Carbon Nanomaterials for Advanced Energy Systems E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 897

Veröffentlichungsjahr: 2015

Beschreibung

With the proliferation of electronic devices, the world will need to double its energy supply by 2050. This book addresses this challenge and discusses synthesis and characterization of carbon nanomaterials for energy conversion and storage.

• Addresses one of the leading challenges facing society today as we steer away from dwindling supplies of fossil fuels and a rising need for electric power due to the proliferation of electronic products
• Promotes the use of carbon nanomaterials for energy applications
• Systematic coverage: synthesis, characterization, and a wide array of carbon nanomaterials are described
• Detailed descriptions of solar cells, electrodes, thermoelectrics, supercapacitors, and lithium-ion-based storage
• Discusses special architecture required for energy storage including hydrogen, methane, etc.

Leseprobe

Table of Contents

COVER

TITLE PAGE

LIST OF CONTRIBUTORS

PREFACE

PART I: SYNTHESIS AND CHARACTERIZATION OF CARBON NANOMATERIALS

1 FULLERENES, HIGHER FULLERENES, AND THEIR HYBRIDS: SYNTHESIS, CHARACTERIZATION, AND ENVIRONMENTAL CONSIDERATIONS

1.1 INTRODUCTION

1.2 FULLERENE, HIGHER FULLERENES, AND NANOHYBRIDS: STRUCTURES AND HISTORICAL PERSPECTIVE

1.3 SYNTHESIS AND CHARACTERIZATION

1.4 ENERGY APPLICATIONS

1.5 ENVIRONMENTAL CONSIDERATIONS FOR FULLERENE SYNTHESIS AND PROCESSING

REFERENCES

2 CARBON NANOTUBES

2.1 SYNTHESIS OF CARBON NANOTUBES

2.2 CHARACTERIZATION OF NANOTUBES

2.3 SUMMARY

REFERENCES

3 SYNTHESIS AND CHARACTERIZATION OF GRAPHENE

3.1 INTRODUCTION

3.2 OVERVIEW OF GRAPHENE SYNTHESIS METHODOLOGIES

3.3 GRAPHENE CHARACTERIZATIONS

3.4 SUMMARY AND OUTLOOK

REFERENCES

4 DOPING CARBON NANOMATERIALS WITH HETEROATOMS

4.1 INTRODUCTION

4.2 LOCAL BONDING OF THE DOPANTS

4.3 SYNTHESIS OF HETERODOPED NANOCARBONS

4.4 CHARACTERIZATION OF HETERODOPED NANOTUBES AND GRAPHENE

4.5 POTENTIAL APPLICATIONS

4.6 SUMMARY AND OUTLOOK

REFERENCES

PART II: CARBON NANOMATERIALS FOR ENERGY CONVERSION

5 HIGH-PERFORMANCE POLYMER SOLAR CELLS CONTAINING CARBON NANOMATERIALS

5.1 INTRODUCTION

5.2 CARBON NANOMATERIALS AS TRANSPARENT ELECTRODES

5.3 CARBON NANOMATERIALS AS CHARGE EXTRACTION LAYERS

5.4 CARBON NANOMATERIALS IN THE ACTIVE LAYER

5.5 CONCLUDING REMARKS

ACKNOWLEDGMENTS

REFERENCES

6 GRAPHENE FOR ENERGY SOLUTIONS AND ITS PRINTABLE APPLICATIONS

6.1 INTRODUCTION TO GRAPHENE

6.2 ENERGY HARVESTING FROM SOLAR CELLS

6.3 OPV DEVICES

6.4 LITHIUM-ION BATTERIES

6.5 SUPERCAPACITORS

6.6 GRAPHENE INKS

6.7 CONCLUSIONS

REFERENCES

7 QUANTUM DOT AND HETEROJUNCTION SOLAR CELLS CONTAINING CARBON NANOMATERIALS

7.1 INTRODUCTION

7.2 QD SOLAR CELLS CONTAINING CARBON NANOMATERIALS

7.3 CARBON NANOMATERIAL/SEMICONDUCTOR HETEROJUNCTION SOLAR CELLS

7.4 SUMMARY

REFERENCES

8 FUEL CELL CATALYSTS BASED ON CARBON NANOMATERIALS

8.1 INTRODUCTION

8.2 NANOCARBON-SUPPORTED CATALYSTS

8.3

INTERFACE INTERACTION BETWEEN Pt

CLUSTERS AND GRAPHITIC SURFACE

8.4

CARBON CATALYST

REFERENCES

PART III: CARBON NANOMATERIALS FOR ENERGY STORAGE

9 SUPERCAPACITORS BASED ON CARBON NANOMATERIALS

9.1 INTRODUCTION

9.2 SUPERCAPACITOR TECHNOLOGY AND PERFORMANCE

9.3 NANOPOROUS CARBON

9.4 GRAPHENE AND CARBON NANOTUBES

9.5 NANOSTRUCTURED CARBON COMPOSITES

9.6 OTHER COMPOSITES WITH CARBON NANOMATERIALS

9.7 CONCLUSIONS

REFERENCES

10 LITHIUM-ION BATTERIES BASED ON CARBON NANOMATERIALS

10.1 INTRODUCTION

10.2 IMPROVING LI-ION BATTERY ENERGY DENSITY

10.3 IMPROVEMENTS TO LITHIUM-ION BATTERIES USING CARBON NANOMATERIALS

10.4 CARBON NANOMATERIALS AS CONDUCTIVE ADDITIVES

10.5 SWCNT ADDITIVES TO INCREASE ENERGY DENSITY

10.6 CARBON NANOMATERIALS AS CURRENT COLLECTORS

10.7 IMPLEMENTATION OF CARBON NANOMATERIAL CURRENT COLLECTORS FOR STANDARD ELECTRODE COMPOSITES

10.8 IMPLEMENTATION OF CARBON NANOMATERIAL CURRENT COLLECTORS FOR ALLOYING ACTIVE MATERIALS

10.9 ULTRASONIC BONDING FOR POUCH CELL DEVELOPMENT

10.10 CONCLUSION

REFERENCES

11 LITHIUM/SULFUR BATTERIES BASED ON CARBON NANOMATERIALS

11.1 INTRODUCTION

11.2 FUNDAMENTALS OF LITHIUM/SULFUR CELLS

11.3 NANOSTRUCTURE CARBON–SULFUR

11.4 CARBON LAYER AS A POLYSULFIDE SEPARATOR

11.5 OPPORTUNITIES AND PERSPECTIVES

REFERENCES

12 LITHIUM–AIR BATTERIES BASED ON CARBON NANOMATERIALS

12.1 METAL–AIR BATTERIES

12.2 Li–AIR CHEMISTRY

12.3 CARBON NANOMATERIALS FOR LI–AIR CELLS CATHODE

12.4 AMORPHOUS CARBONS

12.5 GRAPHITIC CARBONS

12.6 CONCLUSIONS

REFERENCES

13 CARBON-BASED NANOMATERIALS FOR H2 STORAGE

13.1 INTRODUCTION

13.2 HYDROGEN STORAGE IN FULLERENES

13.3 HYDROGEN STORAGE IN CARBON NANOTUBES

13.4 HYDROGEN STORAGE IN GRAPHENE-BASED MATERIALS

13.5 CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

INDEX

END USER LICENSE AGREEMENT

List of Tables

Chapter 04

Table 4.1 First Reported Instances of Doped Nanocarbon Syntheses Found in the Literature

Table 4.2 First Reported Instances in the Literature of Characterizing Doped Nanocarbons with the Most Important Analytical Techniques

Chapter 06

Table 6.1 Comparison of Strengths and Drawbacks of Various ITO Replacement Technology Aspirants

Table 6.2 Comparison of Performance of CVD Graphene with Graphene Inks

Chapter 10

Table 10.1 Comparison of Carbon Nanomaterial-Based Anode Active Materials versus Conventional Ones

Table 10.2 Current Collector Options and Their Properties

Chapter 12

Table 12.1 Characteristics of Metal–Air Cells with Oxygen Cathode and Aqueous Electrolyte

Table 12.2 Physical Properties and Discharge Capacity of Several Carbon Nanomaterials

List of Illustrations

Chapter 01

Figure 1.1 (a) Fullerenes. (b) Fullerene derivatives: (i) C

60

derivative [6,6]-phenyl-C

61

-butyric acid methyl ester (PCBM) and (ii) trifluoromethyl derivative of C

84

([C

84

](CF

3

)

12

). (c) Higher-order fullerenes. (d) (i) Nanobud (fullerenes covalently bound to the outer sidewalls of single-walled carbon nanotube), (ii) peapod (fullerenes encapsulated inside a single-walled carbon nanotube), and (iii) nano-onion (multishelled fullerenes).

Figure 1.2 Flow diagram showing steps for fullerene synthesis via carbon soot formation and fullerene separation and purification.

Figure 1.3 Arc discharge process for fullerene synthesis.

Figure 1.4 Laser ablation process for fullerene synthesis.

Figure 1.5 UV–visible spectra of Pluronic modified C

60

and C

70

aqueous suspensions.

Figure 1.6 HRTEM of Pluronic modified (a) C

60

and (b) C

70

aqueous suspensions. Zoomed-in micrographs showing (c) C

60

and (d) C

70

crystalline features.

Figure 1.7 (a) Time-dependent aggregation profile of C

60

at different NaCl concentrations. (b) Stability plot for C

60

aqueous suspension at different NaCl concentrations.

Figure 1.8 (a) Total number of publications on fullerene and related materials on energy topics. Note: Others correspond to HOFs, derivatives, and hybrids. (b) Energy applications of fullerenes, HOFs, hybrids, and its derivatives.

Figure 1.9 Likely environmental fate, transport, transformation, and toxicity of fullerenes and related nanomaterials.

Figure 1.10 Structures of commonly used solvents for fullerene synthesis and processing.

Chapter 02

Figure 2.1 The 2D graphene sheet is shown along with the vector that specifies the chiral nanotubes. The chiral vector OA or C

h

 = 

na

1

+ ma

2

is defined on the honeycomb lattice by unit vectors

a

1

and

a

2

and chiral angle

θ

is defined with respect to the zigzag axis. Along the zigzag axis

θ

 = 0°. Also shown are lattice vector OB = 

T

of the 1D tubule unit cell, and the rotation angle

ψ

and the transition

τ

which constitute the basic symmetry operation

R

 = (

ψ

/

τ

). The diagram is constructed for (

n

,

m

) = (4, 2).

Figure 2.2 By rolling up a graphene sheet (a single layer of carbon atoms from a 3D graphite crystal) as a cylinder and capping each end of the cylinder with half of a fullerene molecule, a “fullerene-derived tubule,” one layer in thickness, is formed. Shown here is a schematic theoretical model for a single-wall carbon tubule with the tubule axis OB (see Fig. 2.1) normal to (a) the

θ

 = 30° direction (an “armchair” tubule), (b) the

θ

 = 0° direction (a “zigzag” tubule), and (c) a general direction B with 0 < 

θ

 < 30° (a “chiral” tubule). The actual tubules shown in the figure correspond to (

n

,

m

) values of: (a) (5, 5), (b) (9, 0), and (c) (10, 5).

Figure 2.3 Layout of CO flow-tube reactor, showing water-cooled injector and “showerhead” mixer.

Figure 2.4 Antenna-type remote plasma CVD.

Figure 2.5 SEM micrographs of vertically aligned SWCNT bundles grown on quartz surface with different magnifications, taken at 20° from the horizon. Fractured substrate edges were observed to study cross-sectional morphology. The inset shows the substrate without CVD (left) and that with CVD used for synthesis of vertically aligned SWCNT film (right); its upper left corner is blank because it was covered during the dip-coat process.

Figure 2.6 Typical characterizations of the as-grown densely packed and vertically aligned SWCNTs: (a) the cross-sectional FE-SEM morphology and (b) high-resolution TEM images; the inset shows an individual SWCNT with a diameter of about 2.8 nm.

Figure 2.7 Raman spectra along the height of a forest grown on a top Al

2

O

3

/Fe/bottom Al

2

O

3

sandwich catalytic substrate with a Ti layer on the top, with nanotube diameters estimated via

d

(

n

,

m

) = 248/

x

(cm

−1

) [69]. The upper inset is an SEM image of the forest. The colored circles on the forest show the measurement points of Raman spectroscopy. The lower inset is a magnified image of RBM (for Raman spectra shown in the red square). The laser excitation wavelength was 532 nm.

Figure 2.8 SWCNTs on miscut sapphire. Comparative analysis of representative samples with different miscut inclination and azimuth angles: (a)

θ

 = 3.4 ± 0.3°,

ϕ

 = 42 ± 5°; (b)

θ

 = 2.3 ± 0.2°,

ϕ

 = −33 ± 5°; (c)

θ

 = 2.1 ± 0.2°,

ϕ

 = 0 ± 5°; (d)

θ

 = 1.7 ± 0.1°,

ϕ

 = 18 ± 5°; (e)

θ

 = 0.4 ± 0.2°,

ϕ

 = −5 ± 5°; and (f)

θ

 = 0.3 ± 0.2°,

ϕ

 = −50 ± 5° (image sizes are 2.5 µm, except (e), 5 µm). The vectors indicate the relevant lattice directions and the step vector

s

(black) obtained from XRD (except in (e) and (f), where s is from AFM). Insets show AFM topographic images of the respective annealed samples (inset scale bars 100 nm) with macrosteps. In (f), the atomic steps are spaced enough to be observed and are decorated with inactive catalyst nanoparticles.

Figure 2.9 Environmental TEM images showing a growing MWCNT from a nanoparticle of (Fe, Mo)

23

C

6

. The arrow indicates the bend of the graphitic walls.

Figure 2.10 Resonant Raman scattering spectra of the as-grown SWCNT samples by thermal CVD at 800°C (A), and by Microwave-PCVD at 700°C (B), 600°C (C), and 500°C (D), respectively, by using the same batch of catalyst. The right panel is a magnified view of the low-frequency RBM region. The excitation laser line was 532 nm. The spectra in the left panel are normalized to the G-band at ca. 1593 cm

−1

, while the magnified RBM signals in the right panel are normalized to the strongest peak.

Figure 2.11 Typical Raman spectra (wavelength,

λ

excitation = 633 nm in panels (a–e)) from fibers obtained with (a) carbon disulfide and (b) thiophene as the sulfur precursors. (c) M, iTOLA, and (d) IFM regions in the Raman spectra of the carbon disulfide fibers. (e) The internal structure of the G band, with the Lorentzian G+ and the G− exhibiting the Fano line shape with fit parameters

I

0

,

ω

,

T

, and

q

 = 2256, 1556, 49.5, and −0.20, respectively. (f) RBM regions with a peak at 195 cm

−1

with

λ

 = 633 nm and the absence of the RBM peak with

λ

 = 514 nm. (g) RBM regions for

λ

 = 785 nm and 830 nm. (h) Kataura plot with mapping of the four wavelengths and the measured diameter range from high-resolution TEM. Black points represent families of metallic nanotubes while red and blue represent semiconducting nanotubes.

Figure 2.12 Contour plots of fluorescence spectra as a function of excitation wavelength and the resultant emission: (a) 850°C, (b) 750°C, (c) 650°C, and (d) HiPco.

Figure 2.13 SEM images of carbon nanotubes grown after annealing treatment of SiO

2

in Ar/H

2

for different time: (a) 1, (b) 5, and (c) 30 min.

Figure 2.14 Aligned carbon nanotube film on the SiC (0 0 0 −1) C-face formed by surface decomposition of SiC. (a) TEM micrographs taken from cross-sectional and plan-view directions (upper right). (b) A selected-area electron diffraction pattern obtained from the circled area shown in (a). (c) A schematic of the diffraction pattern shown in (b). The intensity distribution is classified into three types of reflections: solid circles—an SiC crystal (electron beam/[1 −1 0 2]

SiC

); small dots—horizontal plane of CNTs; and gray circles—vertical planes of CNTs.

Figure 2.15 Raman spectra from a metallic (top) and a semiconducting (bottom) SWCNT at the single nanotube level. The spectra show the radial breathing modes (RBM), D-band, G-band, and G′ band features, in addition to weak double resonance features associated with the M-band and the iTOLA second-order modes. The isolated carbon nanotubes are present on an oxidized silicon substrate that contributes to the Raman spectra denoted by “*.”

Figure 2.16 Superposition of SWCNT Raman spectra produced by CCVD method and ones synthesized by electric arc discharge, using an excitation wavelength of 676.4 nm. (a) Complete Raman spectrum, (b) detail of the RBM frequency range, and (c) detail of the TM frequency range.

Figure 2.17 UV–Vis–NIR spectrum of the soot synthesized at Ce concentration of 1.7 at.%, He 500 Torr, and arc-discharge current of 70 A and subsequently burned in the air at 533 K for 1 h. Inset shows the raw UV–Vis–NIR spectrum. Asterisk (*) indicates absorption peak due to the quartz substrate.

Figure 2.18 PLE contour map of (a) CoMoCAT-IL (ionic liquids) and (b) CoMoCAT-SDS versus excitation and emission wavelengths with corresponding chiral assignments.

Figure 2.19 (a) A model situation of STM tip and SWCNT. (b) A high-resolution SWCNT STM image and projection of ideal tube. (c) A low-resolution distorted STM image and correction of the inflation effect. (d) Average cross-section of scan line of SWCNT STM image and fitting of the equation for a phenomenological form of the tunneling current.

Figure 2.20 (a) HRTEM image of a chiral SWCNT with atomic resolution and (b) its corresponding optical diffraction (top) with profile of the equatorial line (solid line) and simulated result for solution (27, 17) (dot line) (bottom). (c) Reconstructed image and simulation image of SWCNT (27, 17) with tilting angle

β

 = 10°. (d) An armchair tube (17, 17).

β

 = 6°. (e) A zigzag tube (34, 0).

β

 = 4°. Scale bar is 2 nm.

Chapter 03

Figure 3.1 The 2D hexagonal nanosheets of graphene as a building block of other forms of carbon nanomaterials.

Figure 3.2 (a) The year-wise number of publication trends in graphene research showing exponentially increasing behavior [using SciFinder, American Chemical Society database, Search Date: June 19, 2013]. (b) Scalability versus cost and graphene quality trends for different synthesis techniques of graphene.

Figure 3.3 The classifications of the different graphene synthesis processes.

Figure 3.4 Schematic illustrating the quality of a graphene produced with a number of layers for the different synthesis processes.

Figure 3.5 (a and b) Scanning electron micrographs of mechanically exfoliated thin graphite layers from highly oriented pyrolytic graphite (HOPG) by AFM tip.

Figure 3.6 (a) Optical micrograph of a few layer graphene flake produced by scotch tape methods on top of a 300 nm thick thermal oxide coated Si substrate (Scale bar 50 µm) (b) A graphene layer of various thicknesses on SiO

2

/Si substrate (c) Optical micrograph shows the field effect transistor (FET) device fabricated using nano-patterning on mechanically exfoliated graphene on 300 nm thick SiO

2

/Si and (d) bright-field TEM image of suspended graphene (scale bar 500 nm)

Figure 3.7 (a and b) Mechanical exfoliation process by using tipless AFM cantilever. (c) Scanning electron micrograph (SEM) image showing the exfoliated graphene layers. (d) A mesoscopic graphite-based devise demonstrated out of the peeled-off graphene sheet.

Figure 3.8 (a) Schematic illustrating the mechanism of chemical exfoliation process by Viculis et al. [31]. (b) and (c) The SEM pictures of chemically exfoliated graphite nanoplatelets, which show ~10 nm thickness of ~30 layers of single graphite sheet.

Figure 3.9 Flow diagram of GIC-assisted exfoliation process of graphene.

Figure 3.10 Flow diagram of the graphene exfoliation process via horn sonication followed by ultracentrifugation. (b) Photograph showing 90 µg ml

−1

graphene dispersion in SC 6 weeks after it was prepared. (c) Schematic illustrating an ordered SC monolayer on graphene.

Figure 3.11 (a) SEM image of pristine graphite before sonication and (b) transmission electron microscopy of graphene flake prepared in

N

-methylpyrrolidone after the sonication process.

Figure 3.12 The process flow chart of graphene synthesis derived from graphene oxide.

Figure 3.13 (a) Mechanism proposed by Stankovich et al. on isocyanate-treated GO where organic isocyanates react with the hydroxyl (left oval) and carboxyl groups (right oval) of graphene oxide sheets to form carbamate and amide functionalities, respectively. (b) Representative FTIR spectra of GO and phenyl isocyanate-functionalized GO.

Figure 3.14 (a) Schematic showing the aqueous suspension of graphene fabrication mechanism via chemical technique. The process step consists of (1) graphite oxide production with greater interlayer distance, (2) sonication of GO in order to prepare mechanically exfoliated colloidal suspension of GO in water, and (3) conversion of GO to graphene using hydrazine reduction. (b) Representative data of zeta potential of GO and chemically converted graphene (CCG) as a function of pH. (c) Tapping mode atomic force micrograph of drop-casted CCG flakes on silicon wafer.

Figure 3.15 Schematic showing the 3D GO (carbon in gray, oxygen in red, and hydrogen in white) restoring its planar structure when reduced and dispersed with N

2

H

4

.

Figure 3.16 Schematic diagram illustrating the electrochemical process for graphene synthesis.

Figure 3.17 Schematic of (a) thermal CVD and (b) plasma-enhanced CVD (PECVD).

Figure 3.18 (a and b) Scanning electron micrograph of graphene syntheses on Ni(111) by DC discharge method.

Figure 3.19 (a) HRTEM image of graphene precipitated on Ni. (b) Raman spectra confirming the effect of cooling rate on graphene formation. (c) Schematic representing the mechanism of carbon segregation on Ni.

Figure 3.20 (a–c) Pictures illustrate HRTEM images of one to few layers of graphene grown on Ni using thermal CVD process. (d) Representative Raman plot for successive layers of graphene.

Figure 3.21 (a and b) Pictographic illustrations of the Cu foil before and after the thermal CVD process of graphene growth, respectively; (c and d) demonstrate the large scale (~16 cm diagonal length) and flexible graphene on PET, respectively; (e) the hot press lamination method of fabricating graphene-PET film.

Figure 3.22 (a) Large-scale CVD of graphene on Cu foil. (b) HRTEM images demonstrating the growth of 1-layer, 2-layer, and 3-layer graphene on Cu.

Figure 3.23 Schematic illustration of the mechanism of graphene synthesis via CVD on a dielectric substrate (a) deposition of very thin Cu film on dielectric substrate, (b) graphene growth using thermal CVD, (c) de-wetting of copper films, and (d) deposition of graphene on the dielectric substrate.

Figure 3.24 (a) Electron beam-scattered diffraction (EBSD) of a polycrystalline Cu foil showing different crystal planes of Cu. (b) Graphene on two Cu grains, Cu(310) and Cu(111). (c) Large-scale deposition of graphene on Cu using CVD process. (d and e) The 2.3 mm size of a single-crystal graphene grown on Cu foil using a CVD method. (f) The clear formation of grain boundaries at the junction between the two graphene grains, producing tilt boundaries.

Figure 3.25 (a) Color plot for the expected contrast as a function of SiO

2

thickness and wavelength. (b) Optical micrograph showing single- (1L), bi- (2L), and trilayer (3L) graphene on SiO

2

/Si substrate. (c) Schematic illustrating the mechanism of the Michelson contrast as per the equation. (d) Optical micrograph of CVD graphene on Cu showing graphene grain boundaries.

Figure 3.26 (a) Comparison Raman spectra of graphene and graphite. (b) Raman spectra of one to four layers of graphene on SiO

2

/Si (laser power ~532 nm). (c) Shift of 2D band of graphene with different numbers of layers (laser power ~532 nm). (d) Effect of substrates on the Raman spectrum of single-layer graphene (laser power ~532 nm). (e and f) Effect of laser power on the 2D peak position of single-layer graphene.

Figure 3.27 (a) TEM image showing a graphene flake. (b) The hexagonal honeycomb lattice of single-layer suspended graphene under HRTEM (scale bar 2 Å). (c) The clear step between single- and bilayer graphene. (d) The same HRTEM image of (c) marked with the two overlay layers (red line, bottom layer; blue line, top layer) of graphene (scale bar 2 Å). (e) HRTEM image of grain boundary of CVD graphene (scale bar 5 Å).

Figure 3.28 (a) AFM image of a mechanically exfoliated graphene (scale bar 1 µm). (b) AFM image illustrating the surface topography of graphene oxide flakes and the step height measurement profile of graphene flakes using AFM. (c) Atomic resolution scanning tunneling microscopy of graphene showing hexagonal close-packed lattice structure. (d–f) High-resolution STM images of epitaxial graphene on SiC and the coexistence of single-layer and bilayer domain with distinct domain boundaries.

Chapter 04

Figure 4.1 The number of publications yearly from 2002 to 2013 on nitrogen-doped carbon nanotubes (N-CNTs) in general, nitrogen-doped single-walled carbon nanotubes (N-SWCNTs) specifically, nitrogen-doped graphene (N-graphene), boron-doped CNTs (B-CNTs), boron-doped SWCNTs (B-SWCNTs), boron-doped graphene (B-graphene), and both phosphorus-doped nanotubes and graphene (P doped). The inset shows the few publications from the years 1993 to 2001.

Figure 4.2 Nitrogen dopant configurations in a model graphene unit cell marked by the dashed line: (a) substitutional (also called graphitic or quaternary), (b) triple pyridinic vacancy, (c) single pyridinic vacancy, (d) double pyridinic vacancy, and (e) quadruple pyridinic divacancy. Note that nitrogen substitutions on both 2nd [31] and 3rd [32] nearest neighboring sites have also been observed in graphene and that the boron simple substitution corresponds geometrically to (a). All structures are very closely planar.

Figure 4.3 Substitutions with atoms significantly larger than carbon, such as phosphorus, are expected to protrude from the graphene plane based on density functional theory calculations.Note that other more complex configurations, such as the P analogue of the triple pyridinic vacancy, have been proposed, again with expected significant out-of-plane character [39].

Figure 4.4 XPS spectra corresponding to N- and B-doped SWCNTs. The N 1

s

signal recorded from a sample of N-SWCNTs produced with benzylalmine is shown in (a). The line-shape analysis takes into account the presence of pyridinic and

sp

2

-like bonding environments. The dotted line represents the contribution to the spectral shape arising from the presence of catalytic material, which must be carefully considered in order to use XPS effectively for the characterization of doping levels and doping configurations. The nitrogen incorporation profile according to synthesis temperatures using the same methods is shown in (b). The

sp

2

, pyridine, and N volatile species that can be found in that specific kind of material are shown. The lower panels show the C 1

s

core signal corresponding to B-doped SWCNTs synthesized by arc discharge, compared to a scan corresponding to pristine material of similar characteristics. The incorporation of B in the lattice induces the formation of a shoulder at lower binding energy in the B-SWCNT sample. The spectrum shown in (d) corresponds to the B 1

s

signal recorded from a similar sample, where it is clear that in the best synthesis conditions, the stronger signals correspond to substitutional doping or elemental boron remaining from the synthesis process.

Figure 4.5 Longitudinal slices extracted at the same depth and orientation from shape-sensitive reconstructions of EELS energy-filtered images of an N-MWCNT, measured at the C–K edge for the carbon map and the N–K edge for the nitrogen map. The panels show the mean density (left), C and N 3D elemental maps (middle), and C-to-N 3D relative map (right). The relative map was obtained by superimposing the two elemental 3D maps with different colors, nitrogen in green and carbon in red. The presence of two types of arches (i.e., transverses and rounded ones), which is typical for the highly doped MWCNTs, can be observed.

Figure 4.6 STM/STS signatures of nitrogen doping. (Left) (a) SWCNTs labeled

A

and

B

, with

B

showing a defect in the scan area. The colored boxes in image (a) represent the points where the spectra in (e) were recorded. (b) (7 × 1.2 nm

2

) constant current image of the defect observed in image (a) at a bias voltage

V

s

 = −1.00 V

s

. (c) (7 × 1.2 nm

2

) constant current image of the defect observed in image (a) at

V

s

 = +1.00 V. (d) STM image shown in panel (c) corrected by a line-by-line flattening; the red dots indicate the periodicity of a superstructure “donut” pattern. (e) Tunneling spectra measured on the two tubes, with the colors of the lines corresponding to the positions of the colored boxes in (a). Note that the peak around 0.9 eV in the red curve corresponds to the donor state measured at the defect, while the peak at 0.6 eV in the blue curve corresponds to the first Van Hove singularity of the pristine tube A assigned with a (12,4) chirality. (Right) (a) STM image of a single substitutional N dopant in graphene on copper foil. Inset: Line profile across the dopant shows atomic corrugation and the apparent height of the site. (b) STM image of N-graphene showing 14 substitutional dopants and extended electronic perturbations due to intervalley scattering. Inset: Fast Fourier transform of the topography shows both atomic peaks (outer hexagon) and intervalley scattering peaks (inner hexagon). (c) dI/dV curves taken on a N atom (bottom) and on the bright topographic features near the N atom, offset vertically for clarity. The top curve was taken approximately 2 nm away from the dopant. Inset: positions where the spectra were taken.

Figure 4.7 Scanning transmission electron microscopy (STEM) imaging and electron energy loss spectroscopy (EELS) mapping of iron and nitrogen atoms in a doped carbon nanotube–graphene hybrid structure. (a) Bright-field and (b) annular dark-field (ADF) STEM images of a carbon nanotube partially covered with nanosized graphene pieces. The area marked by the white square in (b) was characterized by (c) EELS, (d) ADF intensity mapping, (e) nitrogen EELS mapping, (f) iron EELS mapping, and (g) an overlaid iron and nitrogen EELS map. In this system, iron atoms were frequently observed on the edges of graphene sheets close to nitrogen.

Figure 4.8 Shifts and splitting in the Raman G’ (2D) response have been proposed as a convenient signature of doping.

Figure 4.9 The effect of B or N doping on the transport properties of SWCNTs. (a) Conductance of a (10,10) SWCNT doped with a boron (left) or a nitrogen (right) substitution, as calculated using an ab initio pseudopontential method. Boron or nitrogen dopants produce quasibound impurity states of a definite parity, reducing the tube conductance by one quantum (2e

2

h) via resonant backscattering. (b) Quantum conductance of a single (10,10) nanotube containing 0.1% of randomly positioned boron (left) or nitrogen (right) impurities, calculated using a tight-binding model. The conductance is plotted as a function of energy for different device lengths, and a decrease is observed near the energies of dopant donor/acceptor states and near the Van Hove singularities.

Figure 4.10 The effect of B or N doping on the resistances of SWCNT films. (a) The sheet resistance and transmittance measured at 550 nm of undoped and B-doped SWCNT films, showing reduced resistance of the films upon doping. (b) The optoelectronic figures of merit (related to the inverse of sheet resistance) used to compare films with different transmittance for undoped and N-doped SWCNT films, showing a significant increase in resistance (68–86% decrease in the figure of merit) upon doping, even when the effect of decreased bundle lengths is taken into account.

Figure 4.11 The effect of B or N doping on the electronic structure of graphene. (Top) (a) On/off current and carrier mobility of B-graphene synthesized with various doping levels using a reactive trimethylboron microwave plasma treatment, as determined from measurements of 20 field-effect transistor (FET) devices. (b) Experimental band gaps and corresponding results from density functional theory calculation. Inset: The dependence of doping level (the position of the Fermi level from the Dirac point) on substitutional B content. (c) Calculated DOS of graphenes doped with different B content, with the Fermi level labeled by the dashed line. (Bottom) (a) Angle-resolved photoemission spectrum of N-graphene synthesized by CVD of molecular precursors (s-triazine) on a tungsten-supported 10 nm Ni film and annealed in high temperature after gold intercalation. The spectrum was measured at a photon energy of 35 eV, through the K-point and a few degrees off the direction perpendicular to ΓK direction in reciprocal space. (b) Photoemission spectrum at the K-point. (c) N 1

s

XPS spectrum of the sample, showing the predominance of graphitic nitrogen.

Chapter 05

Figure 5.1 Introduction to polymer solar cells. (a) Typical structure of a polymer solar cell device. (b) Chemical structures of a typical polymer electron donor (P3HT) and a typical organic electron acceptor (PC

61

BM). (c) Energy level diagram of a typical polymer solar cell device. (d) A typical current density–voltage curve of a polymer solar cell device under illumination.

Figure 5.2 Carbon nanomaterials used in every layer in polymer solar cell devices. Top: typical polymer solar cell device structure. Bottom: schematic of the structures of carbon nanomaterials, including CNT, graphene, and graphene oxide.

Figure 5.3 (a) Schematic drawing of multilayer graphene films made by normal wet transfer (A) and by LBL assembly (B) (

N

 = 0,1,2,3…). (b) Optical images of multilayer graphene films (from 1 to 8 layers) on quartz substrates. (c, d) Typical optical microscope images of 2- and 3-layer graphene films on SiO

2

/Si substrates. (e) Schematic of photovoltaic device structure. (f) Current density–voltage curves of the devices with the anode of ITO or MoO

3

-coated graphene (device structure: anode/PEDOT:PSS/P3HT:PCBM/LiF/Al).

Figure 5.4 Better wettability of PEDOT:PEG(PC) than PEDOT:PSS on the graphene surface. Optical microscopy images of PEDOT:PEG(PC) (a) and PEDOT:PSS (b) on graphene and bare quartz substrates. The white dotted lines indicate the edge of the graphene, and the arrows denote dewetted PEDOT:PSS. Contact angle images of graphene/PEDOT:PEG(PC) (c) and graphene/PEDOT:PSS (d). (e) Current density–voltage curves for the graphene-based PSC device and the ITO-based PSC device.

Figure 5.5 (a) Schematic illustration of G-CNT electrode. (b) A representative SEM image of a G-CNT film. (c) Current density–voltage curves of the device with a G-CNT film as the electrode in dark and under AM 1.5G illumination.

Figure 5.6 (a) UPS spectra of the rGO–SWCNT doped with various alkali carbonates. The work functions were determined from the UPS secondary electron cutoff. (b) Current density–voltage curves of the inverted P3HT:PCBM PSCs incorporating rGO–SWCNT doped with various alkali carbonates as the cathode.

Figure 5.7 (a) Schematic of the PSC device structure with GO as the hole extraction layer (ITO/GO/P3HT:PCBM/Al). (b) Energy level alignment in the PSC devices. (c) Current density–voltage characteristics of PSC devices with no hole extraction layer and with 30 nm PEDOT:PSS layer and 2 nm thick GO film. (d) Current density–voltage characteristics of ITO/GO/P3HT:PCBM/Al devices with different GO layer thickness under simulated AM 1.5 illumination.

Figure 5.8 (a) Chemical structures of the PTB7 donor, PC

71

BM acceptor, and GO. (b) Schematic of the PSC device indicating the location of the GO. (c) Representative current density–voltage plots under AM 1.5G solar simulated light for PSCs with PEDOT:PSS and GO as the hole extraction layer. (d) Thermal degradation of encapsulated devices at 80°C under a N

2

atmosphere. (e) Environmental degradation of unencapsulated devices fabricated with air-stable electrodes at 25°C under 80% relative humidity.

Figure 5.9 (a) Synthetic route to GO–OSO

3

H. Current density–voltage curves (b) and external quantum efficiency curves (c) of the PSC devices with PEDOT:PSS (25 nm), GO (2 nm), or GO–OSO

3

H (2 nm) as the hole extraction layer.

Figure 5.10 (a) Synthetic route from GO to GO–Cs. Device structure (b) and current density–voltage curve (c) of the normal device with GO as the hole extraction layer and GO–Cs as the electron extraction layer. Device structure (d) and current density–voltage curve (e) of the inverted device with GO as the hole extraction layer and GO–Cs as the electron extraction layer.

Figure 5.11 (a) Schematic of the device with P3OT/SPFGraphene thin film as the active layer. (b) Energy level diagram of P3OT and SPFGraphene. (c) Schematic representation of the reaction of phenyl isocyanate with graphene oxide to form SPFGraphene. (d) Current density–voltage curves of PSC devices based on P3OT/SPFGraphene composite with an SPFGraphene content of 5 wt% without or with thermal annealing at different conditions.

Figure 5.12 Schematic device structure (a) and energy diagram (b) of a PSC device with CNTs blended in the active layer. (c) Current density–voltage characteristics of the PSC devices without or with different CNTs.

Figure 5.13 (a) Schematic of a PSC device architecture with QD:N-CNTs blended in the active layer. (b) Chemical structure of P3HT donor and ICBA acceptor as well as schematic of QD:N-CNTs. (c) Current density–voltage characteristics of the devices with QD, N-CNT, and QD:N-CNT.

Figure 5.14 (a) Reaction scheme for grafting P3HT chains to carbon nanotubes. Device structure (b) and current density–voltage curves (c) of photovoltaic cells based on the P3HT, mixture of P3HT and MWCNTs (1%), and P3CNT under AM 1.5G illumination.

Figure 5.15 (a) Schematic representation of grafting C

60

onto graphene through lithiation reaction with

n

-butyllithium. (b) Schematic of a device with the C

60

-G:P3HT blend as the active layer. (c) Current density–voltage curves of the photovoltaic devices with the C

60

-G:P3HT, C

60

:P3HT, or C

60

/G mixture (12 wt% G):P3HT as the active layer.

Figure 5.16 (a) Schematic and synthetic route of P3HT-grafted graphene (G-P3HT). (b) Schematic of the bilayer device with the structure of ITO/PEDOT/C

60

:G-P3HT/Al. (c) Current density–voltage curves of the PSC devices with C

60

:P3HT or C

60

:G-P3HT as the active layer in dark and under AM 1.5G illumination.

Chapter 06

Figure 6.1 Schematic of an I–V chart.

Figure 6.2 General principle of operation of (a) a DSSC with redox couple in the liquid electrolyte. (b) a solid state DSSC with a p-type semiconductor.

Figure 6.3 Schematic diagram of GN-based DSSC.

Figure 6.4 Schematic description of the preparation of GNS/Pt-NHB-based CEs.

Figure 6.5 Enhanced transparency due to the addition of graphene nanoribbons in the electrolyte.

Figure 6.6 Schematic of a bulk heterojunction solar cell.

Figure 6.7 Incorporation of a graphene layer within an OPV cell.

Figure 6.8 Schematic of a lithium-ion battery.

Figure 6.9 Hollow, graphene-functionalized carbon spheres as anode materials.

Figure 6.10 Sn-decorated graphene sheets.

Figure 6.11 Graphene-functionalized VO

2

ribbons for high rate applications.

Figure 6.12 Broken egg conformation of graphene porous cathodes for enhanced Li

2

O

2

deposition.

Figure 6.13 PANI coating on graphene electrodes for supercapacitor applications.

Figure 6.14 Surface utilization with (a) parallel and (b) normally aligned graphene sheets.

Chapter 07

Figure 7.1 Device structure and band diagram of the tandem cell and the quantum funnel solar cells. (a) Device structure and band diagram of the tandem cell. The two junctions contain two layers of QDs of different sizes and a graded recombination layer (GRL) lies in between. (b) Device structure and band diagram of the quantum funnel solar cell. The quantum funnel is formed by the same QDs but in different sizes.

Figure 7.2 The device structure of the IR solar cell. (a) Al/PbS/PEDOT:PSS/graphene electrode. (b) TEM and HRTEM (inset) images of PbS QDs.

Figure 7.3 EQE and current density–voltage (

J–V

) characteristics of graphene electrode and ITO electrode solar cells. (a) EQEs of PbS solar cell based on graphene electrode and ITO electrode. The blue line represents the absorption of PbS QDs. The inset shows the

J–V

curves of two samples under AM 1.5 (100 mW/cm

2

). (b)

J–V

curves under 500 nm illumination (2.519 mW/cm

2

). (c)

J–V

curves under 1500 nm illumination (0.368 mW/cm

2

).

Figure 7.4 Photocurrent generation by CdSe–

n

C

60

clusters.

Figure 7.5 Illustration of the equilibrated band diagram for SWCNT/QD polymer solar cell.

Figure 7.6 Fabrication process of CdS/SWCNT/Si solar cells.

Figure 7.7 Fabrication process of layered graphene/CdS QDs on ITO/glass substrate.

Figure 7.8 The structure of colloidal GQDs containing (a) 1:168 carbon atoms, (b) 2:132 carbon atoms, and (c) 3:170 carbon atoms.

Figure 7.9 The structure of ZnO/GQD solid-state solar cell.

Figure 7.10 Energy band diagrams of carbon/semiconductor heterojunction. (a) p–n (semiconductor/semiconductor) junction. (b) Schottky (metal/semiconductor) junction.

Figure 7.11 (a) The structure of the a-C/n-Si heterojunction solar cell. (b)

J–V

characteristics of a-C/n-Si heterojunction solar cells in the dark and under simulated 15 mW/cm

2

light with wavelengths between 400 and 800 nm.

Figure 7.12 (a) Illustration of the fabrication process of DWCNT/n-Si solar cell. As-grown DWCNT films were conformally transferred to a patterned Si substrate. (b) Dark and light (100 mW/cm

2

illumination)

J–V

curves of a heterojunction solar cell, showing a PCE of 7.4%.

Figure 7.13 (a) Illustration of the solar cell structure based on a CNT/Si and infiltration of nitric acid into the CNT network to form photoelectrochemical units. (b)

J–V

curves of the solar cell before (black curve) and after (red) infiltration of dilute HNO

3

. (c) Illustration of the fabrication process of a TiO

2

/CNT/Si solar. (d)

J–V

curves of a CNT/Si cell recorded in original state (without coating), with a TiO

2

antireflection layer, and after HNO

3

/H

2

O

2

treatment, respectively.

Figure 7.14 (a) Preparation of the aligned CNT/Si solar cells. (b) Schematic showing the structure of the PV device. (c) Optical image showing aligned CNT/Si solar cell. (d)

J–V

curves of the aligned CNT/Si solar cell under AM 1.5 illumination and in the dark.

Figure 7.15 (a) Schematic illustration of a CdSe nanobelt covered by a CNT film. Arrows show the flow direction of charge carriers when the device is illuminated. (b)

J–V

curves recorded when the solar cell is illuminated from the front (CNT film) or back (CdSe nanobelt) sides, with PCE of 0.59 and 0.49%, respectively. (c) SEM image of a CdSe nanobelt transferred to an array of 8 CNTs in parallel. (d)

J–V

curves (75 mW/cm

2

) of the three solar cells containing 2, 6, and 8 CNTs.

Figure 7.16 (a) Schematic illustration of the PV device configuration. Bottom-left inset: photogenerated holes (h

+

) and electrons (e

−

) are driven into the graphene and Si, respectively. Bottom-right inset: photograph of a graphene/Si Schottky solar cell. (b)

J–V

curves of the 0.1 and 0.5 cm

2

solar cells illuminated with simulated AM 1.5.

Figure 7.17 (a) Schematics of graphene/planar Si and graphene/SiNW junctions. (b) Top-view SEM images of graphene/SiNW junction. (c) Reflection spectra of planar Si, SiNWs, graphene/Si, and graphene/SiNWs. (d) Schematic structure of the cross-sectional SPA substrate. (e) A top-view SEM microstructure of graphene film covering on one silicon pillar. (f)

J–V

curves of graphene/SPA solar cell in dark and under illumination.

Figure 7.18 (a) Approaches to achieving work function modulation of graphene. (b) Schematic structure of TFSA-doped graphene/Si Schottky solar cell. (c)

J–V

curves of graphene/Si (blue) and doped graphene/Si (red) Schottky solar cells in dark and after illumination. (d) Schematic illustration of the vapor-doping process. (e) Light

J–V

curves of the pristine and doped cells with increasing doping time.

Figure 7.19 (a) Schematic illustration of the spin-coating process in which a colloidal TiO

2

was applied to a graphene/Si cell as antireflection coating. (b) Light reflection spectra of a graphene/Si solar cell before (black) and after (red) coating the TiO

2

colloid. (c) Light

J–V

curves of graphene/Si solar cell, after HNO

3

doping and after TiO

2

coating, respectively.

Figure 7.20 (a) Schematic illustration of the graphene-based heterostructure device with the principal layers shown. (b) The external quantum efficiency of the devices is the ratio of the number of measured charge pairs to absorbed incident photons. (c) The MoS

2

/graphene solar cell. (d) Band alignment at a MoS

2

/graphene interface.

Chapter 08

Figure 8.1 Performance of 12 wt% Pt/CNT and 29 wt% Pt/CB electrodes. (a)

I–V

curves. (b) Power density–current density curves [2].

Figure 8.2 TEM images of PtRu/CNT catalysts. The loadings of Pt and Ru are 20 and 10 wt%, respectively.

Figure 8.3 (a) HAADF-STEM image of 20 wt% Pt/GNS catalyst. (b) The histogram of Pt subnanoclusters of Pt/GNS in a [3].

Figure 8.4 Pt amount on GNS (wt%) measured by TG/DTA versus calculated Pt amount on GNS (). The results for 20 and 40 wt% Pt/CB commercial catalysts are also shown () [11].

Figure 8.5 TEM images and histogram of 10, 15, 20 and 30 wt%Pt [11]. The mean size of Pt cluster is 0.87, 1.03, 1.20 and 1.85 nm, respectively.

Figure 8.6 Average Pt particle size (nm) estimated by TEM versus Pt amount on GNS (). The results for 20 and 40 wt% Pt/CB commercial catalysts () are also shown [11].

Figure 8.7 CO stripping voltammograms of 10–70 wt% Pt/GNS and 20 and 40 wt% Pt/CB commercial catalysts measured in 0.1 M HClO

4

at 60°C with the scan rate of 10 mV s

−1

[11].

Figure 8.8 Threshold voltages of CO electro-oxidation peak in CO stripping voltammogram as a function of Pt amount on GNS (wt%) (). The results for the 20 and 40 wt% Pt/CB commercial catalysts are also shown () [11].

Figure 8.9 Pt 4f

7/2

binding energy (eV) versus Pt amount on GNS (wt%) of 10–70 wt% Pt/GNS (). The results for the 20 and 40 wt% Pt/CB commercial catalysts are also shown () [11].

Figure 8.10 (a) Temperature dependence of the rate constant

k

m

for the H

2

−D

2

exchange reaction conducted on the Pt/HOPG surface with

θ

Pt

 = 0.1. The solid circles and triangles represent the results of the heating mode and those of the cooling mode, respectively (see text). The solid line corresponds to the slope of the cooling mode used for the estimation of the activation energy. (b) STM images (40 × 40 nm) of Pt/HOPG at

θ

Pt

 = 0.1 before and after the series of the H

2

−D

2

exchange reaction (active Pt and normal Pt, respectively). Tunneling current

I

t

and sample bias voltage

V

s

are 0.55 nA and −0.50 V for active Pt and 0.2 nA and −0.2 V for normal Pt, respectively. (c) Cluster height distribution of Pt clusters on HOPG observed by STM measurements as a function of the corresponding cluster diameter (diameter of cluster in top-view STM image) [12].

Figure 8.11 (a) Atomic-scale STM image (2 × 2 nm) of Pt/HOPG before the H

2

−D

2

exchange reaction.

I

t

and

V

s

are 0.58 nA and −0.50 V, respectively. (b) Schematic model of the Pt monolayer cluster on HOPG. Pt atoms are located on the β-site carbon. (c) XPS spectra of Pt/HOPG at

θ

Pt

 = 0.1 before and after the series of the H

2

−D

2

exchange reaction (active Pt and normal Pt, respectively). (d) Pt4f

7/2

peak position energy of the Pt/HOPG before and after the series of the H

2

−D

2

exchange reaction (active Pt and normal Pt, respectively) at various Pt coverages [12].

Figure 8.12 (a) Rate constant,

k

m

, for H

2

−D

2

exchange reaction on Pt/N-HOPG as a function of inverse temperature. The solid circles and triangles represent the results of the heating and cooling modes, respectively. (b) Height and size distributions of the protrusions, dips, or both in the STM images for Pt/N-HOPG after the reaction cycles [16].

Figure 8.13 Temperature programmed desorption of CO from Pt/HOPG with different Pt coverage (

θ

Pt

) [14]. The heating rate is 0.5 K s

−1

. (a) The results on the Pt/HOPG, where Pt atoms are dominantly deposited on the terrace of graphite. (b) The results on the Pt/HOPG, where Pt atoms are dominantly deposited on the step and defects of graphite (see text in detail).

Figure 8.14 ORR voltammogram of polyimide-derived catalyst [32]. ORR voltammogram of polyimide-derived catalyst (H22 and H24) and Pt/Carbon; temperature, RT; anode, 0.2 mg cm

−2

on glassy carbon; electrolyte, O

2

saturated H

2

SO

4

(0.5 M); rotation, 1500 rpm.

Figure 8.15 O1s photoelectron spectra of oxygen adsorbed on (a) A-NH

3

-900°C and (b) A-N

2

-900°C [33]. A-NH

3

-900°C and A-N

2

-900°C are the samples prepared from the activated carbon of “Anthraur” that were heated in NH

3

and N

2

atmosphere at 900°C followed by cooling in N

2

atmosphere, respectively. Each sample was exposed at 1000 L O

2

at ca. 78 K. The temperature was then raised stepwise to the indicated values.

Figure 8.16 Schematic of the graphitic-N and pyridinic-N in the carbon-based material.

Figure 8.17 N1s XPS spectra and STM images of nitrogen-doped graphite [37]. (a) N1s XPS spectra of graphite surface after nitrogen ion bombardment at 200 eV. The results before and after annealing at 900 ± 50 K for 300 s are shown. Deconvoluted components are pyridinic-N (398.5 eV; before, 32.6%; after, 31.4%), pyrrolic-N (399.9 eV; before, 17.4%; after, 7.6%), graphitic-N (401.1 eV; before, 40.1%; after, 54.3%), and oxide-N (403.2 eV; before, 9.8%; after, 6.8%). (b) Typical STM topographic image of the graphite surface at about 5.3 K (scan size: 49.45 × 46.97 nm

2

, tunneling current

I

t

 = 179 pA, sample bias

V

s

 = 98.8 mV). (c and d) STM topographic images of regions A and B in (b), respectively (in both case, scan size: 9.88 × 9.26 nm

2

,

I

t

 = 97.5 pA,

V

s

 = −109 mV).

Figure 8.18 STM and STS of pyridinic-N [37]. (a) STM topographic image of region A in Figure 8.19b (scan size: 4.81 × 4.61 nm

2

,

I

t

 = 96.9 pA,

V

s

 = −108 mV). The simulated STM image (

V

 = −0.1 V) is also shown for comparison. (b) STS spectrum measured at the position indicated by the arrow in (a). (c) The equilibrium geometry of pyridinic-N defect calculated by DFT. (d) Simulated STS spectrum of pyridinic-N.

Figure 8.19 STM and STS of graphitic-N [37]. (a) STM topographic image corresponding to the defect shown in region B in Figure 8.19b (image was taken from different sample, scan size: 5.09 × 5.08 nm

2

,

I

t

 = 39.0 pA,

V

s

 = 500 mV). The simulated STM image (V = +0.5 V) is also shown for comparison. (b) STS spectrum measured at the position indicated by the arrow in (a). (c) The equilibrium geometry of graphitic-N defect calculated by DFT. (d) Simulated STS spectrum of graphitic-N.

Chapter 09

Figure 9.1 Typical commercial supercapacitors cells (5000F, 2700F, 200F) at 2.5 V; AA size battery for comparison

Figure 9.2 Winding of two aluminum foils coated with carbon-based electrode films and thin paper as separator between electrodes extracted from a sample of commercial supercapacitor package

Figure 9.3 Cross section through carbon-based electrodes on both sides of aluminum foil substrate (Fig. 9.2); scale bar 500 µm

Figure 9.4 Typical SEM image at the porous carbon electrode surface from Figure 9.2; scale bar 2 µm

Figure 9.5 Typical SEM image of activated carbon particles from a commercial material sample

Figure 9.6 Discharge of a commercial supercapacitor cell on a load resistance of 0.5 Ω: (a) initially charged at about 2.5 V, 0.5 V/div, and 20 s/div and (b) initially charged at about 1 V, 0.15 V/div, and 10 s/div

Figure 9.7 Schematics of cycling current voltage characteristic (voltammogram) for a commercial supercapacitor cell for low voltage scan rate (pure electric double-layer charge storage)

Figure 9.8 Schematics of galvanostatic charging–discharging curve for a supercapacitor cell with a voltammogram shape as in Figure 9.7;

I

 × ESR is the voltage drop given by the internal equivalent series resistance (ESR).

Figure 9.9 Schematics of cyclic voltammogram for a supercapacitor with pseudocapacitance contribution (type I).

Figure 9.10 Schematics of galvanostatic charging–discharging curve for supercapacitor cell with voltammogram shape as in Figure 9.9 (type I).

Figure 9.11 Schematics of cyclic voltammogram for a supercapacitor with pseudocapacitance contribution (type II).

Figure 9.12 Schematics of galvanostatic charging–discharging curve for supercapacitor cell with voltammogram shape as in Figure 9.11 (type II).

Figure 9.13 Discharge of an experimental supercapacitor cell with pseudocapacitance contribution.

Chapter 10

Figure 10.1 Ragone plot showing power and energy capabilities for current Li-ion batteries.

Figure 10.2 (a) Schematic of the inside of a Li-ion battery. (b) Active material options for the cathode and anode as a function of voltage versus Li.

Figure 10.3 Voltage profiles of (a) cathode active materials and (b) anode active materials. Curves shown tested against Li foil at C/10 rate using 1.2M LiPF

6

EC:EMC (3:7 v/v).

Figure 10.4 Discharge voltage profiles of NCA cathode versus varying anode chemistries. Cells testing performed at a C/10 rate and with 1.2M LiPF

6

EC:EMC 3:7 in all cases.

Figure 10.5 Charge–discharge profile comparison of pure SWCNT and Si–SWCNT hybrid for use as an anode in lithium-ion battery.

Figure 10.6 Scanning electron microscopy images of LiNiCoAlO

2

composites with varying conductive additives. Representative images demonstrating the interaction between active particle and conductive additive are shown below SEM images.

Figure 10.7 Comparison of 4 mAh/cm

2

LiNiCoAlO

2

(NCA) cathode areal loadings with 4.0% w/w Super C65 (carbon black) and 2.0% w/w SWCNT additives at increasing discharge rates.

Figure 10.8 Images of 8 mAh/cm

2

composites with (a) 4% carbon black additive and (b) 1% SWCNT additive. (c) Cross section of 8 mAh/cm

2

composite and (d) SEM of NCA composite with 1% SWCNTs.

Figure 10.9 Comparison of 4 and 8 mAh/cm

2

NCA cathode areal loadings with 2% w/w SWCNT additives at increasing discharge rates.

Figure 10.10 (a) Electrode specific capacity for NCA coated onto Al or CNT as a function of areal loading and (b) electrode specific capacity for MCMB coated onto Cu or CNT as a function of areal loading.

Figure 10.11 (a) First cycle voltage profiles of MCMB active material coated onto Cu foil and Nanocomp CNT sheets, (b) second cycle voltage profiles of MCMB coated onto Cu and purified Nanocomp CNT sheets, (c) SEM images of an MCMB slurry coated onto a CNT current collector, and (d) SEM image showing CNTs bridging between the MCMB coating and the CNT current collector.

Figure 10.12 Voltage profiles of NCA coated onto Al and Nanocomp CNT paper with inset photograph of the NCA–CNT cathode.

Figure 10.13 (a) Si–CNT anode, (b) SEM image of bare CNT paper before CVD Si deposition, (c) Si–CNT anode after Si deposition, (d) Ge–SWCNT anode formed by e-beam deposition of Ge onto SWCNT paper, (e) SEM image of e-beam deposited Ge–SWCNT anode, and (f) Ge–NP–SWCNT hybrid anode.

Figure 10.14 (a) Photograph of copper tab extension and Si–CNT anode before ultrasonic bonding, (b) photograph ultrasonic bonder with a copper tab extension bonded to a Si–CNT anode, and (c) a flexed Si–CNT anode ultrasonically bonded copper tab extension.

Figure 10.15 Voltage profile of a pouch cell (inset photograph) with an NCA cathode paired with a free-standing Si–CNT anode.

Figure 10.16 (a) Gravimetric energy density predictions and (b) volumetric energy density predictions for the improvements that can be achieved by using Si active material, CNT current collectors, or both.

Chapter 11

Figure 11.1 Comparison of theoretical specific energy and energy density of the lithium/sulfur cell with those of current lithium-ion cells.

Figure 11.2 Introduction to the Li/S cell. (a) Schematic diagram of common configurations of lithium/sulfur cells. (b) The voltage profile and chemistry of sulfur cathode in the organic electrolyte.

Figure 11.3 (a) A schematic diagram of the sulfur (gray) confined in the interconnected pore structure of mesoporous carbon (black), CMK-3, formed from carbon tubes that are propped apart by carbon nanofibers. (b) Schematic diagram of composite synthesis by impregnation of molten sulfur, followed by its densification on crystallization. The lower diagram represents subsequent discharging–charging with Li, illustrating the strategy of pore filling to tune for volume expansion/contraction.

Figure 11.4 Illustration of the different lithiation mechanisms of sulfur confined in mesopores and micropores.

Figure 11.5 SEM images of a porous CNF–S nanocomposite electrode before (a) and after (b) 30 charge–discharge cycles at a constant rate of 0.05C.

Figure 11.6 (a) Cycling performance of GO–S electrodes. (b) Representative drawing of GO immobilizing sulfur. Yellow, red, and white balls represent S, O, and H atoms, while others are C atoms. (c) C K-edge XAS spectra of GO and GO–S nanocomposites after heat treatment.

Figure 11.7 (a) Schematic of the S−GO nanocomposite structure. The presence of CTAB on the S−GO surface was confirmed by Fourier transform infrared spectroscopy (FTIR) and shown to be critical for achieving improved cycling performance by minimizing the loss of sulfur. (b) Enlarged view of Raman spectra on CTAB, synthesized sulfur, and CTAB-modified sulfur from 500 to 1000 cm

−1

. It clearly shows the formation of a new peak, which can be assigned as a C–S bond (600–700 cm

–1

), confirming that there is strong interaction between CTAB and sulfur. (c) Voltage profiles of CTAB-modified S−GO composite cathodes at different rates. (d) Long-term cycling test results of the Li/S cell with CTAB-modified S−GO composite cathodes. This result represents the longest cycle life (exceeding 1500 cycles) with an extremely low decay rate (0.039% per cycle) demonstrated so far for a Li/S cell. The S−GO composite contained 80% S, and elastomeric SBR/CMC binder was used. 1 M LiTFSI in PYR

14

TFSI/DOL/DME mixture (2:1:1 by volume) with 0.1 M LiNO

3

was used as the electrolyte (total 60 µl).

Figure 11.8 (a) A model and the structure of the S/CNT cathode. (b) Stress–strain curve of a flexible S/CNT membrane cathode. Inset shows a bent S/CNT membrane.

Figure 11.9 (a) Schematic configuration of a Li/S cell with a bifunctional microporous carbon interlayer inserted between the sulfur cathode and the separator. (b) Cycle life and coulombic efficiency of the cell with MCP at 1C and 2C for long cycles.

Chapter 12

Figure 12.1 Scheme of a metal–air cell.

Figure 12.2 Scheme of a lithium–air cell with aqueous electrolyte.

Figure 12.3 Scheme of a lithium–air cell with nonaqueous aprotic electrolyte.

Figure 12.4 Scheme of a lithium–air cell with mixed aqueous/aprotic electrolyte.

Figure 12.5 Scheme of an all solid-state lithium–air cell.

Figure 12.6 SEM micrographs of the cathode films with (a) 80:20 and (b) 20:80 carbon–Kynar ratio, respectively.

Figure 12.7 (a) Discharge characteristics of the HCC-400 and HCC-100 electrodes at various current densities of (A) 0.05 mA cm

−2

, (B) 0.2 mA cm

−2

, and (C) 0.5 mA cm

−2

. (b) FESEM micrograph of HCC-100 carbon.

Figure 12.8 SEM images of as-prepared CS-CNT-based cathodes (a and b) before and (c–e) after discharge.

Figure 12.9 Heat-treated CNTs after discharge.

Figure 12.10 Structure of the rechargeable Li–air battery based on GNS as an air electrode.

Figure 12.11 SEM (a) and TEM (b) images of GNS electrodes.

Figure 12.12 SEM images of (a and b) pristine electrodes, (c–e) electrodes discharged to 2 V in triglyme–LiTFSI (1 M) electrolyte solution, and (f) electrodes charged to 4.3 V in triglyme–LiTFSI (1 M) electrolyte solution.

Figure 12.13 Three-dimensional continuous passage of electrons, ions, and oxygen. Electrons conduct along the carbon nanotubes. Lithium ions transferred from the ionic liquid electrolyte outside into the cross-linked network gel become coordinated by the inside-anchored [NTf2] ion. Oxygen in the cross-linked network incorporates with the lithium ions and electrons along the CNTs, thereby turning into the discharge products.

Chapter 13

Figure 13.1 (a) C

60

[ScH

2

(H

2

)

4

]

12

, (b) C

48

B

12

[ScH(H

2

)

5

]

12

, (c) Cp[ScH

2

]chain, and (d) [ScH

3

]

3

(left) and ScH

3

(H

2

)

6

(right).

Figure 13.2 Two configurations of Ti

12

C

60

: (a) 12 individual Ti atoms are located above 12 pentagons, (b) a cluster of 12 Ti atoms is attached to C

60

.

Figure 13.3 Adsorption of hydrogen molecules on alkali metal-doped fullerenes. (a) C

60

Li(H

2

)

2

, (b) C

60

Na(H

2

)

6

, (c) C

60

K(H

2

)

6

, and (d) C

60

Na

2

(H

2

)

12

.

Figure 13.4 Na-coated fullerene C

60

Na

12

.

Figure 13.5 Schematic of TM-decorated C

24

N

24

for hydrogen storage.

Figure 13.6 Two high-density hydrogen coverages on a Ti-coated (8,0) nanotube. (a) and (b) have different Ti modification ratios.

Figure 13.7 Schematic plots for the storage material: (a) the Li-dispersed carbon nanotube with Li:C (1:8), (b) the relaxed (H

2

)

64

/Li

8

/C

64

system.

Figure 13.8 (a) Isolated and (b) clustered configurations of the Ca

6

/GNT complexes.

Figure 13.9 The optimized structures of (a) CNT–5(BH

3

 + 4H

2

) and (b) CNT–10(BH

3

 + 4H

2

).

Figure 13.10 (a) The design for a nanocontainer with the cap and the ball (C

60

) together serving as a molecular valve that traps the hydrogen after the release of the external pressure; (b) the side view of the atomistic model of a nanocontainer, in which two C

60

molecules are attached to a (20,0) SWCNT.

Figure 13.11 The structure of Ti-GO fully loaded with H

2

. It has a 2 × 2 Ti periodicity, and the O−O separation on the same side is d

O−O

 = 5.1 Å.

Figure 13.12 Schematic diagram of the GO–LiAB system used for chemical.

Figure 13.13 The optimized atomic structure of (a) atomic Ca in CBG(3) with four H

2

molecules adsorbed [Ca(H

2

)

4

 + CBG(3)] and (b) Ca chain in CBG(3) with six H

2

molecules adsorbed in total [Ca(H

2

)

4

 + Ca(H

2

)

2

 + CBG(3)].

Figure 13.14 (a) Snapshot from the GCMC simulations of pure pillared structure at 77 K and 3 bar; (b) snapshot from the GCMC simulations of lithium-doped pillared structure at 77 K and 3 bar. Hydrogen molecules are represented in green, while lithium atoms are in purple.

Figure 13.15 Representations of (a) boronic ester and (b) GOF formation. Idealized graphene oxide framework (GOF) materials proposed in this study are formed from layers of graphene oxide connected by benzenediboronic acid pillars.

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