240s
  34. 34
    Bao, L.; Zhang, Z. L.; Tian, Z. Q.; Zhang, L.; Liu, C.; Lin, Y.; Qi, B.; Pang, D. W. Electrochemical Tuning of Luminescent Carbon Nanodots: From Preparation to Luminescence Mechanism. Adv. Mater. 2011, 23, 58015806,  DOI: 10.1002/adma.201102866
  35. 35
    Dong, Y.; Chen, C.; Zheng, X.; Gao, L.; Cui, Z.; Yang, H.; Guo, C.; Chi, Y.; Li, C. M. One-Step and High Yield Simultaneous Preparation of Single- and Multi-Layer Graphene Quantum Dots from CX-72 Carbon Black. J. Mater. Chem. 2012, 22, 87648766,  DOI: 10.1039/c2jm30658a
  36. 36
    Gao, T.; Wang, X.; Yang, L. Y.; He, H.; Ba, X. X.; Zhao, J.; Jiang, F. L.; Liu, Y. Red, Yellow, and Blue Luminescence by Graphene Quantum Dots: Syntheses, Mechanism, and Cellular Imaging. ACS Appl. Mater. Interfaces 2017, 9, 2484624856,  DOI: 10.1021/acsami.7b05569
  37. 37
    Fan, T.; Zeng, W.; Tang, W.; Yuan, C.; Tong, S.; Cai, K.; Liu, Y.; Huang, W.; Min, Y.; Epstein, A. J. Controllable Size-Selective Method to Prepare Graphene Quantum Dots from Graphene Oxide. Nanoscale Res. Lett. 2015, 10, 55  DOI: 10.1186/s11671-015-0783-9
  38. 38
    Abdul, G.; Zhu, X.; Chen, B. Structural Characteristics of Biochar-Graphene Nanosheet Composites and Their Adsorption Performance for Phthalic Acid Esters. Chem. Eng. J. 2017, 319, 920,  DOI: 10.1016/j.cej.2017.02.074
  39. 39
    Ghani, W. A. W. A. K.; Mohd, A.; da Silva, G.; Bachmann, R. T.; Taufiq-Yap, Y. H.; Rashid, U.; Al-Muhtaseb, A. H. Biochar Production from Waste Rubber-Wood-Sawdust and Its Potential Use in C Sequestration: Chemical and Physical Characterization. Ind. Crops Prod. 2013, 44, 1824,  DOI: 10.1016/j.indcrop.2012.10.017
  40. 40
    Das, O.; Kim, N. K.; Kalamkarov, A. L.; Sarmah, A. K.; Bhattacharyya, D. Biochar to the Rescue: Balancing the Fire Performance and Mechanical Properties of Polypropylene Composites. Polym. Degrad. Stab. 2017, 144, 485496,  DOI: 10.1016/j.polymdegradstab.2017.09.006
  41. 41
    Vázquez-Nakagawa, M.; Rodríguez-Pérez, L.; Herranz, M. A.; Martín, N. Chirality Transfer from Graphene Quantum Dots. Chem. Commun. 2016, 52, 665668,  DOI: 10.1039/c5cc08890a
  42. 42
    Dervishi, E.; Ji, Z.; Htoon, H.; Sykora, M.; Doorn, S. K. Raman Spectroscopy of Bottom-up Synthesized Graphene Quantum Dots: Size and Structure Dependence. Nanoscale 2019, 11, 1657116581,  DOI: 10.1039/c9nr05345j
  43. 43
    Jia, H.; Cai, Y.; Lin, J.; Liang, H.; Qi, J.; Cao, J.; Feng, J.; Fei, W. D. Heterostructural Graphene Quantum Dot/MnO2 Nanosheets toward High-Potential Window Electrodes for High-Performance Supercapacitors. Adv. Sci. 2018, 5, 1700887  DOI: 10.1002/advs.201700887
  44. 44
    Liu, J.; Zhou, Y.; Xie, Z.; Li, Y.; Liu, Y.; Sun, J.; Ma, Y.; Terasaki, O.; Chen, L. Conjugated Copper–Catecholate Framework Electrodes for Efficient Energy Storage. Angew. Chem., Int. Ed. 2020, 59, 10811086,  DOI: 10.1002/anie.201912642
  45. 45
    Luo, J.; Wang, J.; Liu, S.; Wu, W.; Jia, T.; Yang, Z.; Mu, S.; Huang, Y. Graphene Quantum Dots Encapsulated Tremella-like NiCo2O4 for Advanced Asymmetric Supercapacitors. Carbon 2019, 146, 18,  DOI: 10.1016/j.carbon.2019.01.078
  46. 46
    El-Kady, M. F.; Strong, V.; Dubin, S.; Kaner, R. B. Laser Scribing of High-Performance and Flexible Graphene-Based Electrochemical Capacitors. Science 2012, 335, 13261330,  DOI: 10.1126/science.1216744

Cited By

ARTICLE SECTIONS
Jump To

This article is cited by 5 publications.

  1. Qihang Cao, Rui Lou, Longhua Dong, Taoyuan Niu, Guodong Wei, Gaojin Lyu. Evaluation of Gelation Time Affecting the Self-Assembled Framework of Lignin Nanoparticle-Based Carbon Aerogels and Their Electrochemical Performances. ACS Applied Energy Materials 2023, 6 (21) , 10874-10882. https://doi.org/10.1021/acsaem.3c01574
  2. Jason D. Orlando, Ravi M. A. P. Lima, Li Li, Stefanie A. Sydlik, Helinando P. de Oliveira. Electrochemical Performance of N-Doped Carbon-Based Electrodes for Supercapacitors. ACS Applied Electronic Materials 2022, 4 (10) , 5040-5054. https://doi.org/10.1021/acsaelm.2c01059
  3. Elmira Payami, Reza Teimuri-Mofrad. Ternary nanocomposite of GQDs-polyFc/Fe3O4/PANI: Design, synthesis, and applied for electrochemical energy storage. Electrochimica Acta 2023, 439 , 141706. https://doi.org/10.1016/j.electacta.2022.141706
  4. Guojie Chao, Dong Wang, Yang Wang, Xu Zhang, Suli Chen, Yufeng Wang, Wei Zong, Wei Fan, Longsheng Zhang, Tianxi Liu. Modulation of hierarchical porosity in metal-doping graphene/carbon hybrid aerogels for capacitive energy storage. Journal of Energy Storage 2022, 55 , 105445. https://doi.org/10.1016/j.est.2022.105445
  5. Ting Zhang, Lu Sun, Xiaohong Sun, Heng Dong, Han Yu, Hongbing Yu. Radical and non-radical cooperative degradation in metal-free electro-Fenton based on nitrogen self-doped biochar. Journal of Hazardous Materials 2022, 435 , 129063. https://doi.org/10.1016/j.jhazmat.2022.129063
  • Abstract

    Figure 1

    Figure 1. Schematic representation of the preparation steps for GD-doped carbon aerogel. (a) Preparation of carbon aerogel from lignin/CNF suspension. (b) Synthesis of GDs from biochar using oxidative acid treatment involving 3:1 concentration of H2SO4/HNO3; the reaction mixture was refluxed for 6 h at 90 °C. (c) Surface doping of prepared carbon aerogels using GDs synthesized from biochar.

    Figure 2

    Figure 2. (a) UV–visible spectrum. (b) Photoluminescence (PL) spectra at different excitation wavelengths, showing the optical properties of the produced GDs in an aqueous medium (0.01 wt %). (c) Atomic force microscopic image of GDs. (d) TEM image showing graphene particles with an ordered carbon structure and a size range of 5–15 nm.

    Figure 3

    Figure 3. (a) FTIR spectrum of GDs exhibiting numerous surface functional groups. (b) Thermogravimetric analysis of GDs compared to the biochar precursor showing a higher weight loss of GDs owing to the decomposition of carboxylic acid groups. (c) Thermogravimetric analysis of KL and CNF. (d) Raman spectra of biochar precursor, GDs prepared from biochar, and carbon aerogel KLCA60. (e) X-ray diffractometry of the GDs and KLCA60.

    Figure 4

    Figure 4. Microstructure of the prepared materials. (a) and (e) Longitudinal views of KLCA60 and GD-doped KLCA60; magnified images of the longitudinal sections showing the surface texture of both are shown in (b) and (f). Cross-sectional views of KLCA60 and GD-doped KLCA60 are shown in (c) and (g), and the respective high magnification images are shown in (d) and (h).

    Figure 5

    Figure 5. (a) Solid-state photoluminescence (PL) spectrum of KLCA60 doped with GDs at 315 nm excitation wavelength. (b) Nitrogen adsorption isotherms of KLCA60 and GD-incorporated KLCA60.

    Figure 6

    Figure 6. (a) and (b) CV curves of supercapacitors composed of KLCA60 and GD-doped KLCA60 at different scan rates. (c) and (d) GCD curves of KLCA60 and GD-doped KLCA60 at different current densities.

    Figure 7

    Figure 7. Results from the electrochemical analysis. (a) Specific capacitances for KLCA60 at different current densities and (b) specific capacitances of GD-doped KLCA60 at different current densities obtained from GCD analysis. Capacitance contribution calculation using Trasatti method: (c) plot of the reciprocal of the gravimetric capacitance (C–1) against the square root of the scan rate (ν0.5). (d) Plot of C against the reciprocal of the square root of the scan rate (ν–0.5). (e) Nyquist plots obtained from EIS measurements and (f) Ragone plots of the carbon aerogels and GD-incorporated carbon aerogels.

  • References

    ARTICLE SECTIONS
    Jump To

    This article references 46 other publications.

    1. 1
      Zhang, S.; Sui, L.; Dong, H.; He, W.; Dong, L.; Yu, L. High-Performance Supercapacitor of Graphene Quantum Dots with Uniform Sizes. ACS Appl. Mater. Interfaces 2018, 10, 1298312991,  DOI: 10.1021/acsami.8b00323
    2. 2
      Tan, Z.; Chen, G.; Zhu, Y. Carbon-Based Supercapacitors Produced by the Activation of Graphene Nanocarbons. Nanocarbons Adv. Energy Storage 2015, 16, 211225,  DOI: 10.1126/science.1200770
    3. 3
      Baños, R.; Manzano-Agugliaro, F.; Montoya, F. G.; Gil, C.; Alcayde, A.; Gómez, J. Optimization Methods Applied to Renewable and Sustainable Energy: A Review. Renewable Sustainable Energy Rev. 2011, 15, 17531766,  DOI: 10.1016/j.rser.2010.12.008
    4. 4
      Lee, K.; Lee, H.; Shin, Y.; Yoon, Y.; Kim, D.; Lee, H. Highly Transparent and Flexible Supercapacitors Using Graphene-Graphene Quantum Dots Chelate. Nano Energy 2016, 26, 746754,  DOI: 10.1016/j.nanoen.2016.06.030
    5. 5
      Abdullah, M. A.; Muttaqi, K. M.; Agalgaonkar, A. P. Sustainable Energy System Design with Distributed Renewable Resources Considering Economic, Environmental and Uncertainty Aspects. Renewable Energy 2015, 78, 165172,  DOI: 10.1016/j.renene.2014.12.044
    6. 6
      Wang, J.; Ding, B.; Xu, Y.; Shen, L.; Dou, H.; Zhang, X. Crumpled Nitrogen-Doped Graphene for Supercapacitors with High Gravimetric and Volumetric Performances. ACS Appl. Mater. Interfaces 2015, 7, 2228422291,  DOI: 10.1021/acsami.5b05428
    7. 7
      Ganganboina, A. B.; Dutta Chowdhury, A.; Doong, R. A. New Avenue for Appendage of Graphene Quantum Dots on Halloysite Nanotubes as Anode Materials for High Performance Supercapacitors. ACS Sustainable Chem. Eng. 2017, 5, 49304940,  DOI: 10.1021/acssuschemeng.7b00329
    8. 8
      Zhu, Y.; Ji, X.; Pan, C.; Sun, Q.; Song, W.; Fang, L.; Chen, Q.; Banks, C. E. A Carbon Quantum Dot Decorated RuO 2 Network: Outstanding Supercapacitances under Ultrafast Charge and Discharge. Energy Environ. Sci. 2013, 6, 36653675,  DOI: 10.1039/c3ee41776j
    9. 9
      Jian, X.; Li, J. G.; Yang, H. M.; Cao, L. L.; Zhang, E. H.; Liang, Z. H. Carbon Quantum Dots Reinforced Polypyrrole Nanowire via Electrostatic Self-Assembly Strategy for High-Performance Supercapacitors. Carbon 2017, 114, 533543,  DOI: 10.1016/j.carbon.2016.12.033
    10. 10
      Ahmed, S.; Ahmed, A.; Rafat, M. Supercapacitor Performance of Activated Carbon Derived from Rotten Carrot in Aqueous, Organic and Ionic Liquid Based Electrolytes. J. Saudi Chem. Soc. 2018, 22, 9931002,  DOI: 10.1016/j.jscs.2018.03.002
    11. 11
      Genc, R.; Alas, M. O.; Harputlu, E.; Repp, S.; Kremer, N.; Castellano, M.; Colak, S. G.; Ocakoglu, K.; Erdem, E. High-Capacitance Hybrid Supercapacitor Based on Multi-Colored Fluorescent Carbon-Dots. Sci. Rep. 2017, 7, 11222  DOI: 10.1038/s41598-017-11347-1
    12. 12
      Kai, D.; Tan, M. J.; Chee, P. L.; Chua, Y. K.; Yap, Y. L.; Loh, X. J. Towards Lignin-Based Functional Materials in a Sustainable World. Green Chem. 2016, 18, 11751200,  DOI: 10.1039/C5GC02616D
    13. 13
      Bajwa, D. S.; Pourhashem, G.; Ullah, A. H.; Bajwa, S. G. A Concise Review of Current Lignin Production, Applications, Products and Their Environment Impact. Ind. Crops Prod. 2019, 139, 111526  DOI: 10.1016/j.indcrop.2019.111526
    14. 14
      Geng, S.; Wei, J.; Jonasson, S.; Hedlund, J.; Oksman, K. Multifunctional Carbon Aerogels with Hierarchical Anisotropic Structure Derived from Lignin and Cellulose Nanofibers for CO2 Capture and Energy Storage. ACS Appl. Mater. Interfaces 2020, 12, 74327441,  DOI: 10.1021/acsami.9b19955
    15. 15
      Thomas, B.; Geng, S.; Sain, M.; Oksman, K. Hetero-Porous, High-Surface Area Green Carbon Aerogels for the next-Generation Energy Storage Applications. Nanomaterials 2021, 11, 653  DOI: 10.3390/nano11030653
    16. 16
      Liu, C.; Yu, Z.; Neff, D.; Zhamu, A.; Jang, B. Z. Graphene-Based Supercapacitor with an Ultrahigh Energy Density. Nano Lett. 2010, 10, 48634868,  DOI: 10.1021/nl102661q
    17. 17
      Li, Z.; Qin, P.; Wang, L.; Yang, C.; Li, Y.; Chen, Z.; Pan, D.; Wu, M. Amine-Enriched Graphene Quantum Dots for High-Pseudocapacitance Supercapacitors. Electrochim. Acta 2016, 208, 260266,  DOI: 10.1016/j.electacta.2016.05.030
    18. 18
      Yoo, J. J.; Balakrishnan, K.; Huang, J.; Meunier, V.; Sumpter, B. G.; Srivastava, A.; Conway, M.; Mohana Reddy, A. L.; Yu, J.; Vajtai, R.; Ajayan, P. M. Ultrathin Planar Graphene Supercapacitors. Nano Lett. 2011, 11, 14231427,  DOI: 10.1021/nl200225j
    19. 19
      Abbas, A.; Mariana, L. T.; Phan, A. N. Biomass-Waste Derived Graphene Quantum Dots and Their Applications. Carbon 2018, 140, 7799,  DOI: 10.1016/j.carbon.2018.08.016
    20. 20
      Yan, Y.; Gong, J.; Chen, J.; Zeng, Z.; Huang, W.; Pu, K.; Liu, J.; Chen, P. Recent Advances on Graphene Quantum Dots: From Chemistry and Physics to Applications. Adv. Mater. 2019, 31, 1808283  DOI: 10.1002/adma.201808283
    21. 21
      Li, Y.; Wu, F.; Jin, X.; Xu, H.; Liu, X.; Shi, G. Preparation and Electrochemical Properties of Graphene Quantum Dots/Biomass Activated Carbon Electrodes. Inorg. Chem. Commun. 2020, 112, 107718  DOI: 10.1016/j.inoche.2019.107718
    22. 22
      Li, L.; Wu, G.; Yang, G.; Peng, J.; Zhao, J.; Zhu, J. J. Focusing on Luminescent Graphene Quantum Dots: Current Status and Future Perspectives. Nanoscale 2013, 5, 40154039,  DOI: 10.1039/c3nr33849e
    23. 23
      Gong, X.; Hu, Q.; Chin Paau, M.; Zhang, Y.; Zhang, L.; Shuang, S.; Dong, C.; Choi, M. M. F. High-Performance Liquid Chromatographic and Mass Spectrometric Analysis of Fluorescent Carbon Nanodots. Talanta 2014, 129, 529538,  DOI: 10.1016/j.talanta.2014.04.008
    24. 24
      Fringes, S.; Volk, C.; Terrés, B.; Dauber, J.; Engels, S.; Trellenkamp, S.; Stampfer, C. Tunable Capacitive Inter-Dot Coupling in a Bilayer Graphene Double Quantum Dot. Phys. Status Solidi C 2012, 9, 169174,  DOI: 10.1002/pssc.201100340
    25. 25
      Feng, J.; Dong, H.; Yu, L.; Dong, L. The Optical and Electronic Properties of Graphene Quantum Dots with Oxygen-Containing Groups: A Density Functional Theory Study. J. Mater. Chem. C 2017, 5, 59845993,  DOI: 10.1039/C7TC00631D
    26. 26
      Zhu, C.; Yang, S.; Wang, G.; Mo, R.; He, P.; Sun, J.; Di, Z.; Kang, Z.; Yuan, N.; Ding, J.; Ding, G.; Xie, X. A New Mild, Clean and Highly Efficient Method for the Preparation of Graphene Quantum Dots without by-Products. J. Mater. Chem. B 2015, 3, 68716876,  DOI: 10.1039/c5tb01093d
    27. 27
      Zong, J.; Zhu, Y.; Yang, X.; Shen, J.; Li, C. Synthesis of Photoluminescent Carbogenic Dots Using Mesoporous Silica Spheres as Nanoreactors. Chem. Commun. 2011, 47, 764766,  DOI: 10.1039/c0cc03092a
    28. 28
      Wang, L.; Wang, Y.; Xu, T.; Liao, H.; Yao, C.; Liu, Y.; Li, Z.; Chen, Z.; Pan, D.; Sun, L.; Wu, M. Gram-Scale Synthesis of Single-Crystalline Graphene Quantum Dots with Superior Optical Properties. Nat. Commun. 2014, 5, 5357  DOI: 10.1038/ncomms6357
    29. 29
      Ding, Z.; Li, F.; Wen, J.; Wang, X.; Sun, R. Gram-Scale Synthesis of Single-Crystalline Graphene Quantum Dots Derived from Lignin Biomass. Green Chem. 2018, 20, 13831390,  DOI: 10.1039/c7gc03218h
    30. 30
      Berglund, L.; Anugwom, I.; Hedenström, M.; Aitomäki, Y.; Mikkola, J. P.; Oksman, K. Switchable Ionic Liquids Enable Efficient Nanofibrillation of Wood Pulp. Cellulose 2017, 24, 32653279,  DOI: 10.1007/s10570-017-1354-2
    31. 31
      Suryawanshi, A.; Biswal, M.; Mhamane, D.; Gokhale, R.; Patil, S.; Guin, D.; Ogale, S. Large Scale Synthesis of Graphene Quantum Dots (GQDs) from Waste Biomass and Their Use as an Efficient and Selective Photoluminescence on-off-on Probe for Ag+ions. Nanoscale 2014, 6, 1166411670,  DOI: 10.1039/c4nr02494j
    32. 32
      Ran, C.; Wang, M.; Gao, W.; Yang, Z.; Shao, J.; Deng, J.; Song, X. A General Route to Enhance the Fluorescence of Graphene Quantum Dots by Ag Nanoparticles. RSC Adv. 2014, 4, 2177221776,  DOI: 10.1039/c4ra03542a
    33. 33
      Gan, Z. X.; Xiong, S. J.; Wu, X. L.; He, C. Y.; Shen, J. C.; Chu, P. K. Mn2+-Bonded Reduced Graphene Oxide with Strong Radiative Recombination in Broad Visible Range Caused by Resonant Energy Transfer. Nano Lett. 2011, 11, 39513956,  DOI: 10.1021/nl202240s
    34. 34
      Bao, L.; Zhang, Z. L.; Tian, Z. Q.; Zhang, L.; Liu, C.; Lin, Y.; Qi, B.; Pang, D. W. Electrochemical Tuning of Luminescent Carbon Nanodots: From Preparation to Luminescence Mechanism. Adv. Mater. 2011, 23, 58015806,  DOI: 10.1002/adma.201102866
    35. 35
      Dong, Y.; Chen, C.; Zheng, X.; Gao, L.; Cui, Z.; Yang, H.; Guo, C.; Chi, Y.; Li, C. M. One-Step and High Yield Simultaneous Preparation of Single- and Multi-Layer Graphene Quantum Dots from CX-72 Carbon Black. J. Mater. Chem. 2012, 22, 87648766,  DOI: 10.1039/c2jm30658a
    36. 36
      Gao, T.; Wang, X.; Yang, L. Y.; He, H.; Ba, X. X.; Zhao, J.; Jiang, F. L.; Liu, Y. Red, Yellow, and Blue Luminescence by Graphene Quantum Dots: Syntheses, Mechanism, and Cellular Imaging. ACS Appl. Mater. Interfaces 2017, 9, 2484624856,  DOI: 10.1021/acsami.7b05569
    37. 37
      Fan, T.; Zeng, W.; Tang, W.; Yuan, C.; Tong, S.; Cai, K.; Liu, Y.; Huang, W.; Min, Y.; Epstein, A. J. Controllable Size-Selective Method to Prepare Graphene Quantum Dots from Graphene Oxide. Nanoscale Res. Lett. 2015, 10, 55  DOI: 10.1186/s11671-015-0783-9
    38. 38
      Abdul, G.; Zhu, X.; Chen, B. Structural Characteristics of Biochar-Graphene Nanosheet Composites and Their Adsorption Performance for Phthalic Acid Esters. Chem. Eng. J. 2017, 319, 920,  DOI: 10.1016/j.cej.2017.02.074
    39. 39
      Ghani, W. A. W. A. K.; Mohd, A.; da Silva, G.; Bachmann, R. T.; Taufiq-Yap, Y. H.; Rashid, U.; Al-Muhtaseb, A. H. Biochar Production from Waste Rubber-Wood-Sawdust and Its Potential Use in C Sequestration: Chemical and Physical Characterization. Ind. Crops Prod. 2013, 44, 1824,  DOI: 10.1016/j.indcrop.2012.10.017
    40. 40
      Das, O.; Kim, N. K.; Kalamkarov, A. L.; Sarmah, A. K.; Bhattacharyya, D. Biochar to the Rescue: Balancing the Fire Performance and Mechanical Properties of Polypropylene Composites. Polym. Degrad. Stab. 2017, 144, 485496,  DOI: 10.1016/j.polymdegradstab.2017.09.006
    41. 41
      Vázquez-Nakagawa, M.; Rodríguez-Pérez, L.; Herranz, M. A.; Martín, N. Chirality Transfer from Graphene Quantum Dots. Chem. Commun. 2016, 52, 665668,  DOI: 10.1039/c5cc08890a
    42. 42
      Dervishi, E.; Ji, Z.; Htoon, H.; Sykora, M.; Doorn, S. K. Raman Spectroscopy of Bottom-up Synthesized Graphene Quantum Dots: Size and Structure Dependence. Nanoscale 2019, 11, 1657116581,  DOI: 10.1039/c9nr05345j
    43. 43
      Jia, H.; Cai, Y.; Lin, J.; Liang, H.; Qi, J.; Cao, J.; Feng, J.; Fei, W. D. Heterostructural Graphene Quantum Dot/MnO2 Nanosheets toward High-Potential Window Electrodes for High-Performance Supercapacitors. Adv. Sci. 2018, 5, 1700887  DOI: 10.1002/advs.201700887
    44. 44
      Liu, J.; Zhou, Y.; Xie, Z.; Li, Y.; Liu, Y.; Sun, J.; Ma, Y.; Terasaki, O.; Chen, L. Conjugated Copper–Catecholate Framework Electrodes for Efficient Energy Storage. Angew. Chem., Int. Ed. 2020, 59, 10811086,  DOI: 10.1002/anie.201912642
    45. 45
      Luo, J.; Wang, J.; Liu, S.; Wu, W.; Jia, T.; Yang, Z.; Mu, S.; Huang, Y. Graphene Quantum Dots Encapsulated Tremella-like NiCo2O4 for Advanced Asymmetric Supercapacitors. Carbon 2019, 146, 18,  DOI: 10.1016/j.carbon.2019.01.078
    46. 46
      El-Kady, M. F.; Strong, V.; Dubin, S.; Kaner, R. B. Laser Scribing of High-Performance and Flexible Graphene-Based Electrochemical Capacitors. Science 2012, 335, 13261330,  DOI: 10.1126/science.1216744
  • Supporting Information

    Supporting Information

    ARTICLE SECTIONS
    Jump To

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsaelm.1c00487.

    • (a) GD dispersion in normal light and 365 nm UV light; (b) height profile of GDs from AFM; (c) size distribution histogram of GDs based on AFM image (Figure S1); results from elemental analysis, EDX spectra of (a) pristine KLCA60 and (b) GD-doped KLCA60 (Figure S2); electrochemical parameters of carbon aerogels and GD-doped carbon aerogels based on cyclic voltammetry (CV) curves (Table S1); electrochemical properties of carbon aerogels and GDs-incorporated carbon aerogels based on galvanostatic charge–discharge (GCD) curves (Table S2); (a) schematic representation of supercapacitor (SC) assembly; (b) equivalent circuit for electrode interface fitted using ZView software showing equivalent series resistance (RESR), double-layer capacitance (CEDL), charge-transfer resistance (RCT), constant phase element (CPE) representing pseudocapacitance along with faradaic resistance (RF); (c) experimental and fitted Nyquist plots; and (d) experimental and fitted |Z| vs frequency plots for the supercapacitor demonstrating good fitting of equivalent circuit with SC (Figure S3); EIS parameters obtained after fitting the equivalent circuit using ZView (Table S3); capacitance retention for the GD-doped KLCA60 electrode after 3000 cycles in the cyclic stability measurements using three-electrode system at 3 A g–1; inset showing the charge–discharge cycles for 2990–3000 cycles; Trasatti method (Figure S4) (PDF)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

You’ve supercharged your research process with ACS and Mendeley!

STEP 1:
Click to create an ACS ID

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

MENDELEY PAIRING EXPIRED
Your Mendeley pairing has expired. Please reconnect