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Earth Abundant Metals and Metal Chalcogenides as Efficient and Durable Electrocatalysts for Alkaline Water Electrolyzer

Title
Earth Abundant Metals and Metal Chalcogenides as Efficient and Durable Electrocatalysts for Alkaline Water Electrolyzer
Translated Title
알칼리성 수전해조를 위한 효율적이고 내구성있는 전기 촉매로서의 지구상에 풍부한 금속 및 금속 칼코겐화물
Authors
Arumugam Sivanantham
DGIST Authors
Sivanantham, Arumugam; Kim, SoonhyunShanmugam, Sangaraju
Advisor(s)
상가라쥬샨무감
Co-Advisor(s)
Soonhyun Kim
Issue Date
2019
Available Date
2019-10-03
Degree Date
2019-02
Type
Thesis
Table Of Contents
I. INTRODUCTION 1.1. Global energy consumption and CO2 emission 1 1.2. Motivation on alternative energy source of hydrogen (H2) 2 1.3. Hydrogen production methods 3 1.4. Water electrolysis 4 1.5. Operating principles of water electrolyzers 5 1.6. Components of water electrolyzer system 7 1.7. Cost breakdown of cell components 8 1.8. Significant features in the selection of catalysts 9 1.9. Metals availability and cost analysis 11 1.9.1. Metal availability 11 1.9.2. Cost analysis of precious and non-precious metals (Dec. 2017 – Oct. 2018) 12 1.10. DOE technical target on alkaline water electrolysis 13 1.11. Earth abundant catalysts for alkaline water electrolysis 14 1.12. Activity and stability issues of electrocatalysts in alkaline water electrolysis 15 1.13. Trends in electrochemical activity (Sabatier Principle)16 1.14. Electronic structure and activity relationships 17 1.15. Activity-stability relations 18 1.16. Concurrent improvements in both activity and stability of catalysts 19 1.16.1. Metal(s)-carbon hybrids/composites 19 1.16.2. Metal(s)-chalcogenides 20 1.17. Objectives of my research work 21 II. EXPERIMENTAL METHODOLOGY 2.1. Materials 23 2.1.1. Electrospinning method 23 2.1.1.1. Synthesis of Co-CeO2/N-CNR electrocatalyst 23 2.1.2. Co-precipitation method 24 2.1.2.1. Synthesis of monometallic-PB analogues 24 2.1.2.2. Synthesis of bimetallic-PB analogues 24 2.1.2.3. Formation of monometallic@NC electrocatalysts 25 2.1.2.4. Formation of bimetallic@NC electrocatalysts 25 2.1.2.5. Formation of Co, Co3O4 and NC (Nitrogen-doped carbon) 26 2.1.3. Catalysts ink preparation and coating 26 2.1.3.1. Catalysts ink preparation 26 2.1.3.2. Catalysts coating on electrodes (glassy carbon and nickel foam) 26 2.1.4. Hydrothermal method (in-situ catalysts growth) 27 2.1.4.1. Synthesis of NiCo2S4 nanowire arrays on Ni foam (NF) 27 2.1.4.2. Synthesis of Ni3Se2 on Ni foam (Ni3Se2/NF) electrocatalyst 28 2.2. Characterizations 28 2.3. Electrochemical analyses 29 2.4. Assembly of prototype anion exchange membrane water electrolozer single cell 30 2.4.1. Hydrogen (H2 gas) quantification 32 2.4.1.1. Water displacement method 32 2.4.1.2. Columbic efficiency calculation 32 III. Co AND CeO2 EMBEDDED NITROGEN-DOPED CARBON NANORODS AS OXYGEN ELECTRODE FOR OXYGEN EVOLUTION REACTION IN WATER SPLITTING 3.1. Introduction 33 3.2. Results and discussion 34 3.2.1. Formation of the nanostructured catalysts via electrospinning 34 3.2.2. Characterizations of catalysts 35 3.2.2.1. XRD analysis 35 3.2.2.2. SEM analysis 36 3.2.2.3. TEM analysis 37 3.2.2.4. BET analysis 38 3.2.2.5. XPS analysis 40 3.2.2.6. Raman analysis 45 3.2.2.7. Elemental analysis (CHNS) 46 3.2.3. Electrochemical performance 47 3.2.3.1. Oxygen Evolution Reaction 47 3.2.3.2. Spillover effect of CeO2 in OER 49 3.2.3.3. Tafel slope 49 3.2.3.4. Cyclic durability tests 49 3.2.3.5. Electrochemical active surface area analysis 50 3.2.3.6. Nyquist plots analysis 52 3.3. Summary 53 3.4. Shortcomings 53 IV. METAL(S)-RICH AND CARBON-LESS CORE-SHELL ELECTROCATALYSTS FOR WATER SPLITTING 4.1. Nanocarbon-Encapsulated, Cobalt-Rich Core-Shell Co@NC as an OER Electrocatalyst in Alkaline Water Electrolyzer 4.1.1. Introduction 54 4.1.2. Results and discussion 55 4.1.2.1. Synthesis and characterization of the core-shell Co@NC electrocatalyst 55 4.1.2.2. SEM and TEM analyses 56 4.1.2.3. XRD and XPS analyses 60 4.1.2.4. Elemental (CHNS) and BET surface area analyses 64 4.1.2.5. Oxygen evolution reaction: Catalysts on glassy carbon (GC) 66 4.1.2.6. Oxygen evolution reaction: Catalysts on nickel foam (NF) 67 4.1.2.7. Significant features of the electrochemical activity and stability 75 4.1.2.8. Solar-to-hydrogen conversion 77 4.1.2.9. Single cell water electrolyzer with Co@NC-600/NF//AEM//Co@NC- 600/NF-MEA 78 4.1.3. Summary 79 4.1.4. Shortcomings 79 4.2. Investigation of Electrocatalytic Activity and Active Sites on Ni, Co and Fe Centered Bimetallic Alloy Electrocatalysts for Overall Water Splitting 4.2.1. Introduction 80 4.2.2. Results and discussion 81 4.2.2.1. N-doped-carbon-layer-coated bimetallic catalysts 81 4.2.2.2. XRD analysis 81 4.2.2.3. SEM and TEM analyses 83 4.2.2.4. XPS analysis 84 4.2.2.5. Hydrogen evolution reaction on GC and NF (HER) 87 4.2.2.6. Oxygen evolution reaction on GC and NF (OER) 92 4.2.2.7. Density functional theory (DFT) 94 4.2.2.8. Overall water splitting 97 4.2.2.9. Single cell water electrolyzer with NiFe@NC-600/NF//AEM//CoFe@NC- 600/NF-MEA 98 4.2.3. Summary 99 4.2.4. Shortcomings 99 V. IN-SITU GROWN METAL(S)-CHALCOGENIDES AS AN EFFICIENT AND DURABLE ELECTROCATALYSTS FOR OVERALL WATER SPLITTING 5.1 Bimetal-Chalcogenide Electrocatalyst for Both Oxygen and Hydrogen Evolution Reactions: In-Situ Growth of NiCo2S4 Nanowire Arrays on Ni Foam 5.1.1. Introduction 100 5.1.1.1. Advantages of metal chalcogenide electrocatalysts 101 5.1.2. Results and discussion 102 5.1.2.1. Formation of NiCo2S4 nanowire arrays on nickel foam (NF) 102 5.1.2.2. XRD analysis 103 5.1.2.3. SEM analysis 104 5.1.2.4. TEM analysis 106 5.1.2.5. XPS analysis 107 5.1.2.6. Oxygen evolution reaction 108 5.1.2.7. Hydrogen evolution reaction 114 5.1.2.8. Electrochemical impedance spectroscopy (EIS) 117 5.1.2.9. Electrochemical active surface area (ECSA) 118 5.1.2.10. Wettability analysis (Contact angle) 119 5.1.2.11. Overall water splitting 119 5.1.2.12. Solar-to-hydrogen generation 120 5.1.2.13. Single cell water electrolyzer with NiCo2S4/NF//AEM//NiCo2S4/NF - MEA 122 5.1.3. Summary 123 5.1.4. Shortcomings 123 5.2 Directly Grown 3D Nickel Selenide Anode as an Efficient and Durable Non-Precious Electrocatalyst for the Alkaline Water Electrolysis 5.2.1. Introduction 124 5.2.2. Results and discussion 125 5.2.2.1. In-situ formation of Ni3Se2 on 3D-Ni foam 125 5.2.2.2. XRD analysis 126 5.2.2.3. SEM analysis 127 5.2.2.4. XPS analysis 128 5.2.2.5. Oxygen evolution reaction (OER) 129 5.2.2.6. Electrochemical impedance spectroscopy (EIS) 134 5.2.2.7. Electrochemical surface area (ECSA) 136 5.2.2.8. Overall water splitting 137 5.2.2.9. Solar-to-hydrogen generation 138 5.2.2.10. Single cell water electrolyzer with Ni3Se2/NF//AEM//NiCo2S4/NF-MEA140 5.2.3. Summary 141 VI. CONCLUSIONS REFERENCES 145
URI
http://dgist.dcollection.net/common/orgView/200000171507
http://hdl.handle.net/20.500.11750/10685
DOI
10.22677/thesis.200000171507
Degree
DOCTOR
Department
Energy Science&Engineering
University
DGIST
Related Researcher
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Department of Energy Science and EngineeringThesesPh.D.


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