| 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
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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
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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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