| 1. |
- Willfahrt, Andreas, 1977-
(författare)
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Screen Printing Technology for Energy Devices
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The technical application of screen and stencil printing has been state of the art for decades. As part of the subtractive production process of printed circuit boards, for instance, screen and stencil printing play an important role. With the end of the 20th century, another field has opened up with organic electronics. Since then, more and more functional layers have been produced using printing methods. Printed electronics devices offer properties that give almost every freedom to the creativity of product development. Flexibility, low weight, use of non-toxic materials, simple disposal and an enormous number of units due to the production process are some of the prominent keywords associated with this field.Screen printing is a widely used process in printed electronics, as this process is very flexible with regard to the materials that can be used. In addition, a minimum resolution of approximately 30 µm is sufficiently high. The ink film thickness, which can be controlled over a wide range, is an extremely important advantage of the process. Depending on the viscosity, layer thicknesses of several hundred nanometres up to several hundred micrometres can be realised.The conversion and storage of energy became an increasingly important topic in recent years. Since regenerative energy sources, such as photovoltaics or wind energy, often supply energy intermittently, appropriate storage systems must be available. This applies to large installations for the power supply of society, but also in the context of autarkic sensors, such as those used in the Internet of Things or domestic/industrial automation. A combination of micro-energy converters and energy storage devices is an adequate concept for providing energy for such applications.In this thesis the above mentioned keywords are addressed and the feasibility of printed thermoelectric energy converters and supercapacitors as energy storage devices are investigated. The efficiency of thermoelectric generators (TEG) is low, but in industrial environments, for example, a large amount of unused low temperature heat energy can be found. If the production costs of TEGs are low, conversion of this unused heat energy can contribute to increasing system efficiency.Additionally, printing of supercapacitor energy storage devices increases the usability of the TEG. It is appropriate to use both components as complementary parts in an energy system.
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| 2. |
- Ghorbani Shiraz, Hamid, 1989-
(författare)
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Electrochemical reduction of protons and organic molecules in hydrogen technologies : Liquid Organic Hydrogen carrier and Hydrogen Evolution
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In accordance with preventable actions to mitigate the effect of climate change in the modern societal applications, renewable energy is an unavoidable and decisive factor in the energy industry. The energy sources that offer non-depleted and environment-friendly pathways for the energy sector are in focus. Amongst, hydrogen has been defined as one of the best candidates to meet the criteria such as high energy-content and zero-emission of CO2, and of course, renewability. In this work, we focused on the areas of hydrogen generation and hydrogen storage.In the first part, we employed an inorganic electrocatalyst (nanosheets) to drive the hydrogen evolution reaction (HER), where we proved that the overpotential of few millivolts (0.016 V) is enough to run the HER reaction. We studied the effect of interlayer gap (for the nanosheets) on the catalytic performance. The chemical intercalation showed a huge effect for the suppression of the HER, which could be applicable for the devices like batteries the formation of any gaseous species has detrimental effect on the performance. It should not be left unmentioned that the measurements were carried out in a platinum group metal free (PGM-free) system, where graphite felt were used as a counter electrode, to avoid any platinum contamination. Next, we investigated the effect of oxygen poisoning on both pristine electrocatalyst and intercalated one. The XPS and UPS measurements confirmed the formation of oxygen-containing groups on the electrocatalysts. Electrochemical measurements showed the increase of the overpotential toward HER as the electrocatalysts are exposed to air for longer time. However, study of the hydrogen oxidation reaction (HOR) showed that there is an optimum concentration of oxygenic functional groups that can lead to a high current density of HOR process. The study of exchange current density showed that, after 10 days of exposure of electrocatalyst to atmospheric air, pristine sample possesses the best performance toward HER and intercalated one shows the highest performance for the HOR. In the other section, hydrogen storage for the organic redox-active molecule (dissolved in organic solvent) was studied. One of the main problems in hydrogen economy concept, is the storage of the hydrogen for transportation. The new concept of Liquid Organic Hydrogen Carrier (LOHC) offers a low-cost and safe approach to this challenge. Herein, we demonstrated an electrochemical pathway to hydrogenate the organic system via conversion of proton of a proton donor into a covalent-bonded hydrogen, through a proton coupled electron transfer (PCET) reaction of 2nH+ + 2ne¯ + Rox nH2Rred. Here, we studied the 9-fluorenone/fluorenol (Fnone/Fnol) as a model PCET reaction. The electrochemical activation of starting component of (Fnone), through two successive electron transfers was investigated with in-situ and operando spectroscopies purely, and in presence of different proton donors of different reactivity. We succeed to both quantify and qualify the investigated the reaction. The hydrogen release step was demonstrated chemically with the aid of catalyst. To conclude, we employed a PGM-free system to demonstrate and characterize a high performing electrocatalyst for hydrogen evolution. Surprisingly, HOR was revealed to perform well using the oxygen poisoned electrocatalyst for HER. In the other section of this work, an electrochemical assisted synthesis of LOHC, in the lab-scale, was proved. A PCET pathway was conceptualized with mechanistic insight. Our work opens new avenue for the technology of hydrogenation of LOHC as we showed for the first time that this could be realized by electrochemistry without the need of hydrogen gas as a prerequisite. We believe that in the future both works could contribute slightly to the concept of the hydrogen economy.
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| 3. |
- Kim, Donghyun, 1986-
(författare)
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Computational study of Polymerization, Crystallization and Mechanical Properties of Conducting Polymers
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nowadays, electronic devices that include conducting polymers, ranging from batteries and OLED panel for TVs and smartphones to bioelectronics devices such as sensors and ion-pumps for drug-delivery are widely used in our life. The use of conducting polymer in many electronic applications was driven by demand for light weight, flexibility or biocompatibility with the performance on pair with conventional inorganic counterparts. As a result, during last two decades conducting polymers have been a subject of significant interest in both academia and industry. Though many aspects of conducting polymers’ nature have been disclosed, it is still challenging to design a conducting polymer that meets required electrical and mechanical properties. It is because these properties are simultaneously influenced by many various factors such as charge carrier concentration, molecular weight, chemical structure. Thus, understanding the polymerization, crystallization and morphology of conducting polymers is a crucial key to realize flexible, stretchable or wearable electric applications based on conducting polymers. Computational methods represent an important tool in studies of conducting polymer since they not only provide information about morphology of polymer films on molecular level, but also can describe physical properties such as thermodynamic potential and pair-wise interaction between chains that experimental studies can rely on. This thesis is focused on two classes of conducting polymers: Thiophene-based polymers (PEDOT and p(g42T-T)) and NDI-based polymers (pNDI-TVT-TET). The former is one of the most versatile p-type materials, while the latter is known to have ambipolar charge transport owing to its donor-acceptor structure. First, we corroborated the mechanism of in-situ chemical polymerization of PEDOT with Fe(TOS)3 as oxidant by reaction energy calculation for the conventional oxidation polymerization mechanism. We found that doping of PEDOT chain became energetically unfavorable beyond of 33% doping level and we explained it in terms of polaron localization. To explore the impact of polymerization temperature on PEDOT length, we developed a polymerization model for in-situ chemical polymerization of PEDOT:TOS. The results demonstrate that the average PEDOT length is 6, 7, and 11 monomer units at 298, 323, and 373K respectively, and we concluded that the diffusivity of reactants was a dominant factor determining the PEDOT length. We also investigated the effect of molecular doping on the morphology of p(g42T-T) films and their mechanical properties. Doping of p(g42T-T) by TFSI from 0% to 10% gradually increases the - stacking between polymers. It is also found that when doped by F4TCNQ, the elastic modulus and electrical conductivity of films increases until the doping level of about 18%. We attribute these results to the increasing of -stacking between inter-polymer backbones upon increasing the doping levels from 0% to 18%. Finally, the impact of the ratio of TVT/TET in pNDI-TVTx-TET1-x on the morphology and mechanical properties was studied. From MD simulations, we find that the π-π stacking between polymers as the TVT content increases till 50% and afterwards slightly decreases. In addition, a thin-film transistor with the TVT content of 60 or 80% shows a better conductivity than the one with 100% content when it is bent. Our findings on polymerization of conducting polymers, evolution of crystalline and mechanical properties provide theoretical insight that can help a practical improvement in the field of flexible organic electric devices.
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| 4. |
- Lander, Sanna, 1990-
(författare)
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Sulfonated Cellulose Membranes for Energy Storage Applications
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the ongoing efforts to reduce the dependency of mankind on fossil fuels for the supply of energy, renewable energy sources such as solar cells and wind turbines are employed to an increasing extent. Transitioning a large portion of electrical grids to intermittent power sources come with several problems that need to be taken into account and handled, such as ensuring supply at peak power demand and considering frequency regulation and other issues related to the stability of the grid. One possible way to increase the amount of intermittent energy sources while maintaining a stable grid and power supply is to use large scale energy storage systems to store energy that can then be used as needed.One of the most promising energy storage systems for this purpose is the redox flow battery, an electrochemical energy storage system in which the power output and total energy storage capacity are decoupled, the former relating to the area of the electrochemical cell and the latter to the amount of electrolyte. This decoupling is a great advantage since large electrolyte tanks can be used to store huge amounts of energy in a stationary manner.Redox flow batteries and other devices such as fuel cells and certain types of batteries are dependent on a selective membrane for their function. The membrane needs to efficiently transport certain species while blocking others, and the function of the membrane is often greatly influencing the performance of the devices that employ them. Current state-of-the-art ion selective membranes are often produced from PFSA-based materials, which are problematic in terms of sustainability and cost. Finding ways to replace such membranes with equally functional components produced from bio-based materials would be a large step forward in terms of improving the sustainability and cost-efficiency of large scale electrochemical energy storage.In this work, functionalized cellulose nanofibrils are used as starting material to produce novel bio-based selective membranes aimed to be employed in electrochemical energy storage systems, in particular redox flow batteries. The possibility to precisely tune the properties of membranes via the degree of modification of the starting material is investigated, as well as some strategies to further improve the performance of membranes via additives and post-fabrication modifications.
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| 5. |
- Wu, Zhixing, 1990-, et al.
(författare)
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Conducting Polymer‐Based e‐Refinery for Sustainable Hydrogen Peroxide Production
- 2023
-
Ingår i: Energy & Environmental Materials. - : Wiley-Blackwell. - 2575-0356.
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Tidskriftsartikel (refereegranskat)abstract
- Electrocatalysis enables the industrial transition to sustainable production of chemicals using abundant precursors and electricity from renewable sources. De-centralized production of hydrogen peroxide (H2O2) from water and oxygen of air is highly desirable for daily life and industry. We report an effective electrochemical refinery (e-refinery) for H2O2 by means of electrocatalysis-controlled comproportionation reaction (2(H)O + O -> 2(HO)), feeding pure water and oxygen only. Mesoporous nickel (II) oxide (NiO) was used as electrocatalyst for oxygen evolution reaction (OER), producing oxygen at the anode. Conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) drove the oxygen reduction reaction (ORR), forming H2O2 on the cathode. The reactions were evaluated in both half-cell and device configurations. The performance of the H2O2 e-refinery, assembled on anion-exchange solid electrolyte and fed with pure water, was limited by the unbalanced ionic transport. Optimization of the operation conditions allowed a conversion efficiency of 80%.
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| 6. |
- Ajjan, Fátima, 1986-, et al.
(författare)
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Doped Conjugated Polymer Enclosing a Redox Polymer : Wiring Polyquinones with Poly(3,4‐Ethylenedioxythiophene)
- 2020
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Ingår i: Advanced Energy and Sustainability Research. - : John Wiley & Sons. - 2699-9412. ; 1:2
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Tidskriftsartikel (refereegranskat)abstract
- The mass implementation of renewable energies is limited by the absence of efficient and affordable technology to store electrical energy. Thus, the development of new materials is needed to improve the performance of actual devices such as batteries or supercapacitors. Herein, the facile consecutive chemically oxidative polymerization of poly(1-amino-5-chloroanthraquinone) (PACA) and poly(3,4-ethylenedioxythiophene (PEDOT) resulting in a water dispersible material PACA-PEDOT is shown. The water-based slurry made of PACA-PEDOT nanoparticles can be processed as film coated in ambient atmosphere, a critical feature for scaling up the electrode manufacturing. The novel redox polymer electrode is a nanocomposite that withstands rapid charging (16 A g−1) and delivers high power (5000 W kg−1). At lower current density its storage capacity is high (198 mAh g−1) and displays improved cycling stability (60% after 5000 cycles). Its great electrochemical performance results from the combination of the redox reversibility of the quinone groups in PACA that allows a high amount of charge storage via Faradaic reactions and the high electronic conductivity of PEDOT to access to the redox-active sites. These promising results demonstrate the potential of PACA-PEDOT to make easily organic electrodes from a water-coating process, without toxic metals, and operating in non-flammable aqueous electrolyte for large scale pseudocapacitors.
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| 7. |
- Che, Canyan, 1988-
(författare)
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Electrochemical Reactions of Quinones at Conducting Polymer Electrodes
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Proton-coupled multielectron transfer reactions are of great abundance in Nature. In particular, two-proton-two-electron transfers in quinone/hydroquinone redox couples are behind oxidative phosphorylation (ADP-to-ATP) and photosystem II. The redox processes of neurotransmitters, as a platform for brain activity read-out, are two-proton two-electron transfers of quinones. Moreover, humic acids, which constitute a major organic fraction of soil, turf, coal, and lignin, which forms as a large-scale surplus product from forest and paper industry, contain a large quantity of polyphenols, which can undergo the exchange of two electrons per aromatic ring accompanied with transfers of two protons. This makes polyphenol-based biopolymers, such as lignin, promising green-chemistry renewable materials for electrical energy storage or generation. The application of intact or depolymerized polyphenols in electrical energy devices such as fuel cells and redox flow batteries requires appropriate electrode materials to ensure efficient proton-coupled electron transfer reactions occurring at the solid-liquid interface. Moreover, investigation of the biological quinones reaction calls for porous, soft, biocompatible materials as implantable devices to reduce the rejection reaction and pain.At common electrode materials such as platinum and carbons, quinone/hydroquinone redox processes are rather irreversible; in addition, platinum is very costly. Conducting polymers (CPs), poly(3,4-ethylenedioxythiophene) (PEDOT) in particular, offer an attractive option as metal-free electrode material for these reactions due to their molecular porosity, high electrical and ionic conductivity, solution processability, resistance to acid media, as well as high atomic abundance of their constituents.This thesis explores the possibility of utilizing CPs as electrode materials for driving various quinone redox reactions. Firstly, we studied the electrocatalytic activity and mechanism of PEDOTs for the generic hydroquinone reaction and their application in a fuel cell. Secondly, the mechanism of integrating lignosulfonate (LS) into CP matrices and optimization strategies were explored in order to boost energy storage capacity. Thirdly, we attained mechanistic understanding of the influence of ionic transport and proton management on the thermodynamics and kinetics of the electrocatalysis on CPs, thereby providing steps towards the design of quinone-based electrical energy storage devices, such as organic redox flow batteries (ORFB).
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| 8. |
- Ghorbani Shiraz, Hamid, 1989-, et al.
(författare)
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3R-TaS2 as an Intercalation-Dependent Electrified Interface for Hydrogen Reduction and Oxidation Reactions
- 2022
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:40, s. 17056-17065
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen technology, as a future breakthrough for the energy industry, has been defined as an environmentally friendly, renewable, and high-power energy carrier. The green production of hydrogen, which mainly relies on electrocatalysts, is limited by the high cost and/ or the performance of the catalytic system. Recently, studies have been conducted in search of bifunctional electrocatalysts accelerating both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR). Herein, we report the investigation of the high efficiency bifunctional electrocatalyst TaS2 for both the HER and the HOR along with the asymmetric effect of inhibition by organic intercalation. The linear organic agent, to boost the electron donor property and to ease the process of intercalation, provides a higher interlayer gap in the tandem structure of utilized nanosheets. XRD and XPS data reveal an increase in the interlayer distance of 22%. The HER and the HOR were characterized in a Pt group metal-free electrochemical system. The pristine sample shows a low overpotential of -0.016 Vat the onset. The intercalated sample demonstrates a large shift in its performance for the HER. It is revealed that the intercalation is a potential key strategy for tuning the performance of this family of catalysts. The inhibition of the HER by intercalation is considered as the increase in the operational window of a water-based electrolyte on a negative electrode, which is relevant to technologies of electrochemical energy storage.
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| 9. |
- Han, Shaobo, 1988-
(författare)
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Thermoelectric polymer-cellulose composite aerogels
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermoelectric materials are scrutinized as energy materials and sensing materials. Indeed, they convert thermal energy into electrical energy. In addition, those materials are actively sensitive to a temperature modification through the generation of an electric signal. Organic thermoelectric (OTE) materials are complementary to inorganic thermoelectric materials, as they possess unique properties such as solution processing, ionic conductivity, flexibility, and softness. While thin-film OTE materials have been widely studied because they are easily manufactured by various coating techniques, little is done in the creation of three-dimensional morphologies of OTE materials; which is important to develop large temperature gradients.Cellulose is the most abundant biopolymer on the planet. Recently, the applications of cellulose are not only limited in making papers but also in electronics as the cellulose provide 3-D microstructures and mechanical strength. One promising approach to make 3-D OTE bulks is using cellulose as scaffold because of their properties of relatively high mechanical strength, water processability and environmentally friendly performance.The aims of the thesis have been to enlarge the applications of an OTE material poly(3,4-ethylenedioxythiophene) (PEDOT), with an approach of making 3-D aerogels composite with nanofibrillated cellulose (NFC), in two main areas: (1) multi-parameter sensors and (2) solar vapor generators. In the first application, we demonstrate that the new thermoelectric aerogel responds independently to pressure P, temperature T and humidity RH. Hence, when it is submitted to the three stresses (T, P, RH), the electrical characterization of the material enables to measure the three parameters without cross-talking effects. Thermoelectric aerogels are foreseen as active materials in electronic skins and robotics. In the second application, the conducting polymer aerogels are employed as solar absorbers to convert solar energy into heat and significantly increased the water evaporation rate. The IR absorption is efficient because of the free-electron in the conducting polymer PEDOT nano-aggregates. Because of the low cost of those materials and the water stability of the crosslinked aerogels, they could be of importance for water desalination.
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| 10. |
- Kumar, Divyaratan, et al.
(författare)
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Self-Discharge in Batteries Based on Lignin and Water-in-Polymer Salt Electrolyte
- 2022
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Ingår i: Advanced Energy and Sustainability Research. - : Wiley. - 2699-9412. ; 3:10
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Tidskriftsartikel (refereegranskat)abstract
- Lignin, the most abundant biopolymer on earth, has been explored as an electroactive material in battery applications. One essential feature for such lignin-based batteries to reach successful usage and implementation, e.g., large-scale stationary grid applications, is to have slow self-discharge characteristics on top of the essential safety and life-cycle properties. Water-in-polymer salt electrolytes (WIPSEs) have been demonstrated as an attractive route to solve this issue; however, little has been done to understand the fundamentals of actual self-discharge mechanisms. Herein, the impact of some critical chemical and physical parameters (pH, dissolved oxygen, viscosity, and cutoff potential) on self-discharge of batteries based on WIPSE and lignin has been investigated. The pH range is crucial as there is an interplay between long-term stability and high energy density. Indeed, lignin derivatives typically store relatively more charge in acidic media but later promote corrosion affecting device stability. A robust and high-performing organic battery, incorporating potassium polyacrylate as WIPSE, is demonstrated, which expresses good self-discharge behavior for a broad range of pH and with little impact on the atmosphere used for manufacturing. It is believed that the investigation will provide critical insights to the research community to promote the advancement of printed large-scale energy storage devices.
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| 11. |
- Kumar, Divyaratan, 1995-
(författare)
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Water-in-polymer Salt Electrolyte (WIPSE) for Sustainable Lignin Batteries
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic electrolytes are widely used in energy storage technologies, but they are known to have safety, cost, and eco friendliness concerns. Water based electrolytes do not have those issues but are limited by their narrow range potential range of operation to 1.2V. Above that voltage, significant side reactions lead to gas evolution, side reaction and high selfdischarge rate in organic batteries. Because of their superior ionic conductivities, which are critical for reducing device resistance and improving power; as well as their cost-effective ness and non-flammability, researchers have had a second look at water-based electrolyte and found out that super concentrated aqueous solutions behave differently, and their electrochemical stability window can be widened.In this thesis, polyacrylate (PAAK) based "water in polymer salt" electrolyte (WIPSE) has been identified as a promising solution for large-scale energy storage devices. This new family of "water in salt" electrolytes offers a broad electrochemical stability window of up to 3V, a high ionic conductivity (100 mS/cm) and is non-flammable, making it ideal for high power electrochemical storage devices. However, little is known about the matter transport in PAAK based WIPSE and in "water in salt" electrolytes in general. Therefore, this thesis also aims to investigate the properties of PAAK using spectroscopic techniques such as Raman spectroscopy and diffusion NMR to understand the behavior of water and the mechanism of ionic transport in relation to water and polymer chain dynamics. Since the electrolyte only transports cations, it is suitable for use in "cation rocking chair" batteries that utilize two types of polymeric quinones, lignin, and polyimide redox polymers, as positive and negative electrodes, respectively. The electrochemically active redox polymers with K+ ions at neutral pH are ions at neutral pH are advantageous for avoiding corrosion in metal collectors. Further for understanding the fundamental of self-discharge mechanism, the impact of some critical chemical and physical parameters on performance of lignin-based batteries have been investigated.The final chapter of the thesis introduces a novel approach to address the challenges associated with Zn-ion batteries by utilizing the "water-inpolymer salt" electrolyte concept modified by salt additives. The goal is to enable the use of lignin-carbon (L-C) electrodes in a Zinc battery. Lignin, carbon and zinc are among the most affordable, environmentally friendly and sustainable options for energy storage for energy storage. By incorporating WIPSE electrolytes these batteries can offer additional benefits, such as improved safety and the prevention of dendrite formation. Our findings demonstrate that acrylate groups in the electrolyte stabilize the flux on the zinc electrode surface, promoting parallel deposition and significantly reducing dendritic formation through vertical growth. The assembled Zn-lignin battery delivers a maximum energy of 23 Wh/kg and a maximum power of 610 W/kg, with an exceptional 82% retention after 8000 cycles. With the reduced expected environmental impact of green and the cost- effectiveness of these polymer electrolytes, the resulting battery shows great promise in the battery market. Its emergence has opened a new avenue in the pursuit of safe and efficient batteries, which has been a major area of focus within the energy storage industry.
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| 12. |
- Molaei, Arman, 1988-
(författare)
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Functionalized Porous Carbon Fiber Electrodes for Applications in Electrochemical Flow Cells
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Corrosion of metals in close-loop cooling or heating systems originates from tiny leakages at joints releasing oxygen into the thermal fluids. The presence of dissolved oxygen (DO) in thermal fluids, such as water with various additives forms a rust coating and some rust particles are released in the fluids and accumulate in an undesired place. Overall, these phenomena decrease the efficiency of heat exchangers and boilers in energy systems. There are various techniques to remove DO but each has drawbacks either related to their efficiency, cost, or minimum DO level reachable. Herein, we propose an electrochemical technique to achieve a low-cost and efficient deoxygenation. We investigate both the fundamentals and make a proof of concept for a deoxygenation electrolyser that consumes the DO through the oxygen reduction reaction (ORR). First, we designed a simple and low-cost flow-through electrode by adding macro-porous carbon fiber papers (CFPs) with calibrated loads of carbon microporous particles (CPs) to combine both a high surface area and an open structure for good fluid dynamics. Then, the faradic performance of carbon electrodes is evaluated in a designed static deoxygenation electrolyser that shows three regimes of complex kinetic side reactions involving various species such as O2, H2O2, H2O, and anodic carbon oxidation. The functionalization of redox-active quinone molecules operating by electron mediators over the anode electrode is developed to improve the ORR efficiency and remove the issue of degradation of the carbon anode. Finally, we investigate the use of a new electrocatalytic polymer poly(benzimidazobenzophenanthro-line) (BBL) to drive the ORR toward water instead of forming H2O2. The combination of both the polymer catalyst at the cathode and the quinone molecules designs a path for an efficient deoxygenation electrolyser that could become a key device to slow down corrosion rate and improve the efficiency in energy systems.
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| 13. |
- Shiran Chaharsoughi, Mina, 1986-
(författare)
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Hybrid Plasmonics for Energy Harvesting and Sensing of Radiation and Heat
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The special optical properties of subwavelength metallic structures have opened up for numerous applications in different fields. The interaction of light with metal nanostructures leads to the excitation of collective oscillations of conduction-band electrons, known as plasmons. These plasmon excitations are responsible for the high absorption and high scattering of light in metallic nanostructures. High absorption of light and the subsequent temperature increase in the nanostructures make them suitable as point-like heat sources that can be controlled remotely by light.The research presented in this thesis focuses on the development and studies of hybrid devices that combine light-induced heating in plasmonic nanostructures with other materials and systems. Particular focus is put on hybrid organic-inorganic systems for applications in energy harvesting as well as in heat and radiation sensing. Harvesting energy from light fluctuations was achieved in a hybrid device consisting of plasmonic gold nanodisk arrays and a pyroelectric copolymer. In this concept, fast and efficient light-induced heating in the gold nanodisks modulated the temperature of the pyroelectric layer, which could be used to extract electrical energy from fluctuations in simulated sunlight.Integrating plasmonic nanostructures with complementary materials can also provide novel hybrid sensors, for monitoring of temperature, heat flux and radiation. In this thesis work, a hybrid sensor was designed based on the combination of a plasmonic gold nanohole layer with a pyroelectric copolymer and an ionic thermoelectric gel. The gold nanohole arrays acted both as broadband light absorbers in the visible to near-infrared spectral range of the solar spectrum and also as one of the electrodes of the sensor. In contrast to the constituent components when used separately, the hybrid sensor could provide both fast and stable signals upon heat or radiation stimuli, as well as enhanced equilibrium signals.Furthermore, a concept for heat and radiation mapping was developed that was highly sensitive and stable despite its simple structure. The concept consisted of a gel-like electrolyte connecting two separated metal nanohole electrodes on a substrate. Resembling traditional thermocouples, this concept could autonomously detect temperature changes but with several orders of magnitudes higher sensitivity. Owing to its promising sensing properties as well as its compatibility with inexpensive mass production methods on flexible substrates, such concept may be particularly interesting for electronic skin applications for health monitoring and for humanoid robotics. Finally, we improved the possibilities for the temperature mapping of the concept by modifying the structure from lateral to vertical form. Similar to the lateral device, the vertical temperature sensor showed high temperature sensitivity and stability in producing signals upon temperature changes.
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| 14. |
- Ahmed, Fareed, et al.
(författare)
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Manufacturing Poly(3,4-Ethylenedioxythiophene) Electrocatalytic Sheets for Large-Scale H2O2 Production
- 2022
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Ingår i: Advanced Sustainable Systems. - : John Wiley and Sons Inc. - 2366-7486. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Producing thick films of conducting polymers by a low-cost manufacturing technique would enable new applications. However, removing huge solvent volume from diluted suspension or dispersion (1–3 wt%) in which conducting polymers are typically obtained is a true manufacturing challenge. In this work, a procedure is proposed to quickly remove water from the conducting polymer poly(3,4-ethylenedioxythiophene:poly(4-styrene sulfonate) (PEDOT:PSS) suspension. The PEDOT:PSS suspension is first flocculated with 1 m H2SO4 transforming PEDOT nanoparticles (≈50–500 nm) into soft microparticles. A filtration process inspired by pulp dewatering in a paper machine on a wire mesh with apertures dimension between 60 µm and 0.5 mm leads to thick free-standing films (≈0.5 mm). Wire mesh clogging that hinders dewatering (known as dead-end filtration) is overcome by adding to the flocculated PEDOT:PSS dispersion carbon fibers that aggregate and form efficient water channels. Moreover, this enables fast formation of thick layers under simple atmospheric pressure filtration, thus making the process truly scalable. Thick freestanding PEDOT films thus obtained are used as electrocatalysts for efficient reduction of oxygen to hydrogen peroxide, a promising green chemical and fuel. The inhomogeneity of the films does not affect their electrochemical function. © 2021 The Authors.
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| 15. |
- Che, Canyan, 1988-, et al.
(författare)
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Twinning Lignosulfonate with a Conducting Polymer via Counter-Ion Exchange for Large-Scale Electrical Storage
- 2019
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Ingår i: Advanced Sustainable Systems. - : Wiley-VCH Verlag. - 2366-7486. ; 3:9
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Tidskriftsartikel (refereegranskat)abstract
- Lignosulfonate (LS) is a large-scale surplus product of the forest and paper industries, and has primarily been utilized as a low-cost plasticizer in making concrete for the construction industry. LS is an anionic redox-active polyelectrolyte and is a promising candidate to boost the charge capacity of the positive electrode (positrode) in redox-supercapacitors. Here, the physical-chemical investigation of how this biopolymer incorporates into the conducting polymer PEDOT matrix, of the positrode, by means of counter-ion exchange is reported. Upon successful incorporation, an optimal access to redox moieties is achieved, which provides a 63% increase of the resulting stored electrical charge by reversible redox interconversion. The effects of pH, ionic strength, and concentrations, of included components, on the polymer–polymer interactions are optimized to exploit the biopolymer-associated redox currents. Further, the explored LS-conducting polymer incorporation strategy, via aqueous synthesis, is evaluated in an up-scaling effort toward large-scale electrical energy storage technology. By using an up-scaled production protocol, integration of the biopolymer within the conducting polymer matrix by counter-ion exchange is confirmed and the PEDOT-LS synthesized through optimized strategy reaches an improved charge capacity of 44.6 mAh g−1.
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| 16. |
- Chen, Shangzhi, et al.
(författare)
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Unraveling vertical inhomogeneity in vapour phase polymerized PEDOT:Tos films
- 2020
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 8, s. 18726-18734
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Tidskriftsartikel (refereegranskat)abstract
- The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) forms a promising alternative to conventional inorganic conductors, where deposition of thin films via vapour phase polymerization (VPP) has gained particular interest owing to high electrical conductivity within the plane of the film. The conductivity perpendicular to the film is typically much lower, which may be related not only to preferential alignment of PEDOT crystallites but also to vertical stratification across the film. In this study, we reveal non-linear vertical microstructural variations across VPP PEDOT:Tos thin films, as well as significant differences in doping level between the top and bottom surfaces. The results are consistent with a VPP mechanism based on diffusion-limited transport of polymerization precursors. Conducting polymer films with vertical inhomogeneity may find applications in gradient-index optics, functionally graded thermoelectrics, and optoelectronic devices requiring gradient doping.
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| 17. |
- Fahlman, Mats, 1967-, et al.
(författare)
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Interfaces in organic electronics
- 2019
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Ingår i: Nature Reviews Materials. - : Nature Publishing Group. - 2058-8437. ; 4:10, s. 627-650
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Forskningsöversikt (refereegranskat)abstract
- Undoped, conjugated, organic molecules and polymers possess properties of semiconductors, including the electronic structure and charge transport, which can be readily tuned by chemical design. Moreover, organic semiconductors (OSs) can be n-doped or p-doped to become organic conductors and can exhibit mixed electronic and ionic conductivity. Compared with inorganic semiconductors and metals, organic (semi)conductors possess a unique feature: no insulating oxide forms on their surface when exposed to air. Thus, OSs form clean interfaces with many materials, including metals and other OSs. OS–metal and OS–OS interfaces have been intensely investigated over the past 30 years, from which a consistent theoretical description has emerged. Since the 2000s, increased attention has been paid to interfaces in organic electronics that involve dielectrics, electrolytes, ferroelectrics and even biological organisms. In this Review, we consider the central role of these interfaces in the function of organic electronic devices and discuss how the physico-chemical properties of the interfaces govern the interfacial transport of light, excitons, electrons and ions, as well as the transduction of electrons into the molecular language of cells.
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| 18. |
- Jiang, Qinglin, et al.
(författare)
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High Thermoelectric Performance in n-Type Perylene Bisimide Induced by the Soret Effect
- 2020
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 32:45
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Tidskriftsartikel (refereegranskat)abstract
- Low-cost, non-toxic, abundant organic thermoelectric materials are currently under investigation for use as potential alternatives for the production of electricity from waste heat. While organic conductors reach electrical conductivities as high as their inorganic counterparts, they suffer from an overall low thermoelectric figure of merit (ZT) due to their small Seebeck coefficient. Moreover, the lack of efficient n-type organic materials still represents a major challenge when trying to fabricate efficient organic thermoelectric modules. Here, a novel strategy is proposed both to increase the Seebeck coefficient and achieve the highest thermoelectric efficiency for n-type organic thermoelectrics to date. An organic mixed ion-electron n-type conductor based on highly crystalline and reduced perylene bisimide is developed. Quasi-frozen ionic carriers yield a large ionic Seebeck coefficient of -3021 mu V K-1, while the electronic carriers dominate the electrical conductivity which is as high as 0.18 S cm(-1)at 60% relative humidity. The overall power factor is remarkably high (165 mu W m(-1)K(-2)), with aZT= 0.23 at room temperature. The resulting single leg thermoelectric generators display a high quasi-constant power output. This work paves the way for the design and development of efficient organic thermoelectrics by the rational control of the mobility of the electronic and ionic carriers.
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| 19. |
- Kim, Nara, 1985-, et al.
(författare)
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Electric transport properties in PEDOT thin films
- 2019. - 4
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Ingår i: Conjugated polymers. - Boca Raton : CRC Press. - 9780429190520 ; , s. 45-128
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Bokkapitel (refereegranskat)abstract
- In this chapter, the authors summarize their understanding of Poly(3,4-ethylenedioxythiophene) (PEDOT), with respect to its chemical and physical fundamentals. They focus upon the structure of several PEDOT systems, from the angstrom level and up, and the impact on both electronic and ionic transport. The authors discuss the structural properties of PEDOT:X and PEDOT:poly(styrenesulfonate) based on experimental data probed at the scale ranging from angstrom to submicrometer. The morphology of PEDOT is influenced by the nature of counter-ions, especially at high oxidation levels. The doping anions intercalate between PEDOT chains to form a “sandwich” structure to screen the positive charges in PEDOT chains. The authors provide the main transport coefficients such as electrical conductivity s, Seebeck coefficient S, and Peltier coefficient σ, starting from a general thermodynamic consideration. The optical conductivity of PEDOT has also been examined based on the effective medium approximation, which is normally used to describe microscopic permittivity properties of composites made from several different constituents.
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| 20. |
- Mardi, Saeed, et al.
(författare)
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Interfacial Effect Boosts the Performance of All-Polymer Ionic Thermoelectric Supercapacitors
- 2022
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 9:31
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Tidskriftsartikel (refereegranskat)abstract
- Ionic thermoelectric supercapacitors (ITESCs) have recently been developed for converting low-grade waste heat into electricity. Until now, most reports of ITESCs have been focused on the development of electrolytes, which then have been combined with a specific electrode material. Here, it is demonstrated that the electrode is not only critical for electrical energy storage but also greatly affects the effective thermopower (S-eff) of an ITESC. It is shown that the same ion gel can generate a positive thermopower in an ITESC when using gold nanowire (AuNW) electrodes, while generating a negative thermopower when using poly(3,4-ethylendioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes. The achieved negative sign of the S-eff could be attributed to the Donnan exclusive effect from the polyanions in the PEDOT:PSS electrodes. After examining the thermovoltage, capacitance and charge retention performance of the two ITESCs, it is concluded that PEDOT:PSS is superior to AuNWs as electrodes. Moreover, a new strategy of constructing an ionic thermopile of multiple p- and n-type legs is achieved by series-connecting these legs with same electrolyte but different electrodes. Using interfacial effect at ionic gels/PEDOT:PSS electrode interface, an enhanced thermoelectric effect in ITESCs is obtained, which constitutes one more step towards efficient, low-cost, flexible, and printable ionic thermoelectric modules for energy harvesting.
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| 21. |
- Mitraka, Evangelia, 1986-
(författare)
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Conducting Polymer Electrodes for Oxygen Reduction Reaction
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Both the pollution level of the environment and the increasing energy demands have stimulated intense research on the development of low-cost environmentally-friendly energy conversion and storage systems with high efficiency, such as metal-air batteries and fuel cells.One of the most essential parts of both fuel cells and metal–air batteries is the air-electrode which is responsible for the reduction of O2. The air-electrode can use O2 from air facilitating the layout of the device; however, the process taking place on it is significantly complex. Currently, platinum (Pt) is the benchmark for air-electrodes in such technologies, although it is expensive and exhibits other important disadvantages which diminish the fuel cell performance. Therefore, extensive research has been devoted to reduce the amount of Pt used in air-electrodes and to develop a noble metal-free version of these electrodes.The area of printed electronics could facilitate the development of low-cost electrodes produced in high volume for such applications. Conducting polymers are attractive materials for this technology because they may combine several desired properties, like electronic conduction, ionic conduction and catalysis of electrochemical reactions.Among other conducting polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) emerged as an alternative cathode catalyst material to Pt, due to its ability to effectively catalyze the oxygen reduction reaction (ORR), while it also exhibits high electrical and ionic conductivity.The focus of this thesis is to study the electrocatalytic activity and mechanism of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) when employed as an airelectrode in energy storage devices, such as fuel cells and metal-air batteries. Although PEDOT is extensively studied during the last decade as an air-electrode for fuel cell and metal-air batteries, vital pieces of the catalytic mechanism that PEDOT follows remain unknown, namely: (i) the sites of PEDOT on which O2 interacts and (ii) the intermediate species which are formed during the ORR. The content of this thesis tackles these topics, both from experimental and theoretical point of view. Moreover, it investigates the use of PEDOT as an active electrocatalyst in a polymer exchange membrane (PEM) fuel cell, by embedding the polymer in a cellulose matrix, aiming to fabricate a gas diffusion electrode for the ORR side of the device. Finally, the goal of the thesis surpasses the limit of the p-doped PEDOT and undertakes the evaluation of a n-type conjugated polymer of high electron affinity as a cathode in reduction processes.
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| 22. |
- Mitraka, Evangelia, 1986-, et al.
(författare)
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Electrocatalytic Production of Hydrogen Peroxide with Poly(3,4-ethylenedioxythiophene) Electrodes
- 2019
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Ingår i: Advanced Sustainable Systems. - : Wiley-VCH Verlagsgesellschaft. - 2366-7486 .- 2366-7486. ; 3:2, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Electrocatalysis for energy‐efficient chemical transformations is a central concept behind sustainable technologies. Numerous efforts focus on synthesizing hydrogen peroxide, a major industrial chemical and potential fuel, using simple and green methods. Electrochemical synthesis of peroxide is a promising route. Herein it is demonstrated that the conducting polymer poly(3,4‐ethylenedioxythiophene), PEDOT, is an efficient and selective heterogeneous catalyst for the direct reduction of oxygen to hydrogen peroxide. While many metallic catalysts are known to generate peroxide, they subsequently catalyze decomposition of peroxide to water. PEDOT electrodes can support continuous generation of high concentrations of peroxide with Faraday efficiency remaining close to 100%. The mechanisms of PEDOT‐catalyzed reduction of O2 to H2O2 using in situ spectroscopic techniques and theoretical calculations, which both corroborate the existence of a chemisorbed reactive intermediate on the polymer chains that kinetically favors the selective reduction reaction to H2O2, are explored. These results offer a viable method for peroxide electrosynthesis and open new possibilities for intrinsic catalytic properties of conducting polymers.
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| 23. |
- Molaei, Arman, 1988-, et al.
(författare)
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Faradic Side Reactions at Novel Carbon Flow-Through Electrodes for Desalination Studied in a Static Supercapacitor Architecture
- 2023
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Ingår i: Advanced Energy and Sustainability Research. - : Wiley. - 2699-9412. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Desalination by capacitive deionization (CDI) is a promising technique to combine desalination and energy storage. The efficiency of charge storage process, which is equivalent to the desalination process, depends strongly on the presence of Faradic side reactions on the electrode. Herein, the performance of a new low-cost designed flow-through electrode with porous carbon nanoparticles (CP) coating on carbon-fiber paper (CFP) is evaluated. The CP layer enables high capacitance while the CFP core makes fluid dynamics along and across the electrode. The electrodes are evaluated by studying the effective operational CDI parameters, such as operational voltage, degassing of electrolyte, and salt concentration. The Faradic side reaction and its effect on charge efficiency (CE) are evaluated which are estimated to decrease to 46% by liquid flow bringing dissolved oxygen from the air-electrolyte interface to the electrode. The CE enhances to 59% with a salt concentration of 1 m. By purging N-2 gas, CE is much higher (>85%) with a maximum efficiency of 97% at 0.6 V. Three regimes of the complex kinetic of side reactions are found involving various species such as O-2, H2O2, H-2, and carbon oxidation and the implication of those regimes for real applications are discussed.
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| 24. |
- Sultana, Ayesha, et al.
(författare)
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An ionic thermoelectric ratchet effect in polymeric electrolytes
- 2022
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 10:37, s. 13922-13929
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Tidskriftsartikel (refereegranskat)abstract
- Ionic thermoelectric materials can generate extraordinarily high thermal voltage under small temperature differences due to their orders of magnitude larger Seebeck coefficient than that of electronic materials. Together with their low-cost, environmentally friendly compositions and solution processability, electrolytes have brought renewed prosperity in thermoelectric fields. Despite the rapid growing number of good-performance materials, yet to be implemented in devices, the main challenge is the understanding of the mechanism of the large Seebeck coefficient in practical electrolytes. Here, we show that the ion/polymer interaction in PEG based electrolytes does not only affect the mobility of the ions, but also has a great impact on the Seebeck coefficient. By delicately varying the types of solvent and the concentration of the solute, we could tune the molar conductivity of the electrolytes and correlate with the Seebeck coefficient. The linear relation between the Seebeck coefficient and the logarithm of the molar conductivity is in agreement with the recently reported thermoelectric ratchet effect in ions with hopping dynamics. This could lead to new design rules for ionic thermoelectrics.
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| 25. |
- Wijeratne, Kosala, 1983-
(författare)
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Conducting Polymer Electrodes for Thermogalvanic Cells
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fossil fuels are still the dominant (ca. 80%) energy source in our society. A significant fraction is used to generate electricity with a heat engine possessing an efficiency of approximately 35%. Therefore, about 65% of fossil fuel energy is wasted in heat. Other primary heat sources include solar and geothermal energies that can heat up solid and fluids up to 150°C. The growing demand and severe environmental impact of energy systems provide an impetus for effective management and harvesting solutions dealing with waste heat. A promising way to use waste heat is to directly convert thermal energy into electrical energy by thermoelectric generators (TEGs). Solid state TEGs are electronic devices that generate electrical power due to the thermo-diffusion of electronic charge carriers in the semiconductor upon application of the thermal field. However, there is another type of thermoelectric device that has been much less investigated; this is the thermogalvanic cell (TGCs). The TGC is an electrochemical device that consists of the electrolyte solution including a reversible redox couple sandwiched between two electrodes. In our study, we focus on iron-based organometallic molecules in aqueous electrolyte. A temperature difference (Δ?) between the electrodes promotes a difference in the electrode potentials [Δ?(?)]. Since the electrolyte contains a redox couple acting like electronic shuttle between the two electrodes, power can be generated when the two electrodes are submitted to a temperature difference. The focus of this thesis is (i) to investigate the possibility to use conducting polymer electrodes for thermogalvanic cells as an alternative to platinum and carbon-based electrodes, (ii) to investigate the role of viscosity of the electrolyte in order to consider polymer electrolytes, (iii) to understand the mechanisms limiting the electrical power output in TGCs; and (iv) to understand the fundamentals of the electron transfer taking place at the interface between the polymer electrode and the redox molecule in the electrolyte. These findings provide an essential toolbox for further improvement in conducting polymer thermogalvanic cells and various other emerging electrochemical technologies such as fuel cells, redox flow battery, dye-sensitized solar cells and industrial electrochemical synthesis.
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