Basic Insights Into the Reductive Activation and Covalent Functionalization of Graphene and SWCNTs to Yield Novel and Highly Modified Carbon Structures Grundlegende Einblicke in die Reduktive Aktivierung und Kovalente Funktionalisierung von Graphen und SWCNTs zur Erzeugung neuartiger und hochmodifizierter Kohlenstoffstrukturen Der Naturwissenschaftlichen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg zur Erlangung des Doktorgrades Dr. rer. nat. vorgelegt von Oliver Martin aus Lindau (am Bodensee) 1 Als Dissertation genehmigt von der Naturwissenschaftlichen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU). Tag der mündlichen Prüfung: 10.05.2021 Vorsitzender der Prüfungsorgans: Prof. Dr. Wolfgang Achtziger Gutachter: Prof. Dr. Andreas Hirsch Prof. Dr. Bernd Meyer I Hiermit versichere ich, dass die vorliegende Dissertationsarbeit vollständig meinen eigenen Forschungsarbeiten entspringt. Sämtliche Beiträge von Dritten, die der Entstehung dieses Werkes dienlich waren, sowie von mir selbst in wissenschaftlichen Journalen publizierte Artikel, die während der Promotionszeit entstanden sind, sind deutlich gekennzeichnet. Die hier vorliegende Arbeit entstand in der Zeit vom März 2016 bis Juni 2020 am Lehrstuhl für Organische Chemie II der Friedrich-Alexander- Universität Erlangen-Nürnberg sowie am Zentralinstitut für Neue Materialien und Prozesstechnik (ZMP) in Fürth. II “Chemistry begins in the stars. The stars are the source of the chemical elements, which are the building blocks of matter and the core of our subject” (Peter Atkins) III Index of Abbreviations a.u. Arbitrary Units abs absolute AFM Atomic Force Microscopy Atm Standard Atmosphere BLG Bilayer Graphene CDH Cyclodehydrogenation CHP N-Cyclohexyl-2-pyrrolidone CNT Carbon Nanotube CoMoCat Cobalt-Molybdenum Catalyst CVD Chemical Vapour Deposition 1D 1-Dimensional 2D 2-Dimensional 3D 3-Dimensional DME 1,2-Dimethoxyethane DoF Degree of Functionalization DOS Density of States DWCNT Double-walled Carbon Nanotube EDS Energy dispersive X-ray spectroscopy Et2O Diethyl Ether EtOH Ethanol ETR Electron Transfer Rate EF Fermi Energy EF Fermi Level IV FLG Few Layer Graphene FWHM Full-Width at Half-Maximum GIC Graphite Intercalation Compound GNR Graphene Nanoribbons GO Graphene Oxide GQD Graphene Quantum Dots HBC Hexabenzocoronene HEM High Energy Modes HiPco High Pressure Carbon Monoxide Decomposition iLA In Plane Longitudinal Acoustical iLO In Plane Longitudinal Optical IR Infrared iTA In Plane Transversal Acoustical iTO In Plane Transversal Optical LD Distance of Defects MALDI Matrix-Assisted Laser Desorption Ionization MeOH Methanol MLG Monolayer Graphene MS Mass Spectrometry MWCNT Multi-walled Carbon Nanotube m/z mass to charge ratio nIR Near Infrared NMP N-Methylpyrilidone NT Nanotube V PAH Polycyclic Aromatic Hydrocarbon PES Photo Electron Spectroscopy PhCN Benzonitrile PLV Pulsed Laser Vaporization QED Quantum Electrodynamics QHE Quantum Hall Effect RBM Radial Breathing Mode RDI Raman Defect Index rGO Reduced Graphene Oxide RT Room Temperature S Scattering Coefficient SCA Synthetic Carbon allotrope SCH Sodium Cholate SDBS Sodium Lauryl benzenesulfonate SDS Sodium Dodecyl Sulfate SET Single Electron Transfer SLG Single Layer Graphene SRS Statistical Raman Spectroscopy SWCNT Single-walled Carbon Nanotube TBAF Tetra-n-butylammonium Fluoride TBAP Tetra-n-butylammonium Bromide TEM Transmission Electron Microscopy TGA Thermogravimetric Analysis TG-GC-MS Thermogravimetric Analysis coupled with Mass Spectrometry and Gas Chromatography TG-MS Thermogravimetric Analysis coupled with Mass Spectrometry VI THF Tertrahydrofuran TM Tangential Modes ToF Time of flight UHV Ultra-High Vacuum US Ultrasonication UV-vis Ultraviolet-Visible vHS Van Hove Singularities XPS X-ray Photo Electron Spectroscopy λE Excitation Wavelength ѵf Fermi Velocity VII Table of Contents 1 Introduction ................................................................................................. 1 1.1 About Carbon Allotropes ............................................................................... 1 1.2 Carbon Nanotubes ........................................................................................ 3 1.2.1 Structure and Properties .......................................................................... 3 1.2.2 Synthesis and Purification ........................................................................ 7 1.2.3 Functionalization .................................................................................... 11 1.3 Graphene .....................................................................................................19 1.3.1 Structure and Properties ........................................................................ 19 1.3.2 Production .............................................................................................. 21 1.3.3 Discharging of Graphenides .................................................................. 27 1.3.4 Functionalization .................................................................................... 28 1.4 Characterization Methods .............................................................................35 1.4.1 Raman Spectroscopy ............................................................................. 35 1.4.2 TG-MS/ TG-GC-MS ............................................................................... 41 2 Proposal ......................................................................................................43 3 Results and Discussion .............................................................................46 3.1 Solvent-driven Oxidation of Carbon Allotropides by PhCN ...........................46 3.1.1 Reactivity of various Types of Graphite after Activation ......................... 46 3.1.2 Influence of PhCN on SWCNTs and Different Activation Routes ........... 60 3.1.3 Impact of PhCN after Covalent Functionalization................................... 69 3.2 Mechanistic Investigations of the Reductive Functionalization Process .......76 3.2.1 Hydrogenation of Monolayer Graphene Flakes...................................... 78 3.2.2 Hydrogenation of the Peripheral Regions of CVD Graphene ................. 82 3.2.3 Expansion of Defects ............................................................................. 87 3.2.4 Ditopic Hydrogenation Approach of CVD Graphene .............................. 90 3.2.5 Dehydrogenation .................................................................................... 94 VIII 3.3 Reductive Functionalization of oxo-Graphene ..............................................96 3.3.1 Reductive Functionalization of rGO on Substrates .............................. 101 3.3.2 Reductive Bulk Functionalization of rGO ............................................. 102 3.4 Evaluation of the Quantitative Degrees of Functionalization ......................108 3.4.1 Graphene Functionalization ................................................................. 110 3.4.2 SWCNT Functionalization .................................................................... 118 3.4.3 Comparison of Additions ...................................................................... 127 3.5 Halogenation of Carbon Allotropes .............................................................130 3.5.1 Reductive Halogenation of Carbon Allotropes ..................................... 130 3.5.1.1 Halogenation of SWCNTs .................................................................. 131 3.5.1.2 Substitution of halogenated SWCNTs ............................................... 134 5.5.1.3 Halogenation of Graphene ................................................................. 140 3.5.1.4 Comparison of Reductive Approaches .............................................. 142 5.5.1.5 Halogenation of Monolayer Graphene ............................................... 148 3.5.2 In situ Chlorination of Graphite............................................................. 151 4 Conclusion ................................................................................................155 5 Zusammenfassung ...................................................................................160 6 Experimental part .....................................................................................166 6.1 Chemicals and Materials ............................................................................166 6.2 General Procedures ...................................................................................169 6.3 Instrumentation ...........................................................................................182 7 References ................................................................................................185 8 Appendix ...................................................................................................200 IX 1 Introduction 1.1 About Carbon Allotropes Carbon represents one of the earth’s most abundant elements in the periodic table. Due to its ability to bind to itself and almost every other element in various manners, it provides the foundation of life on earth. The resulting diversity of organic compounds and molecules together with a broad range of chemical and physical properties make it a useful tool in modern synthetic chemistry and essential for the usage in various technological applications. When carbon forms bonds solely to itself, it is called a carbon allotrope. While elemental carbon can exist in two natural allotropes with either sp2- or sp3-hybridized