Alkaline Anion Exchange Membranes for Fuel Cells E-Book

• Herausgeber: Wiley-VCH GmbH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch
• Veröffentlichungsjahr: 2024

Seitenzahl: 830

Beschreibung

A comprehensive introduction to the science and technology of polymeric electrolyte anion exchange membranes that includes novel membranes with tailored cationic groups for use in fuel cells and related energy applications.

Leseprobe

Table of Contents

Cover

Table of Contents

Title Page

Copyright

Preface

1 An Introduction to Polymeric Electrolyte Alkaline Anion Exchange Membranes

1.1 Introduction

1.2 Different Types of Electrolytes

1.3 Why Polymer Electrolytes Are Important?

1.4 Anion Exchange Membrane (AEM)

1.5 AEMs in Fuel Cells

1.6 Conclusion and Outlook

References

2 Historical and Recent Developments in Anion Exchange Membranes (AEM)

2.1 Introduction

2.2 Fuel Cell: Conventional Versus Modern Approach

2.3 Role of AEM in Fuel Cell Technology

2.4 Preparation of AEMs

2.5 Challenges in Existing AEMs

2.6 Recent Advancement

2.7 Major Challenges

2.8 Commercially Available AEMs

2.9 Current Scenario and Future Market

2.10 Summary and Concluding Remarks

References

3 Fabrication Processes and Characterization Procedures of Anion Exchange Membranes

3.1 Introduction

3.2 Fabrication Processes of Anion Exchange Membranes

3.3 Characterization Procedures of AEMs

3.4 Conclusions

References

4 Types of Polymeric Electrolyte Anion Exchange Membranes: Heterogeneous and Grafted Membranes, Interpenetrating Polymer Networks and Homogeneous Membranes

4.1 Heterogenous Anion Exchange Membranes

4.2 Grafted Anion Exchange Membranes

4.3 Interpenetrating Anion Exchange Membranes

4.4 Homogenous Membranes

4.5 Conclusions

References

5 Proton Exchange Membranes Versus Anion Exchange Membranes

5.1 Introduction

5.2 Proton Exchange Membrane (PEM)

5.3 Comparison with AEM

5.4 Conclusion

References

6 Transport and Conductive Mechanisms in Anion Exchange Membranes

6.1 Introduction

6.2 Transport Mechanisms of Hydroxide Ion in AEMs

6.3 AEM Structure–Transport Efficiency Relationships

6.4 Ion Conductivity Measurement

6.5 Carbonation Process in AEMs

6.6 Conclusion and Outlook

References

7 Anion Exchange Membranes Based on Quaternary Ammonium Cations and Modified Quaternary Ammonium Cations

7.1 Introduction

7.2 Quaternary Ammonium (QA)‐Based AEMs – Recent Developments and Performances

7.3 Other Factors Affecting Performance of Fuel Cells

7.4 Summary and Perspectives

Acknowledgments

References

8 Guanidinium Cations and Their Derivatives‐Based Anion Exchange Membranes

8.1 Introduction

8.2 General Synthetic Method of Various Guanidiniums

8.3 Degradation Mechanism and Alkaline Stability of Guanidinium Cations

8.4 Preparation of Guanidinium and Their Derivative‐Based AEMs

8.5 Prospect

References

9 Anion Exchange Membranes Based on Imidazolium and Triazolium Cations

9.1 Introduction

9.2 AEMs Based on Imidazolium Cations

9.3 AEM Based on Triazolium Cations

9.4 Summary and Future Perspectives

Acknowledgments

References

10 Radiation‐Grafted and Cross‐linked Polymers‐Based Anion Exchange Membranes

10.1 Historic Overview

10.2 Sources of Radiation

10.3 Types of Radiation‐Induced Grafting

10.4 Base Polymer

10.5 Grafting Solution

10.6 Physicochemical Properties of RG‐AEMs

10.7 Cross‐linking in AEMs

10.8 Conclusions

References

11 Degradation Mechanisms of Anion Exchange Membranes due to Alkali Hydrolysis and Radical Oxidative Species

11.1 Introduction

11.2 Necessity to Investigate the Degradation Mechanism in AEMs

11.3 Structure and Degradation Mechanism of Tailored Anion Exchange Groups and Polymers

11.4 Prospects and Outlook

11.5 Conclusion

References

12 Computational Approaches to Alkaline Anion Exchange Membranes

12.1 Introduction

12.2 Why Computational Studies Are Important in Anion Exchange Membranes?

12.3 Tools of

In Silico

Approaches in Anion Exchange Membranes

12.4 Challenges and Outlook

12.5 Conclusion

References

13 An Overview of Commercial and Non‐commercial Anion Exchange Membranes

13.1 Introduction

13.2 Summary and Outlooks

Acknowledgment

References

14 Membrane Electrode Assembly Preparation for Anion Exchange Membrane Fuel Cell (AEMFC): Selection of Ionomers and How to Avoid CO

2

Poisoning

14.1 The Preparation of Membrane Electrode Assembly

14.2 Selection of Ionomers

14.3 Effect of CO

2

on AEMFCs

14.4 Strategies to Avoid CO

2

Poisoning

14.5 The Improvement of AEMFC Output

14.6 Conclusions

References

15 Applications of Anion Exchange Membranes Excluding Fuel Cells

15.1 AEMs in Alkaline Water Electrolysis

15.2 AEMs in CO

2

Electrolysis

15.3 AEMs in Redox Flow Batteries

15.4 AEMs in Alkali Metal–Air Batteries

15.5 AEMs in Reverse Electrodialysis

15.6 AEMs in Electrodialysis

15.7 AEMs in Diffusion Dialysis

15.8 AEMs in Microbial Fuel Cells

15.9 AEMs in Other Applications

15.10 Summary

Abbreviations

References

16 Research Challenges and Future Directions on Anion Exchange Membranes for Fuel Cells

16.1 Prelude to Anion Exchange Membranes

16.2 Progress in AEM Development

16.3 Durability of Anion Exchange Membrane Fuel Cells

16.4 Future Directions

16.5 Concluding Remarks

Acknowledgments

References

Index

End User License Agreement

List of Tables

Chapter 1

Table 1.1 Advantages and disadvantages of liquid‐state and solid‐state elect...

Table 1.2 Comparison of anion exchange membranes and cation exchange membran...

Table 1.3 Pros and cons of anion exchange membranes.

Chapter 2

Table 2.1 AFCs outline of chronicled advancement and accomplishment of AEMs ...

Table 2.2 A range of polymer and cationic functional groups used in preparat...

Table 2.3 Recent studies on synthesis of AEMs for AFC application.

Table 2.4 Advantages and disadvantages of AEM based AFCs.

Table 2.5 Commercially available AEMs for fuel cell applications.

Chapter 3

Table 3.1 Anion‐exchange membranes reported in literature.

Table 3.2 Commercial anion‐exchange membranes.

Table 3.3 Summary of the main characterization procedures of AEMs.

Chapter 6

Table 6.1 Time for complete replacement of OH

−

ion with bicarbonate in...

Table 6.2 Ionic Stokes radii, diffusion coefficient, and ionic conductivity ...

Chapter 7

Table 7.1 Properties of various AEMs and their fuel cell performance.

Chapter 8

Table 8.1 Comparison of conductivity, alkaline stability, and fuel cell effi...

Chapter 9

Table 9.1 AEMs with imidazole functional groups reported in various literatu...

Chapter 11

Table 11.1 The properties of AEMs with variable cycloaliphatic and hetero‐cy...

Table 11.2 The lowest unoccupied molecular orbital energy (LUMO) values of v...

Chapter 13

Table 13.1 The applications of commercial AEMs.

Table 13.2 Half‐life of different cations at 160 °C in 6 M NaOH.

Chapter 14

Table 14.1 A comparison of properties between AEM and AEI.

Table 14.2 Technical data sheet of Fumion

®

FAA‐3 solution.

Table 14.3 A series of ionomers with peak power density (

P

max

) higher than 1...

Table 14.4 A comparison of the effect of CO

2

on AEMFC performance.

List of Illustrations

Chapter 1

Figure 1.1 Classification of electrolytes.

Figure 1.2 Important application of anion exchange membranes.

Chapter 2

Figure 2.1 Schematic representation of liquid‐electrolyte‐based AFC versus a...

Figure 2.2 The statistics of the number of published articles indexed in the...

Figure 2.3 The general reaction steps for the preparation of homogeneous AEM...

Chapter 3

Figure 3.1 Main requirements for fabrication of good alkaline fuel cell memb...

Figure 3.2 Ion‐exchange groups usually employed in AEMs.

Figure 3.3 Degradation reactions of the quaternary ammonium group in the pre...

Chapter 4

Figure 4.1 Synthetic route of QPSU/QPbGs hybrid anion exchange membranes....

Figure 4.2 Synthetic route for the organic–inorganic hybrid anion exchange m...

Figure 4.3 Outline of the synthetic route of the RG‐AEM.

Figure 4.4 Chemical structure of comb‐shaped CyDx copolymers.

Figure 4.5 Multication side chain AEMs based on PPO.

Figure 4.6 Structures of the long‐side‐chain grafted AEMs.

Figure 4.7 Structural representation of semi‐interpenetrating polymer networ...

Figure 4.8 Fabrication process of IPN AEMs.

Figure 4.9 Illustration of semi‐IPN AEM. Blue lines represent quaternary amm...

Figure 4.10 Synthetic route of quaternary ammonium polysulfone in hydroxide ...

Figure 4.11 Synthetic route of quaternary ammonium‐containing polymers from ...

Figure 4.12 Synthetic route of trimethylbenzylammonium functionalized PS via...

Figure 4.13 Chemical structure of the tri(2,4,6‐trimethoxyphenyl) polysulfon...

Figure 4.14 Synthetic strategy of SEBS AEMs.

Figure 4.15 Synthesis of quaternized SEBS via iridium‐catalyzed aromatic C–H...

Figure 4.16 Synthetic route for the poly(2,6‐dimethyl‐1,4‐phenylene oxide)‐

b

Figure 4.17 Synthetic route of the AEMs containing ammonium groups via flexi...

Figure 4.18 Synthetic route for PPO modified with heptyltrimethylammonium si...

Figure 4.19 Synthetic route of QPE.

Figure 4.20 Polymer structures of fluorene‐based AEMs.

Figure 4.21 Synthetic route for polyolefin‐based AEMs using the Ziegler–Natt...

Figure 4.22 Chemical structure of hydroxide‐conducting AEMs based on benzimi...

Figure 4.23 Synthetic strategy for the fluorene single‐side chain poly(2,6‐d...

Figure 4.24 Chemical structure of branched poly(terphenyl piperidinium)s....

Chapter 5

Figure 5.1 Comparison of AAEMFC and PEMFC working principles.

Figure 5.2 Classification of membranes based on materials of synthesis and p...

Figure 5.3 Preparation scheme of Nafion and its structure.

Chapter 6

Figure 6.1 (a) Proton exchange membrane fuel cell (PEMFC), and (b) anion exc...

Figure 6.2 (a) Schematic representation of the different transport mechanism...

Figure 6.3 (a) Comparison of the OH

−

conductivities of AEM‐ETFE and AE...

Figure 6.4 (a) Schematic view of the experimental setting for DC and EIS mea...

Figure 6.5 Representation of AEMFC operating on (a) pure O

2

and (b) ambient ...

Figure 6.6 Schematic representation of the (a) experimental setup, (b) proce...

Chapter 7

Figure 7.1 Degradation of a quaternary ammonium group by (a) Hoffmann elimin...

Figure 7.2 Synthesis of PPOCOPhPi (i) aluminum chloride and 4‐fluorobenzoyl ...

Figure 7.3 Schematic illustration of the blend membrane.

Figure 7.4 Synthesis of the PBP‐xQ4 membrane.

Chapter 8

Figure 8.1 The common synthesis methods of guanidinium cations.

Figure 8.2 The degradation mechanism of guanidinium in alkaline solution [10...

Figure 8.3 (a) Model compounds (QGx) of guanidinium cations. (b) HMBC spectr...

Figure 8.4 Model compounds (M1–M9) of guanidinium cations [14].

Figure 8.5 (a) The alkaline stability of M4. (b) Remaining cations of model ...

Figure 8.6 (a) Resulting cations of the model compounds after different imme...

Figure 8.7 LUMO energies of M3, M5, and M8 [14].

Figure 8.8 (a) The single‐crystal structure of M8. (b) The single‐crystal st...

Figure 8.9 (a) Synthetic route of PSGOH‐x [4]. (b) Synthetic procedure of GP...

Figure 8.10 The synthetic route of PSU‐P‐EG and PSU‐P‐PG AEMs (the counterio...

Figure 8.11 (a) Synthetic route of poly(aryl ether sulfone) containing hexaa...

Figure 8.12 (a) Synthetic route of phenyl‐guanidinium‐functionalized poly(ar...

Chapter 9

Figure 9.1 Number of research articles published on QA, IM, and triazolium‐b...

Figure 9.2 Degradation pathways of imidazolium cations under alkaline condit...

Figure 9.3 Schematic representation of AEMs based on IM‐type ionic liquids: ...

Figure 9.4 Molecular structure of imidazolium cations with different substit...

Figure 9.5 Schematic representation of anion‐conductive copolymer based on 1...

Chapter 10

Figure 10.1 Illustration of radiation‐induced graft polymerization.

Figure 10.2 Possible reactions happening during irradiation of polyethylene ...

Figure 10.3 Possible reactions occurring during irradiation of ethylene tetr...

Figure 10.4 (a) Elongation at break of 0.2 mm thick ETFE films after irradia...

Figure 10.5 Chemical structures of few non‐fluorinated, partially fluorinate...

Figure 10.6 Examples of monomers used for the preparation of radiation‐induc...

Figure 10.7 Cations structures that can be used in AEMs.

Figure 10.8 Scheme of chemical and physical cross‐linking methods.

Figure 10.9 Cross‐linking agents employed in AEM synthesis.

Chapter 11

Figure 11.1 Structures of various anion exchange head groups studied in AEM ...

Figure 11.2 (a) The electro‐static potential (ESP) values on poly(sulfone) p...

Figure 11.3 (a) Multi‐cation side chain type AEMs with different spacer leng...

Figure 11.4 (a) Alkaline hydrolysis by‐products of variable cationic head gr...

Figure 11.5 Influence of microstructure perturbation on alkaline hydrolysis ...

Figure 11.6 (a) Chemical structure of 1,1,3,3‐tetramethyl‐2‐butylguanidinium...

Figure 11.7 Alkaline hydrolysis mechanism and stereochemistry in

N

‐methyl pi...

Figure 11.8 The photograph of PPOPip1.7 AEM showing transparent yellow color...

Figure 11.9 (a, b) Influence of concentration of spirocyclic cations on the ...

Figure 11.10 (a) The degradation time via alkaline hydrolysis of variable qu...

Figure 11.11 (a) Synthesis of various Tröger base‐based polymeric materials ...

Figure 11.12 (a)

In situ

degradation analysis: EDX‐SEM elemental mapping of ...

Figure 11.13 The degradation time via alkaline hydrolysis of variable imidaz...

Figure 11.14 Stability trend of C‐4 and C‐5‐substituted imidazolium cations ...

Figure 11.15 A photograph of Ru(II) functionalized AEM prepared by Zha et al...

Figure 11.16 Scheme for the alkaline hydrolysis of cobaltocenium‐based AEMs ...

Figure 11.17 (a, b) Scheme for the synthesis of cobaltocenium‐based stable A...

Figure 11.18 Scheme showing the (a, b) conventional and (c) proposed degrada...

Figure 11.19 (a) Changes in number‐average molecular weight (

M

n

) of (a) PSU,...

Figure 11.20 Dehydrofluorination mechanism of poly(vinylidene fluoride) in a...

Figure 11.21 Degradation mechanism of poly(benzimidazole)‐based AEM (a)

mes

‐...

Figure 11.22 Benchmark alkaline stability of the HMT‐PMPI membrane in litera...

Figure 11.23 Changes in number‐average molecular weight (

M

n

) of SEBS and chl...

Figure 11.24 The reaction mechanism showing the generation of ROS by one ele...

Figure 11.25 Proposed oxidative degradation mechanism of (a) LDPE‐

g

‐VBC‐base...

Chapter 12

Figure 12.1 Chemical structure of

N

‐spirocyclic QA under study.

Figure 12.2 LUMO of

N

‐spirocyclic QA cations.

Figure 12.3

1

H NMR of

N

‐spirocyclic QA cations after alkali treatment.

Figure 12.4 Mulliken charges and LUMO energies of QA cations.

Figure 12.5 ESP plots of QA cations.

Figure 12.6 Noncovalent interaction isosurface and scatter plot of

δg

in

...

Figure 12.7 Free energy for degradation of QA cations.

Figure 12.8 (a) Structure of two AEMs with PPO‐polymers embedded with two di...

Figure 12.9 2D‐LMC results of a study on a polymer network with different cr...

Chapter 13

Figure 13.1 Chemical structure of AEMION AEMs [7].

Figure 13.2 Chemical structure of sustainion AEMs [8].

Figure 13.3 The chemical constitution of the Orion TM1 [9].

Figure 13.4 The chemical constitution of (a) Xion‐Dappion, (b) Xion‐Durion, ...

Figure 13.5 The chemical constitution of the PiperION TP‐85 AEM [14].

Figure 13.6 The chemical structure of AMI‐7001 [16].

Figure 13.7 The comparison of conductivity and mechanical properties of the ...

Figure 13.8 Degradation routes of QA groups [22, 23].

Figure 13.9 Polymer degradation pathways for poly(vinylidene fluoride) and p...

Figure 13.10 Chemical structure and the conductivity of PPO nQm.

Figure 13.11 (a) Schematic diagram and (b) structures of AEMs containing dif...

Figure 13.12 Quaternized ammonium‐substituted fluorene‐based poly(arylene et...

Figure 13.13 Schematic diagram of locally dense type structure.

Figure 13.14 Schematic diagram of QAPBPip‐PBF‐X and PBPip‐QAPBF‐X.

Figure 13.15 Synthesis of the AEM based on the TB structure.

Figure 13.16 Synthesis pathways of QABNP and QAQPP.

Figure 13.17 Chemical structures of advanced cross‐linked AEMs [39–48].

Figure 13.18 Chemical structures of blend‐modified AEMs.

Figure 13.19 Chemical structures of SIPN AEMs.

Figure 13.20 Chemical structures of doping modified AEMs.

Figure 13.21 Scheme of the electrospinning setup and characteristics of ion‐...

Figure 13.22 Synthetic pathway to spiro‐ionene‐based AEMs.

Figure 13.23 Chemical structure of TPQPOH [69].

Figure 13.24 Synthesis of the corresponding AEM.

Figure 13.25 (a) Synthetic route of PE‐based AEM and (b) corresponding fuel ...

Figure 13.26 The preparation process of QP‐AF and QP‐QAF.

Figure 13.27 General chemical structure of PAP‐TP‐

x

[15].

Chapter 14

Figure 14.1 The structure of MEA for the AEMFC.

Figure 14.2 Different methods of loading catalysts on the AEM: (A) GDE; (B) ...

Figure 14.3 Summary of AEIs and binders in current research.

Figure 14.4 Schematic representation for fabrication of the MEA.

Figure 14.5 The self‐purging process of AEM under different current densitie...

Chapter 15

Figure 15.1 Schematic diagram of an AEMWE.

Figure 15.2 Long‐term performance of commercialized AEM‐based water electrol...

Figure 15.3 (a) Chemical structure of ether‐bond‐free backbone polymers, (b)...

Figure 15.4 The illustration of ion‐solvating membrane and comparison.

Figure 15.5 Schematic diagram of a CO

2

E.

Figure 15.6 Schematic diagram of a VRFB.

Figure 15.7 Polysulfone‐based AEMs with C

2

‐protected imidazolium cations for...

Figure 15.8 (a) The chemical structure and (b) cell performance of graft PBI...

Figure 15.9 Schematic diagram of a rechargeable ZAB.

Figure 15.10 Strategies used to prepare alkaline stable AEMs. Source: Tsehay...

Figure 15.11 Schematic diagram of a RED cell.

Figure 15.12 Schematic diagram of an ED cell.

Figure 15.13 The chemical structure and ED performance of CrPSf‐x AEMs condu...

Figure 15.14 Schematic diagram of a DD cell.

Figure 15.15 Schematic diagram of an MFC.

Chapter 16

Figure 16.1 The schematic illustration of the degradation mechanism of ether...

Figure 16.2 The timeline progression of ether‐free polymers used in AEMs and...

Figure 16.3 The cross‐linked AEM synthesis. (a) Grafted a flexible side chai...

Figure 16.4 The criteria for high‐performance AEMs are chemical stability, m...

Figure 16.5 The fabrication process of TATA

+

‐OH‐based AEM. (1) Tris(2,6‐dime...

Figure 16.6 The scanning electron image of the microporous network structure...

Guide

Cover

Table of Contents

Title Page

Copyright

Preface

Begin Reading

Index

End User License Agreement

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Alkaline Anion Exchange Membranes for Fuel Cells

From Tailored Materials to Novel Applications

Edited by Jince Thomas, Alex Schechter, Flavio Grynszpan, Bejoy Francis, and Sabu Thomas

Editors

Dr. Jince ThomasInternational and Inter University Center for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam 686560, Kerala, India

Prof. Dr. Alex SchechterAriel UniversityAriel 40700Israel

Prof. Dr. Flavio GrynszpanAriel UniversityAriel 40700Israel

Dr. Bejoy FrancisMahatma Gandhi UniversitySt. Berchmans CollegeChanganasseryKottayam 686101, KeralaIndia

Prof. Dr. Sabu ThomasInternational and Inter University Center for Nanoscience and Nanotechnology, Mahatma Gandhi UniversityPriyadarshini Hills P.O.Kottayam 686560, KeralaIndia

Cover Image: © Forance/Shutterstock; Olivier Le Moal/Adobe Stock Photos

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Preface

The urgent need to tackle the global challenges of climate change and resource depletion has made the development of sustainable and efficient energy technologies imperative. Fuel cells are one such clean energy solution that holds great promise for revolutionizing the way we generate electricity and power our vehicles. The advancement of fuel cell technology largely depends on the pivotal role played by membranes, particularly anion exchange membranes (AEMs), which have recently gained significant attention. Alkaline Anion Exchange Membranes for Fuel Cells: From Tailored Materials to Novel Applications is an all‐inclusive exploration of the science and engineering of AEMs and their crucial role in the fuel cell industry. The book delves into the intricate world of AEMs, examining their design, synthesis, properties, and applications in detail. It covers fundamental principles as well as the most cutting‐edge research, providing a roadmap for researchers, engineers, and innovators in the field of renewable energy. Notable contributions from esteemed academics, industry experts, and government–private research labs worldwide make this book an essential tool for university and college faculty members, as well as post‐doctoral research fellows. Within the upcoming pages, readers will embark on an exhilarating journey through the dynamic realm of AEMs. We will explore the historical landscape of fuel cells and membrane technologies, observing their evolution and transformation into viable, sustainable energy solutions. This book unites esteemed experts and visionaries who have devoted their careers to unraveling the intricacies of AEMs, unlocking their potential for a more environmentally friendly future.

Chapter 1 provides both a concise summary and a comprehensive analysis of the current state of AEMs. Additionally, the chapter discusses the latest challenges and prospects in the field. It offers an overview of the fundamental principles of AEMs, including their unique properties, synthesis techniques, performance features, and essential design factors. Chapter 2 delves into the rich history and latest developments in alkaline fuel cell applications utilizing AEMs. This book chapter has been inspired by the remarkable progress and research undertaken in the membrane field for alkaline fuel cells in recent decades. The focal point of the chapter is primarily centered on the fundamental requirements for AEMs in alkaline fuel cell assembly, along with their modifications and methodologies. Chapter 3 covers the challenges and procedures for creating AEMs. It assesses and compares different fabrication processes based on factors like cost, durability, scalability, and performance targets. Chapter 4 analyzes the various types of polymeric electrolytes that can be utilized in alkaline exchange membrane fuel cell (AEMFC), water electrolyzers, and CO2 electrolyzers. The chapter covers the benefits and drawbacks of each type of polymeric electrolyte, as well as their chemical composition and properties. Furthermore, the chapter delves into the suitability of each type of electrolyte for specific applications and how they can affect the performance of the respective electrochemical devices. Chapter 5 explores proton and AEMs, their characteristics, investigative techniques, measurements, transport mechanisms, and water management strategies for proton exchange membrane fuel cell (PEMFC) and AEMFC. Chapter 6 covers transportation and conductive mechanisms in AEMs, as well as the carbonation process and methods to regulate its effects. Additionally, the chapter evaluates the use of electrochemical impedance spectroscopy for monitoring ionic conductivity and stability during fuel cell operations. Chapter 7 discusses recent approaches to polymer membrane modification using quaternary ammonium (QA) cations for improved stability and electrochemical performance. Techniques, including tethering alkyl chains and fabricating multi‐cation side chains using different quaternization strategies, are also discussed at length. Chapter 8 highlights recent applications of guanidinium‐based alkaline exchange membranes in energy conversion. It enriches the systematic study of AEMs and provides a valuable reference for the design of new cationic groups. Chapter 9 provides a comprehensive and in‐depth critical analysis of AEMs that utilize imidazolium and thiazolium cations. The chapter discusses various aspects of these membranes, including their properties, performance, and potential applications. Chapter 10 covers the grafting method and synthesis parameters for optimized AEMs. It discusses radiation‐induced graft copolymerization for anion‐exchange membranes and crosslinked structures for fuel cells and other applications. The insight toward the pathways leading to the degradation of organic and inorganic cationic functionalities, including β‐hydride elimination, nucleophilic substitution reactions, and ring‐opening reactions in heterocyclic systems, is discussed in Chapter 11. Chapter 12 confidently asserts the critical role of computational simulations in comprehending the underlying mechanisms, optimizing the design, and forecasting the performance of AEM systems. Chapter 13 delves into the characteristics and challenges of commercial membranes. Additionally, a comparison between commercial and non‐commercial AEMs is explored in detail, highlighting the obstacles faced by commercial AEMs. Furthermore, the current research on non‐commercial AEMs emphasizes their distinct properties and traits. Chapter 14 discusses the recent advancements in preparing membrane electrode assemblies (MEA) for AEMFCs. The chapter covers different methods, such as catalyst‐coated membrane (CCM) and gas diffusion electrode (GDE), to prepare MEAs. Chapter 15 expertly examines the multiple applications of AEMs in various cutting‐edge technologies, including alkaline water electrolyzers, CO2 electrolysis, redox flow batteries, alkali metal–air batteries, reverse electrodialysis, electrodialysis, diffusion dialysis, and microbial fuel cells. Chapter 16 of this book discusses cutting‐edge innovations in crafting high‐performance AEMs using polymer‐based substances. It also explores potential avenues for further research in this area, as well as the endurance of AEMFCs and the challenges of designing durable AEMs.

We extend our gratitude to all the contributors who have shared their expertise, as well as to the readers who embark on this journey with us. We sincerely thank Wiley‐VCH GmbH, Germany, for their invaluable support in bringing this book to fruition. Our collaborative efforts will explore the exciting realm of alkaline AEMs and their potential to transform the energy industry with eco‐friendly and renewable power generation. Step into the future of energy with us.

Thanks to All for the successful completion of this book!

February 2024

Jince ThomasAlex SchechterFlavio GrynszpanBejoy FrancisSabu Thomas

1An Introduction to Polymeric Electrolyte Alkaline Anion Exchange Membranes

Jince Thomas1, Minu Elizabeth Thomas2, Bejoy Francis3, and Sabu Thomas1

1 Mahatma Gandhi University, International and Inter University Center for Nanoscience and Nanotechnology, Kottayam, 686560, Kerala, India

2 Mahatma Gandhi University, School of Polymer Science and Technology, Kottayam, 686560, Kerala, India

3 Mahatma Gandhi University, St. Berchmans College, Department of Chemistry, Kottayam, 686101, Kerala, India

1.1 Introduction

Currently, the magnitude of energy usage cannot be denied. It is indispensable in every aspect of life, and a booming population results in increasing energy demand. Recognizing that nonrenewable sources will eventually run out, the value of renewable sources cannot be underestimated because they are sourced from unlimited sources. The most crucial consideration of renewable sources is their environmental impact while using them. The proper use of energy appears to be a major topic these days, and one must decide which type of energy should be used, and why it is vital?

The urgent necessity of researching, developing, and commercializing renewable energy sources and the technologies accompanying them is universally acknowledged as a prime focus. Time and place are essential components of most renewable energy systems. Therefore, it is crucial to build relevant energy conversion and storage devices to capture these unreliable energy sources effectively. The most prominent electrochemical energy storage and energy conversion devices are batteries, electrochemical super capacitors, and fuel cells.

Electrolytes are vital components of electrochemical energy storage and conversion devices, and their properties and performance can significantly impact the overall efficacy, safety, and longevity of these systems. Although electrolytes have been recognized and researched for centuries, their physiological role was not fully understood until the late nineteenth and early twentieth centuries [1, 2]. Starting from that point, researchers delved deeper into the behavior of electrolytes, focusing on their conductive properties. This led to the creation of innovative electrochemical techniques and tools, like the pH meter and the potentiometer. Later on, advancements in materials science and engineering resulted in the development of solid‐state electrolytes with high ion conductivity, which are widely used in batteries, fuel cells, and electrochromic devices. Nowadays, there is a growing interest in crafting new electrolytes for emerging electrochemical applications, such as energy storage and conversion, electrochemical water treatment, sensing, and biosensing.

1.2 Different Types of Electrolytes

Understanding the classification of electrolytes can provide valuable information about their behavior and properties in different applications, depending on the specific context and purpose. There are various ways to classify electrolytes, such as the type of ions they contain, their physical form, and their conductivity [3]. Below are some of the most frequently used methods for categorizing electrolytes,

Based on the origin

The type of ions present

Its physical state

Conductivity measure

The contrast between acidic and alkaline properties

The most popular is the classification based on the physical nature of electrolytes (Figure 1.1). During the early 1970s, researchers began exploring the potential of solid‐state materials such as ceramic, glass, crystalline, and polymer electrolytes. This led to various types of polymer electrolytes with different compositions and structures, including solid‐state polymer electrolytes (polymer–salt complex), gel polymer electrolytes, composite polymer electrolytes, and ionic liquid polymer electrolytes.

Figure 1.1 Classification of electrolytes.

The solid‐state electrolytes have more advantages than conventional liquid electrolytes. The advantages and disadvantages of solid‐state and conventional liquid‐state electrolytes are presented in Table 1.1.

Table 1.1 Advantages and disadvantages of liquid‐state and solid‐state electrolytes.

Electrolyte

Advantages

Disadvantages

Liquid

 Effortless processing

 Gas solubility is low

 Low cost

 Change on concentration

 Ionic conductivity is high

 Potential window is short

 Using different ions

 Parallel reactions

 Interactions with other gases

Solid

 A wider potential window

 Complex processing

 No parallel reactions

 Low ionic conductivity

 Gas solubilization is not required

 Expensive

 Low external interferences

Our focus is on solid‐state electrolytes, specifically polymer electrolytes. A polymer electrolyte is a membrane that has alkali–metal–ion conductivity. It is composed of a polymer matrix as a solvent and solutions of salts that are dissociated within the polymer matrix. Polymer electrolyte is a remarkable solid‐state system that showcases impressive ionic conduction abilities, making it an ideal choice for a wide range of electrochemical devices like rechargeable batteries [4], solid‐state batteries [5], fuel cells [6], supercapacitors [7], electrochemical sensors [8], electrochromic windows, and analog memory devices [3, 9, 10].

1.3 Why Polymer Electrolytes Are Important?

Polymer electrolytes have distinct advantages over conventional electrolytes, making them essential in many fields and applications. They offer increased safety, especially in high‐energy applications like lithium‐ion batteries, as they are solid or gel‐like, reducing the risk of fire or explosion. Polymer electrolytes also exhibit improved chemical and electrochemical stability, which minimizes electrode degradation and corrosion, leading to better device performance and longer lifespan. They have a broad electrochemical stability window, which enables operation at higher voltages without decomposition, which is critical for high‐voltage batteries and supercapacitors. Although their ionic conductivity is lower than that of liquid electrolytes, advancements in polymer chemistry have improved conductivity, expanding their suitability for diverse applications.

Another benefit of polymer electrolytes is their ability to be processed into various shapes and forms, such as thin films or membranes, making them versatile for different device configurations and facilitating complex system integration and device miniaturization. Additionally, many polymer electrolytes are eco‐friendly and are made from sustainable and recyclable materials, providing a greener alternative to liquid electrolytes containing hazardous components. Their compatibility with different materials and ability to function in various conditions make them ideal for numerous technologies. Some important benefits to using polymer electrolytes in comparison to traditional liquid electrolytes are

High ionic conductivity

Solvent‐free

Reduced leakage

Safety

Easy processability

Thin‐film forming ability and transparency

Light‐weight and flexibility

Polymer electrolyte membranes are mainly categorized into two types: anion exchange membranes (AEMs) and cation exchange membranes (CEMs). They are designed in a way that enables them to selectively transport either anions or cations, depending on their characteristics. The two membranes have significant functions in different electrochemical devices. The choice of the membrane is determined by the system's unique needs and ion transport goals. In Table 1.2, a comparison between AEM and CEM is presented.

Table 1.2 Comparison of anion exchange membranes and cation exchange membranes.

Properties

AEM

CEM

Ion transport selectivity

Selective transport of anions

Selective transport of cations

pH operating range

Suitable for alkaline environments

Suitable for acidic environments

Requirement of the catalyst

Non‐precious metal catalysts

Precious metal catalysts

Hydration tolerance

Excessive hydration can lead to swelling and instability, while insufficient hydration can hinder ion transport

More tolerant to varying water content compared to AEMs

Fuel flexibility

High

Limited

The choice between AEMs and CEMs is often driven by the electrochemical device's specific requirements and operating conditions. Although AEMs have advantages, like lower cost, the ability to utilize various renewable fuels directly, and higher pH operation, CEMs are also beneficial due to their higher proton conductivity and compatibility with acidic environments. Choosing between AEMs and CEMs depends on factors like the required pH range, cost, fuel accessibility, and performance objectives. These two types of membranes are essential in the progress of sustainable energy technologies, and their unique features aid in the overall enhancement and refinement of electrochemical devices. To reap the full benefits of ion exchange membranes in electrochemical applications, it is imperative to have a comprehensive comprehension of the pros and cons of AEMs versus CEMs. Thoughtful contemplation is critical.

1.4 Anion Exchange Membrane (AEM)

AEMs are made up of ion‐conducting polymers that possess functional groups that attract and transport anions. Their primary purpose is to facilitate the movement of anions, such as hydroxide (OH−) and bicarbonate (HCO3−), while hindering the transfer of cations. The selectively permeable AEMs contain positively charged functional groups that facilitate anion transport while preventing cation crossover. Various materials are utilized in the production of AEMs, including quaternary ammonium ions [11], imidazolium ions [12, 13], guanidinium ions [14–16], phosphonium ions [17], spirocyclic cations [18], carbocations [19], ionic liquids [20], multi‐cations [21, 22], and metal cations [23], which are all functionalized with polymers [24].These remarkable functional groups exhibit the fundamental capability of ion exchange by attracting and transporting anions across the membrane while simultaneously maintaining the balance of the overall charge.

1.4.1 Fundamental Concepts of Anion Exchange Membranes as Polymer Electrolytes

Understanding the fundamental concepts underlying AEMs is crucial in grasping their significance in polymer electrolyte applications. These specialized membranes possess unique characteristics that enable them to function effectively and are critical in ensuring effective ion conduction. By recognizing their value, we can unlock the full potential of polymer electrolyte systems. It is crucial to carefully evaluate the membrane's performance under operational conditions, durability, and cost targets to ensure the successful commercial development of the AEM as an electrolyte. These key factors significantly influence the desired properties and demand careful consideration. The membrane is designed to facilitate the transport of anions while blocking the flow of cations, gases, and electrons. Choosing the cationic group is essential to achieve a high concentration of charges in the membrane and ensure sufficient ionic mobility. It is even more critical to select the right cationic group as it directly impacts the chemical stability of the membrane in optimal operating conditions. Also, a viable approach is to augment the ionic groups within the membrane to improve ionic conductivity.

However, the high concentration of the cationic group can adversely affect the mechanical properties due to excessive water absorption. Therefore, it becomes imperative to implement stringent control measures over the membrane's morphology to enhance its mechanical attributes. However, when the membrane is too hydrated or brittle due to intensive dryness, it will deteriorate the membrane's mechanical properties and have a profoundly negative impact on cell performance. Therefore, maintaining the appropriate level of water uptake is crucial for optimal membrane performance.

Thus, in a nutshell, for optimal performance of the AEM, the following requirements are the desired prerequisites:

High anion conductivity is essential for efficient ion transportation in materials.

Maintain chemical stability to withstand the effects of the electrolyte environment and avoid degradation.

Strong and stable materials are essential for device longevity and proper functioning, maintaining structural integrity and minimizing deterioration.

Need high selectivity for anions to avoid cation crossing.

Function as an absolute barrier to prevent the passage of undesirable particles like electrons and gases.

A balance of water uptake and retention is necessary.

Manufacturable using scalable and cost‐effective techniques to ensure their commercial viability.

Thus, to fully maximize the effectiveness of polymer electrolytes in various electrochemical applications, it is crucial to have a solid grasp on the core concepts of AEMs. This includes understanding their selective ion transport, ion exchange capacity, and water uptake. Through the use of precise and meticulous characterization techniques, the researchers were able to confirm these essential parameters.

Several techniques and measurements are employed to evaluate the structural, morphological, chemical, and electrochemical properties of AEMs. These characterizations offer valuable insights into the behavior and performance of AEMs, facilitating their optimization and comprehension. To identify the AEM’s chemical structure, the polymer backbone and functional groups are analyzed through spectroscopic techniques like Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR). Furthermore, membrane morphology can be analyzed using microscopic techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). To evaluate a membrane’s chemical stability over time, subjecting them to harsh chemical environments for desired time is necessary. Meanwhile, their mechanical strength can be analyzed by measuring parameters like tensile strength, Young's modulus, and elongation at break. To measure the thickness of AEMs, techniques such as micrometers or profilometers can be used. The swelling behavior of the membrane is related to its dimensional changes upon water absorption, which can also be examined by measuring its thickness.

The ion exchange capacity is an important factor that measures the amount of ion exchange locations in the AEM material. It is calculated using titration methods, wherein the membrane is subjected to a known concentration of an ion, and the number of exchanged ions is measured. The determination of membrane conductivity can be achieved through either electrochemical impedance spectroscopy (EIS) or conductivity measurements conducted under controlled conditions. Water uptake can be evaluated by comparing the weight or volume of the dry membrane to that of the fully hydrated membrane.

Currently, computational simulations and machine learning methods are utilized to explore the properties and efficiencies of AEM. These techniques aid in proposing novel membrane structures, transport mechanisms, and stability, as well as identifying discrepancies and factors that may be challenging to determine through experimental results.

1.4.2 Classification of AEM

Researchers are currently experimenting with new techniques to create membranes that meet the basic requirements necessary for their function. As a result, there are now numerous types of membrane structures, each classified according to their unique morphology [24, 25]. They are

Heterogeneous

Ion solvating polymers

Hybrid membranes

Interpenetrated polymer networks

Homogeneous

Copolymerization of monomers

Radiation grafting

Chemical modification

A heterogeneous membrane consists of an anion‐exchange material embedded within an inert compound. These membranes can be categorized into two types based on their composition. The first type comprises ion‐solvating polymers composed of a water‐soluble polymeric matrix containing electronegative heteroatoms, hydroxide ions, and plasticizers. This combination results in a material that possesses the polymeric matrix's mechanical properties and the hydroxide ions' electrochemical properties. Materials fabricating ion‐solvating polymers include polyethylene oxide (PEO), polyvinyl alcohol (PVA), and chitosan. These polymers exhibit good mechanical properties, and their ionic conductivity at contact electrodes tends to be low due to their thickness and high electrical resistance. On the other hand, hybrid membranes are composed of both organic and inorganic segments. The organic components contribute to the electrochemical properties, while the inorganic elements, typically silica or siloxane, enhance the mechanical properties. Examples of hybrid membranes include combinations of PEO, PVA, and polyphenylene oxide (PPO) with silica (SiO2) or titanium dioxide (TiO2). Despite the good mechanical properties of incorporating inorganic components, membranes in this category still suffer from the nonuniformity issue observed in ion‐solvating polymers. Consequently, their ionic conductivity remains similar or even lower.

Interpenetrated polymer network membranes, which belong to another class of AEMs, demonstrate higher ionic conductivities compared to heterogeneous membranes. These membranes are created by blending two polymeric materials through cross‐linking without promoting the formation of covalent bonds between them. One of the polymers is hydrophobic and possesses excellent chemical, mechanical, and thermal properties, while the other polymer acts as an ionic conductor. Fabrication of interpenetrated polymer network membranes is simple, and various polymers may be employed, making them cost‐effective. The primary focus of research on membranes in this category includes materials such as polyethylene, PVA, polysulfone, and PPO. These membranes exhibit low electrical resistance, high mechanical strength, chemical stability, and durability. However, due to the absence of covalent bonds between the constituent materials, the conductive polymer slowly diffuses out of the membrane over time. This leads to gradual decreases in conductivity and ion exchange capacity. Homogeneous membranes represent another class of AEMs. These membranes are formed using polymers composed of a single material modified to possess ion exchange capacity. The modification involves covalently attaching cationic functional groups to the polymer backbone, creating ionic sites within the membrane along with associated mobile counterions. The classification of homogeneous membranes is based on the specific methods used for functionalization, including copolymerization, radiation grafting, and chemical modification. Detailed discussions on these classifications will be presented in the forthcoming chapters dedicated to this subject.

1.4.3 Pros and Cons of AEM

Understanding the advantages and disadvantages of AEMs is crucial for enhancing their utilization in various electrochemical applications and advancing the development of efficient and long‐lasting energy conversion devices. Table 1.3 highlights the pros and cons of using AEMs as an electrolyte.

Table 1.3 Pros and cons of anion exchange membranes.

Pros

Cons

High ionic conductivity

Excessive water uptake can lead to swelling and reduced mechanical stability

Precise control over selective ion transport

Limited stability at high temperatures

Operate over a broad pH range

The diffusion of mobile counterions out of the membrane decreased conductivity and ion exchange capacity over time

Good resistance to chemical degradation

Require periodic cleaning or replacement due to the susceptibility to fouling by organic and inorganic species

Long‐term stability in aggressive environments

Manufacturing complexity and limited material options compared to other membranes

Exhibit high mechanical strength and resilience

Compatible with aqueous electrolytes

Manufactured at a reasonable cost

Researchers and engineers can make educated judgments about selecting, optimizing, and building AEMs for specific applications by knowing their strengths and limits. Addressing the issues with these membranes will result in improved performance, longer lifespan, and wider use of AEM‐based systems in the field of energy conversion and storage.

1.4.4 Application of AEM

AEMs are highly adaptable membranes with the unique ability to hinder cations while permitting a selective flow of anions. Their versatility makes them indispensable in numerous industries, ranging from energy to water treatment and beyond. Their ability to control the movement of ions makes them a crucial tool for many vital processes, including separation, purification, and desalination, in addition to their role as electrolytes. The following are some of the significant applications of AEMs.

Electrochemical Energy Conversion

:

Alkaline fuel cell

s (

AFC

s) and alkaline water electrolyzers frequently use AEMs, which are electrochemical devices. In AFCs, AEMs facilitate the electrochemical reaction by transporting hydroxide ions (OH

−

) from the cathode to the anode. In alkaline water electrolyzers, AEMs play a crucial role in separating gases by selectively conducting hydroxide ions.

Water Treatment

: AEMs are useful in different water treatment methods like electrodialysis and electro‐deionization. They serve to eliminate undesired anions, specifically nitrates, sulfates, and chlorides, from water sources, which is beneficial for both water purification and desalination.

Electrodialysis

:

AEMs have the vital function of letting only anions pass through the membrane while preventing the migration of cations in electrodialysis. This crucial process facilitates separating and eliminating undesired ions from a solution.

Electrochemical Sensors

:

AEMs can be integrated with ion‐selective electrodes to identify specific anions present in solutions. These AEM‐based sensors are extensively used for environmental monitoring, water quality analysis, and industrial process control.

Chlor‐alkali Industry

:

The chlor‐alkali industry is responsible for producing chlorine gas (Cl

2

), sodium hydroxide (NaOH), and hydrogen gas (H

2

) via the electrolysis of saltwater. AEMs are utilized as ion exchange membranes in the electrolytic cells to facilitate this process. These membranes permit the migration of chloride ions (Cl

−

) and hydroxide ions (OH

−

) while preventing the passage of sodium ions (Na

+

), which guarantees the desired separation of products.

The most significant application of AEMs is prominently displayed in the diagrammatical representation of Figure 1.2. AEMs find extensive usage in fuel cell applications, specifically in AFCs. The primary area of research for AEMs is centered on fuel cells, aiming to improve their performance, stability, selectivity, and cost‐effectiveness.

Figure 1.2 Important application of anion exchange membranes.

1.5 AEMs in Fuel Cells

A fuel cell is an energy conversion device that directly converts the fuel's chemical energy into electrical energy by chemically reacting a fuel with an oxidant, usually oxygen from the air. Although the origins of the fuel cell invention are uncertain, two notable individuals are associated with its discovery. Christian Friedrich Schönbein's work on the concept was published in the January 1839 issue of Philosophical Magazine, according to the United States Department of Energy. Meanwhile, Sir William Grove developed the fuel cell and published his findings in the February 1839 issue of the same magazine, as noted by Grimes. Fuel cell technology has grown substantially since its discovery in the nineteenth century. Through the years, researchers and engineers have made significant strides in enhancing fuel cells' efficiency, durability, and practicality. This progress results in the emergence of diverse fuel cell types, each with its distinct features and uses.

The fundamental design of a fuel cell involves an electrolyte layer that separates two electrodes – the anode and the cathode. The electrolyte facilitates the movement of ions while simultaneously preventing any mixing of the fuel and oxidant gases. In the early stages, AFCs utilize a liquid electrolyte solution containing potassium hydroxide (KOH), as it is the most conductive among alkaline hydroxides. Compared to other fuel cells, these AFCs have certain benefits. They are easier to manage as they operate at a relatively lower temperature, have electrodes made of inexpensive metals, and exhibit higher reaction kinetics at the electrodes compared to acidic conditions. However, the sensitivity of the KOH solution to CO2 limits the AFC's use of liquid electrolytes. Optimal operation requires low CO2 concentrations in the oxidant stream. If oxygen is replaced with air, the hydroxyl ions may react with CO2 present in the air, leading to the formation of K2CO3. This leads to the precipitation of K2CO3 crystals and reduces the availability of hydroxyl ions, leading to decreased efficiency. Incorporating solid electrolytes in proton fuel cells (PFCs) has paved the way for anion‐conducting polymer electrolyte membranes to be integrated into AFCs. This move effectively resolves most issues caused by liquid electrolytes, giving rise to a new subfield of AFCs – the anion exchange membrane fuel cell (AEMFC) – and leading to unprecedented growth in the industry. Using a membrane instead of a liquid electrolyte has several advantages. One significant benefit is eliminating the adverse effects of CO2, which reduces electrode weeping and corrosion. Other membrane benefits include leak‐proof properties, volumetric stability, solvent‐free conditions, and easy handling. Additionally, the size and weight of the fuel cell are reduced, which expands its potential uses. Thus, AEM is used in an AFC to enhance efficiency and lifespan by slowing down performance degradation over time. It is essential to continue researching and developing AEMs to advance fuel cell technology and facilitate its widespread use as a reliable and eco‐friendly energy conversion solution. Although AEM fuel cells have potential advantages and commercial significance, they are still in their early stages of commercialization and have not yet been widely deployed compared to other fuel cell types, such as proton exchange membrane fuel cells (PEMFCs). Nevertheless, there has been growing interest and research in AEM fuel cells.

The demand for clean and sustainable energy solutions is rising, and AEMFCs are gaining commercial significance due to their advantages over other types of fuel cells. AEMFCs use a polymer membrane that is more resistant to degradation, reducing maintenance and replacement costs. They also use low‐cost materials, such as non‐precious metal catalysts, making them more cost‐effective than other fuel cell types. AEMFCs offer fuel flexibility, allowing for the use of various fuels, making them adaptable to different energy sources, and enabling the utilization of existing infrastructure and fuel distribution networks. They have shown promising efficiency levels, potentially converting more fuel energy into usable electrical energy, leading to improved overall energy conversion. Additionally, the polymer membrane used in AEMFCs allows for efficient control of water transport, preventing flooding and facilitating better performance under varying operating conditions. They produce clean electricity without the combustion of hydrocarbon fuels, resulting in lower greenhouse gas emissions and improved air quality.

1.6 Conclusion and Outlook

AEMs as the polymer electrolyte have garnered much attention in electrochemical devices such as fuel cells, batteries, and electrolyzers. AEMs possess unique properties that make them well‐suited for various energy conversion and storage applications. Their primary function is to conduct negatively charged ions or anions while impeding the transport of positively charged ions or cations. This selective ion transport is achieved through positive charges or functional groups embedded in the polymer matrix of the membrane. These polymers have excellent mechanical strength, chemical stability, and suitable conductivity for hydroxide (OH−). The OH− conductivity is a crucial characteristic of AEMs, enabling efficient anion transport in alkaline environments. Due to their cost‐effectiveness, durability, and fuel flexibility, they are highly valued and widely used in commercial settings.

AEM has a broad range of applications. For instance, AEM‐based AFCs have shown improved tolerance to carbon monoxide poisoning, enhanced catalyst kinetics, and reduced reliance on expensive platinum catalysts. Compared to other fuel cell types, AEMFCs have these benefits, making them a commercially significant option for clean energy generation in various industries. Additionally, AEMs are widely used in alkaline water electrolyzers, which split water into hydrogen and oxygen using electricity.

One of the significant advantages of AEMs as polymer electrolytes is their ability to operate at low temperatures. Unlike proton exchange membranes (PEMs), which require high operating temperatures, AEMs can function effectively at room temperature or even lower. This feature offers opportunities for developing energy conversion devices that are more cost‐effective, efficient, and durable. Moreover, AEMs have environmental benefits, making them a desirable and viable option for the future.

Despite holding great promise in various electrochemical applications, AEMs face challenges such as alkaline stability, ion transport, water management, mechanical stability, and catalyst compatibility. These challenges need to be addressed for widespread adoption. However, with continued research and development, AEM‐based devices have the potential to contribute significantly to a cleaner and more sustainable energy future.

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