Hybrid Water Electrolysis

Myong Yong Choi is a senior academic staff member of the Department of Chemistry, Gyeongsang National University, South Korea, and Director of the Core-Facility Center for Photochemistry and Nanomaterials. He specializes in spectroscopy, laser photochemistry, and nanomaterials, and serves as Program Manager at the National Research Foundation of Korea.Jayaraman Theerthagiri is a Brain Pool Fellow in the Department of Chemistry, Gyeongsang National University, South Korea. His research focuses on developing electrocatalysts for energy applications, hydrogen evolution reaction, and catalysis for energy and environmental remediations.M. L. Aruna Kumari is an Assistant Professor at the Department of Chemistry, The Oxford College of Science, Bangalore, India. Her research focuses on photocatalytic organic transformations, metal oxide hybrids for energy and environmental applications, and Advanced Oxidation Processes.Gilberto Maia is a senior academic staff member at the Institute of Chemistry, Federal University of Mato Grosso do Sul, Brazil. His research centers on nanostructured metal electrocatalysts for ORR, HER, OER, CO2RR, and NO3-RR, and density functional theory for metallic surfaces in electrocatalysis.Soorathep Kheawhom is an Associate Professor at the Department of Chemical Engineering, Chulalongkorn University, Thailand, where he leads the research cluster on energy storage. His research focuses on sustainable energy storage technologies including zinc-air batteries and zinc-ion batteries.

• List of Contributors xvAbout the Editors xxiPreface xxiiiPart I Fundamental 11 Fundamentals and Advantages of Hybrid Water Electrolysis 3Vipada Aupama, Phonnapha Tangthuam, Ahmad Azmin Mohamad, and Soorathep Kheawhom1.1 Concept and Scope 31.2 Thermodynamic and Kinetic Basis for Energy Reduction 71.3 Anodic Reaction Space and Substrate Selection 91.4 Advantages Beyond Voltage: Coproduction, Safety, and Sustainability 131.4.1 Coproduction: Transforming the Anode into a Chemical Manufacturing Module 141.4.2 Safety and Operational Flexibility: Reducing Oxygen-related Constraints 141.4.3 Sustainability and Circularity: Coupling Hydrogen with Waste Conversion 151.4.4 Interdependence of Advantages and the Role of System-level Metrics 161.5 Remaining Challenges and Outlook 16References 19Part II Alcohol-assisted Water Electrolysis 232 Metal Carbides and Nitrides Electrocatalysts for Alcohol-assisted Water Electrolysis 25Phonnapha Tangthuam, Vipada Aupama, Ahmad Azmin Mohamad, and Soorathep Kheawhom2.1 Background and Scope 252.2 Intrinsic Properties Governing Electrocatalytic Activity 272.3 Catalytic Roles in Alcohol-assisted Electrolysis Systems 292.3.1 Cathode: HER 302.3.2 Anode: AOR 302.4 Surface Dynamics and Stability Under Operating Conditions 312.4.1 Surface Reconstruction as Activation and Degradation 322.4.2 Oxidation, Corrosion, and the Conductive-core/Active-shell Picture 332.4.3 Adsorbate-driven Effects and Selectivity Drift 332.4.4 Defects, Vacancies, and Stability–Activity Trade-offs 342.4.5 Electrode-level Stability 342.4.6 Assessing Stability in Hybrid Electrolysis 342.4.7 Design Implications 352.5 Reaction Pathways and Product Selectivity in Alcohol Oxidation 352.5.1 Elementary Steps and Pathway Competition 352.5.2 Adsorption Energetics as a Selectivity Lever 362.5.3 Surface Oxygenated Species and Reconstructed States 362.5.4 Poisoning, Carbon Balance, and Long-term Selectivity 362.5.5 Multicomponent Carbides and Nitrides in Selectivity Tuning 372.5.6 Selectivity Metrics and Benchmarking 372.6 Engineering Strategies to Enhance Performance 372.6.1 Nanostructuring and Hierarchical Porosity 382.6.2 Morphology and Surface Termination Control 392.6.3 Defect and Vacancy Engineering 392.6.4 Heteroatom Doping 392.6.5 Multicomponent Carbides and Nitrides 392.6.6 Heterostructures and Interfaces 402.6.7 Conductive Scaffolds and Self-supported Electrodes 402.6.8 Electrode Architecture and Transport 402.6.9 Benchmarking During Engineering Optimization 402.7 Comparative Summary of Carbides vs. Nitrides 402.8 Outlook and Remaining Challenges 41References 443 Single-atom Electrocatalysts for Alcohol-assisted Water Electrolysis 47P. Keerthana, Soorya S. Raj, and M. L. Aruna Kumari3.1 Introduction 473.2 Fundamentals of AAWE 493.2.1 Methanol-assisted Hydrogen Production 503.2.2 Ethanol-assisted Hydrogen Production 513.2.3 Propanol-assisted Hydrogen Production 523.2.4 Glycerol-assisted Hydrogen Production 523.3 SAECs: Concept and Design Principles 533.3.1 NM-SACs 543.3.2 SACs@ATMs 553.4 Synthesis Strategies of SAECs 583.4.1 Bottom-up Methods 583.4.1.1 Atomic Layer Deposition Method 583.4.1.2 Electrodeposition Method 593.4.1.3 Pyrolysis-assisted Method 603.4.1.4 Wet-chemical Synthesis 613.4.2 Top-down Method 623.5 Integration of SAECs into AAWE 633.6 Challenges and Perspectives 673.7 Conclusion 69References 694 Metal Alloys Electrocatalysts for Alcohol-assisted Water Electrolysis 81Rafael M. P. Araujo, Sidney C. Z. Costa, M. Janete Giz, and Giuseppe A. Camara4.1 Fundamentals of Water Electrolysis 814.2 Hybrid Water Electrolysis 824.3 Alcohol-assisted Water Electrolysis 824.4 Metal Alloys for Alcohol Electrooxidation 834.5 Metal Alloys for Hydrogen Evolution Reaction 884.6 Summary of the Current Landscape 89References 905 Metal Borides and Selenides for Alcohol-assisted Water Electrolysis 95Yogapriya Selvaraj, Senthilkumar Nangan, Kiruthika Paramasivam, Anbazhagan Venkattappan, Vijayakumar Elayappan, and Soorathep Kheawhom5.1 Introduction 955.2 Electrochemical Reactions Involved in OER, HER, and Alcohol Oxidation Reaction at Electrode Material 975.2.1 Mechanism of OER 975.2.2 Mechanism of HER 985.2.3 Mechanism of Alcohol Oxidation Reaction 995.3 Electrocatalytic Performance in Alcohol-assisted Electrolysis in Metal Borides and Selenides 1005.3.1 Significance of HER 1005.3.2 HER Activity of Borides and Selenides 1015.3.2.1 HER Activity of Borides 1015.3.2.2 HER Activity of Selenides 1025.3.3 Synergistic Effects in Bimetallic or Hybrid Systems 1045.4 Tafel Slope, Onset Potential, and Overpotential 1055.4.1 Tafel Slope 1055.4.2 Onset Potential 1055.4.3 Overpotential 1065.5 Alcohol Oxidation Reaction Mechanism of Ethanol, Methanol, and Glycerol Oxidation 1075.5.1 Ethanol Oxidation 1075.5.2 Methanol Oxidation 1085.5.3 Glycerol Oxidation 1105.5.4 Borides and Selenides as Anodic Catalysts 1125.5.5 Selectivity and Product Distribution 1145.5.6 Overall Electrolysis Performance 1165.6 Challenges and Future Perspective 1165.7 Conclusion 117Acknowledgments 118References 1186 Non-oxide Electrocatalysts for Glycerol Oxidation-coupled Water Electrolysis 127Phonnapha Tangthuam, Vipada Aupama, and Soorathep Kheawhom6.1 Introduction and Scope 1276.2 Fundamentals of Glycerol Oxidation in Hybrid Electrolysis 1296.2.1 Thermodynamic Comparison of OER and Glycerol Oxidation 1306.2.2 Glycerol Oxidation Reaction Network 1316.2.3 Performance Metrics for Glycerol-assisted Electrolysis 1316.3 Non-oxide Electrocatalyst Families and Design Strategies for Glycerol Oxidation 1326.3.1 Comparative Overview Under Glycerol Oxidation Conditions 1326.3.2 Design Motifs Across Non-oxide Families 1356.4 Mechanistic Insights: Activity and Selectivity Tuning on Non-oxide Surfaces 1366.4.1 Active Phase and In Situ Reconstruction 1366.4.2 Activity Descriptors 1366.4.3 Selectivity: Glycerol Oxidation vs. OER and Within the Glycerol Network 1396.4.4 Consolidated Design Rules 1406.5 Durability, Poisoning, and Hybrid Electrolyzer Architectures 1406.5.1 Degradation Modes 1416.5.2 Strategies for Durability and Poisoning Resistance 1426.5.3 Alkaline–Alkaline and Hybrid Alkali–Acid Architectures 1436.5.4 Device-level Benchmarking 1436.6 Operando Characterization and Future Directions 1446.6.1 Role of Operando and In Situ Methods 1446.6.2 Key Techniques 1446.6.3 From Operando Data to Design Rules 1466.6.4 Future Directions 146References 147Part III Hydrazine-assisted Water Electrolysis 1517 Metal Sulfides as Electrocatalysts for Hydrazine-assisted Water Electrolysis 153Aravindhan Selvaraj, Hemalatha Parangusan, Dhanasekaran Vikraman, Hyun-Seok Kim, Akram Alfantazi, and K. Karuppasamy7.1 Introduction 1537.2A Basic Understanding of N 2 H 4 -assisted HER 1547.2.1 Parameters Required to Estimate the Catalytic Performance 1547.2.2 Exchange Current Density (j 0) and Tafel Slope 1557.2.3 Turnover Frequency 1557.2.4 Stability 1567.3 Hydrazine-assisted HER Applications 1567.3.1 Nickel-based Catalysts 1567.3.2 Cobalt-based Catalysts 1587.4 Design and Mechanism 1607.5 Conclusion 161References 1618 Metal Phosphides Electrocatalysts for Hydrazine-assisted Water Electrolysis 167Rahul D. Kerkar8.1 Introduction 1678.2 Fundamentals of Hydrazine-assisted Water Electrolysis 1708.3 Transition-metal Phosphides 1718.3.1 Structure, Electronic Properties, and Relevance to Electrocatalysis 1718.3.1.1 Crystal Structure and Classification of Metal Phosphides 1718.3.1.2 Electronic Structure and Conductivity 1728.3.1.3 Relevance to Electrocatalysis 1738.3.2 Synthesis Strategies for Metal Phosphides 1748.3.2.1 Phosphidation of Metal Hydroxide or Metal Oxide Precursors 1748.3.2.2 Direct Solid-state Reaction 1758.3.2.3 Hydrothermal Phosphidation 1768.3.2.4 CO 2 Laser-assisted Method 1768.3.2.5 Template or MOF-derived Methods 1768.3.2.6 Electrochemical In Situ Phosphidation 1778.4 Characterization Techniques 1778.4.1 X-ray Diffraction 1788.4.2 Transmission Electron Microscopy 1798.4.3 X-ray Photoelectron Spectroscopy 1798.4.4 Inductively Coupled Plasma 1808.4.5 Study of Surface Area, Porosity, and Active Sites 1808.5 Electrochemical Performance Evaluation 1818.6 Post-characterization Techniques 1838.7 Conclusion 184References 1859 Metal Carbides and Nitrides Electrocatalysts for Hydrazine-assisted Water Electrolysis 191Binaya Kumar Sahu and Pooja Sahoo9.1 Introduction 1919.2 Structure and Properties of Metal Carbides and Nitrides 1949.3 Fundamentals of Hydrazine-assisted Water Catalysis for Hydrogen Production 1989.4 Fundamentals of Hydrazine-assisted Water Catalysis for Fuel Cells 2009.5 Measurement Criteria for HzOR-assisted Water Electrocatalysis 2029.5.1 Overpotential 2029.5.2 Tafel Slope 2029.5.3 Electrochemical Active Surface Area 2039.5.4 Electrochemical Impedance 2039.5.5 Stability 2039.6 Metal Carbides for Hydrazine-assisted Water Electrocatalysis 2049.7 Metal Nitrides for Hydrazine-assisted Water Electrocatalysis 2099.8 Conclusion 212Acknowledgments 213References 21310 Metal Alloy Electrocatalysts for Hydrazine-assisted Water Electrolysis 221Shreyanka Shankar NaikReferences 22711 Metal Borides and Selenides for Hydrazine-assisted Water Electrolysis 231Soumya Ranjan Mishra, Shalu Rawat, Vishwajit Chavda, and B. M. Nagaraja11.1 Introduction 23111.2 Fundamentals of Hz-WE 23211.3 Chemistry and Structure of Metal Borides 23411.3.1 Structural Features and Stability 23411.3.2 Synthesis of Compositional Control 23511.3.3 Electrocatalytic Behavior in Hz-WE 23611.4 Chemistry and Structure of Metal Selenides 23711.4.1 Structural Features and Stability 23711.4.2 Synthesis and Compositional Control 23711.4.3 Electrocatalytic Behavior in Hz-WE 23811.5 Challenges and Future Prospects 24111.6 Conclusion 242Acknowledgments 242References 24312 Single-atom Electrocatalysts for Hydrazine-assisted Water Electrolysis 249Talshyn Begildayeva and Juan A. Lopez-Ruiz12.1 Introduction 24912.2 SACs: What They Are, How They Work, and Why They Matter 25112.3 HzOR as a Promising Alternative to the OER in Hybrid WE 25612.4 Challenges for WE Coupled With Hydrazine Oxidation on SACs 261References 262Part IV Urea and Furfural-assisted Water Electrolysis 26913 Metal Sulfides and Phosphides Electrocatalysts for Urea-assisted Water Electrolysis 271Marciélli Karoline Rodrigues de Souza, Eduardo dos Santos Freitas Cardoso, and Marcos Roberto de Vasconcelos Lanza13.1 Introduction 27113.2 The Mechanism Involving UOR in Alkaline Media 27213.3 Synthesis of Sulfides and Phosphides-based Electrocatalysts 27413.3.1 Integrated Techniques for the Synthesis of Sulfides and Phosphides-based Electrocatalysts 27413.3.1.1 Hydrothermal, Solvothermal, and Electrochemical Synthesis Techniques 27413.4 Structural and Catalytic Performances of Metal Sulfides and Phosphides 27513.4.1 Morphological and Interface Engineering 27613.4.1.1 Heterostructures Engineering 27613.4.1.2 Incorporation of Conductivity Phases and Controlled Morphology 27913.4.2 Compositional Modulation and Synergistic Effects 28013.4.2.1 Bimetallic Integration and Controlled Doping 28013.4.3 Hybrid Architectures and MOF-derived Platforms 28213.4.4 Summary of Structure–Performance Relationship 28513.5 Conclusions 288References 28814 Metal Carbides and Nitrides Electrocatalysts for Urea and Furfural-assisted Water Electrolysis 293Soorya S. Raj, M. L. Aruna Kumari, P. Keerthana14.1 Introduction 29314.2 Fundamentals of Urea and Furfural-assisted Water Electrolysis 29414.2.1 Thermodynamics and Kinetics of UOR 29414.2.2 FOR: Pathways and Value-added Products 29514.2.3 Comparison with OER: Potential Reduction and Efficiency Gains 29614.2.4 Dual Benefits: Sustainable Hydrogen Generation + Chemical Coproduction 29614.3 MCNs as Electrocatalysts 29714.3.1 Unique Physicochemical Properties 29714.3.2 Synergy with Transition Metals for Enhanced Activity 29714.3.3 Stability and Corrosion Resistance in Harsh Electrolytes 29814.3.4 Structure–Activity Relationship Principles 29814.4 Synthesis and Strategies 29914.4.1 Carbothermal Reduction and Nitridation Methods 29914.4.2 Template-assisted Synthesis 30014.4.3 Sol–Gel and Hydrothermal Approaches 30014.4.4 Plasma-enhanced and CVD Techniques 30014.4.5 Challenges in Phase Control, Morphology, and Scalability 30014.5 MCNs for UOR 30214.5.1 Molybdenum and Tungsten Carbides/Nitrides 30214.5.2 Iron, Cobalt, and Nickel Carbides/Nitrides 30214.5.3 Mixed-metal Carbides and Nitrides 30314.5.4 Reaction Mechanism Insights and Performance Benchmarks 30314.6 MCNs for FOR 30314.6.1 Ni-, Mo-, and Co-based Carbides/Nitrides for Furfural Valorization 30414.6.2 Selectivity Control and Product Distribution 30414.6.3 Coupling Furfural Oxidation with HER 30514.7 Challenges and Future Perspectives 30614.8 Conclusion 306References 30715 Metal Sulfides and Phosphides Electrocatalysts for Furfural-assisted Water Electrolysis 313Jessica J. P. Nascimento, Paulo N. S. Casciano, Francisco W. P. Ribeiro, Thiago M. B. F. Oliveira, Adriana N. Correia, and Pedro de Lima-Neto15.1 Introduction 31315.2 Importance of Transition-metal-based Catalysts 31515.3 Electrocatalytic Performance for FF Compounds Oxidation and Her 31715.3.1 Metal Phosphides Electrocatalysts for FF-assisted Water Electrolysis 31915.3.2 Metal Sulfides Electrocatalysts for FF-assisted Water Electrolysis 32115.4 Pathways of FF Oxidation Reaction 32415.4.1 Pathways in Acidic Media 32415.4.2 Pathways in Alkaline/Neutral Media 32415.4.3 Electrochemical Synergy Between FOR and HER 32615.5 Challenges and Prospects 327Acknowledgments 327References 32716 Single-atom Electrocatalysts for Urea and Furfural-assisted Water Electrolysis 337Xiangyu You, Julio C. Lourenço, Tulio P. Porto, Dhananjai Pangotra, Luciana Vieira, Huize Wang, Marc Ledendecker, Robson S. Rocha, Alexsandro J. dos Santos, Marcos Roberto de Vasconcelos Lanza, Gilberto Maia, and Guilherme V. Fortunato16.1 Introduction 33816.2 Fundamentals of Single-atom Electrocatalysts 33816.2.1 Definition and Features of SACs 33816.2.2 Common Synthesis Methods 34016.2.3 Characterization Techniques 34116.3 Advantages of Using SACs for Electrooxidation Reactions and the Stability Issues 34216.4 UOR and SACs 34316.4.1 Mechanisms of UOR, Kinetics, and Energy Advantages Compared to OER 34316.4.2 State-of-the-art Electrocatalysts and the Advantages of SACs for Uor 34516.4.3 Long-term Stability and Practical Perspectives of SACs for UOR 34616.5 Furfural Oxidation and SACs 34716.5.1 Oxidation Pathways and Products of Furfural 34716.5.2 Electrocatalysts for FOR and Opportunities for SACs 34916.6 Hybrid Electrolyzer Configuration, Integration, and Challenges of Using SACs 35016.6.1 System-level Considerations 35016.6.2 Catalyst-level Considerations and SAC Challenges 35116.6.3 Selectivity–Current Density Trade-offs 35316.7 Conclusion 353References 35417 Non-oxide Electrocatalysts for Glucose-oxidation-coupled Water Electrolysis 365P. H. Gangadharagowda, K. Chandana, S. K. Vinoth, K. Yogesh Kumar , and Arun Varghese17.1 Introduction 36517.2 Importance of Glucose-oxidation-coupled Water Electrolysis 36717.3 Performance Evaluation Using Non-oxide Electrocatalysts 37017.4 Conclusions and Future Perspectives 380References 380Part V Future Prospects 38518 Future Prospects and Commercialization of Energy-saving Hybrid Water Electrolysis 387Juan A. Lopez-Ruiz and Talshyn Begildayeva18.1 Introduction 38718.2 Bridging the Lab-to-plant Divide in Electrolyzers 38818.3 Key Performance Indicators 39318.3.1 Normalized Reaction Rates 39418.3.2 Energy Consumption and Efficiency 39618.4 Process Consideration 39718.4.1 Integration of Oxidation and Reduction Processes into a Single Unit 39818.4.2 Mild Operation Conditions 40118.4.3 Simpler and Safer Operation 40118.4.4 Electrification With Diverse Sources 40218.5 Scale-up Considerations 40218.5.1 Electrolyzer Design 40318.5.2 Component Manufacturing 40418.5.3 Dynamic Operations and Advanced Controls 40518.6 Future Research Direction and Commercialization Strategies 406References 409Index 415