Functional Nanomaterials E-Book
169,99 €
Mehr erfahren.
- Herausgeber: Wiley-VCH GmbH
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Functional Nanomaterials
Presents the most recent advances in the production and applications of various functional nanomaterials
As new synthetic methods, characterization technologies, and nanomaterials (NMs) with novel physical and chemical properties are developed, researchers and scientists across disciplines need to keep pace with advancements in the dynamic field. Functional Nanomaterials: Synthesis, Properties, and Applications provides comprehensive coverage of fundamental concepts, synthetic methods, characterization technologies, device fabrication, performance evaluation, and both current and emerging applications.
Contributions from leading scientists in academia and industry present research developments of novel functional nanomaterials including metal nanoparticles, two-dimensional nanomaterials, perovskite-based nanomaterials, and polymer-based nanomaterials and nanocomposites. Topics include metal-based nanomaterials for electrochemical water splitting, cerium-based nanostructure materials for electrocatalysis, applications of rare earth luminescent nanomaterials, metal complex nanosheets, and methods for synthesizing polymer nanocomposites.
- Provides readers with timely and accurate information on the development of functional nanomaterials in nanoscience and nanotechnology
- Presents a critical perspective of the design strategy, synthesis, and characterization of advanced functional nanomaterials
- Focuses on recent research developments in emerging areas with emphasis on fundamental concepts and applications
- Explores functional nanomaterials for applications in areas such as electrocatalysis, bioengineering, optoelectronics, and electrochemistry
- Covers a diverse range of nanomaterials, including carbonaceous nanomaterials, metal-based nanomaterials, transition metal dichalcogenides-based nanomaterials, semiconducting molecules, and magnetic nanoparticles
Functional Nanomaterials is an invaluable resource for chemists, materials scientists, electronics engineers, bioengineers, and others in the scientific community working with nanomaterials in the fields of energy, electronics, and biomedicine.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 1035
Veröffentlichungsjahr: 2022
Ähnliche
Table of Contents
Cover
Title Page
Copyright
Preface
About the Editor
1 Earth‐Abundant Metal‐Based Nanomaterials for Electrochemical Water Splitting
1.1 Electrochemical Water Splitting
1.2 Earth‐Abundant Metallic Nanomaterials
1.3 Computer‐Assisted Materials Discovery
1.4 Challenge and Outlook
References
2 Studies on Cerium‐Based Nanostructured Materials for Electrocatalysis
2.1 Introduction
2.2 Cerium‐Based Nanostructure Materials
2.3 Cerium‐Based Electrocatalysts for HER
2.4 Cerium‐Based Electrocatalysts for OER
2.5 Cerium‐Based Electrocatalysts for ORR
2.6 Cerium‐Based Electrocatalysts for Other Electrochemical Reactions
2.7 Conclusions and Outlooks
Acknowledgment
References
3 Metal‐Free Carbon‐Based Nanomaterials: Fuel Cell Applications as Electrocatalysts
3.1 Introduction
3.2 Heteroatom‐Doped Carbon Nanomaterials
3.3 Undoped Carbon Nanomaterials
3.4 Carbon‐Based Organic Framework
3.5 Application in Fuel Cells
3.6 Conclusion
References
4 Rare Earth Luminescent Nanomaterials and Their Applications
4.1 Introduction
4.2 Rare Earth Based UCNPs
4.3 Rare Earth Based DCNPs
4.4 Summary and Outlook
References
5 Metal Complex Nanosheets: Preparation, Property, and Application
5.1 Introduction
5.2 Preparation of Metal Complex Nanosheets
5.3 Properties of Metal Complex Nanosheets
5.4 Outlook on Metal Complex Nanosheets
References
6 Synthesis, Properties, and Applications of Metal Halide Perovskite‐Based Nanomaterials
6.1 Introduction
6.2 Properties of Metal Halide Perovskite Materials
6.3 Synthesis of Metal Halide Perovskite‐Based Nanomaterials
6.4 Application of Metal Halide Perovskite‐Based Nanomaterials
References
7 Progress in Piezo‐Phototronic Effect on 2D Nanomaterial‐Based Heterostructure Photodetectors
7.1 Introduction
7.2 Piezo‐Phototronic Effect on the Junctions
7.3 Piezo‐Phototronic Effect on the Performance of P–N Junction Photodetectors
7.4 Conclusion and Future Perspectives
Acknowledgments
References
8 Synthesis and Properties of Conducting Polymer Nanomaterials
8.1 Introduction
8.2 Synthesis and Properties
8.3 Summary
References
9 Conducting Polymer Nanomaterials for Electrochemical Energy Storage and Electrocatalysis
9.1 Introduction
9.2 Electrode Materials of Batteries
9.3 Electrocatalysis
9.4 Supercapacitors
9.5 Summary and Perspective
References
10 Conducting Polymer Nanomaterials for Bioengineering Applications
10.1 Introduction
10.2 Electronic Skin
10.3 Bioengineering
10.4 Chemical Sensors and Biosensors
10.5 Summary and Perspective
References
11 Methods for Synthesizing Polymer Nanocomposites and Their Applications
11.1 Factors for Synthesizing Polymer Nanocomposites
11.2 Solution Mixing
11.3 Emulsion Polymerization
11.4 Dispersion Polymerization and Dispersion Copolymerization
11.5 Self‐Assembly
11.6 Melting
11.7
In situ
Polymerization
11.8 Tailoring of Polymers Nanocomposite
11.9 Application of Polymer Nanocomposites
11.10 Outlook
List of Abbreviations
References
12 Spin‐Related Electrode Reactions in Nanomaterials
12.1 Introduction
12.2 Factors Influencing the Electrochemical System
12.3 Spin‐Related Electrode Reactions
12.4 Conclusion and Outlook
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Selected earth‐abundant metal single‐atom electrocatalyst for HER....
Chapter 2
Table 2.1 Summarized overpotentials and Tafel slopes for the HER performance...
Table 2.2 Summarized overpotentials and Tafel slopes for the OER performance...
Chapter 4
Table 4.1 Typical synthetic methods to lanthanide‐doped upconversion nanocry...
Chapter 6
Table 6.1 The ionic radius of ion used in ABX
3
perovskite.
Chapter 7
Table 7.1 Parameters used for photodetector performance evaluation.
Table 7.2 Piezo‐phototronic effect enhanced performance of heterostructure p...
Chapter 11
Table 11.1 The condition for preparing of PMPC‐
b
‐PDMA‐bPHPMA
z
by RAFT aqueou...
Chapter 12
Table 12.1 Typical forces acting in aqueous electrolytes.
List of Illustrations
Chapter 1
Figure 1.1 Simplified illustration of an electrolyzer for water splitting dr...
Figure 1.2 Pourbaix diagram (pH potential) of water under standard temperatu...
Figure 1.3 Earth‐abundant metals that are currently used for water electroly...
Figure 1.4 HER volcano plots with measured exchange current density of polyc...
Figure 1.5 Illustration of various forms of metallic electrocatalysts, from ...
Figure 1.6 (a) Model of metal atoms supported on graphene via metal–carbon c...
Figure 1.7 (a) Alkaline HER mechanism on Co–N SAC. Inset shows the electron ...
Figure 1.8 HER volcano plot of TMPs showing the average H
2
turnover frequenc...
Figure 1.9 Mechanism of OER: (a) adsorbate evolution mechanism and (b) latti...
Figure 1.10 (a) Linear scaling relation of
M
–OOH and
M
–OH Gibbs free energy ...
Figure 1.11 Experimental OER activity vs. turnover frequencies (TOF, O
2
gene...
Figure 1.12 (a) Comparison of the OER activity of bulk NiO
x
and Ni(OH)
2
with...
Figure 1.13 Perspective and top views of M‐doped NiOOH (001) surface: (a) cl...
Figure 1.14 Precatalytic conversion of ZIF‐67 to α/β‐Co(OH)
2
and the experim...
Figure 1.15 Computational high‐throughput screening of HER catalyst for Δ
G
H
...
Chapter 2
Figure 2.1 (a) Atomic configurations of the unit cell and the (100), (110), ...
Figure 2.2 (a) Calculated free energy diagram for HER on different facets of...
Figure 2.3 (a) Top view of Pd
4
@CeO
2
model and the possible adsorption sites ...
Figure 2.4 (a) Scanning electron microscopy (SEM) images of Ni–CeO
2
/TM.(...
Figure 2.5 (a) Schematic illustration of the selective phosphidation in the ...
Figure 2.6 (a) Representation of the theoretical overpotential as a function...
Figure 2.7 (a) TEM and (b) Scanning transmission electron microscopy (STEM) ...
Figure 2.8 (a) Diagrams of CeO
2
‐embedded NiO (Ce–NiO–E) (up) and CeO
2
‐surfac...
Figure 2.9 (a) Three‐dimensional view of the PtCe alloy during sputter‐clean...
Figure 2.10 (a) Schematic illustration of the resulting Cu–Ce–O oxide. (b) C...
Figure 2.11 (a) Schematic illustration of the reaction mechanism during cycl...
Figure 2.12 (a) Schematic illustration for the electrochemical NRR by cataly...
Figure 2.13 Geometric partial current density (a) and Faradaic efficiency (b...
Chapter 3
Figure 3.1 Schematic structure of nitrogen‐doped graphene.
Figure 3.2 Important molecular orbitals involved in the O
2
adsorption on BCN...
Figure 3.3 (a) LSV curves of various electrodes in O
2
‐saturated 0.1 M KOH el...
Figure 3.4 (a) Bonded B and N co‐doped CNT(5,5). (b) HOMO plot of the corres...
Figure 3.5 Typical cyclic voltammograms (CVs) (a) and LSVs (b) for the ORR o...
Figure 3.6 (a) Rotating ring‐disk electrode (RRDE) voltammograms for the ORR...
Figure 3.7 (a) XPS spectra of the original graphene film (red) and the as‐pr...
Figure 3.8 High‐resolution (a) XPS C 1s and (b) XPS B 1s of BCN graphene in ...
Figure 3.9 (a) LSVs of different samples at 1600 rpm. (b) Spin and charge de...
Scheme 3.1 Schematic representation of nitrogen bonding configurations in N‐...
Scheme 3.2 A schematic representation of the ball‐milling process.
Scheme 3.3 A schematic representation for mechanochemically driven edge‐halo...
Figure 3.10 The optimized O
2
adsorption geometries onto XGnPs, in which halo...
Figure 3.11 (a) LSVs of PAMTa/rGO, N‐S‐G 600, N‐S‐G 700, N‐S‐G 850, N‐S‐G 10...
Figure 3.12 The disk current density obtained from the LSV testing on electr...
Figure 3.13 (a) LSV curves of the ORR on SG and graphene in an O
2
‐saturated ...
Figure 3.14 FESEM and EDS elemental mapping images of the prepared N 550‐GD ...
Figure 3.15 LSV curves for GD, N‐doped GD, and Pt/C on an RDE in O
2
‐saturate...
Scheme 3.4 Fabrication and formation mechanism of the 3D hierarchically poro...
Scheme 3.5 Schematic illustration of the synthesis of ND‐GLC.
Scheme 3.6 Illustrated procedure of fabricating N‐doped fullerene‐like carbo...
Scheme 3.7 Schematic representation of the synthesis of hierarchically porou...
Scheme 3.8 Illustration of self‐assembly of colloidal silica with PANI and t...
Scheme 3.9 Schematic illustration of the synthesis of NCNR using melamine fi...
Scheme 3.10 Schematic illustration of the formation process of bowl‐like mes...
Figure 3.16 Microscopy characterizations of bowl‐like mesoporous carbon part...
Scheme 3.11 (a) Structure of PA template and schematic for the synthesis of ...
Figure 3.17 (a, b) Typical HRTEM images of ordered mesoporous g‐C
3
N
4
@CMK‐3 n...
Scheme 3.12 Schematic illustration of Se‐CNT–graphene preparation.
Figure 3.18 (a) Schematic illustration of the process for co‐assembling carb...
Scheme 3.13 Synthesis of NDCN‐X. (a) CTAB‐directed hydrolysis of TEOS on GO ...
Figure 3.19 (a and c) The high‐resolution XPS spectra of NSCA: (a) S 2p and ...
Scheme 3.14 Schematic synthesis of a NC‐1 : 1 : 10 catalyst.
Figure 3.20 (a) Micro‐apparatus for the ORR electrochemical experiment. (b) ...
Figure 3.21 (a) RRDE experiments with pristine graphite and graphite ball‐mi...
Scheme 3.15 Illustration of the preparation of the edge‐rich and dopant‐free...
Figure 3.22 Pictorial representation of G585 defects in graphene.
Figure 3.23 Perfect and defective graphene clusters. (a) Perfect graphene cl...
Scheme 3.16 Schematic illustration of the preparation of the CSs.
Scheme 3.17 Condensation reaction of 3,6‐dicyanocarbazole to a discrete trim...
Scheme 3.18 Synthetic scheme toward fabrication of two redox active and semi...
Scheme 3.19 Schematic representation of the synthesis of NDI‐COF.
Figure 3.24 Schematic of zinc–air fuel cell.
Scheme 3.20 Synthesis of the CNT/HDC core–sheath nanostructures.
Figure 3.25 Performance of MEAs that employ CNT/HDC‐1000, CNTs, or Pt/C as t...
Scheme 3.21 Schematic illustration. The synthetic route of zigzag‐type graph...
Figure 3.26 Proton exchange membrane fuel cell evaluation. Polarization and ...
Figure 3.27 (a) Potential applications of the defective graphene as cathodic...
Figure 3.28 (a) Polarization curves and power density plots and (b) discharg...
Scheme 3.22 (a) Chemical structures of P‐Ph, P‐Se, and P‐T linear conjugated...
Scheme 3.23 Syntheses and structures of JUC‐527 and JUC‐528.
Figure 3.29 (a) LSV (at 1600 rpm) curves of PDA‐TAPB‐COF, JUC‐527, and JUC‐5...
Chapter 4
Figure 4.1 TEM image of cubic NaYF
4
:Yb/Er UCNPs (a) and photographs of the U...
Figure 4.2 Principal UC mechanisms of lanthanide‐doped materials.
Figure 4.3 Typical TEM images of lanthanide‐doped (a) LaF
3.
(b–d) NaYF
4
n...
Figure 4.4 Typical instrumentation tools used for the characterization of UC...
Figure 4.5 X‐ray powder diffraction patterns of the NaYF
4
:Yb/Er (18/2 mol%) ...
Figure 4.6 SEM images of different morphologies of NaYF
4
:Yb,Er: (a) elongate...
Figure 4.7 (a–c) TEM images of NaYF
4
:Yb
3+
/Er
3+
(15%/2%) core NCs (
t
...
Figure 4.8 Upconversion emission spectra of (a) NaYF
4
:Yb/Er (18/2 mol%), (b)...
Figure 4.9 (a) Principal concept of the dye‐sensitized nanoparticle.(b) ...
Figure 4.10 Tuning upconversion through energy migration in core–shell nanop...
Figure 4.11 The structure (a) and energy transfer mechanisms (b), TEM (c), H...
Figure 4.12 (a, b) UC emission of NaGdF
4
:Yb
3+
/Tm
3+
nanoparticles wit...
Figure 4.13 (a) PL and PLE spectra of the CD solution. (b) UV–vis absorption...
Figure 4.14 (a) Simplified energy‐level scheme of LiYbF
4
:0.5%Tm
3+
@LiYF
4
...
Figure 4.15 (a) Temporal multicolor tuning in NaYF
4
‐based core–shell nanocry...
Figure 4.16 (a) Multicolor UCL imaging of three UCNPs solutions and a nude m...
Figure 4.17 (a) A schematic illustration of KillerRed‐UCNPs assembly and the...
Figure 4.18 Rational design of polymer–UCNPs hybrid scaffolds for optogeneti...
Figure 4.19 (a) The intensity ratio of green upconversion emission bands fro...
Figure 4.20 (a) Mechanism of near‐infrared‐activated photocatalysis. (ET: en...
Figure 4.21 (a) Scheme illustrating the ring‐opening and release reactions o...
Figure 4.22 (a) Pattern image identification with a portable apparatus consi...
Figure 4.23 TEM images of (a) YAG precursor, (b) YAG obtained after heating ...
Figure 4.24 (a) Excitation and (b) emission spectra of nano‐YAG:0.06 Ce and ...
Figure 4.25 Transmission electron microscopy images of nano‐YAG:Tb particles...
Figure 4.26 (a) TEM images of YAG:Ce
3+
(1%) NPs prepared using the solvot...
Figure 4.27 SEM images of hydrothermal sheet products under different magnif...
Figure 4.28 SEM images of the samples prepared with different precipitating ...
Figure 4.29 SEM images of strontium aluminate fiber before (a) and after (b)...
Figure 4.30 FE‐SEM of the as‐prepared precursor (upside) and calcined Y
2
O
3
(...
Figure 4.31 Schematic illustration of the formation on process of Y
2
O
3
:Eu ho...
Figure 4.32 Schematic diagram showing the formation and self‐assembly proces...
Figure 4.33 SEM images of YVO
4
crystals prepared under different reaction me...
Figure 4.34 Fluorescence photos of (Ln,P)Y‐VO
4
nanoparticles in glass slides...
Figure 4.35 TEM and HRTEM images (inset) of the LaPO
4
:Ce,Tb. (a) Nanopolyhed...
Figure 4.36 Fluorescence images of HeLa cells incubated with Bi20YPAA2 nanop...
Figure 4.37 (a) The thermal images of H
2
O, NdVO
4
, NdVO
4
+ Au and NdVO
4
/Au (3...
Figure 4.38 (a) Anti‐counterfeiting patterns consisting of (a) the letter sy...
Figure 4.39 (a) Schematic diagram of a smartphone with a QR code scanning ap...
Chapter 5
Figure 5.1 Fully reticulated nanoporous Fe‐diterephthalate grid assembled on...
Figure 5.2 (a, b) Projections of [Fe(acac
2
‐trien)][MnCr(Br
2
‐An)
3
]⋅(CH
3
CN)
2
i...
Figure 5.3 (a) Crystal‐phase structure of the MOF studied herein: detail vie...
Figure 5.4 (a) Schematic illustration of the overall process developed to pr...
Figure 5.5 (a) Chemical structures of the three‐way dipyrrin ligand molecule...
Figure 5.6 (a) Molecular structures of H
2
TCPP. (b, c) Structure of NAFS‐2. (...
Figure 5.7 (a) Chemical structure of the terpyridine ligand molecule and sch...
Figure 5.8 (a) Chemical structure and redox reactions associated with counte...
Figure 5.9 (a) Color change in the Fe‐terpyridine nanosheet upon the reversi...
Figure 5.10 (a, b) Photos of the Zn‐terpyridine nanosheet under ambient and ...
Figure 5.11 (a) Chemical structure of the porphyrin‐hybridized bis(dipyrrina...
Figure 5.12 (a) Layered structure of MUV‐1‐Cl showing the Cl atoms located a...
Chapter 6
Figure 6.1 (a) The crystal structure of metal halide perovskite.(b) Comm...
Figure 6.2 (a) The crystal phase of CsPbI
3
in different temperature.(b) ...
Figure 6.3 (a) The bandgap of ABX
3
perovskite with different components. (b)...
Figure 6.4 (a) Schematic representation of strain relaxation during MABr all...
Figure 6.5 (a) Location of alkali metal cations in the perovskite crystal st...
Figure 6.6 (a) Thermogravimetric analyses of MABr, MAPbBr
3
, PbBr
2
, CsPbBr
3
, ...
Figure 6.7 (a) SEM images,
J
–
V
curves and (b) XRD of FASnI
3
perovskite films...
Figure 6.8 (a) IPCE spectra of the devices based on CH
3
NH
3
Sn
1−
x
Pb
x
I
3
(
Figure 6.9(a) Calculated natural band offsets of CH3NH3PbI3and related materials...
Figure 6.10 (a) The scheme for the physical process of photoluminescence. (b...
Figure 6.11 The synthesis approaches of metal halide perovskite‐based nanoma...
Figure 6.12 (a) Synthesis scheme of perovskite nanocrystals using the hot in...
Figure 6.13 (a) Synthesis process of perovskite nanocrystals by the ligand‐a...
Figure 6.14 (a) One‐step spin‐coating procedures for the formation of CH
3
NH
3
Figure 6.15 (a) Schematic illustration of perovskite film formation through ...
Figure 6.16 (a) Illustration of doctor‐blade coating of mixed cation perovsk...
Figure 6.17 (a) The potential perovskite photovoltaic applications: (i) The ...
Figure 6.18 (a) Schematic illustration for the strategies to improve the sta...
Chapter 7
Figure 7.1 Summary of advantages and properties of 2D piezoelectric material...
Figure 7.2 Schematic energy band diagrams. P–N junction constructed with p‐t...
Figure 7.3 (a) Optical image of MoS
2
/WSe
2
P–N heterojunction transferred ont...
Figure 7.4 Multilayer γ‐InSe self‐powered photodetector. (a) Optical image o...
Figure 7.5 MoS
2
P–N junction photodiode. (a) Self‐made apparatus for loading...
Figure 7.6 (a)
I
–
V
curve of WS
2
and WS
2
/CsPbBr
3
heterostructure photodetecto...
Figure 7.7 (a) Schematic diagram of fabrication process of flexible WSe
2
/ZnO...
Figure 7.8
I
–
V
curve of WSe
2
/CdS heterostructure detector (a) with increasin...
Figure 7.9 (a) Fabrication process of CuO/MoS
2
heterostructure photodetector...
Figure 7.10 (a) Optical image of MoS
2
/WSe
2
P–N heterojunction photodiode....
Figure 7.11 V‐doped ferroelectric‐ZnO nanosheets and p‐Si heterostructure ph...
Chapter 8
Figure 8.1 (a) Molecular structure of typical CPs: (1) trans‐polyacetylene, ...
Figure 8.2 Several examples of applications of CPs. (1) Photocatalysis.(...
Figure 8.3 (a) SEM image of zero‐dimensional PEDOT/LS(sulfonated lignin) nan...
Figure 8.4 (a,b) The response and recovery times of Ag NPs/PEDOT NTs with in...
Figure 8.5 (a) Photos of polymerization processes via the micelle‐mediated p...
Figure 8.6 (a) SEM image of the 3D‐boxlike PANI microstructures assembled fr...
Figure 8.7 (a–e) Snapshots showing interfacial polymerization of aniline in ...
Figure 8.8 (a) Schematic depiction of PPy nanowire preparation by electroche...
Figure 8.9 (a) Schematics of the surface‐imprinting strategy for fabrication...
Figure 8.10 (a) Reverse micelles are adsorbed on the substrate. (a′) TEM obs...
Figure 8.11 (a) The effects of temperature and functional groups on the nano...
Figure 8.12 (a) Conventional method for forming a CP film on an anode surfac...
Figure 8.13 (a) Diagram of an electrospinning apparatus.(b) Electrospun ...
Figure 8.14 (a,b) SEM images of HCl‐doped PANI fibers obtained from differen...
Figure 8.15 The BNNS filler mass fraction increases. (a,b) The thermal condu...
Figure 8.16 (a) Schematic of the electrospinning setup used for the producti...
Figure 8.17 (a) TEM images of EDOT/PVA fibers with 15% EDOT.(b) A schema...
Figure 8.18 (a) Schematic description of the preparation processes of PEDOT:...
Figure 8.19 SEM images of PLLA/PPy composites when pyrrole
in situ
polymeriz...
Figure 8.20 (a) Different concentrations of PEDOT:PSS printing ink. (b) Imag...
Chapter 9
Figure 9.1 (a) TEM image of ordered HClO
4
‐doped PANI nanotubes.(b) Cycli...
Figure 9.2 (a) Schematic illustration of the synthesis procedure for PEDOT‐c...
Figure 9.3 (a) Schematic illustration of the fabrication process of Li
3
V
2
(PO
Figure 9.4 (a) Schematic illustration of electron transfer and Li
+
trans...
Figure 9.5 (a) Chemical structure of the polymers: PEDOT:PSS, PEO, and PEI u...
Figure 9.6 (a) Schematic illustration of the polymerization reaction between...
Figure 9.7 (a) Schematic illustration of the fabrication of V
2
O
5
@PEDOT/CC....
Figure 9.8 Scheme of PEDOT:PSS‐coated CMK‐3/sulfur composite for improving t...
Figure 9.9 (a) Depiction of PEDOT‐AQ, PEDOT‐BQ, pyridine‐based proton donors...
Figure 9.10 Schematic working principle and general redox chemistries of a M...
Figure 9.11 (a) Crosslinking process of PEDOT‐PSS hydrogel and schematic pro...
Figure 9.12 (a) Synthesis of PPy/IL nanoparticles. (b) Polarization curve ob...
Figure 9.13 (a–d) SEM images of different electro‐polymerized films.(a, ...
Figure 9.14 (a) SEM image of Pd‐PEDOT nanocomposite film.(b) The cyclic ...
Figure 9.15 (a) Faradaic efficiency‐time diagram of CO
2
reduction on PAn ele...
Figure 9.16 SEM images of PANI nanostructures with different aspect ratios s...
Figure 9.17 (a–c) SEM images of PANI samples were prepared in [emim][Br], [e...
Figure 9.18 (a–c) SEM images of the H‐PANI under different magnifications....
Figure 9.19 Microstructures and capacitance performance of PPy hydrogels wit...
Figure 9.20 (a) Schematic illustration of the preparation of PANI and corres...
Figure 9.21 SEM images of (a) bare paper, (b) and (c) PEDOT/paper.(d–f) ...
Figure 9.22 (a,b) SEM images of PTh and PTh/MWCNT composites.(c) CV of P...
Figure 9.23 (a–c) SEM images of RGO‐IL/PANI at different magnifications....
Figure 9.24 SEM images of (a) the graphene foam, (b) graphene/PPy‐300, (c) g...
Figure 9.25 (a) A schematic illustration shows the fabrication of CDPY hybri...
Figure 9.26 The TEM images of MoS
2
(a), PEDOT (b), and PEDOT@MoS
2
/PEDOT (c)...
Figure 9.27 SEM images of the Ag/PPy composites obtained by controlling the ...
Figure 9.28 SEM images of (a) PNT@NiCo‐LDH nanocages and (b) NiCo‐LDH nanoca...
Figure 9.29 (a) Schematic illustration of the synthetic procedure for NiCo
2
O
Figure 9.30 SEM images of the cross‐section of bare Ti wire (a) cross‐sectio...
Figure 9.31 (a–c) SEM images of Vö‐V
2
O
5
/CPs. (a) CV curves of Vö‐V
2
O
5
/CPs an...
Figure 9.32 (a–c) SEM images of the obtained 3D AgNW/PUS, PEDOT:PSS/AgNW/PUS...
Figure 9.33 TEM images of PANI/G paper (a) () and PANI/G/MnO
2
paper (b)....
Figure 9.34 SEM images of (a) ZIF–PPy‐1 (), (b) ZIF–PPy‐2, (c) ZIF–PPy‐3...
Figure 9.35 SEM images of PANI (a) (), ZIF‐67 (b), ZIF‐67/PANI (c), and ...
Figure 9.36 (a–d) TEM images of ZIF‐67/PEDOT composite at different magnific...
Figure 9.37 SEM images of (a) PTh () and (b) Fe
3+
‐doped PTh. Cyclic ...
Chapter 10
Figure 10.1 (a) Schematics of the polymerization process. (b) PPy:CNT hollow...
Figure 10.2 (a, b) Schematic diagram of the PEDOT:PSS‐printed fabric, and th...
Figure 10.3 (a) Illustration of the water‐assisted wedging method used to ob...
Figure 10.4 (a) Schematic diagram to illustrate the fabrication processes of...
Figure 10.5 (a) Schematic illustration of the preparation of the PCPZ hydrog...
Figure 10.6 (a) Electrostatic self‐assembly process of GO and ANI on silk fa...
Figure 10.7 (a) Schematic representation of the functionalized titanium prep...
Figure 10.8 Synthetic route of conductivity mussel‐inspired poly(ATMA‐
co
‐DOP...
Figure 10.9 (a) The design of the conductive biospring
in vitro
. (b)
I
–
V
cur...
Figure 10.10 (a) Chemical structures of PEDOT, CUR, and PCL. (b) CUR release...
Figure 10.11 (a) Illustration of the cumulative Dex release over a period of...
Figure 10.12 Cumulative mass of IBU released during 5 minutes from 1 cm
2
dru...
Figure 10.13 (a) Schematic representation of PPy‐functionalized PCL‐PTX memb...
Figure 10.14 (a) Cumulative DOX release from D‐PPy@PNA nanogels with or with...
Figure 10.15 (a) Tip displacements under a DC excitation of 3 V voltage. Dig...
Figure 10.16 Bottom‐up fabricated actuator devices (or “fingers”) with indiv...
Figure 10.17 (a) Schematic representation for the selectively electrochemica...
Figure 10.18 (a) Fabrication process of the AFP immunosensor based on macrop...
Figure 10.19 (a) Schematic representation of the 3D heterostructure of the P...
Figure 10.20 (a) Schematic diagram of MIP‐based photoelectrochemical sensor ...
Figure 10.21 (a) AuNPs@PPyNPs nanocomposite preparation process and sensitiv...
Figure 10.22 (a) The chemical route to the preparation of PPy/CNTs‐MIPs....
Figure 10.23 (a) The preparation flow chart of electrodepositing gold nanopa...
Figure 10.24 (a) Illustration of the construction of the PANI/PEG nanofiber ...
Chapter 11
Figure 11.1 (a) The published paper increasing in the recent 20 years. The d...
Figure 11.2 TEM and AFM images of the AEAM‐inserted objects by diluting the ...
Figure 11.3 (a) The schematic of polymerization of ionic monomer to produce ...
Figure 11.4 (a) Schematic of preparation of PEG
45
‐
b
‐PS/PS‐
b
‐PEG
45
‐
b
‐PS. (b) ...
Figure 11.5 The polymer/inorganic nanoparticle composites were prepared by u...
Figure 11.6 The BaTiO
3
/PVDF composites prepared by using solution mixing: (a...
Figure 11.7 (A) The schematic of modification of multiple walled carbon nano...
Figure 11.8 (a) The schematic of preparation CNT‐PPO. The TEM images of CNT ...
Figure 11.9 (A) The illustration of synthesizing P(S‐
b
‐2VP‐
b
‐EO). (B) The AF...
Figure 11.10 (a) The TEM images of PDEAEMA‐
co
‐SMA prepared emulsion polymeri...
Figure 11.11 (a) The schematics of preparing Ni‐CMGG composites. (b,c) The S...
Figure 11.12 (a) The schematic of π–π interaction between RGO and polymer ch...
Figure 11.13 (a) The schematic for preparing the PA‐66@UiO‐66‐NH
2
. (b) The c...
Figure 11.14 (a) Scheme of preparing the PMAA‐
b
‐PMAAz BCP NPs via RAFT dispe...
Figure 11.15 (a) The schematic of preparation of PBAT/SiO
2
‐EO/CNF‐NH
2
. (b) T...
Figure 11.16 (A) The SEM images of the impact‐fractured surface of the obtai...
Figure 11.17 (a–d) the SEM images of PVA/cellulose polymer nanocomposites: (...
Figure 11.18 (a) The schematic of in‐situ ring‐open polymerization for combi...
Figure 11.19 (a) The schematic of preparation of indirect Z‐scheme BiOBr/Ag/...
Figure 11.20 (a) TEM images of SWNT/PANI composites. (b) The Seebeck coeffic...
Figure 11.21 (a) The schematic of
in‐situ
polymerization for preparing...
Figure 11.22 (A) The Schematic illustration for the controlling iron oxides ...
Figure 11.23 (A) The schematic illustration of PMPC
25
‐
b
‐PDMA
4
‐
b
‐PHPMA. (B) V...
Figure 11.24 (a) The schematic of preparation of NRMG composites. (b,c) The ...
Figure 11.25 (a) Scheme of the formation of OMC coated SiO
2
NPs. (b) Spectra...
Figure 11.26 (a) The schematic of preparation (b) The TEM image of Pt. (c,d)...
Figure 11.27 (a–c) The TEM images of prepared Ppy (a) and the multimetallic ...
Figure 11.28 (a) The schematics of synthesis of Au NPs/PTPA polymer nanocomp...
Figure 11.29 (a) Schematic of the synthetic strategy of Pd nanoparticles/POP...
Chapter 12
Figure 12.1 The flow caused by the Lorentz forces under homogeneous magnetic...
Figure 12.2 Magnetic gradient force under the magnetic field parallel (a) wi...
Figure 12.3 The optical images of the magnetic field template (a), the Cu el...
Figure 12.4 SEM images for a CoNiMo alloy electrodeposited from bath deposit...
Figure 12.5 XRD (a) and HRTEM patterns of Co
3
O
4
in the absence (b) and the p...
Figure 12.6 Hydrogen bubble growth at single hydrophobic islet with magnetic...
Figure 12.7 Bubbles release from the pair of neighboring hydrophobic islets ...
Figure 12.8 Total (full line) and partial Mo 4d densities of states for 1T (...
Figure 12.9 Polarization curves (a) and the corresponding Tafel plots (b) (d...
Figure 12.10 (a) Schematic of electron transfer in bowl‐like MoS
2
flakes dur...
Figure 12.11 Molecular orbital diagram of O
2
, H
2
O, and OH
−
.
Figure 12.12 (a) Representative cyclic voltammetry (CV) curves (the second c...
Figure 12.13 Projected DOS (pDOS) for O 2p orbital and Mn 3d orbital of ZnMn
Figure 12.14 (a) Temperature dependence of magnetization (
M
–
T
) curves under ...
Figure 12.15 Spin configuration relative stabilities for unit‐cell (a) and s...
Figure 12.16 (a) Scheme of a molecular orbit of a singlet‐state oxygen molec...
Figure 12.17 (a) The quantified Mn and Co valence states obtained from XANES...
Figure 12.18 Simulated surface magnetic field induced by (a) L1
0
‐PtFe NF and...
Figure 12.19 (a) Schematic diagram to show spin‐dependent oxidation of oxala...
Figure 12.20 Transmission path of Li
+
(Fuchsia ball) in (a) reference an...
Figure 12.21 (a) Schematic illustrating the proof‐of‐concept magnetic field‐...
Figure 12.22 The mechanism of lithium electrodeposition on metallic substrat...
Figure 12.23 Electrochemical performances of lithium metal anode with or wit...
Guide
Cover
Table of Contents
Title Page
Copyright
Preface
About the Editor
Begin Reading
Index
End User License Agreement
Pages
iii
iv
xi
xii
xiii
xiv
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
435
436
437
438
439
440
441
442
443
444
445
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
Functional Nanomaterials
Synthesis, Properties, and Applications
Edited by Wai‐Yeung Wong and Qingchen Dong
Editors
Prof. Wai‐Yeung WongThe Hong Kong Polytechnic UniversityDepartment of Applied Biology and Chemical TechnologyHung Hom, KowloonHong KongChina
Prof. Qingchen DongShanghai UniversityMOE Key Laboratory of Advanced Display and System Applications149 Yanchang RoadJingan District200072 ShanghaiChina
Cover Image: © SEBASTIAN KAULITZKI/SCIENCE PHOTO LIBRARY/Getty Images
All books published by WILEY‐VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.
Library of Congress Card No.: applied for
British Library Cataloguing‐in‐Publication DataA catalogue record for this book is available from the British Library.
Bibliographic information published by the Deutsche NationalbibliothekThe Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.
© 2022 WILEY‐VCH GmbH, Boschstr. 12, 69469 Weinheim, Germany
All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.
Print ISBN: 978‐3‐527‐34797‐1ePDF ISBN: 978‐3‐527‐82854‐8ePub ISBN: 978‐3‐527‐82855‐5oBook ISBN: 978‐3‐527‐82856‐2
Preface
Since Feynman gave the speech “There's Plenty of Room at the Bottom” at the annual conference of American Physical Society at California Institute of Technology in 1959, nanoscience and nanotechnology emerged as times require, and the field has developed for more than half century. This has achieved leap forward development in the past two decades. Nanoscience is a newly emerging discipline for exploring the micro‐world. Due to the specific small size effect, macroscopic quantum tunneling effect, surface and interface effect, etc., nanomaterials have displayed extensive and attractive application perspectives in the fields of optics, electronics, magnetism, catalysis, sensing, and biomedicine. With the development of nanotechnology, some interdisciplinary research works such as nanoelectronics, nanobiology, nanomaterials, nanomedicine, etc. have also been successively established, which also promotes the mutual penetration and integration of multidisciplinary researches. By changing the size, morphology, chemical structure, and composition, a number of advanced functional nanomaterials have been designed, synthesized, and applied in various areas.
Therefore, to bring a focus on the recent research developments of some novel functional nanomaterials such as metal nanoparticles, metal oxide nanomaterials, metal‐free carbon‐based nanomaterials, polymer nanomaterials, two‐dimensional nanomaterials, and perovskite‐based nanomaterials and their applications in catalysis, optoelectronics, sensing, biomedicine, etc., a collection of chapters from leading scientists is presented in this book. The fundamental concepts and theories, synthetic strategies, properties characterization, device fabrication, and performance evaluation of the above nanomaterials and devices are covered, which provide readers with a good source of information in understanding the development trend of advanced nanoscience and nanotechnology and exploring more functional nanomaterials. These include the investigation of functional earth‐abundant metal‐based nanomaterials (by Weiran Zheng, Yong Li, Lawrence Yoon Suk Lee), metal oxide nanomaterials (by Xuemei Zhou, Mingkai Zhang, Yuwei Jin, Yongquan Qu), and metal‐free carbon‐based nanomaterials (by Lai‐Hon Chung, Zhi‐Qing Lin, Jun He) for catalysis and the spin‐related catalytic reaction in nanomaterials (by Shengnan Sun, Yanglong Hou); the studies on rare‐earth luminescent nanomaterials (by Jianle Zhuang, Xuejie Zhang), metal complex nanosheets (by Ryota Sakamoto), metal halide perovskite‐based nanomaterials (by Mei‐Li Sun, Cai‐Xiang Zhao, Jun‐Feng Shu, Xiong Yin), and two‐dimensional nanomaterials (by Yuqian Zhao, Ran Ding, Feng Guo, Zehan Wu, Jianhua Hao) for applications in optoelectronics and sensing; and the comprehensive introduction of the synthesis, electrochemistry, and bioengineering applications of conducting polymer‐based nanomaterials (by Ziyan Zhang, Tianyu Sun, Mingda Shao, Mingwei Fang, Xingpu Wang, Xueyan Li, Xiang Sun, Meiling Wang, You Liu, Xin Zhang, Yalan Chen, Shiying Li, Ying Zhu) and polymers‐based nanocomposites (by Muwei Ji, Jintao Huang, Caizhen Zhu).
Nanotechnology has extended the means and ability of human beings to understand and transform the material world to atoms and molecules and provided us with a new concept of designing nanomaterials with unique physical and chemical properties different from the traditional materials. We believe that nanotechnology and nanomaterials with excellent physical and chemical properties will help us address some challenging issues such as energy and climate crisis, healthy problems, information storage, and transmission and display that are confronted by human society in the twenty‐first century. We are grateful to all the contributors who have participated in the preparation of this book. Finally, we deeply thank Dr. Lifen Yang, Program Manager, and Ms. Katherine Wong, Senior Managing Editor, of John Wiley & Sons Inc. for their helpful suggestions and discussion on the organization of this book. Without their support, this huge work would not have been possible.
We thank the financial support from the Science, Technology and Innovation Committee of Shenzhen Municipality (JCYJ20180507183413211), National Natural Science Foundation of China (52073242, 62174116, 61774109), the Hong Kong Research Grants Council (PolyU 153062/18P), the RGC Senior Research Fellowship Scheme (SRFS2021-5S01), The Hong Kong Polytechnic University (1-ZE1C), Research Institute for Smart Energy (RISE), Miss Clarea Au for the Endowed Professorship in Energy (847S) and the startup fund of Shanghai University.
Wai‐Yeung Wong and Qingchen Dong
Hong Kong05 January 2022
About the Editor
Wai‐Yeung Wong is currently Chair Professor and Dean of Faculty of Applied Science and Textiles at The Hong Kong Polytechnic University (PolyU). He is also Professor at the PolyU Shenzhen Research Institute. He received his BSc (1992) and PhD (1995) degrees from the University of Hong Kong. After postdoctoral training with Prof. F. Albert Cotton at Texas A&M University in 1996 and Profs. The Lord Lewis and Paul R. Raithby at the University of Cambridge in 1997, he joined Hong Kong Baptist University (HKBU) from 1998 to 2016. His research interests lie in the areas of metallopolymers and metallo‐organic molecules with energy functions and photofunctional properties. His research activities are documented in more than 700 scientific articles, 4 books, 18 book chapters, and 2 US patents. Professor Wong has been named in the list of Highly Cited Researchers from 2014 to 2020 published by Thomson Reuters/Clarivate Analytics. He becomes the first Chinese scientist to be presented with the Chemistry of the Transition Metals Award by the Royal Society of Chemistry in 2010. He has also won the Federation of Asian Chemical Societies (FACS) Distinguished Young Chemist Award from the Federation of Asian Chemical Societies in 2011, Ho Leung Ho Lee Foundation Prize for Scientific and Technological Innovation in 2012, State Natural Science Award (Second Class) of China in 2013, Japanese Photochemistry Association Lectureship Award for Asian and Oceanian Photochemist (Eikohsha Award) in 2014, and Research Grants Council (RGC) Senior Research Fellow Award in 2020. Professor Wong is currently the Editor‐in‐Chief of Topics in Current Chemistry, Editor of Journal of Organometallic Chemistry, and Associate Editor of Journal of Materials Chemistry C and Materials Advances. At present, he is the Chairman of the Hong Kong Chemical Society.
Qingchen Dong obtained her PhD degree under the tutelage of Prof. Wai‐Yeung Wong in 2012 at HKBU. She also worked at Caltech with Prof. H. B. Gray from 2010 to 2011. She joined Taiyuan University of Technology (TYUT) from 2012 to 2021 and now works at Shanghai University (SHU) as a full‐time professor. Her research involves the design and synthesis of functional organic and metallo‐organic compounds and carbon‐based materials for applications in data storage, artificial synapse and neuromorphic computing, optoelectronics, etc. Prof. Dong has published more than 50 papers in Chemical Society Reviews, Advanced Materials, Advanced Functional Materials, Angewandte Chemie International Edition, Advanced Electronic Materials, Journal of Materials Chemistry A, etc., edited 2 book chapters, and awarded 3 CN patents. She won the Natural Science Award (Second Class) of Shanxi Province, China, in 2019.
1Earth‐Abundant Metal‐Based Nanomaterials for Electrochemical Water Splitting
Weiran Zheng Yong Li and Lawrence Yoon Suk Lee
The Hong Kong Polytechnic University, Department of Applied Biology and Chemical Technology, Hung Hom, Kowloon, Hong Kong SAR, China
1.1 Electrochemical Water Splitting
Since the oil crisis in the 1970s and 1980s, hydrogen has been widely recognized to be an efficient and promising energy carrier for our future. Yet, as of 2019, about 95% of global hydrogen production relies on fossil fuels, emitting an excessive amount of carbon into the atmosphere [1]. Typically, for every ton of hydrogen produced by steam reforming of natural gas, around 9–12 tons of CO2 is released and wasted [2,3]. One of the most attractive options to produce hydrogen sustainably is to split water molecules using electrical energy generated by sustainable sources, such as wind, hydropower, nuclear energy, etc.
1.1.1 General Principle
In general, the electrochemical water splitting process requires passing electricity through two electrodes in water (Figure 1.1), where the oxidation occurs on the anode to generate oxygen (oxygen evolution reaction [OER]) and the reduction occurs on the cathode to produce hydrogen (hydrogen evolution reaction [HER]). The overall reaction can be simplified as Eq. (1.1):
Water splitting to hydrogen and oxygen is a thermodynamically uphill process, which requires a Gibbs free energy of ΔG° = 237.22 kJ mol−1 or enthalpy of ΔH° = 285.84 kJ mol−1 at standard conditions of temperature and pressure (298 K, 1 bar). When converting electrical energy to chemical energy, the equation of ΔG° = nFE0 applies, where n is the number of transferred electrons (two electrons exchanged for the splitting of one water molecule), F is the Faraday's constant, and E0 is the standard cell voltage required. Therefore, the thermodynamically required voltage for water splitting is 1.229 V. It should be noted that the voltage value depends on the temperature and water status. For example, the electrochemical dissociation of water vapor needs only 1.18 V. Since the electrolysis reaction is endothermic, if the reaction is performed without an external heat source, the extra voltage is needed to compensate the temperature factor in the enthalpy. In this case, the equation of ΔH° = nFE0 applies, producing a value of 1.481 V at standard conditions, known as the thermoneutral potential.
Figure 1.1 Simplified illustration of an electrolyzer for water splitting driven by a power source. The electrons travel through the external circuit and promote the HER at cathode and OER at the anode. A separator, often semipermeable membrane, is used for proton transfer and product separation.
From an electrochemical perspective, the cell voltage needs to drive the two half‐reactions at the electrodes:
where , , and represent the standard cell, cathodic, and anodic potential, respectively.
Although the overall reaction is irrelevant to electrolyte conditions, the two half‐reactions follow two routes depending on the proton concentration of the electrolyte (Figure 1.2).
Under acidic conditions:
Under alkaline conditions:
The Nernst equation can express the thermodynamical potential to drive the anodic side in acidic conditions:
Figure 1.2 Pourbaix diagram (pH potential) of water under standard temperature and pressure (298 K, 1 bar).
where and are the activity of proton and water and is the fugacity of oxygen in the anodic compartment. In a simplified case when the activity coefficient of the proton is unity and the water activity is the same at all concentration,
Similarly, for the cathodic side,
Such expressions also apply for the alkaline conditions providing the electrolyte shares the same proton activity coefficient and water activity. Therefore, the standard potential for both anodic and cathodic reactions depends on pH.
1.1.2 Overpotential and Tafel Slope
Even if the desired potential is met, the reaction may not proceed, and extra potential (overpotential, η) beyond the thermodynamic value (E0) is commonly required to overcome the reaction energy barriers caused by many factors:
The causes of overpotential can be divided mainly into three categories: the resistance overpotential due to the ohmic losses in the electric circuit, the concentration overpotential caused by the concentration gradient in the double layer region of electrolyte, and the kinetic overpotential to drive the surface reaction [4]. Both electrode and electrolyte contribute to the ohmic loss. In a laboratory‐scale reaction, the potential drop due to ohmic loss is generally small and often not taken into account because the resistance of both electrode and electrolyte is negligible. However, industrial water electrolysis often suffers from the joule heat due to the ohmic resistance and large current. The concentration overpotential is the direct result of reactants consumption in the double‐layer region near the electrode, therefore mainly controlled by the diffusion rate of the proton for water electrolysis. Conventionally, using electrolyte with highly acidic/alkaline conditions (extreme pH values) can offset such concentration effect and maximize efficiency. Accordingly, most researchers often employ electrolytes with pH = 1 or 14, and the current understanding of water splitting is also heavily based on the results from extreme pH levels. Industrial alkaline water electrolysis uses 20–40% NaOH or KOH aqueous solutions.
Like the concepts in heterogeneous catalysis, electrocatalysis also requires the reactants to be adsorbed first on the electrode to conduct further bond breaking and/or formation processes. Moreover, the electron transfer from/to the adsorbed reactants suffers resistance. As Eqs. (1.2)–(1.5) indicate, both anodic and cathodic processes demand an overpotential for proton/hydroxide and charge transfer for water splitting. The kinetic overpotential is referred to as the energy required to make the reactions proceed at appreciable rates. The faster the speed of water splitting is (measured as normalized charge flowing in the circuit, or current density), the higher overpotential must be supplied. The kinetic parameter used to describe such dependency is the Tafel slope (unit: mV dec−1), defined as the overpotential needed to increase the current density by a factor of 10.
Due to the existence of overpotential, the energy efficiency of an electrolysis process is not 100%. When considering the efficiency in the lab, the Faradaic efficiency (ratio of the electrons used for hydrogen production vs. the total charge passed) is commonly used. The experimental value may approach 100% but is always lower than 100% because of some parasitic processes such as the conversion of the electrocatalyst. The energy loss due to resistance, however, cannot be revealed by the Faradaic efficiency. Industrial water electrolyzers often use a more practical way to evaluate the energy efficiency of water splitting by dividing the energy available from the produced hydrogen by the total energy consumed by the cell. Such value reflects the energy loss due to the overpotentials and uncovers the commercial viability of the system.
To achieve the highest energy efficiency, the energy spent on overcoming the extra barriers needs to be minimized. The role of electrocatalysts is to reduce the kinetic overpotential as much as possible. Over the past decades, electrochemists have been working on finding the best electrocatalysts for both HER and OER under acidic and alkaline conditions. Two indicators are generally used in literature for comparison: the overpotential to achieve a current density of 10 mA cm−2 and the Tafel slope within a specific current range.
1.1.3 Current Techniques
Two main techniques have been commercialized for electrochemical water splitting, including alkaline electrolysis and proton exchange membrane (PEM) electrolysis. The alkaline electrolysis follows the alkaline pathway described in reactions (1.4) and (1.5) and remains the dominating commercial approach. Both cathode and anode are often made of nickel‐based materials, and the separator is a polymer that allows hydroxide ions and water molecules to pass. The PEM electrolysis that has emerged more recently follows the acidic pathway (reactions (1.2) and (1.3)) with a PEM separator placed between the electrodes to allow proton transfer. Considering the highly acidic conditions, the electrocatalysts engaged in the PEM electrolysis need to be stable under the operating environment, leaving far less choices comparing with alkaline electrolysis. The current state‐of‐the‐art catalysts in PEM electrolysis is platinum and iridium/ruthenium oxides for HER and OER, respectively.
Although the alkaline electrolysis is more technologically mature and relatively cost‐effective compared with the PEM electrolysis, it has some drawbacks such as low current density, low partial load range, low operational pressures, and hydrogen crossover through the separator. The high efficiency of PEM electrolysis, on the other hand, cannot redeem the expensive noble metal‐based electrode materials. Based on the calculation by Chatzitakis and coworkers [5] a typical PEM electrolyzer requires 0.4 mg cm−2 Pt on the cathode and 1.54 mg cm−2 Ir and 0.54 mg cm−2 Ru on the anode, respectively. Yet, for a power density of 1.18 W cm−2, 1.5, 180, and 12 years of the annual production of Pt, Ir, and Ru, respectively, are demanded.
To further improve both techniques, the development of electrocatalyst for alkaline water electrolysis needs to focus on materials bearing high current at relatively low overpotential. As to the PEM electrolysis, finding suitable alternatives that are stable under extremely acidic conditions while showing similar activities to the noble metal‐based ones is essential.
1.2 Earth‐Abundant Metallic Nanomaterials
The key to large‐scale commercialization is to lower the cost of water electrolysis systems. Apart from increasing the activity of noble metal atoms, using earth‐abundant metal‐based materials as the electrocatalysts is generally appreciated by the research community. The elements currently of particular interest are nickel (Ni), cobalt (Co), iron (Fe), manganese (Mn), titanium (Ti), vanadium (V), and molybdenum (Mo), as shown in Figure 1.3.
Figure 1.3 Earth‐abundant metals that are currently used for water electrolysis and their relative positions in the periodic table. Their abundance in Earth's crust [6] is shown in the unit of mg kg−1.
In the following contents, the current research progress of individual metal‐based materials in different forms (metal, metal oxide, metal hydroxide, metal chalcogenide, metal sulfide, etc.) will be introduced based on their application: HER and OER. In many cases, the electrocatalytic materials involve more than one metal element. For clarity, their descriptions are listed under the major element responsible for active sites.
1.2.1 Hydrogen Evolution Reaction (HER)
1.2.1.1 Mechanism
The well‐established mechanism for HER (heavily based on Pt electrode) can be generally described as the electrochemical hydrogen adsorption followed by hydrogen desorption reactions and/or chemical desorption [7].
Under acidic conditions (M represents the HER active sites on electrocatalysts):
In acidic media, the proton first gains an electron at the active site to form M − Hads intermediate (reaction (1.6)). In alkaline media, instead of proton adsorption, the water molecule is involved in the elemental reactions (reactions (1.9) and (1.10)).
Under alkaline conditions:
Most HER catalytic systems adopt either the Volmer–Heyrovsky or Volmer–Tafel pathway for mechanism understanding. An approximate way to determine the mechanism is to use the Tafel slope, derived from the HER polarization curve. If the Volmer step is the rate‐determining step (RDS), the slope is 120 mV dec−1, and when Heyrovsky and Tafel steps are the RDS, the Tafel slopes of 40 and 30 mV dec−1 result, respectively.
Both the bonding strength of the M − Hads intermediate and the free energy of hydrogen adsorption (ΔGH) on the cathode can be used to describe the interaction between the hydrogen atom and active sites. When plotting the two descriptors with the experimentally measured exchange current densities from polycrystalline metal electrodes, a typical volcano relationship emerges (Figure 1.4), demonstrating the so‐called Sabatier principle. Neither too strong nor too weak bonding benefits the HER. Only a moderate value of ΔGH helps the hydrogen gas discharge following the Heyrovsky step (reaction (1.7)) and/or Tafel step (reaction (1.8)).
Figure 1.4 HER volcano plots with measured exchange current density of polycrystalline metal vs. (a) the energy of the intermediate metal–hydrogen bond formation.
Source: Trasatti [8]. Reproduced with permission of Elsevier.
(b) The calculated free energy of H adsorption.
Source: Skúlason et al. [9]. Reproduced with permission of American Chemical Society.
The earth‐abundant metallic elements are marked in blue.
1.2.1.2 Metal (M0) Nanoparticles
The metallic form of earth‐abundant metals usually shows limited HER activity and stability in both acidic and alkaline media [10,11]. Major efforts have been devoted to increasing metal sites' activity and stability. Decreasing the size of metals to the nanoscale is a proven strategy to alter the electronic properties of metal sites (Figure 1.5) [13,14]. The high surface energy of metallic nanoparticles, however, renders them instable. The most straightforward solution is to stabilize the nanoparticles using supports, which can be structurally engineered to affect the electronic properties of the metal nanoparticles to benefit HER activity.
Figure 1.5 Illustration of various forms of metallic electrocatalysts, from isolated metal atoms to bimetallic nanoparticles supported on conventional solid carriers.
Source: Liu and Corma [12]. Reproduced with permission of Springer Nature.
One typical example is Co nanoparticles. A recent report shows that Co nanoparticles encapsulated in nitrogen‐enriched carbon material can deliver a reasonable overpotential (at a current density of 10 mA cm−2, or η10) of 265 mV in acid and 337 mV in base [15]. It was claimed that the synergistic effects between Co nanoparticles and N‐doped carbon can significantly enhance the activity of Co sites. Similarly, by decorating TiO2 nanoparticles on the surface of Co nanostructure, the hydrogen adsorption free energy at the material junction can be optimized to achieve a η10 of 229 mV in 1.0 M KOH, which is highly enhanced compared with 356 mV using unmodified Co nanomaterial [16]. Similar strategies are frequently applied to other earth‐abundant metal nanoparticles. The commonly used supports include the following: for Co nanoparticles, carbon‐nanotube (CNT)‐grafted graphene sheet [17]; for Ni nanoparticles, nitrogen‐doped graphitized carbon driven by Ni(II)–dimeric complex [18], nitrogen‐doped CNT [19,20], carbon fiber cloth [21], hydrophilic graphene [22], and graphene [23]; and for Fe nanoparticles, carbon shell encapsulation [24] and nitrogen‐doped carbon [25]. Notably, the formation of metal–N local environment has been proven an efficient method to promote the HER activity of metal nanoparticles. Meanwhile, the employment of support is essential for small metal clusters, especially for the stability during reactions.
Another commonly employed approach is to change the shape of the metal nanoparticle, which exposes highly active sites or desired surface features, such as corners and edges, as demonstrated in the HER study of Cu nanoparticles with different shape [26]. However, the tunability of the single element metal nanoparticle is limited by the intrinsic properties of the element.
Involving two or more earth‐abundant metals for the construction of HER electrocatalyst is more popular as more flexibility is possible. The introduction of another/multiple metal(s) into a hosting metal lattice can modify the original electronic structure via strain effect and the bonding strength of adsorbed hydrogen atoms. By combining metals on opposite slopes of the volcano‐type plots (Figure 1.4), new materials systems are proposed to produce suitable intermediate hydrogen binding energy and improved HER activity. For instance, although both Cu and Ti are poor HER electrocatalysts, their combination allows the creation of Cu–Cu–Ti hollow sites with hydrogen binding energy close to that of Pt [27]. The various combinations of metals, tunable ratios, and multiple morphologies (core–shell, alloy, etc.) allow nearly infinite possibility to be explored. Some of the most exciting systems include Cu–Ti [27], Cu–Co [28], Cu–Ni [29], Ni–Mo [30], Fe–Co [31], and Ni–Co–Fe [32]. Depending on the mechanism, one element may serve as the primary active sites for HER and the heteroatoms can aid either proton adsorption or electron transfer [30]. In other cases, the active sites are identified as the hollow sites surrounded by different atoms [27].
1.2.1.3 Metal (M0) Single‐Atom Catalysts
Decreasing the size of metal nanoparticle to the extreme leads to the development of single‐atom electrocatalysts (Figure 1.5). Since its first appearance in 2011 [33], the concept of using single‐atom catalysts (SACs) has been drawing wide attention due to the maximum atomic utilization close to 100%. The initial intention for SACs as HER catalysts is to minimize the Pt loading without sacrificing HER activity [34]. However, when the single atoms are isolated and supported on different materials, their properties change significantly from their bulk nanoparticles [12]. In addition to the noble metals, several earth‐abundant metals, including Co [35], Fe [36], Ni [36,37], Mo [38], and W [39], have shown unexpected HER activities (selected results shown in Table 1.1). Moreover, a series of literature reviews on the topic of SACs were published, covering from their preparation methods to applications [44–47].
Table 1.1 Selected earth‐abundant metal single‐atom electrocatalyst for HER.
Entry
Metal
Coordination environment
Overpotential at 10 mA cm
−2
(mV)
Tafel slope (mV dec
−1
)
Electrolyte
References
1
Co
N‐doped graphene
147
82
0.5 M H
2
SO
4
[35]
2
Co
Phosphorized carbon nitride
89
38
1 M KOH
[40]
3
Fe
Graphdiyne
66
37.8
0.5 M H
2
SO
4
[36]
4
Fe
N‐doped carbon
111
86.1
1 M KOH
[41]
5
Ni
Graphdiyne
88
45.8
0.5 M H
2
SO
4
[36]
6
Ni
Graphene
180
45
0.5 M H
2
SO
4
[37]
7
Mo
N‐doped carbon
132
90
0.1 KOH
[42]
8
W
N‐doped carbon
85
53
0.1 KOH
[39]
9
W, Mo
N‐doped graphene
24
30
0.5 M H
2
SO
4
[43]
10
W, Mo
N‐doped graphene
67
45
1 M KOH
[43]
