Functional Materials for Electrocatalytic Energy Conversion 9783527353651

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Functional Materials for Electrocatalytic Energy Conversion

Functional Materials for Electrocatalytic Energy Conversion Edited by Zhicheng Zhang, Meiting Zhao, and Yuchen Qin

Editors

Department of Chemistry, School of Science; Tianjin Key Laboratory of Molecular Optoelectronic Sciences Tianjin University China

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Prof. Meiting Zhao

Library of Congress Card No.: applied for

Prof. Zhicheng Zhang

Department of Chemistry, Institute of Molecular Aggregation Science, Tianjin Key Laboratory of Molecular Optoelectronic Sciences Tianjin University Tianjin China Prof. Yuchen Qin

College of Science Henan Agricultural University Zhengzhou China Cover: © Andriy Onufriyenko/

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v

Contents Preface xvii Acknowledgments xix About the Editors xxi 1

Introduction 1 Ruoqing Xu, Jie Wang, Lilin Zhang, and Jingjie Ge Acknowledgment 4 References 4

Part I

2

2.1 2.2 2.2.1 2.2.2 2.3 2.3.1 2.3.1.1 2.3.1.2 2.3.1.3 2.3.1.4 2.3.2 2.3.2.1 2.3.2.2 2.3.2.3 2.3.2.4 2.3.3

Advanced Functional Materials for Electrocatalytic Energy Conversion 7

Density Functional Theory for Electrocatalytic Energy Conversion 9 Wei Li and Ding Yi Introduction 9 Computational Methods 10 Reaction Free Energy 10 Electronic Structures 11 Application of DFT in Electrocatalysis 12 Hydrogen Evolution Reaction 12 Reaction Mechanism 12 Detailed Computational Methods for HER 13 Descriptors 13 Structure–Activity Relationship 14 Oxygen Reduction Reaction 15 Reaction Mechanism 17 Detailed Computational Methods for ORR 18 Descriptors 19 Structure–Activity Relationship 20 Nitrogen Reduction Reaction 22

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Contents

2.3.3.1 2.3.3.2 2.3.3.3 2.3.3.4 2.4

Reaction Mechanism 22 Detailed Computational Methods for NRR Descriptors 24 Structure–Activity Relationship 25 Conclusion 26 Acknowledgment 27 References 27

3

Electrocatalytic Reaction Mechanism for Energy Conversion 33 Hao Ma and Yuanmiao Sun Introduction 33 Electrochemical Parameters of Electrocatalysts 34 Overpotential 34 Faradic Efficiency 35 Gibbs Free Energy 35 Tafel Slope 36 Turnover Frequency 36 Exchange Current Density 36 Fundamentals of Electrocatalytic HER 37 Fundamentals of Electrocatalytic OER 38 Fundamentals of Electrocatalytic ORR 41 Fundamentals of Electrocatalytic CO2 RR 42 Fundamentals of Electrocatalytic NRR 45 Summary 47 References 47

3.1 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.3 3.4 3.5 3.6 3.7 3.8

Part II

4

4.1 4.1.1 4.1.2 4.2 4.2.1 4.2.1.1 4.2.1.2 4.2.2 4.3

23

Advanced Functional Materials for Electrocatalytic Hydrogen Evolution Reaction 51

Metal-Based Materials for Electrocatalytic Hydrogen Evolution Reaction 53 Rongbo Sun, Xiaoqian Wang, Gang Xie, Hongwen Huang, and Jingjie Ge Introduction 53 Mechanism of the Electrocatalytic HER 54 Theoretical Method for Describing the Efficient HER Catalyst 55 Electrocatalytic HER Activity on Metal-Based Materials 56 PGM-Based Materials 57 Pt-Based Materials 57 Other PGM-Based Materials 60 Non-PGM-Based Materials 64 Conclusion and Outlook 67 Acknowledgment 68 References 68

Contents

5

5.1 5.2 5.2.1 5.2.1.1 5.2.1.2 5.2.2 5.2.2.1 5.2.2.2 5.2.3 5.2.3.1 5.2.3.2 5.2.3.3 5.2.3.4 5.2.4 5.2.4.1 5.2.4.2 5.2.4.3 5.2.4.4 5.3

6

6.1 6.2 6.2.1 6.2.2 6.3 6.3.1 6.3.1.1 6.3.1.2 6.3.2 6.3.2.1 6.3.2.2 6.3.2.3 6.3.3 6.3.4 6.4

Metal Compounds for Electrocatalytic Hydrogen Evolution Reaction 75 Tingting Yin, Wei Jiang, and Guigao Liu Introduction 75 Metal Compounds as HER Electrocatalysts 76 Metal Chalcogenides 76 Transition Metal Dichalcogenides 76 Non-Layered Metal Chalcogenides 80 Transition Metal Oxides and Hydroxides 81 Transition Metal Oxides 82 Layered Transition Metal Hydroxides 84 Transition Metal Carbides and Nitrides 85 Wx C 87 Mox C 87 Cox C 87 MXenes 88 Transition Metal Phosphide 88 FePx 89 MoP 89 CoP 89 NiP 91 Conclusion and Outlook 92 Acknowledgments 93 References 93 Carbon-Based Materials for Electrocatalytic Hydrogen Evolution Reaction 103 Zhangyou Wang, Sundus Umer, Lu Hao, Fangge Cheng, Jiawen Li, and Jia Liu Introduction 103 The Fundamentals of HER 105 Mechanistic of HER 105 Kinetics and Rate-Determining Steps in HER 106 HER Electrocatalysts of Carbon-Based Materials 108 Carbon-Based Metal-Free Electrocatalysts 108 Acidic HER Performance 109 Alkaline HER Performance 110 Low-Dimensional Carbon Material and Heteroatom-Doped Carbon 111 Carbon Quantum Dots 111 Carbon Nanotube Catalysts for HER 114 Graphene, N-Doped Carbon, and g-C3 N4 118 MOF-Derived Electrocatalysts 122 Atomic Metal Doping of Carbon Materials 124 Summary 127 References 129

vii

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Contents

7

7.1 7.2 7.3 7.4 7.5

Porous Materials for Electrocatalytic Hydrogen Evolution Reaction 139 Lixin Yi, Xiaoyan Qu, and Zhengqing Liu Introduction 139 Porous 1D Nanomaterials 141 Porous 2D Nanomaterials 148 Porous 3D Nanomaterials 153 Conclusion and Outlook 156 Acknowledgment 156 References 157

Part III

8

8.1 8.2 8.2.1 8.2.1.1 8.2.1.2 8.2.2 8.3

9

9.1 9.2 9.2.1 9.2.1.1 9.2.1.2 9.2.1.3 9.2.2 9.2.2.1 9.2.2.2 9.2.2.3 9.2.3 9.3

Advanced Functional Materials for Electrocatalytic Oxygen Reduction Reaction 163

Metal-Based Materials for Electrocatalytic Oxygen Reduction Reaction 165 Congli Qin and Aixin Fan Introduction 165 Metal-Based Materials for ORR 166 Pt-Based Materials for ORR 166 Composition Regulation of Pt-Based ORR Catalysts 166 Structural Design of Pt-Based Catalysts for ORR 167 Non-Pt-Based Metal Materials for ORR 175 Conclusion and Outlook 175 Acknowledgment 176 References 176 Carbon-Based Materials for Electrocatalytic Oxygen Reduction Reaction 183 Congli Qin and Aixin Fan Introduction 183 Carbon-Based Materials for ORR 184 Carbon-Based Metal-Free Materials for ORR 184 Nitrogen-Doped Carbon Nanomaterials 184 Carbon Nanomaterials Doped with Non-Nitrogen Heteroatoms Carbon Nanomaterials Co-Doped with Heteroatoms 186 Carbon-Based Nonprecious Metal Single-Atom Catalyst 187 Fe-Based Single-Atom Catalyst 187 Non-Fe-Based Single-Atom Catalyst 188 Bimetallic Single-Atom Catalyst 189 Carbon-Based Non-Noble Metals for ORR 189 Conclusion and Outlook 190 Acknowledgment 191 References 191

185

Contents

10

10.1 10.2 10.2.1 10.2.2 10.2.3 10.3 10.3.1 10.3.2 10.3.3 10.4 10.4.1 10.4.2 10.4.3 10.5

Porous Materials for Electrocatalytic Oxygen Reduction Reaction 197 Jing Li, Chang Long, and Jun Guo Introduction 197 Noble Metal-Based Porous ORR Catalysts 197 Pt-Based Porous ORR Catalysts 197 Pd-Based Porous ORR Catalysts 200 Other Precious Metal-Based Porous ORR Catalysts 201 Transition Metal-Based Porous ORR Catalysts 201 Transition Metal/Carbon Composite Porous ORR Catalysts 202 Transition Metal Oxide/Carbon Composite Porous ORR Catalysts 203 Transition Metal/Carbon and Nitrogen Composite Porous ORR Catalysts 204 Carbon-Based Metal-Free Porous ORR Catalyst 206 Nitrogen-Doped Carbon-Based Porous ORR Catalysts 206 Heteroatom Co-Doped Carbon-Based Porous ORR Catalysts 206 Undoped Carbon-Based Porous ORR Catalysts 207 Summary 208 References 208

Part IV

11

11.1 11.2 11.3

12

12.1 12.2 12.2.1 12.2.2 12.2.3 12.3 12.3.1

Advanced Functional Materials for Electrocatalytic Oxygen Evolution Reaction 213

Metal-Based Materials for Electrocatalytic Oxygen Evolution Reaction 215 Mengyi Xu, Xu Li, Yurong Su, Meirong Song, Xianfu Zheng, Yuchen Qin, Guangxin Ru, Xiuhong Zhu, Shun Wang, and Xia Sheng Introduction 215 Metal Single-Atom Materials 216 Metal Alloys Materials 221 References 228 Metallic Compounds for Electrocatalytic Oxygen Evolution Reaction 233 Xiaobo Zheng and Yao Wang Introduction 233 Metal Oxides and Their Supported Single-Atom/Nanoparticle Materials 234 Metal Oxides 234 Metal Oxide-Supported Nanoparticle Materials 239 Metal Oxide-Supported Single-Atom Materials 241 Metal Hydroxides and Their Supported Single-Atom/Nanoparticle Materials 242 Metal Hydroxides 244

ix

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Contents

12.3.2 12.3.3 12.4

Metal Hydroxide-Supported Nanoparticle Materials 245 Metal Hydroxide-Supported Single-Atom Materials 245 Conclusion and Perspective 247 Acknowledgments 248 References 248

13

Porous Materials for Electrocatalytic Oxygen Evolution Reaction 255 Zhongjie Yang and Danfei Fu Introduction 255 Metal–Organic Frameworks (MOFs) for OER 257 Pristine MOFs for OER 257 Mixed-Metal Node Engineering 257 Ligand-Based Modification Engineering 257 Structure Engineering 259 MOF Composites for OER 259 MOF/Support Composites 259 MOF/Active Species Composites 261 MOF Derivatives for OER 261 M–N–PC for OER 261 MOs for OER 262 Other Composites for OER 264 Covalent–Organic Frameworks (COFs) for OER 265 Pristine COFs for OER 265 Metal-Free COFs for OER 265 Metal Sites Containing COFs for OER 266 COF Composites for OER 267 Carbon Materials Supporting COF for OER 267 Metal Hybrids Containing COF for OER 268 COF Derivatives for OER 269 Summary and Perspective 269 Acknowledgment 271 References 271

13.1 13.2 13.2.1 13.2.1.1 13.2.1.2 13.2.1.3 13.2.2 13.2.2.1 13.2.2.2 13.2.3 13.2.3.1 13.2.3.2 13.2.3.3 13.3 13.3.1 13.3.1.1 13.3.1.2 13.3.2 13.3.2.1 13.3.2.2 13.3.3 13.4

Part V

14

14.1 14.2 14.2.1

Advanced Functional Materials for Electrocatalytic CO2 Reduction Reaction 279

Cu-Based Metal Materials for Electrocatalytic CO2 Reduction Reaction 281 Mingliang Hu, Junjun Li, Yongxia Shi, Man Hou, Xinyi Wang, Zhenwei Zhao, and Zhicheng Zhang Introduction 281 Cu-Based Metal Materials for Electrocatalytic CO2 Reduction 283 Cu-Based Bimetal Materials for Electrocatalytic CO2 Reduction 283

Contents

14.2.1.1 14.2.1.2 14.2.1.3 14.2.1.4 14.2.1.5 14.2.1.6 14.2.1.7 14.2.1.8 14.2.1.9 14.2.1.10 14.2.2 14.3

15

15.1 15.2 15.2.1 15.2.2 15.3 15.3.1 15.3.2 15.3.3 15.4 15.4.1 15.4.2 15.5

16

16.1 16.2 16.3 16.3.1 16.3.1.1 16.3.1.2

Cu–Co 283 Cu–Ni 283 Cu–Ga 284 Cu–Ce 286 Cu–Bi 287 Cu–In 288 Cu–Zn 289 Cu–Al 291 Cu–Au 292 Cu–Ag 293 Cu-Based Trimetallic Materials for Electrocatalytic CO2 Reduction 295 Conclusion and Outlook 296 Acknowledgment 297 References 297 Non-Cu Metal-Based Materials for Electrocatalytic CO2 Reduction Reaction 305 Liu-Liu Shen and Gui-Rong Zhang Introduction 305 Non-Cu Metal-Based Catalyst for Electrocatalytic CO2 Reduction 307 Monometallic catalysts 307 Multimetallic Catalysts 311 Non-Cu Metal Compounds 314 Metal Oxides 314 Metal Chalcogenides 316 Metal Carbides and Nitrides 318 Non-Cu Metal-Based Molecular Catalysts 320 Molecular Catalysts 320 Single-Site M–N–C Catalysts 321 Concluding Remarks and Outlook 323 Acknowledgment 324 References 324 Carbon-Based Materials for Electrocatalytic CO2 Reduction Reaction 333 Jingjing Wang, Haodong Zheng, Kai Ge, Boxiong Shen, Hui Liu, Xiwen Du, and Pengfei Yin Introduction 333 Fundamentals of Electrochemical CO2 Reduction 334 Categories of Carbon-Based Electrocatalysts 336 Metal-Free Carbon 337 Graphene Materials 337 Carbon Nanotubes 338

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Contents

16.3.1.3 16.3.1.4 16.3.2 16.3.3 16.3.3.1 16.3.3.2 16.4 16.4.1 16.4.2 16.4.3 16.4.4 16.5 16.5.1 16.5.2 16.6

Nanodiamond 339 Graphitic Carbon Nitride (g-C3 N4 ) 339 Metal–N–C SACs 340 Metal/Carbon Composites 342 Carbon-Supported Metal/Alloy 342 Graphitic-Layer-Encapsulated Metal/Alloy 343 Strategies for Modulation of Carbon-Based Electrocatalysts 344 Group Functionalization 344 Heteroatom Doping 344 Coordination Environment Control 345 Defects Control 346 Challenges for Carbon-Based CO2 RR Electrocatalysts 346 In Situ Characterization 346 Commercialization 347 Summary and Outlook 348 References 348

17

Porous Materials for CO2 RR 357 Zibo Zhao, Shun Zhang, and Meiting Zhao Introduction 357 Metal–Organic Frameworks (MOFs) 359 Porphyrin-Based Metal–Organic Framework 359 Zinc Imidazolate Frameworks (ZIFs) 361 Covalent Organic Frameworks (COFs) 364 Porphyrin Covalent Organic Framework 364 Phthalocyanine Covalent Organic Framework 366 Metal Bipyridyl COFs 368 MOF/COF-Derived Porous Materials 370 Copper-Based MOF/COF-Derived Porous Materials 370 Nickel-Based MOF/COF-Derived Porous Material 373 Summary and Prospect 375 Acknowledgments 377 References 377

17.1 17.2 17.2.1 17.2.2 17.3 17.3.1 17.3.2 17.3.3 17.4 17.4.1 17.4.2 17.5

18

18.1 18.1.1 18.1.2 18.1.3 18.1.4 18.1.5 18.1.6

Cu-Based Compounds for Electrocatalytic CO2 Reduction Reaction 381 Teng Wang and Yong Yang Cu-Based Compounds for Electrocatalytic CO2 Reduction 381 Copper(II) Oxide (CuO) 382 Cuprous(I) Oxide (Cu2 O) 383 Copper(II) Sulfide (CuS) 386 Copper(I) Sulfide (Cu2 S) 387 Copper Nitrides (Cu3 N) 387 Conclusion and Outlook 391 References 391

Contents

Part VI

19

19.1 19.2 19.2.1 19.2.2 19.2.3 19.3 19.3.1 19.3.2 19.3.3 19.4 19.4.1 19.4.2 19.5

20

20.1 20.2 20.3 20.4 20.5

21 21.1 21.2 21.2.1 21.2.2 21.2.3 21.2.4 21.2.5 21.3 21.3.1 21.3.2 21.3.3

Advanced Functional Materials for Electrocatalytic Nitrogen Reduction Reaction 395

Metal-Based Nanomaterials for Electrocatalytic Nitrogen Reduction Reaction 397 Yaxiao Guo, Chenhao Xiao, Shinuo Guo, Yi Liu, and Zhaoyang Yao Introduction 397 Precious Metal-Based Catalysts 398 Pt- and Pd-Based Catalysts 398 Au-Based Catalysts 400 Ru- and Rh-Based Catalysts 400 Non-Noble Transition Metal-Based Catalysts 401 Mo-Based Catalysts 402 Co-Based Catalysts 404 Fe-Based Catalysts 405 Center Metal-Coordinated Catalysts 405 MOF- and COF-Based Catalysts 406 Metal Complex-Based Catalysts 406 Conclusion and Outlook 408 Acknowledgment 408 References 408 Carbon-Based Materials for Electrocatalytic N2 Reduction Reaction 415 Wuyong Zhang, Xinsheng Liu, and Lei Dai Introduction 415 Heteroatom-Doping Carbon-Based Materials (HDCBMs) 417 Vacancy-Abundant Carbon Nitride Materials 421 Metal–Carbon Composite Materials 422 Conclusion and Outlook 424 References 425 Porous Materials for NRR 431 Shun Zhang and Meiting Zhao Introduction 431 Porous Metal-Based Materials for NRR 432 Porous Au-Based Electrocatalyst 432 Porous Pd-Based Electrocatalyst 432 Porous Ru-Based Electrocatalyst 435 Other Porous Noble-Based Electrocatalysts 435 Porous Non-Noble-Based Electrocatalysts 436 Metal–Organic Frameworks for NRR 439 Pristine MOF Electrocatalyst 439 MOF Composite Electrocatalyst 441 MOF-Derived Electrocatalyst 442

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Contents

21.3.3.1 21.3.3.2 21.4 21.5

MOF-Derived Metal Composite Electrocatalyst 442 MOF-Derived Carbon-Based Electrocatalyst 444 Covalent Organic Frameworks (COFs) for NRR 446 Conclusion and Outlook 448 Acknowledgment 449 References 450

Part VII Advanced Functional Materials for Liquid Fuel Oxidation 453 22 22.1 22.2 22.2.1 22.2.2 22.2.3 22.2.4 22.2.5 22.2.6 22.3 22.3.1 22.3.1.1 22.3.1.2 22.3.2 22.3.2.1 22.3.2.2 22.3.2.3 22.3.2.4 22.3.2.5 22.3.3 22.3.3.1 22.3.3.2 22.4

23

23.1 23.2 23.2.1 23.2.2

Metal-Based Materials for LFO 455 Yuchen Qin, Chao Gao, Ning Su, and Xia Sheng Introduction 455 Reaction Pathway 456 Methanol Oxidation Reaction 456 Ethanol Oxidation Reaction 456 Ethylene Glycol Oxidation Reaction 458 Glycerol Oxidation Reaction 458 Formic Acid Oxidation Reaction 459 HMF Oxidation Reaction 460 Advanced Metal-Based Electrocatalysts 460 Pt-Based Electrocatalysts 460 Methanol Oxidation Reaction (MOR) 461 Ethanol Oxidation Reaction (EOR) 462 Pd-Based Electrocatalysts 468 Methanol Oxidation Reaction (MOR) 468 Ethanol Oxidation Reaction (EOR) 469 Ethylene Glycol Oxidation Reaction (EGOR) 471 Glycerol Oxidation Reaction (GOR) 471 Formic Acid Oxidation Reaction (FAOR) 472 Other Noble Metal-Based Electrocatalysts 473 Advanced Au-Based Catalysts for LFO 473 Advanced Rh-Based Catalysts for LFO 474 Summary and Perspectives 474 References 476 Non-Noble Metal-Based Materials for Electrocatalytic Liquid Fuel Oxidation 483 Qi Zhou and Zhicheng Zhang Introduction 483 Non-Noble Metal Catalysts are Used for Electrocatalytic Oxidation of Liquid Fuels 485 Single Metal Catalyst 485 Transition Metal Oxides 485

Contents

23.2.3 23.2.4 23.2.5 23.2.6 23.3

Transition Metal Hydroxides 486 Transition Metal Phosphide 488 Transition Metal Sulfides 489 Transition Metal Nitrides 490 Conclusion and Outlook 491 Acknowledgment 492 References 492

24

Nonmetal Materials for Electrocatalytic Liquid Fuel Oxidation 497 Qi Zhou and Zhicheng Zhang Introduction 497 Synthetic Strategies for Heteroatom-Doped Carbon Materials Hard-Templating Synthesis 498 Soft-Templating Synthesis 498 Template-Free Synthesis 500 Heteroatom-Doped Carbon Materials for HzOR 501 Conclusion and Outlook 505 Acknowledgment 506 References 506

24.1 24.2 24.2.1 24.2.2 24.2.3 24.3 24.4

498

Part VIII Advanced Functional Materials for Electrocatalytic Biomass Conversion 509 25

25.1 25.2 25.3 25.4 25.5 25.6 25.7

26

26.1 26.2 26.3

Metal-Based Materials for Electrocatalytic Biomass Conversion 511 Xu Li, Mengyi Xu, Yurong Su, Xianfu Zheng, Yuchen Qin, Fawen Zhang, Guangxin Ru, Xiuhong Zhu, Meirong Song, Shun Wang, and Xia Sheng Introduction 511 Morphology Control 517 Heteroatom Doping 520 Defect Engineering 522 Heterostructuring 525 Single-Atom Modification 528 Challenges and Prospects of Metal-Based Materials in Electrocatalytic Biomass Conversion 530 References 531 Porous Materials for Electrocatalytic Biomass Conversion 539 Shun Zhang and Meiting Zhao Introduction 539 Porous Materials for Biomass Oxidation Reaction 539 Porous Materials for Biomass Reduction Reaction 547

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Contents

26.4

Conclusion and Outlook Acknowledgment 550 References 551

27

Summary and Perspective 553 Ruoqing Xu and Jingjie Ge Index 557

549

xvii

Preface With the continued rise in social energy demand and the decreasing availability of fossil fuels, there has been an increasing need for affordable, environmental friendly, and efficient renewable energy conversion and storage systems. This pursuit has become a critical challenge for modern society. Electrocatalysts play a crucial role in various energy storage and conversion systems, such as fuel cells, metal–air batteries, CO2 conversion, and water splitting. This is accomplished by accelerating electrochemical reactions, which is essential for enhancing the efficiency of energy conversion. This book aims to provide a comprehensive overview of functional materials in the electrocatalytic energy conversion process, including oxygen reduction, electrochemical CO2 reduction, water splitting, nitrogen reduction, liquid fuel oxidation, and electrocatalytic biomass conversion. In the first section, the catalytic mechanisms and pathways of various electrocatalytic reactions are systematically discussed. The second section uncovers the design ideas, geometric/electronic structures, and structure–activity relationships of various state-of-the-art electrocatalysts in detail. Finally, the book proposes the challenges and opportunities of electrocatalytic functional materials for energy conversion in the future. Through the dissemination of knowledge and information in this book, we aim to stimulate increased interest and investment in further research and development in the field of electrocatalysis, ultimately leading to impactful advancements in the use of functional materials for practical applications. 30 January 2024

Zhicheng Zhang Yuchen Qin Meiting Zhao

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Acknowledgments We thank editors Ashok Ravi, Nandhini Karuppiah and Alice Qian from Wiley for their great efforts in editing this book.

xxi

About the Editors Zhicheng Zhang is a professor of Tianjin University, China. He obtained his PhD degree from China University of Petroleum (Beijing) in 2012. Then he worked as a postdoctoral researcher in Tsinghua University. In 2014, he joined Nanyang Technological University (Singapore) as a research fellow. Since 2019, he joined Tianjin University as a full professor. His current research interests focus on the design and synthesis of functional metal-based nanomaterials and their applications in energy conversion and catalysis. Meiting Zhao obtained his PhD degree from National Center for Nanoscience and Technology in 2014 under the guidance of Prof. Zhiyong Tang. Then he worked as a postdoctoral research fellow in Prof. Hua Zhang’s group in Nanyang Technological University. In 2019, he joined Tianjin University as a professor. His research interests include the structure design, controlled synthesis and application of highly stable metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), and their composites with nanomaterials for selective catalysis and energy conversion. Yuchen Qin is currently a professor in College of Sciences, Henan Agricultural University. He received the PhD degree from China University of Petroleum (Beijing) in 2016. His current research interests are metal-based electrocatalysts, electrocatalysis, and photoelectrocatalysis.

1

1 Introduction Ruoqing Xu 1 , Jie Wang 2 , Lilin Zhang 1 , and Jingjie Ge 1 1 The Hong Kong Polytechnic University, Department of Applied Biology and Chemical Technology, 11 YuK Choi Road, Hung Hom, Kowloon, HongKong 2 Xihua University, Key Laboratory of Fluid and Power Machinery of Ministry of Education, Department of Materials Science and Engineering, School of Materials Science and Engineering, No. 9999, Hongguang Street, Pidu Area, Chengdu, 610039, China

With the current rapid growth of energy required by society, the rapid increase in fossil fuel consumption has led to a series of environmental pollution problems, such as global warming, ecosystem destruction, and air pollution. Therefore, the exploration of low-cost, green, and clean renewable energy conversion and storage technologies has become one of the most serious challenges facing today’s society [1]. Electrochemical energy storage and conversion systems such as fuel cells [2], metal–air batteries [3], water electrolysis devices [4], and carbon dioxide capture, storage, and reduction technologies [5] have emerged as important ways of dealing with environmental and energy crises. Electrocatalysis is a key technology for energy conversion, as it accelerates electrochemical reactions essential for improving conversion efficiency. It plays a central role in reactions such as water splitting, carbon dioxide reduction reaction (CO2 RR), nitrogen reduction reaction (N2 RR), and the production of liquid fuels, etc. For example, in water splitting, electrocatalysis facilitates the decomposition of water into hydrogen, a clean energy source essential for establishing a low-carbon economy. Catalysts enhance the energy conversion efficiency of electrocatalysis by reducing the activation energy of the reactants and optimizing the reaction pathways and rates. However, one of the most critical challenges is identifying suitable catalysts for various electrocatalytic reactions. These materials are expected to demonstrate efficient electrocatalytic activity, selectivity, and stability to ensure long-term, reliable energy conversion performance. Consequently, the properties of the electrode materials, such as composition, surface structure, and morphology, have to be carefully controlled according to the electrochemical conditions to achieve efficient and high-performance electrocatalysis. Functional materials offer more attractive solutions for sustainable energy conversion due to their lower costs and wider resource availability compared to conventional noble metal electrocatalytic materials [6, 7]. In addition, research on functional materials has facilitated the development of novel energy conversion

2

1 Introduction

technologies. For instance, CO2 RR enables the conversion of greenhouse gas CO2 into valuable chemical fuels using renewable electricity, providing new opportunities to reduce resource extraction and achieve carbon neutrality [5, 8]. Similarly, N2 RR, which converts of N2 to NH3 by electrochemical reduction is considered a sustainable alternative process [9]. However, in electrocatalysis, the high dissociation energies of the C—O and N≡N bonds in the linear molecules of CO2 and N2 lead to their low chemical activity. The significant energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of CO2 and N2 molecules further enhances their chemical stability. Besides, the low proton affinity of CO2 and N2 complicates direct protonation [10–12]. These properties make CO2 RR and N2 RR challenging. Consequently, scientists are focusing on developing innovative electrocatalysts to overcome the challenges posed by the high dissociation energies and significant energy gaps of CO2 and N2 , while enhancing their chemical reactivity and protons affinity. Functional materials based on covalent organic frameworks (COFs) have emerged as promising catalysts for the efficient utilization of CO2 . In particular, COF-based functional materials with multiple active sites, such as single-metal sites, metal nanoparticles, and metal oxides, offer great potential for realizing CO2 conversion and energy storage [13]. Besides, the researchers also focused on the important effects of vacancies, high-index facets, lattice strain, lattice disorder, and polymer–inorganic interface configurations on the enhancement of CO2 RR and N2 RR performance. They noted that defect engineering can enhance CO2 and N2 uptake and tune the electronic structure of the catalyst. In terms of interfacial engineering, polymers play an important role as supports, modifiers, or blenders of polymer–inorganic composites. The introduction of polymers can inhibit hydrogen evolution reaction (HER), enhance the concentrations of CO2 and N2 , stabilize intermediates, and change the electronic structure of the catalyst. This modulation affects the binding energies of CO2 , N2 , and intermediates on the catalyst surface, leading to more efficient reactions [14]. Despite the significance and promising prospects of the aforementioned electrocatalytic process, a common challenge in these reactions is the relatively low energy conversion efficiency, which remains far from industrial viability. Conventional electrocatalysts and energy storage materials still face technical problems, including complicated preparation processes, high cost, and inadequate catalytic activity and stability. These limitations severely restrict their commercialization and further applications. To enhance the reaction rates of promising catalytic reactions, there is a need for low-cost, highly active, and durable electrochemical materials. In recent years, functional materials, particularly metal- and carbon-based nanomaterials, have garnered significant attention from researchers due to their large specific surface area and high surface activity. Moreover, the bonding and electronic states on the surface of these nanocatalysts are different from those inside the particles, and the incomplete coordination of the surface atoms increases the number of surface-active sites, thereby improving catalytic performance. As a result, functional materials with specific morphologies and architectures show great promise for energy conversion applications. This book focuses on four different types of functional materials, including metal-based materials, metallic compounds,

Hy

1 Introduction

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Figure 1.1 Illustration of advanced functional materials for electrochemical catalysis.

carbon-based materials, and porous materials. By regulating their geometric structures and electronic structures, these functional materials demonstrate specific catalytic effects on various electrochemical reactions in practical applications. The facilitating role of functional materials as catalysts in electrocatalytic energy conversion is explored from several perspectives (Figure 1.1). The catalytic performance of metal-based nanocatalysts is influenced by their geometric and electronic properties, including size, morphology, phase, atomic distance, and composition. For example, the density of active sites and lattice strain on the surface of nanoparticles can be modified by adjusting their shape and size, thereby enhancing catalytic activity and selectivity. The most commonly employed metal electrocatalysts are transition metals, such as platinum, palladium, copper, iron, and nickel. In addition to metal-based catalysts, metallic compounds also exhibit promising catalytic performances for various electrocatalytic processes. These compounds are typically formed from metallic and nonmetallic elements. Similarly, the performance of metal compound catalysts is influenced by their composition, structure, and surface properties. Common metallic catalysts include transition metal oxides, transition metal sulfides, and transition metal nitrides. The metal elements in these compounds often possess a variety of oxidation states and coordination environments, which enable them to interact effectively with reactants and modulate the rate and selectivity of catalytic reactions. In addition to metal-based functional materials, carbon-based materials exhibit excellent properties for electrocatalytic applications. These materials feature a highly specific surface area and abundant pore structure, providing abundant

3

4

1 Introduction

reactive active sites and diffusion pathways to increase the reaction rate. Their good electrical conductivity and chemical stability enable efficient electron transfer during catalytic reactions, allowing them to tolerate harsh conditions such as high temperatures, acid, and alkali. Moreover, carbon-based nanocatalysts possess tunable surface chemistry, and their catalytic activity and selectivity can be adjusted by introducing or modifying surface functional groups, demonstrating excellent catalytic performance in several fields. On the other hand, porous materials as a fundamental category of functional materials also have garnered significant attention and undergone extensive research. Their highly porous structures provide large specific surface areas and pore volumes, facilitating the regulation of adsorption, diffusion, and reaction processes based on different pore sizes. The tunable pore structure and distribution expose various types of active sites on their surfaces, providing abundant opportunities for various catalytic applications. Currently, various types of porous material catalysts have been developed, including metal–organic framework materials (MOFs), mesoporous silica materials (e.g. SBA-15 and MCM-41), oxides (e.g. zirconia, alumina), and carbon-based materials (e.g. activated carbon and carbon nanotubes). Researchers are dedicated to designing and synthesizing novel porous materials to further optimize their catalytic properties and advance catalytic science and engineering. This book provides a comprehensive overview of functional materials and their specific performances in electrocatalytic energy conversions. We focus on metallic compounds, metal-based materials, carbon-based materials, and porous materials. By studying and optimizing the electrocatalytic properties of these functional materials, we aim to advance the development of electrocatalytic energy conversion technologies and contribute to the revolution toward sustainable energy. The goal of this book is to deepen readers’ understanding of functional materials for electrocatalytic energy conversion while offering insights for future research and applications. We hope that through continuous innovation and collaboration, we can overcome the challenges we currently face and pave a way for a more sustainable and cleaner energy future.

Acknowledgment The work was financially supported by the Hong Kong Polytechnic University (grant no. P0047728), the Key Project of Xihua University (grant no. Z222070), and Chengdu Vehicle Environmental Protection Technology Co., Ltd, (No. 2023CDVEPTKF-04).

References 1 Zhang, J.N. (ed.) (2022). Carbon-based Nanomaterials for Energy Conversion and Storage: Applications in Electrochemical Catalysis, Springer Series in Materials Science, vol. 325. Springer.

References

2 Bailey, A., Andrews, L., Khot, A. et al. (2014). Hydrogen storage experiments for an undergraduate laboratory course—clean energy: hydrogen/fuel cells. J. Chem. Educ. 92 (4): 688–692. 3 Wang, H.-F. and Xu, Q. (2019). Materials design for rechargeable metal-air batteries. Matter 1 (3): 565–595. 4 Zhang, J., Zhang, Q., and Feng, X. (2019a). Support and interface effects in water-splitting electrocatalysts. Adv. Mater. 31 (31). 5 de Jesus Gálvez-Vázquez, M., Moreno-García, P., Xu, H. et al. (2020). Environment matters: CO2 RR electrocatalyst performance testing in a gas-fed zero-gap electrolyzer. ACS Catal. 10 (21): 13096–13108. 6 Kulkarni, A., Siahrostami, S., Patel, A., and Nørskov, J.K. (2018). Understanding catalytic activity trends in the oxygen reduction reaction. Chem. Rev. 118 (5): 2302–2312. 7 Wang, G., Jia, S., Gao, H. et al. (2023). The action mechanisms and structures designs of F-containing functional materials for high performance oxygen electrocatalysis. J. Energy Chem. 76: 377–397. 8 Xue, D., Xia, H., Yan, W. et al. (2020). Defect engineering on carbon-based catalysts for electrocatalytic CO2 reduction. Nanomicro Lett. 13 (1): 5. 9 Tong, W., Huang, B., Wang, P. et al. (2020). Crystal-phase-engineered PDCU electrocatalyst for enhanced ammonia synthesis. Angew. Chem. 132 (7): 2671–2675. 10 Li, L., Li, X., Sun, Y., and Xie, Y. (2022). Rational design of electrocatalytic carbon dioxide reduction for a zero-carbon network. Chem. Soc. Rev. 51 (4): 1234–1252. 11 Shen, H., Choi, C., Masa, J. et al. (2021). Electrochemical ammonia synthesis: mechanistic understanding and catalyst design. Chem 7 (7): 1708–1754. 12 Pan, F. and Yang, Y. (2020). Designing CO2 reduction electrode materials by morphology and interface engineering. Energy Environ. Sci. 13 (8): 2275–2309. 13 Lu, M., Zhang, M., Liu, J. et al. (2022). Covalent organic framework based functional materials: important catalysts for efficient CO2 utilization. Angew. Chem. 134 (15): e200200003. 14 Chen, Y., Chen, C., Cao, X. et al. (2023). Recent advances in defect and interface engineering for electroreduction of CO2 and N2 . Acta Phys. -Chim. Sin. 0 (0): 2210053.

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Part I Advanced Functional Materials for Electrocatalytic Energy Conversion

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2 Density Functional Theory for Electrocatalytic Energy Conversion Wei Li and Ding Yi Beijing Jiaotong University, School of Physical Science and Engineering, Department of Physics, No.3 Shangyuancun, Beijing 100044, China

2.1 Introduction Currently, power generation from renewable energy sources, such as solar and wind, has become a mature technology, but the generated electricity is intermittent [1, 2]. Developing electrocatalytic technology is an effective strategy to achieve energy conversion to a more sustainable and efficient form [3, 4]. On the one hand, electrocatalysis can convert abundant molecules into high-value chemicals, such as hydrogen, ammonia and hydrocarbons, under mild conditions. On the other hand, it can convert chemical energy into electricity without carbon emissions, such as fuel cells [5–9]. This involves many important electrocatalytic reactions, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), nitrogen reduction reaction (NRR), carbon dioxide reduction reaction (CO2 RR), and so on. Numerous scientific studies aim to enhance electrocatalytic activity and improve energy conversion efficiency. However, these complex electrocatalytic reactions are often limited by slow kinetic processes and high reaction overpotentials [6, 10, 11]. Therefore, the design and synthesis of catalysts with high catalytic activity and selectivity have become increasingly crucial. Generally, there are two main strategies to enhance catalyst activity. First, designing the geometric structure of a catalyst to expose more active sites. Second, regulating the electronic structure of a catalyst to improve its intrinsic activity [12]. In recent years, a wide range of strategies for preparing electrocatalysts have been proposed, and the mechanisms for many electrocatalytic reactions have also been improved [13–19]. However, the current catalytic performance still lags far behind practical application standards, and in-depth studies through experiments have become more costly and time-consuming, severely limiting the development of highly efficient electrocatalysts. Therefore, the first-principles calculations based on density functional theory (DFT) have gained more and more attention.

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With the rapid development of computer technology, DFT calculations have become an effective tool to study reaction processes and explain reaction mechanisms. In the field of electrocatalysis, DFT calculations have successfully explained and predicted numerous experimental phenomena [20, 21]. First, DFT calculations can provide insights into the changes in Gibbs free energy and transition state energy barriers during reaction processes, offering theoretical support for investigating elementary steps and identifying the potential-determining step (PDS). Second, DFT calculations can intuitively provide adsorption models of various reaction intermediates on the catalyst surface, offering cognition for the reaction process from atomic and molecular levels. Last but not least, DFT calculations can provide information on the electronic structures of catalytic active sites as well as reaction intermediates, including charge transfer, orbital coupling, and even spin states, which are powerful methods to analyze the structure–activity relationships of catalysts. Based on the above, combining DFT with experiments allows for a deeper understanding of the mechanisms of electrocatalytic reactions to reasonably predict and design efficient electrocatalysts. It also enables rapid screening of catalysts, significantly reducing the trial-and-error costs in catalyst development and providing convenience for the preparation. This chapter aims to illustrate how DFT, as a practical research method, is applied in electrocatalytic energy conversion. From a computational perspective, several common electrocatalytic reactions are introduced, including HER, ORR and NRR, and the reaction mechanisms, DFT calculation methods, representative descriptors, and catalyst structure–activity relationships of these electrocatalytic reactions are described in detail, respectively.

2.2 Computational Methods 2.2.1

Reaction Free Energy

Nørskov et al. [22] proposed the computational hydrogen electrode (CHE) model as early as 2004, utilizing the characteristics of the standard hydrogen electrode (SHE), where the reaction described by Eq. (2.1) is in equilibrium. H+ + e− → 1∕2H2 (g)

(2.1)

G(H+ ) + G(e− ) = 0.5G(H2 )

(2.2)

This established a numerical relationship between the Gibbs free energy of proton–electron pairs and the Gibbs free energy of hydrogen gas (Eq. (2.2)). When pH = 0 and U = 0 V vs. SHE, the Gibbs free energy of the proton–electron pair is equal to half of the Gibbs free energy of hydrogen in standard conditions (1 bar in the gas phase at 298 K). This greatly simplifies the computational process for complex electrocatalytic reactions. Combining a portion of thermodynamic data with calculations achievable by DFT itself, one can compare the stability of intermediates, plot the free energy diagrams, and determine the reaction PDS.

2.2 Computational Methods

As is known, the energy provided by DFT calculations is under 0 K, and the simulated atoms are completely static, excluding the effect of zero-point energy, temperature, and entropy. Therefore, to calculate the system’s free energy, it is necessary to make corrections to the energy obtained from DFT calculations, as shown in Eq. (2.3). G = E + EZPE + TS

(2.3)

where E is the energy obtained from the DFT calculations directly, EZPE is the correction of zero-point energy, TS is the contribution of temperature and entropy, which can be obtained by calculating the vibrational frequency through DFT or looking up the standard tables. For each elementary step, the free energy change at pH = 0 and U = 0 V vs. SHE can be written as ΔG0 = G(final) − G(initial) = ΔE + ΔEZPE − TΔS

(2.4)

If we further consider the effect of U and pH, the free energy change can be written as ΔG = ΔG0 + ΔGpH + ΔGU = ΔE + ΔEZPE − TΔS + ΔGpH + ΔGU

(2.5)

where ΔGpH = −kB Tln(H+ ) = pH × kB Tln10 (kB is the Boltzmann constant), and ΔGU = −neU (U is the applied potential relative to SHE, e is the elementary charge, and n is the number of electrons transferred). The above content describes the main computational method of DFT for calculating the change of reaction-free energy. Additionally, depending on specific requirements, DFT can also be used to calculate adsorption energy, formation energy, and so on. The energy analysis of different electrocatalytic reactions will be discussed in detail in subsequent sections.

2.2.2

Electronic Structures

The study of electronic structures of catalysts and various adsorbates is also the core of DFT calculations in electrocatalysis. Here, we briefly introduce several analysis tools that will be mentioned later. First, for the charge (electron) transfer during the reaction process, the Bader charge analysis is widely used, which accurately quantifies the charge of each atom. Charge density difference is also a good method that can visualize the charge transfer in coordinate space. The combination of them enables an accurate analysis of charge distribution. Second, the orbital coupling between catalytic active sites and reaction intermediates can also be well analyzed. By calculating the projected density of states (PDOS), information such as orbital overlap, energy distribution, and electron occupation can be obtained. Moreover, the calculation of crystal orbital Hamilton population (COHP) provides data on the interaction form and strength between any two orbitals of the interacting atoms. The above analysis methods can comprehensively reveal the structure–activity relationship between catalysts and electrocatalytic reactions, providing theoretical guidance for the design of efficient catalysts.

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2.3

Application of DFT in Electrocatalysis

2.3.1

Hydrogen Evolution Reaction

Hydrogen energy is a secondary energy source with great development potential and has attracted much attention because of its advantages such as high energy efficiency and cleanliness [5, 23]. The utilization of renewable energy for hydrogen production through electrocatalytic HER is a promising technology. Currently, noble metal catalysts such as Pt, Ir and Pd are generally used as catalysts in HER [24–26]. However, their large-scale application is impeded by many shortcomings, such as high cost, low stability and susceptibility to poisoning [27, 28]. Therefore, the study and design of electrocatalysts are the key to solving these problems. Using DFT calculations to investigate reaction mechanisms and the electronic structures of catalysts has become a powerful tool for exploring HER. 2.3.1.1 Reaction Mechanism

HER is the cathodic half-reaction of electrochemical water splitting. During the reaction process, proton-coupled electron transfer (PCET) plays an important role [29, 30]. In acidic solutions, the reaction can be represented as: 2H+ + 2e− → H2 . Specifically, the reaction can be divided into two steps: the Volmer step and the Tafel or Heyrovsky step. In the Volmer step, because of the high concentration of H+ in acidic electrolytes, H+ first strongly interacts with the surface of the electrocatalyst via a PCET pathway, leading to the generation of an adsorbed H*. The second step of the reaction has two possible pathways: (i) If the concentration of H* is high, and they are adsorbed on adjacent active sites, two H* can directly combine to generate one molecule of H2, which is then released into the environment (Tafel step). (ii) The H* generated in the Volmer step will generate a H2 molecule via the second PCET pathway (Heyrovsky step). The three steps can be represented by the following reaction equations: Volmer step: H+ + e− + ∗ → H∗

(2.6)

Tafel step: 2H∗ → H2 + 2∗

(2.7)

Heyrovsky step: H+ + e− + H∗ → H2 + ∗

(2.8)

In alkaline or neutral solutions, water splitting is the primary source of H+ , and the reaction can be represented as: 2H2 O + 2e− → H2 + 2OH− , and these three steps are modified as: Volmer step: H2 O + e− + ∗ → H∗ + OH−

(2.9)

Tafel step: 2H∗ → H2 + 2∗

(2.10)

Heyrovsky step: H2 O + e− + H∗ → H2 + OH− + ∗

(2.11)

Generally speaking, in acidic conditions, appropriate adsorption strength of H* is conducive to the reaction, but in alkaline or neutral conditions, the production of H+ requires the splitting of H2 O. Since the breaking of the H−OH bond entails a high

2.3 Application of DFT in Electrocatalysis

dissociation barrier, the Volmer step is typically the rate-determining step (RDS). Compared with acidic HER, alkaline HER is more difficult [31]. 2.3.1.2

Detailed Computational Methods for HER

The adsorption of H* is involved in both acidic and alkaline HER, so the adsorption free energy of hydrogen (ΔGH* ) can be used to describe the performance of HER and is represented as follows: ΔGH∗ = GH∗ − G∗ − 0.5GH2

(2.12)

During the reaction, both the adsorption and desorption of H* are involved, and the two processes compete with each other. As with the Sabatier principle, catalysts with high activity should ensure that the reaction intermediates have an optimal adsorption strength to balance the adsorption and desorption. If the adsorption of H* is too weak, the reaction cannot proceed, but if the adsorption is too strong, desorption becomes difficult, limiting the subsequent generation of H2 and occupying active sites [32]. Therefore, the ΔGH* is closely related to the activity of the electrocatalyst. The ideal value of ΔGH* is close to 0 eV [7, 33], as shown by the red line in Figure 2.1, and the performance of catalysts with weaker H adsorption (blue line), such as Au catalyst and catalysts with stronger H adsorption (green line), such as Pt, Ni, Mo are not perfect yet [19]. This hydrogen adsorption free energy diagram visually demonstrates the catalytic activity of catalysts. For alkaline HER, exploring the free energy change of H2 O dissociation is often required [34]. A lower dissociation barrier as well as an appropriate H* adsorption often corresponds to higher activity of alkaline HER. 2.3.1.3

Descriptors

As mentioned above, the adsorption and desorption of H* on the catalyst surface have a competitive relationship, too strong and too weak adsorption strength 0.6 Weaker H adsorption

Free energy (eV)

0.4

H*

0.2 H+ + e–

Ideal H adsorption

0.0

1/2 H2

–0.2

–0.4

–0.6

Stronger H adsorption Reaction coordinate

Figure 2.1 Diagram of adsorption free energy of hydrogen.

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2 Density Functional Theory for Electrocatalytic Energy Conversion

can affect the activity of HER. Therefore, ΔGH* can provide a semi-quantitative prediction of catalyst activity. Trasatti [35] first proposed a clear linear relationship between the logarithm of HER current density and the strength of metal−hydrogen (M−H) bonds. This work summarized the acidic HER performance on various transition metal (TM) surfaces and observed a volcano-shaped relationship as shown in Figure 2.2a. It can be clearly seen that metal surfaces with both strong and weak H binding correspond to lower HER current density, while metals located at the peak of the volcano plot, such as Pt and Pd, have optimal adsorption strength and thus have the best HER activity. Nørskov et al. [19] calculated the ΔGH* on several TM surfaces by DFT calculations and compared it with the experiment results. The volcano-shaped relationship is also observed as shown in Figure 2.2b. ΔGH* of metals close to 0 eV are near the peak of the volcano plot, corresponding to the highest acidic HER activity. Another useful descriptor is the d-band center, which was first proposed by Nørskov and Hammer in the early 2000s [36], suggesting that the d-band center (relative to Fermi level) of TMs plays an important role in determining the binding strength between the metal and adsorbates (Figure 2.3a). The interaction of an adsorbate state with the d-electrons of a metal surface often gives rise to bonding and antibonding states. Generally, higher (lower) d-band center corresponds to less (more) electron filling into the antibonding state and further corresponds to strong (weak) binding. Figure 2.3b shows the calculated ΔGH* with respect to the d-band centers of different catalysts, and a linear relationship was obtained [37]. Therefore, the d-band center can also be used as an independent descriptor to predict catalytic activity. 2.3.1.4 Structure–Activity Relationship

As mentioned above, regulating the adsorption strength