Graphene–electrolyte systems are commonly found in cutting-edge research on electrochemistry, biotechnology, nanoelectronics, energy storage, materials engineering, and chemical engineering. The electrons in graphene intimately interact with ions from an electrolyte at the graphene–electrolyte interface, where the electrical or chemical properties of both graphene and electrolyte could be affected. The electronic behavior therefore determines the performance of applications in both Faradaic and non-Faradaic processes, which require intensive studies. This book systematically integrates the electronic theory and experimental techniques for both graphene and electrolytes. The theoretical sections detail the classical and quantum description of electron transport in graphene and the modern models for charges in electrolytes. The experimental sections compile common techniques for graphene growth/characterization and electrochemistry. Based on this knowledge, the final chapter reviews a few applications of graphene–electrolyte systems in biosensing, neural recording, and enhanced electronic devices, in order to inspire future developments. This multidisciplinary book is ideal for a wide audience, including physicists, chemists, biologists, electrical engineers, materials engineers, and chemical engineers.

Graphene has grasped the attention of academia and industry world-wide due its unique structure and reported advantageous properties. This was reflected via the 2010 Nobel Prize in Physics being awarded for groundbreaking experiments regarding the two-dimensional material graphene. One particular area in which graphene has been extensively explored is electrochemistry where it is potentially the world’s thinnest electrode material. Graphene has been widely reported to perform beneficially over existing electrode materials when used within energy production or storage devices and when utilised to fabricate electrochemical sensors. This book charts the history of graphene, depicting how it has made an impact in the field of electrochemistry and how scientists are trying to unravel its unique properties, which has, surprisingly led to its fall from grace in some areas. A fundamental introduction into Graphene Electrochemistry is given, through which readers can acquire the tools required to effectively explain and interpret the vast array of graphene literature. The readers is provided with the appropriate insights required to be able to design and implement diligent electrochemical experiments when utilising graphene as an electrode material.

Understanding the mechanism for charge transfer between a graphene biosensor and its electrodes within an electrolyte solution is vital to better understand the sources of electrical noise in the system. By measuring the effective resistance and capacitance of the system at different frequencies, it is possible to develop a circuit model of the system's electrical behavior. This model provides a deeper understanding of the fundamental interactions that occur in a top-gated graphene device and provides opportunities to improve a signal. To reduce noise created at the liquid to graphene interface, a buffer layer of Yttrium Oxide was applied. While the buffer layer did not work as expected, this type of experimental approach and model will provide deeper understanding of the electrical noise.

Graphene Surfaces: Particles and Catalysts focuses on the surface chemistry and modification of graphene and its derivatives from a theoretical and electrochemical point-of-view. It provides a comprehensive overview of their electronic structure, synthesis, properties and general applications in catalysis science, including their relevance in alcohols and their derivatives oxidation, oxygen reduction, hydrogen evolution, energy storage, corrosion protection and supercapacitors. The book also covers emerging research on graphene chemistry and its impact. Chemical engineers, materials scientists, electrochemists and engineers will find information that will answer their most pressing questions on the surface aspects of graphene and its effect on catalysis. - Serves as a time-saving reference for researchers, graduated students and chemical engineers - Equips the reader with catalysis knowledge for practical applications - Discusses the physical and electrochemical properties of graphene - Provides the most important applications of graphene in electrochemical systems - Highlights both experimental and theoretical aspects of graphene

Interfaces offer unique electrical properties different than those of homogeneous phases, and as a result play key roles in electronic and electrochemical devices. It is essential to understand the electrical properties of interfaces in order to design better devices to solve the problems encountered by humanity. In this dissertation, the electrical properties of interfaces within three types of electronic and electrochemical devices are studied – solid oxide fuel cells (SOFCs), supercapacitors (SCs), and graphene barristors. SOFCs are energy conversion devices that efficiently convert chemical energy (fuel) into electrical energy. A central area of research in this field is the reduction of SOFC operation temperature, which requires the discovery and development of electrolyte materials with higher ionic conductivities at lower temperatures. One route to accomplishing this goal is through the inclusion of a dense network of solid-solid interfaces with high ionic conductivity into the electrolyte. First, a better understanding of interfacial ionic conductivity is needed. Nanocrystalline yttia-stabilized zirconia thin films were studied to gain understanding of the ionic conductivity of film-substrate interfaces in the presence of grain boundaries. It was found that Mg diffused from the substrate into the grain boundary cores, nearly eliminating the grain boundary resistance. These results show the potential and complexity of interfacial engineering for superior electrolyte materials. Supercapacitors are an energy storage device well suited to applications that require high power density. They store energy in the form of electrical double layers at the solid-liquid interfaces between the electrode and electrolyte. An important issue for supercapacitors is the relation between device performance and charge/discharge rate; the capacity decays at higher operating rates. Due to the need for high electrode-electrolyte surface area, highly porous electrodes are used. This leading to variance in the accessibility of pore surfaces to electrolyte ions, which leads to a rate-dependence of the available power and energy density. We show that Peukert’s constant, widely applied to the evaluation of the rate-dependent performance of batteries, also allows the straightforward evaluation of the rate-performance of supercapacitors. A novel method for determining Peukert’s constant using impedance spectroscopy is presented. Furthermore, relationships between the pseudocapacitance and porosity and Peukert’s constant are established. Lastly, graphene barristors are a novel type of transistor with simple fabrication and excellent performance, which take advantage of graphene’s unique electrical properties. In a graphene barristor, current passes across a graphene/semiconductor interface. At the interface, a Schottky barrier is formed with a height and resistance that can be modulated with the application of an external electric field, through the change in work function of graphene. In the work presented in this dissertation, impedance spectroscopy is used to investigate the electrical properties of the graphene/semiconductor interface in a high-performance ZnO/graphene thin film barristor. It is found that conduction across the interface is mediated by an electron tunneling process. This leads to consistent device properties over a wide temperature range.

Research on deformable and wearable electronics has promoted an increasing demand for next-generation power sources with high energy/power density that are low cost, lightweight, thin and flexible. One key challenge in flexible electrochemical energy storage devices is the development of reliable electrodes using open-framework materials with robust structures and high performance. Based on an exploration of 3D porous graphene as a flexible substrate, this book constructs free-standing, binder-free, 3D array electrodes for use in batteries, and demonstrates the reasons for the research transformation from Li to Na batteries. It incorporates the first principles of computational investigation and in situ XRD, Raman observations to systematically reveal the working mechanism of the electrodes and structure evolution during ion insertion/extraction. These encouraging results and proposed mechanisms may accelerate further development of high rate batteries using smart nanoengineering of the electrode materials, which make “Na ion battery could be better than Li ion battery” possible.

Significant efforts have been made to understand corrosion since it is important both scientifically and technologically, as the direct cost resulting from corrosion and its prevention has become a non-negligible portion of the gross domestic product. While considerable effort has been made to understand the macroscopic corrosion behavior and empirical knowledge of effective corrosion mitigation strategies is available, a nanoscale description of corrosion processes is still lacking. This dissertation describes efforts to establish a fundamental understanding of the corrosion process at the coating/metal interface on the nanoscale. The dissertation is divided into three parts. In the first part, a nanoscale depiction of the influence of ions on the diffusion of water is garnered from the analysis of X-ray and neutron reflectivity (XR/NR) and electrochemical impedance spectroscopy (EIS) data since metal, water and oxygen are three key ingredients in corrosion and ions play an important part in accelerating corrosion. The diffusion of water or electrolyte in thin polymeric films in different directions, parallel to the film or perpendicular to it, was distinguished. XR/NR measurements were used to probe the diffusion parallel to the film using a customized diffusion cell and that rate was found to be orders of magnitude larger than the diffusion rate in bulk epoxy. In contrast, when EIS data were analyzed using equivalent electrical circuit (EEC) model fitting, the penetration (diffusion perpendicular to the film) rate was found to be orders of magnitude smaller than the diffusion rate in bulk epoxy. Consistent results from XR, NR and EIS showed that the diffusion rates of electrolyte in both the lateral and perpendicular directions are lower than those of water (H2O/D2O), and that the higher the ion concentration, the lower the rate of diffusion. Reflectivity measurements probing at small (nm) length scales and also comparatively short times (hours) complement the widespread use of EIS and provide a means of quantitatively investigating phenomena that occur rapidly as a first step in the metallic substrate corrosion. The second part of this dissertation provides a detailed description of the changes in an epoxy/aluminum interface morphology that occur upon exposure of the interface to water or electrolytes, with information derived from X-ray off-specular scattering and atomic force microscopy (AFM). The interface is quantitatively described using a self-affine model of a randomly rough interface based on height difference correlation function with parameters of roughness, jaggedness, and correlation length. "Rocking curve" measurements show the interface becomes more rough, the texture becomes more jagged and the correlation length becomes smaller. Different electrolytes (NaCl and NaI aqueous solutions) have similar effects on the disruption of the interface morphology, and H2O is less disruptive to the interface as compared to the two electrolytes. In the last part of this dissertation, the surface fluctuations of polystyrene (PS) melt films adsorbed on graphene are compared to the surface fluctuations on films adsorbed on single crystal silicon wafers. The surface fluctuations on polymer thin films have received intense interest since surface fluctuations influence important interfacial properties such as wetting, adhesion, and tribology. Additionally, for sufficiently thin films the surface fluctuations also reflect realities of the chain adsorption and organization at the interface with the substrate and those features of films should be important for dictating the resistance to water or electrolyte incursion at a substrate/film or matrix/filler interface. For 8Rg thick entangled linear polystyrene (PS) films on silicon (8Rg PS/Si) the surface fluctuations can be described using a hydrodynamic continuum theory (HCT), which assumes the thin film viscosity is equivalent to the bulk viscosity throughout its entire depth. For 131000 g/mol linear PS, when the thickness of the film is less than 4Rg, the surface fluctuations show confinement effects and the fluctuations are slowed. The surface fluctuations for an 8Rg thick PS film on graphene (8Rg PS/Graphene) are three orders of magnitude slower than those on 8Rg PS/Si. The 170°C data from the 3Rg PS/Si, 8Rg PS/Si and 8Rg PS/Graphene samples collapse on a universal curve using a two-layer model with a 75 nm (ca. 7Rg) thick highly viscous layer on graphene and a 14 nm (ca. 1.5Rg) thick highly viscous layer on silicon. The layer left after a rinsing and drying procedure reflects a 2.4 times thicker strongly adsorbed layer on graphene compared to that on silicon. Thus the effect of adsorption of melt PS chains on graphene on dynamics of the chains near the graphene is far more profound than the effect of adsorption of PS chains on silicon. This remarkable slowing of material near the polymer/graphene interface could have important implications for the performance of other graphene containing composites and coating systems when the polymer is able to interact as strongly with graphene as does PS.

This thesis focuses on the synthesis and characterization of various carbon allotropes (e.g., graphene oxide/graphene, graphene foam (GF), GF/carbon nanotube (CNT) hybrids) and their composites for electrochemical energy storage applications. The coverage ranges from materials synthesis to electrochemical analysis, to state-of-the-art electrochemical energy storage devices, and demonstrates how electrochemical characterization techniques can be integrated and applied in the active materials selection and nanostructure design process. Readers will also discover the latest findings on graphene-based electrochemical energy storage devices including asymmetric supercapacitors, lithium ion batteries and flexible Ni/Fe batteries. Given the unique experimental procedures and methods, the systematic electrochemical analysis, and the creative flexible energy storage device design presented, the thesis offers a valuable reference guide for researchers and newcomers to the field of carbon-based electrochemical energy storage.