Influence of carbonaceous electrodes on capacitance and breakdown voltage for hybrid capacitor

This paper presents a new type of capacitor and deals with a hybrid approach where the advantages of two systems, dielectric capacitors and the ultracapacitor are combined. The objective is to increase the capacitance and the energy storage capability, while or at least preserving or decreasing the volume of the passive components. In this aim, the surface area and structural properties of ultracapacitor electrodes and the high dielectric strength of a polymer material are associated. The surface roughness of the carbonbased electrodes, namely (activated carbon—AC, and carbon nanotubes—CNTs), has a good impact on the capacitance. However, the surface roughness also depends on the composition of carbonaceous materials and so does the capacitance. Moreover, the choice of the dielectric material is the key parameter. The better the impregnation of the roughness is, the better is the increase of the capacitance. Since the final objective is to improve the electrical energy stored by the capacitor, the effect of surface roughness on the breakdown voltage is also evaluated

Research and development of graphene-based supercapacitors through Graphene Oxide

Supercapacitors (SCs) are energy storage devices suited for high power applications. Due to their growing interest, researchers are looking for their improvement in both performances and scalabililty, including the environmetal impact. In this PhD thesis, after an overview about different SCs and their main lines of research, author's works about innovative graphene-based elecrodes are discussed. In particular, the study and the use of a graphene precursor, Graphene Oxide, are the central elements of such researches

Last Developments in Polymers for Wearable Energy Storage Devices

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] Our modern and technological society requests enhanced energy storage devices to tackle the current necessities. In addition, wearable electronic devices are being demanding because they offer many facilities to the person wearing it. In this manuscript, a historical review is made about the available energy storage devices focusing on super-capacitors and lithium-ion batteries, since they currently are the most present in the industry, and the possible polymeric materials suitable on wearable energy storage devices. Polymers are a suitable option because they not only possess remarkable mechanical resistance, flexibility, long life-times, easy manufacturing techniques and low cost in addition to they can be environmentally friendly, nontoxic, and even biodegradable too. Moreover, the electrical and electrochemical polymer properties can be tunning with suitable fillers giving to versatile conducting polymer composites with a good cost and properties' ratio. Although the advances are promising, there are still many drawbacks that need to be overcome. Future research should focus on improving both the performance of materials and their processability on an industrial scale, where additive manufacturing offers many possibilities. The sustainability of new energy storage devices should not be forgotten, encouraging the use of more environmentally friendly materials and manufacturing processes.The authors thank the financial support from Ministerio de Ciencia e Innovation/FEDER (project ref; PID2020-116976RB-I00) and Xunta de Galicia-FEDER (Program of Consolidation and structuring competitive research units [ED431C 2019/17]). Funding for open access charge from Universidade da Coruña/CISUGXunta de Galicia; ED431C 2019/1

Future scope and directions of nanotechnology in creating next-generation supercapacitors

The primary global research scheme of the 21st century is nanotechnology. Looking forward to the future, nanotechnologies’ generalized diffusion will seem to turn them into supplies, generating more space for privileged and superior values of applications such as information technology, nanoenergy, nanobiotechnologies, and nanomaterials.1-5 In general, nanotechnology is the understanding and controlling of the matters of dimensions of approximately 1-100 nm, in which a unique phenomenon facilitates novel applications.2 The application domains covered by nanotechnology are discussed in detail in this chapter

PHYSICOCHEMICAL MODIFICATIONS AND APPLICATIONS OF CARBON NANO-ONIONS FOR ELECTROCHEMICAL ENERGY STORAGE

Carbon nano-onions (CNOs), concentrically multilayered fullerenes, are prepared by several different methods. We are studying the properties of two specific CNOs: A-CNOs and N-CNOs. A-CNOs are synthesized by underwater arc discharge, and N-CNOs are synthesized by high-temperature graphitization of commercial nanodiamond. In this study the synthesis of A-CNOs are optimized by designing an arc discharge aparatus to control the arc plasma. Moreover other synthesis parameters such as arc power, duty cycles, temperature, graphitic and metal impurities are controlled for optimum production of A-CNOs. Also, a very efficient purification method is developed to screen out A-CNOs from carboneseous and metal impurities. In general, A-CNOs are larger than N-CNOs (ca. 30 nm vs. 7 nm diameter). The high surface area, appropriate mesoporosity, high thermal stability and high electrical conductivity of CNOs make them a promising material for various applications. These hydrophobic materials are functionalized with organic groups on their outer layers to study their surface chemistry and to decorate with metal oxide nanoparticles. Both CNOs and CNO nanocomposites are investigated for application in electrochemical capacitors (ECs). The influences of pH, concentration and additives on the performance of the composites are studied. Electrochemical measurements demonstrate high specific capacitance and high cycling stability with high energy and power density of the composite materials in aqueous electrolyte

Tube-Super Dielectric Materials: Electrostatic Capacitors with Energy Density Greater than 200 J cm ˉ³

The article of record as published may be found at http://dx.doi.org/10.3390/ma8095301The construction and performance of a second generation of super dielectric material based electrostatic capacitors (EC), with energy density greater than 200 J cm ˉ³, which rival the best reported energy density of electric double layer capacitors (EDLC), also known as supercapacitors, are reported. The first generation super dielectric materials (SDM) are multi-material mixtures with dielectric constants greater than 1.0 10⁵, composed of a porous, electrically insulating powder filled with a polarizable, ion-containing liquid. Second-generation SDMs (TSDM), introduced here, are anodic titania nanotube arrays filled with concentrated aqueous salt solutions. Capacitors using TiO₂ based TSDM were found to have dielectric constants at ~0 Hz greater than 10⁷ in all cases, a maximum operating voltage of greater than 2 volts and remarkable energy density that surpasses the highest previously reported for EC capacitors by approximately one order of magnitude. A simple model based on the classic ponderable media model was shown to be largely consistent with data from nine EC type capacitors employing TSDM.US Navy (Naval Research Program, Project: P14-0463)US Marine Corps (Expeditionary Energy Office)US Navy (Naval Research Program, Project: P14-0463)US Marine Corps (Expeditionary Energy Office

Supercapacitive Swing Adsorption of Carbon Dioxide

Carbon capture is essential for reduction of carbon dioxide (CO2) pollution from flue gas which is emitted during fossil fuel combustion. The flue gas is mainly composed of 15% CO2 and 85% N2 and it requires high selectivity for gas purification. Some methods have been developed for carbon capture such as Pressure Swing Adsorption (PSA) and Temperature Swing Adsorption (TSA). Unfortunately, these techniques use a lot of energy during the desorption step that reduces power generation efficiency. An ideally effective carbon capture technique needs to promote CO2 adsorption and desorption at the proper times during the separation cycles, without incurring a large parasitic energy load. A new gas adsorption technique is presented, Supercapacitive Swing Adsorption (SSA), in which CO2 is either actively adsorbed or desorbed by repeated capacitive charge and discharge of supercapacitor carbon electrodes and energy used in adsorption can principally be recovered upon desorption. It is shown that reversible adsorption/desorption of CO2 from a 15% CO2 and 85% N2 gas mixture can be achieved when an electrically conducting high surface area porous carbon material is brought into contact with carbon dioxide gas and an aqueous sodium chloride electrolyte. When the supercapacitor carbon electrodes are charged, the electrolyte ions are spontaneously organized into an electric double layer at the surface of each porous carbon electrode. The presence of this double layer leads to reversible, selective adsorption and desorption of the CO2 as the supercapacitor is charged and discharged. Moreover, it is also shown that SSA has the ability to separate CO2 from N2, with a high selectivity for CO2 and only a weak dependence on the CO2 partial pressure in a CO2/N2 gas mixture. The amount of adsorbed CO2 scales with applied voltage and with the mass of the porous carbon sorbent, which is inexpensive, robust and environmentally friendly. The effect barely depends on temperature

Thin film techniques for the fabrication of nano-scale high energy density capacitors

Dielectric thin films of either TiO₂ or BaTiO₃ were sputtered in O₂/Ar plasmas on Si wafers to thicknesses ranging from approximately 25 to 200 nm with patterned Ni or Pt electrodes sputtered in Ar plasmas at thicknesses from about 20 to 250 nm to form nano-capacitors. Statistical design of experiments (DOE) was used to determine the effects of the deposition power, plasma composition, and deposition temperature on the measured electrical properties of the nano-capacitors. Additional tests to determine the effects of the dielectric and electrode thickness on the measured dielectric responses of the devices were also undertaken. Characterization was performed with a combination of direct current (DC) and alternating current (AC) testing methods including AC impedance, coercive field and leakage current versus voltage, scanning electron microscopy, transmission electron microscopy (TEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy, focused ion beam microscopy, and atomic force microscopy. The dielectric properties were found to depend on complex interactions of the process variables that could be modeled using statistical software. The permittivity was found to range from 100 to 10,000 with losses between 0.013 and 0.570. The resistance at 1 V DC varied from approximately 1.5 to 360 GΩ, and either a ferroelectric or paraelectric hysteretic response was observed for all specimens tested. Chemical analyses showed the films to be oxygen rich, while XRD and TEM data indicated the BaTiO₃ was amorphous. The electrical, chemical, and microstructural properties were found to depend on the sputtering conditions of the BaTiO₃, dielectric thickness, electrode material choice, and the electrode thickness. Collectively, the results indicated that the properties of nanometer thick dielectric and electrode materials have a significant impact on the measured electrical propertie

New generation of interactive platforms based on novel printed smart materials

Programa doutoral em Engenharia Eletrónica e de Computadores (área de Instrumentação e Microssistemas Eletrónicos)The last decade was marked by the computer-paradigm changing with other digital devices suddenly becoming available to the general public, such as tablets and smartphones. A shift in perspective from computer to materials as the centerpiece of digital interaction is leading to a diversification of interaction contexts, objects and applications, recurring to intuitive commands and dynamic content that can proportionate more interesting and satisfying experiences. In parallel, polymer-based sensors and actuators, and their integration in different substrates or devices is an area of increasing scientific and technological interest, which current state of the art starts to permit the use of smart sensors and actuators embodied within the objects seamlessly. Electronics is no longer a rigid board with plenty of chips. New technological advances and perspectives now turned into printed electronics in polymers, textiles or paper. We are assisting to the actual scaling down of computational power into everyday use objects, a fusion of the computer with the material. Interactivity is being transposed to objects erstwhile inanimate. In this work, strain and deformation sensors and actuators were developed recurring to functional polymer composites with metallic and carbonaceous nanoparticles (NPs) inks, leading to capacitive, piezoresistive and piezoelectric effects, envisioning the creation of tangible user interfaces (TUIs). Based on smart polymer substrates such as polyvinylidene fluoride (PVDF) or polyethylene terephthalate (PET), among others, prototypes were prepared using piezoelectric and dielectric technologies. Piezoresistive prototypes were prepared with resistive inks and restive functional polymers. Materials were printed by screen printing, inkjet printing and doctor blade coating. Finally, a case study of the integration of the different materials and technologies developed is presented in a book-form factor.A última década foi marcada por uma alteração do paradigma de computador pelo súbito aparecimento dos tablets e smartphones para o público geral. A alteração de perspetiva do computador para os materiais como parte central de interação digital levou a uma diversificação dos contextos de interação, objetos e aplicações, recorrendo a comandos intuitivos e conteúdos dinâmicos capazes de tornarem a experiência mais interessante e satisfatória. Em simultâneo, sensores e atuadores de base polimérica, e a sua integração em diferentes substratos ou dispositivos é uma área de crescente interesse científico e tecnológico, e o atual estado da arte começa a permitir o uso de sensores e atuadores inteligentes perfeitamente integrados nos objetos. Eletrónica já não é sinónimo de placas rígidas cheias de componentes. Novas perspetivas e avanços tecnológicos transformaram-se em eletrónica impressa em polímeros, têxteis ou papel. Neste momento estamos a assistir à redução da computação a objetos do dia a dia, uma fusão do computador com a matéria. A interatividade está a ser transposta para objetos outrora inanimados. Neste trabalho foram desenvolvidos atuadores e sensores e de pressão e de deformação com recurso a compostos poliméricos funcionais com tintas com nanopartículas (NPs) metálicas ou de base carbónica, recorrendo aos efeitos capacitivo, piezoresistivo e piezoelétrico, com vista à criação de interfaces de usuário tangíveis (TUIs). Usando substratos poliméricos inteligentes tais como fluoreto de polivinilideno (PVDF) ou politereftalato de etileno (PET), entre outos, foi possível a preparação de protótipos de tecnologia piezoelétrica ou dielétrica. Os protótipos de tecnologia piezoresistiva foram feitos com tintas resistivas e polímeros funcionais resistivos. Os materiais foram impressos por serigrafia, jato de tinta, impressão por aerossol e revestimento de lâmina doctor blade. Para terminar, é apresentado um caso de estudo da integração dos diferentes materiais e tecnologias desenvolvidos sob o formato de um livro.This project was supported by FCT – Fundação para a Ciência e a Tecnologia, within the doctorate grant with reference SFRH/BD/110622/2015, by POCH – Programa Operacional Capital Humano, and by EU – European Union

Sacrificial-template-free synthesis of core-shell C@Bi2S3 heterostructures for efficient supercapacitor and H-2 production applications

Core-shell heterostructures have attracted considerable attention owing to their unique properties and broad range of applications in lithium ion batteries, supercapacitors, and catalysis. Conversely, the effective synthesis of Bi2S3 nanorod core@ amorphous carbon shell heterostructure remains an important challenge. In this study, C@Bi2S3 core-shell heterostructures with enhanced supercapacitor performance were synthesized via sacrificial-template-free one-pot-synthesis method. The highest specific capacities of the C@Bi2S3 core shell was 333.43 F g(-1) at a current density of 1 A g(-1). Core-shell-structured C@Bi2S3 exhibits 1.86 times higher photocatalytic H-2 production than the pristine Bi2S3 under simulated solar light irradiation. This core-shell feature of C@Bi2S3 provides efficient charge separation and transfer owing to the formed heterojunction and a short radial transfer path, thus efficiently diminishing the charge recombination; it also facilitates plenty of active sites for the hydrogen evolution reaction owing to its mesoporous nature. These outcomes will open opportunities for developing low-cost and noble-metal-free efficient electrode materials for water splitting and supercapacitor applications