Elektroden aus Legierungen der Übergangsmetalle Vanadium, Titan und Niob und der reinen Metalle reagieren in Abhängigkeit von der Zusammensetzung und des mit ihnen im Kontakt stehenden wässrigen Elektrolyten in höchst unterschiedlicher Weise. Für eine systematische Untersuchung der elektrochemischen Eigenschaften der Elektroden wurden neben den reinen Metallen binäre und ternäre Legierungen aus Vanadium, Titan und Niob, die jeweils Vanadium enthalten, hergestellt. Es wurden zum ersten Mal zusammenhängend ihre physikalischen und chemischen Eigenschaften durch Strukturuntersuchungen und Untersuchungen der Zusammensetzung der Oberfläche sowie der Morphologie bestimmt. Von den, sich mit einer halbleitenden Oxidschicht überziehenden Metallen, wurden die Halbleitereigenschaften im Elektrolytkontakt studiert, die grundlegenden Korrosionseigenschaften sowie ihr elektrochemisches Verhalten als Elektrodenmaterial in potentiometrischen Zellen und durch Strom-Spannungsmessungen bestimmt. Zur Aufklärung der Kinetik der Oxidschichtbildung wurden potentiostatische Stromtransienten ermittelt und mit bekannten Modellen verglichen.

With the rapid growth of the world population and the process of industrialization of modern society, the demand for energy continues to rise sharply. There is a pessimistic prediction that a peak of consumption primarily fossil fuels will happen in the 2020s to 2030s, hence it is urgent to develop alternative renewable clean energy sources before this coming energy crisis. But the availability of renewable clean energy always is discontinuous, uncontrollable, and unstable. Besides, the generated renewable energy cannot be used directly. Therefore, an energy storage system is urgently needed as the medium to harvest and store the energy generated from the intermittent renewable resource, and also to regulate the electricity output, and improve the tolerance ability of the power grid to renewable energy. Rechargeable aqueous zinc-ion battery, especially those that use mild electrolytes, is drawing more and more attention in the past decades and is regarded as the most promising candidate for large-scale energy storage systems. Compared with the widely used lithium-ion battery which dominated the commercial energy market now, the aqueous zinc-ion battery holds the merits of high theoretical capacity (820 mAh/g gravimetric capacity and 5855 mAh/m3 volumetric capacity), low electrochemical potential (-0.763 V vs. SHE) and high energy density due to the two-electron redox reaction, high abundance in the earth crust and high mass production, low toxicity, and environmental benignity, and the most valuable advantage intrinsic safety in aqueous electrolyte. In this dissertation, the first part focuses on the preliminary application of an aqueous zinc-ion battery. One kind of planar on-chip aqueous zinc-ion micro-battery with high-rate performance was designed and fabricated. The PEDOT and MnO2 cathode can suppress the dissolution of electrode material which can highly improve the cycling performance of the micro-battery. The as-prepared micro-battery displays a high specific capacity of 25.8 μAh/cm2 after 25 activation cycles at a current density of 1 mA/cm2. A reversible specific capacity of 6.2 μAh/cm2 is achieved after 200 cycles, with 55.4 % of the initial discharge capacity retention. To improve the cycling performance of the aqueous zinc-ion battery, the second part of this thesis is preparing a highly enhanced reversibility Zn anode by in-situ texturing. The crystal plane (002)-textured Zn anode with an ultrathin passivation layer suppressed the Zn corrosion and enhanced the full battery performance. Based on these merits, the cycling stability of the Zn anode is enhanced from 791 hours to more than 1500 hours. The coulombic efficiency (CE) of a Zn||Ti asymmetric cell is greater than 90% over 500-hour cycles. For the Zn||MnO2 full cell, the addition of H3PO4 into the electrolyte improves both the rate capability and cycling stability of Zn||MnO2 cells. More importantly, a highly reversible Zn||O2 full cell is demonstrated at a large depth of discharge of Zn (DODZn > 10%), projecting the lower bounds of the cell-level specific energy of lithium-ion batteries.:Abstract I Kurzfassung III List of Abbreviations IX Chapter 1 Background and motivation 1 1.1 Research motivation 1 1.2 Aim of this dissertation 2 1.3 Dissertation structure 3 Chapter 2 Introduction of aqueous zinc-ion battery and anode protection strategies 5 2.1 Introduction of aqueous zinc-ion battery 5 2.2 The challenges of zinc anode 8 2.2.1 Dendrites and protrusion 9 2.2.2 Hydrogen evolution reaction 10 2.2.3 Passivation layer 10 2.3 The strategies of zinc anode protection 11 2.3.1 Surface engineering 11 2.3.2 Electrolyte modification 15 2.3.3 3D structural skeleton and alloy strategies 22 Chapter 3 Experiment characterizations and calculations 25 3.1 Electrochemical methods 25 3.1.1 Chronoamperometry 25 3.1.2 Chronopotentiometry 26 3.1.3 Cyclic voltammetry 27 3.1.4 Galvanostatic charge/discharge 28 3.1.5 Electrochemical impedance spectroscopy 29 3.1.6 Tafel measurement 30 3.2 Characterization methods 31 3.2.1 X-ray diffraction 31 3.2.2 Scanning electron microscope 32 3.2.3 X-ray photoelectron spectroscopy 32 3.2.4 Raman spectroscopy 33 3.3 Experimental calculations 34 3.3.1 b value calculation 34 3.3.2 CE calculation 34 3.3.3 RTC calculation 35 3.3.4 DFT calculation 36 3.3.5 DOD calculation 37 3.3.6 Corrosion rate calculation 38 Chapter 4 A planar on-chip aqueous zinc-ion micro-battery with high-rate performance 41 4.1 Introduction 41 4.2 Experimental section 43 4.2.1 Interdigitated electrodes 43 4.2.2 Preparation of micro-battery 44 4.2.3 Microstructural properties characterization 45 4.2.4 Electrochemical characterization 45 4.3 Results and discussion 46 4.3.1 Characterization of micro-battery 46 4.3.2 Electrochemical performance measurement 49 4.4 Conclusions 56 Chapter 5 Highly enhanced reversibility of a Zn anode by in-situ texturing 57 5.1 Introduction 57 5.2 Experimental section 63 5.2.1 Preparation of the textured Zn anode 63 5.2.2 Synthesis of cathode materials 63 5.2.3 Electrochemical and material characterizations 64 5.3 Results and discussions 64 5.3.1 Nonuniform Zn deposition on an epitaxial substrate 65 5.3.2 In-situ texturing and SEI formation during the cycling 72 5.3.3 Full-cell performance 77 5.4 Conclusions 81 Chapter 6 Summary and outlook 83 6.1 Summary 83 6.2 Outlook 84 References： 87 Acknowledgment 99 Publications 101 Curriculum Vitae 103 Selbstständigkeitserklärung 105

This Ph.D. thesis concentrates on the synthesis and characterization of tailor-made metal-based precursors and their application in the metal-organic chemical vapor deposition (MOCVD), combustion chemical vapor deposition (CCVD) and in the spin-coating process. Therefore, different complexes containing copper, ruthenium, palladium and gold were synthesized and investigated concerning their thermal properties, especially their decomposition behavior and volatility. Copper(II) and palladium(II) β-ketoiminates were synthesized and used in MOCVD or spin-coating deposition experiments for the formation of metal and metal oxide materials. Ruthenium complexes of type Ru(CO)2(PEt3)2(O2CR)2 (R = Me, Et, iPr, tBu, CH2OMe, CF3) were investigated concerning their physical characteristics depending on the different carboxylates. While primarily focusing on the thermal decomposition behavior, VT IR (variable temperature infrared) spectroscopy, TG-MS (thermogravimetry-mass-spectrometry) studies and DFT (density-functional theory) calculations were carried out to gain a deeper inside into the degradation of the respective complexes, whereby it was possible to propose decomposition mechanisms. Furthermore, from these results it was possible to propose decomposition mechanisms. Gold carboxylates of type [AuO2CCH2OMe(PR’3)] (R’ = Et, nBu) were synthesized and characterized for the use as precursors within CCVD processes to generate Au and SiOx:Au materials. The deposits were used as heterogeneous catalyst in the reduction of 4-nitrophenol. The deposition behavior of zinc diolate towards zinc oxide layer formation was studied by MOCVD experiments, whereby an influence on the crystallinity of the received films was observed depending on the deposition conditions. The second part of this dissertation focuses on the synthesis of polyaromatic hydrocarbons (napthalene, phenanthrene and pyrene) functionalized with Fc (Fc = Fe(η5-C5H4)(η5-C5H5)) units as redox-active group. Thereby, the main emphasis was on the investigation of the charge transfer properties between the ferrocenyl entities through the π-conjugated bridges. The charge transfer behavior was affected by the substituents or substitution pattern at the aryls resulting in more or less intense intervalence charge transfer (IVCT) excitations of the respective compounds. In order to explore the interaction between the Fc-functionalized arenes and SWCNTs (single-walled carbon nanotubes), these molecules were studied by single-crystal X-ray diffraction analysis and DFT calculations. Moreover, disentangling experiments of SWCNTs with a Fc-functionalized pyrene led to the formation of a novel nanoconjugation, whereby the electrochemical response of the ferrocenyl entities is still present. / Die vorliegende Arbeit befasst sich mit der Synthese und Charakterisierung von maßgeschneiderten Übergangsmetall-basierten Precursoren und deren Anwendung in der metallorganischen chemischen Gasphasenabscheidung (MOCVD), in der Flammenbeschichtung (CCVD), oder in der Rotationsbeschichtung. Dafür wurden Kupfer-, Ruthenium-, Palladium- und Gold-haltige Komplexe hergestellt und bezüglich ihrer thermischen Eigenschaften, insbesondere das Zersetzungsverhalten und die Flüchtigkeit, charakterisiert. Cu(II)- und Pd(II)-β-Ketoiminate wurden synthetisiert und in der MOCVD oder in der Rotationsbeschichtung genutzt, um metallische und metalloxidische Materialien abzuscheiden. Ruthenium Komplexe des Typs Ru(CO)2(PEt3)2(O2CR)2 (R = Me, Et, iPr, tBu, CH2OMe, CF3) wurden hinsichtlich ihrer physikalischen Eigenschaften in Abhängigkeit der verschiedenen Substituenten der Carboxylate untersucht. Dabei lag der Fokus im Besonderen auf der thermischen Zersetzungen, welche mittels VT IR (variable Temperatur-Infrarot) Spektroskopie, TG-MS (Thermogravimetrie-Massenspektrometrie) Untersuchungen und DFT (Dichtefunktionaltheorie) Berechnungen genauer beleuchtet wurden. Dabei war es anhand der erhaltenen Ergebnisse möglich Zersetzungsmechanismen zu formulieren. Weiterhin wurden Goldcarboxylate der Art [AuO2CCH2OMe(PR’3)] (R’ = Et, nBu) synthetisiert und in der CCVD untersucht, um Au und SiOx:Au Materialien herzustellen, welche im Weiteren als heterogene Katalysatoren für die Reduktion von 4-Nitrophenol genutzt wurden. Das Abscheideverhalten von Zinkdiolaten in der MOCVD zur Erzeugung von dünnen Zinkoxidfilmen wurde beispielsweise in Hinblick des Einflusses auf die Kristallinität der Filme untersucht. Im zweiten Teil der Dissertation wird die Synthese von Fc-funktionalisierten (Fc = Fe(η5-C5H4)(η5-C5H5)) polyaromatischen Kohlenwasserstoffen (Naphthalen, Phenanthren, Pyren) diskutiert. Der Schwerpunkt lag dabei auf der Untersuchung des Elektrontransferverhaltens zwischen den Redox-aktiven Gruppen in Abhängigkeit der Substituenten und des Substitutionsmusters der π-konjugierten Brücke. Diese Verbindungen wurden mittels Röntgeneinkristallstrukturanalyse und DFT-Berechnungen untersucht um festzustellen, ob eine Wechselwirkung zwischen den Fcfunktionalisierten Arenen und SWCNTs (einwandige Kohlenstoffnanoröhren) möglich ist. Entbündelungsversuche von SWCNTs in Anwesenheit eines Fc-funktionalisierten Pyrens lieferten ein neuartiges Hybridsystem, welches Fc-basierte Redoxprozesse zeigte.

In dieser Arbeit wurde eine neuartige Möglichkeit zur Funktionalisierung von beliebigen Oberflächen entwickelt und getestet. p-(N-maleimido)phenyl- (MP) und p-Aminophenyl-Reste (AP) wurden auf CVD gewachsenem Graphen via Elektroreduktion der jeweiligen Diazoniumkationen abgeschieden. Die so funktionalisierten Graphenschichten wurden auf verschiedenste Materialien transferiert. Die Präsenz der funktionellen Gruppen wie auch ihre kovalente Anbindung wurde durch Infrarotellipsometrie und Ramanspektroskopie bestätigt. Für das MP-funktionalisierte Graphen wurde mittels optischer Simulation der IRSE-Daten die Dicke der MP-Schicht zu 4.4 nm vor und 4.8 nm nach dem Transfer bestimmt. Die Dicke nach Transfer wurde zusätzlich durch Infrarot-gekoppelte Rasterkraftmikroskopie zu 4.4 nm bestimmt. MP-Graphen wurde via MICHAEL-Addition sowohl mit p-Nitrobenzylmercaptan (NBM), als auch mit Cystein-terminierter Peptidnukleinsäure (PNA) modifiziert. Die jeweiligen Moleküle wurden nach dem Transfer per IRSE nachgewiesen. Die Modifikation mit NBM wurde darüber hinaus in einem Mikrofluidikaufbau in-situ verfolgt. Die Zeitabhängigkeit der Anreicherung an der MP-Oberfläche wurde mit der auf einer Goldoberfläche verglichen. AP-Graphen wurde mittels Zero-Length-Crosslinking mit p-Nitrobenzoesäure (NBA), sowie Carboxyl-funktionalisierten Nanokristallen (Quantum Dots) modifiziert. Die kovalente Anbindung wurde durch Vorhandensein der Amid-I-Bande nachgewiesen und der erfolgreiche Transfer mittels Photolumineszenz-Spektroskopie. Um das herausragende Potential des Transfers von funktionalisiertem Graphen zu zeigen, wurde PNA-modifiziertes MP-Graphen auf ein vorkontaktiertes Sensor-Array transferiert. Durch einfache Widerstandsbestimmung des Graphens konnte die Hybridisierung mit komplementärer DNA von 1b-mismatch DNA unterschieden werden. / A new pathway for the functionalization of arbitrary surfaces was developed and tested. p-(N-maleimido)phenyl (MP) and p-Aminophenyl (AP) residues were deposited on CVD grown graphene on copper, via electroreduction from the respective diazonium cation. The functional graphene layers were subsequently transferred to a variety of substrates, comprising metals (gold), insulators (SiO2, glass) and flexible ones (PTFE tape). The presence and covalent attachment of the desired groups was confirmed via infrared ellipsometry and Raman backscattering spectroscopy. The thickness of the Maleimidophenyl layer was determined via optical simulation of the IR ellipsometry data. The resulting 4.4 nm prior to and 4.8 nm after transfer to a gold film on silicon are in good agreement. The thickness after transfer was additionally measured using AFM, amounting as well to 4.4 nm. All results are in good agreement and confirm the possibility to transfer covalently functionalized graphene without noticeable loss. MP functionalized graphene was modified wet-chemically. MP-functionalized graphene was modified using the MICHAEL addition, attaching p Nitrobenzylmercaptane (NBM) or cysteine terminated peptide nucleic acid (PNA) to the surface. The success of modification and subsequent transfer was confirmed via infrared ellipsometry. MP graphene was furthermore integrated in a microfluidic setup. The time dependence of the accumulation of NBM on the functionalized graphene was compared to a similar on a plain gold surface. The different behaviour strongly hints at a covalent bonding between thiol and maleimide. AP functionalized graphene was modified via zero-length crosslinking with p Nitrobenzoic acid (NBA) and COOH containing Nanocrystals (Quantum Dots). The covalent attachment was shown by the presence of the amide bonds. Additionally, the successful transfer of the Quantum Dots was demonstrated via photoluminescence spectroscopy. To prove the outstanding potential of the transfer of functionalized graphene, PNA-modified MP-graphene was transferred on top of a pre-contacted sensor array. By simple current measurement, complementary DNA strands could be distinguished from the respective 1 b mismatch DNA.

Ausgangspunkt dieser Arbeit war die Frage, inwieweit die zur Herstellung von Compositmaterialien aus leitfähigen Polymerfilmen (Polythiophen, Polypyrrol) und Metalloxidschichten (anodisch oxidiertes Titan, chemisch oxidiertes Silicium bzw. Aluminium) entwickelte Präparationsmethode auf die Herstellung hybrider Core - Shell - Partikel (Core: Metalloxidpartikel; Shell: leitfähiges Polymer) übertragbar ist. Die erfolgreiche Beschichtung dispergierter Oxidpartikel mit leitfähigen Poly- meren zeigte, dass nicht nur eine analoge Verfahrensweise (Adsorption des Monomers auf der Substratoberfläche und anschließende Zugabe des Oxidationsmittels) verwendet werden konnte, sondern dass bei der Pulverbeschichtung infolge der großen spezifischen Oberfläche der Materialien auch ohne Einsatz spezieller Haftvermittler, hervorragende Schichtqualitäten (hohe Haftfestigkeit, hoher Be- deckungsgrad) erreicht wurden, und die auf diesem Wege hergestellten Verbundmaterialien in Pulverform in beliebiger Menge, Partikelgröße und Zusam-mensetzung verfügbar waren. Der durch die Verkapselung der Oxidteilchen mit intrinsich leitfähigen Polymeren bewirkte enge Kontakt zwischen Polymer- und Oxidphase und die auf diesem Wege realisierte Oberflächenmodifizierung führte zu einem im Vergleich zu den reinen Komponenten wesentlich veränderten Eigenschaftsspektrum. Durch die Herstellung von Compositen waren die leitfähigen Polymere leichter dispergierbar, und konnten kathaphoretisch in guter Qualität, auch auf großen Substratflächen abgeschieden werden. / Starting with the question about the possibility of producing composites based on conducting polymer films (polythiophene, polypyrrole) and metal oxide layers (anodically oxidized titanium, chemical oxidized silicon or aluminium) it was the goal of this work to transfer and modify this method for the preparation of hybrid core - shell - particles (core: metal oxide particle; shell: conducting polymer). By the successfully covering of dispersed oxide particles it was shown, that not only an analogous procedure (adsorption of the monomer on the substrate surface and the following addition of an oxidant) can be used, but that in the case of powder covering because of the high specific surface area of the oxide powders, outstanding layer qualities without using adhesion promotors can be produced. Following this way, powder-like compound materials can be ordered and designed in any quantity, particle size and composition. Through the encapsulation of the oxide particles with intrinsic conducting polymers a narrow contact between the polymer and the oxide phase and a surface modification were made by a very simple way. By this surface modification a totally different behaviour of the composites, compared to their components was realized. The producing of composites allowes a better dispersibility of conducting polymers and their cathaphoretically deposition with a good quality, also on larger substrate surfaces.

The physics of transition metal oxides is controlled by the combination and competition of several degrees of freedom, in particular the charge, the spin and the orbital state of the electrons. One important parameter responsible for the physical properties is the density of charge carriers which determines the oxidization state of the transition metal ions. The central objective in this work is the study of transition metal oxides in which the charge carrier density is adjusted and controlled via lithium intercalation/deintercalation using electrochemical methods. Lithium exchange can be achieved with a high degree of accuracy by electrochemical methods. The magnetic properties of various intermediate compounds are studied. Among the materials under study the mixed valent vanadium-oxide multiwall nanotubes represent a potentially technologically relevant material for lithium-ion batteries. Upon electron doping of VOx-NTs, the data confirm a higher number of magnetic V4+ sites. Interestingly, room temperature ferromagnetism evolves after electrochemical intercalation of Li, making VOx-NTs a novel type of self-assembled nanoscaled ferromagnets. The high temperature ferromagnetism was attributed to formation of nanosize interacting ferromagnetic spin clusters around the intercalated Li ions. This behavior was established by a complex experimental study with three different local spin probe techniques, namely, electron spin resonance (ESR), nuclear magnetic resonance (NMR) and muon spin relaxation spectroscopies. Sr2CuO2Br2 was another compound studied in this work. The material exhibits CuO4 layers isostructural to the hole-doped high-Tc superconductor La2-xSr2CuO4. Electron doping is realized by Li-intercalation and superconductivity was found below 9K. Electrochemical treatment hence allows the possibility of studying the electronic phase diagram of LixSr2CuO2Br2, a new electron doped superconductor. The effect of electrochemical lithium doping on the magnetic properties was also studied in tunnel-like alpha-MnO2 nanostructures. Upon lithium intercalation, Mn4+ present in alpha-MnO2 will be reduced to Mn3+, resulting in a Mn mixed valency in this compound. The mixed valency and different possible interactions arising between magnetic spins give a complexity to the magnetic properties of doped alpha-MnO2.

In this paper, we report that various kinds of active sites on graphite surface including active hydrophilic sites markedly affect the electrochemical performance of graphite anodes for lithium ion batteries under different humidity conditions. After depositing metals such as Ag and Cu by immersing and heat-treating, these active sites on the graphite surface were removed or covered and its electrochemical performance under the high humidity conditions was markedly improved. This suggests that lithium ion batteries can be assembled under less strict conditions and that it provides a valuable direction to lower the manufacturing cost for lithium ion batteries.

This master's thesis is focused on in situ observation of the negative electrode of the lead acid accumulator using atomic force microscopy AFM. Discussed topics are lead acid accumulator, atomic force microscopy, cyclic voltammetry and current knowledge of the in situ observation of the lead acid accumulator using AFM. The main task of this project is assembling the experimental cells, make in situ observation of the negative electrode surface of the lead acid accumulator. In the end evaluate if this method is suitable for the lead acid battery observation.

Nowadays, nanostructures fixed on solid substrates and colloidal nanoparticles permeate through all areas of human life, in area of sensors and detection as well. This dissertation thesis deals with the fabrication of nanostructures on the surface of planar electrodes via self-ordered nanoporous template of aluminum trioxide. The nanofabrication, as one of many possible techniques, is used to increase the active surface area of electrodes by creating unique surface types with specific properties. These electrodes are very perspective in the applications, such as biomolecules electrochemical detection and measurement. The transformation of aluminum layer into non-conductive nanoporous template in the process of anodic oxidation is a fundamental technique employed to obtain the array of nanostructures in this thesis. The fabrication of high quality nanoporous membranes with narrow pore size distribution on various types of metallic multilayers is one of the key experimental parts in this work. Several problems associated with the production of the thin-film systems, including the dissolving the barrier oxide layer, are discussed and solved. Another part of this work deals with the use of nanoporous membrane as a template for the production of metallic nanostructures via electrochemical metal ions deposition directly into the pores. The obtained nanostructures as nanowires, nanorods or nanodots are characterized by the scanning electron microscopy and energy-dispersive or wavelength X-ray spectroscopy. The electrode surface, modified by gold nanostructures suitable for the detection of biomolecules, has been chosen for the electrochemical measurements, due to the gold biocompatibility. The nanostructured electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The effect of nanostructured surface geometrical parameters, including the size of the electrochemically active area, on the results of electrochemical measurements has been observed and compared to flat gold electrodes. Two model biomolecules, namely guanine and glutathione, have been chosen for the study of potential application of these nanostructures in biosensors.

This thesis addresses the observed fluorescence intermittency of single semiconductor nanocrystals, so called Quantum Dots (QDs), which is also referred to as blinking. Despite continuous excitation their fluorescence is randomly interrupted by dark periods that can last over several minutes. Especially the extraction of power law dwell time statistics in bright and dark states indicates very complex underlying processes that are not fully understood to date. Here two approaches are followed to reveal the nature of the blinking mechanism. One addresses the common threshold method for extraction of power law dwell times. Its performance is tested with simulations to a broad range of experimentally determined parameters. Strong deviations are found between input and extracted statistics dependent on input parameters themselves. A comparison with experimental data does not support the assignment of power law statistics for the bright state and indicates the existence of distinct blinking mechanisms. The second approach directly aims at the nature of the dark state, which is mostly attributed to charges in the QD or trap states in its vicinity. A method is developed to detect charging processes on single QDs with their fluorescence. Electrochemistry is combined with confocal microscopy also allowing evaluations of excited state lifetimes and emission spectra. Reduction and oxidation of the QD bands are successfully observed as a quenching of QD fluorescence. Single QD observations identify two independent blinking mechanisms, that are assigned to positive and negative charging. Positive charging is not only observed after hole injection but also the extraction of excited electrons. Three additional quenching mechanisms are identified, two of which are assigned to trap relaxation. Differences between two substrate electrodes demonstrate the importance of the substrate material.