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1.	Ahmed, Fareed, et al. (författare) Manufacturing Poly(3,4-Ethylenedioxythiophene) Electrocatalytic Sheets for Large-Scale H2O2 Production 2022 Ingår i: Advanced Sustainable Systems. - : John Wiley and Sons Inc. - 2366-7486. ; 6:1 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.
2.	Che, Canyan, 1988- (författare) Electrochemical Reactions of Quinones at Conducting Polymer Electrodes 2019 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).
3.	Che, Canyan, 1988-, et al. (författare) Twinning Lignosulfonate with a Conducting Polymer via Counter-Ion Exchange for Large-Scale Electrical Storage 2019 Ingår i: Advanced Sustainable Systems. - : Wiley-VCH Verlag. - 2366-7486. ; 3:9 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.
4.	Ding, Penghui, 1994- (författare) Organic Materials-based Electrochemical Flow Cells for Energy Applications 2024 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract To meet the 2015 Paris Agreement requirement of limiting global warming to 1.5 °C, the transition from fossil fuels to renewables (solar and wind) necessitates a rapid change of the energy landscape. The decline of the price for electricity from solar panels and wind turbines is so fast over the last decade that green electricity competes economically with electricity generated from coal, oil, and gas. Considering the output from renewable energy sources is electric current, the conversion and storage of green electricity is the key to the paradigm shift. Both conversion and storage imply transformation of electrical energy into chemical energy of molecules. The former means production of multipurpose energetic molecules. Here such a molecule is hydrogen peroxide, a green oxidant, and our aim is to advance its electrochemical production. The latter is concerned with making the chemical energy readily transformable back into electricity in batteries. In electrochemistry, H-cells are usually used in screening materials and mechanistic understanding of relevant processes. However, the results of H-cell studies sometimes do not directly translate to upscaled systems, such as flow cells. Electrochemical flow cells are attracting attention due to the ability to decouple capacity and power, the long operation time, and the decreased diffusion layer thickness and ohmic resistance. Most flow cells today use inorganic materials, and they are expensive and based on unsustainable mining processes in some geographically concentrated regions. Organic materials, on the contrary, are cheap and readily designed via molecular engineering and electro-organic synthesis. In this thesis, organic materials-based flow cells will be constructed for energy conversion and storage studies. We start with making free-standing poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films with a thickness >50 μm by vacuum filtration, which then are used in electrochemical production of hydrogen peroxide (H2O2) in a H-cell. Due to some drawbacks listed above, we shifted our focus to flow cells. The cathodic generation of H2O2 is combined with oxygen evolution reaction (OER) using nickel (II) oxide (NiO) to explore the possibility of using a polymer material in a flow cell environment. This flow cell system could reach a faradaic efficiency of 80% and the system loss is analyzed from different angles. However, the OER is kinetically sluggish and would need precious catalysts to drive the reaction. Instead of turning to precious catalysts, we proposed to replace the OER in the device with the oxidation of a water-soluble organic molecule oxidation, 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt monohydrate (tiron/BQDS). The tiron oxidation is fast and does not need a catalyst. The tiron transport phenomena are investigated and we find that migration—a less recognized player—has a big role in regulating tiron transport. The last part of the thesis introduces a biomass-based membrane made from cellulose for a tiron-based aqueous organic redox flow battery. The environmentally friendly nanocellulose membranes display reduced crossover of quinone redox couples, higher discharge capacity, and better reusability than the commercial fluoropolymer Nafion™ 115 membranes. We hope the present thesis, which deals with various aspects of flow cells from organic material design to system transport phenomena, will stimulate more people to work on this fascinating topic, paving the way for electrification of everything by tunable and sustainable organic molecules.
5.	Fahlman, Mats, 1967-, et al. (författare) Interfaces in organic electronics 2019 Ingår i: Nature Reviews Materials. - : Nature Publishing Group. - 2058-8437. ; 4:10, s. 627-650 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.
6.	Ghorbani Shiraz, Hamid, et al. (författare) Towards electrochemical hydrogen storage in liquid organic hydrogen carriers via proton-coupled electron transfers 2022 Ingår i: Journal of Energy Challenges and Mechanics. - : Elsevier. - 2056-9386. ; 73, s. 292-300 Tidskriftsartikel (refereegranskat)abstract Green hydrogen is identified as one of the prime clean energy carriers due to its high energy density and a zero emission of CO2. A possible solution for the transport of H2 in a safe and low-cost way is in the form of liquid organic hydrogen carriers (LOHCs). As an alternative to loading LOHC with H2 via a two-step procedure involving preliminary electrolytic production of H2 and subsequent chemical hydrogenation of the LOHC, we explore here the possibility of electrochemical hydrogen storage (EHS) via conversion of proton of a proton donor into a hydrogen atom involved in covalent bonds with the LOHC (R) via a protoncoupled electron transfer (PCET) reaction: . We chose 9-fluorenone/ fluorenol (Fnone/Fnol) conversion as such a model PCET reaction. The electrochemical activation of Fnone via two sequential electron transfers was monitored with in-situ and operando spectroscopies in absence and in presence of different alcohols as proton donors of different reactivity, which enabled us to both quantify and get the mechanistic insight on PCET. The possibility of hydrogen extraction from the loaded carrier molecule was illustrated by chemical activation.
7.	Ghosh, Sarbani, et al. (författare) Electronic Structures and Optical Absorption of N-Type Conducting Polymers at Different Doping Levels 2019 Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:25, s. 15467-15476 Tidskriftsartikel (refereegranskat)abstract Theoretical understanding of the electronic structure and optical transitions in n-doped conducting polymers is still controversial for polaronic and bipolaronic states and is completely missing for the case of a high doping level. In the present paper, the electronic structure and optical properties of the archetypical n-doped conducting polymer, double-stranded benzimidazo-benzophenanthroline ladder (BBL), are studied using the density functional theory (DFT) and the time dependent DFT method. We find that a polaronic state in the BBL chain is a spin-resolved doublet where the spin degeneracy is lifted. The ground state of two electrons corresponds to a triplet polaron pair, which is in stark contrast to a commonly accepted picture where two electrons are postulated to form a spinless bipolaron. The total spin gradually increases until the reduction level reaches c(red) = 100% (i.e., one electron per monomer unit). With further increase of the reduction level, the total spin decreases until it becomes 0 for the reduction level c(red) = 200%. The calculated results reproduce the experimentally observed spin signal without any phenomenological parameters. A detailed analysis of the evolution of the electronic structure of BBL and its absorption spectra with increase in reduction level is presented. The calculated UV-vis-NIR spectra are compared with the available experimental results. The electronic structure and optical absorption for different reduction levels presented here are generic to a wide class of conducting polymers, which is illustrated by the corresponding calculations for another archetypical conducting polymer, poly(3,4-ethylenedioxythiophene) (best known as PEDOT).
8.	Gueskine, Viktor, et al. (författare) Molecular Oxygen Activation at a Conducting Polymer: Electrochemical Oxygen Reduction Reaction at PEDOT Revisited, a Theoretical Study 2020 Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 124:24, s. 13263-13272 Tidskriftsartikel (refereegranskat)abstract Molecular oxygen requires activation in order to be reduced, which prompts extensive searching for efficient and sustainable electrode materials to drive electrochemical oxygen reduction reaction (ORR), of primary importance for energy production and storage. A conjugated polymer PEDOT is a metal-free material for which promising ORR experimental results have been obtained. However, sound theoretical understanding of this reaction at an organic electrode is insufficient, as the concepts inherited from electrocatalysis at transition metals are not necessarily relevant for a molecular organic material. In this work, we critically analyze the basics of electrochemical ORR and build a model for our DFT calculations of the reaction thermodynamics based on this analysis. Altogether, this work leads to a conclusion that outer sphere electron transfer that currently attracts increasing attention in the context of ORR is a viable mechanism at a conducting polymer electrode.
9.	Gueskine, Viktor, et al. (författare) Oxygen reduction reaction at conducting polymer electrodes in a wider context: Insights from modelling concerning outer and inner sphere mechanisms 2023 Ingår i: ELECTROCHEMICAL SCIENCE ADVANCES. - : WILEY. - 2698-5977. ; 3:2 Forskningsöversikt (refereegranskat)abstract Practical interest in oxygen reduction reaction (ORR) has traditionally been due to its application at fuel cells' cathode following its complete 4e route to the water. In search of new electrode materials, it was discovered that conducting polymers (CPs) also are capable of driving ORR, though predominantly halting the process at 2e reduction leading to hydrogen peroxide generation. As alternative ways to produce this "green oxidant" are attracting increasing attention, a detailed study of the ORR mechanism at CP electrodes gains importance. Here, we summarize our recent theoretical work on the topic, which underscores the fundamental difference between CP and electrocatalytic metal ORR electrodes. Our insights also bring to us the attention of outer-sphere electron transfer, not unknown but somewhat ignored in the field. We also put the action of CP electrodes in a more general context of chemical ORR and redox mediation responsible for the electrocatalytic ORR mechanism.
10.	Keene, Scott T., et al. (författare) Exploiting mixed conducting polymers in organic and bioelectronic devices 2022 Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 24:32, s. 19144-19163 Forskningsöversikt (refereegranskat)abstract Efficient transport of both ionic and electronic charges in conjugated polymers (CPs) has enabled a wide range of novel electrochemical devices spanning applications from energy storage to bioelectronic devices. In this Perspective, we provide an overview of the fundamental physical processes which underlie the operation of mixed conducting polymer (MCP) devices. While charge injection and transport have been studied extensively in both ionic and electronic conductors, translating these principles to mixed conducting systems proves challenging due to the complex relationships among the individual materials properties. We break down the process of electrochemical (de)doping, the basic feature exploited in mixed conducting devices, into its key steps, highlighting recent advances in the study of these physical processes in the context of MCPs. Furthermore, we identify remaining challenges in further extending fundamental understanding of MCP-based device operation. Ultimately, a deeper understanding of the elementary processes governing operation in MCPs will drive the advancement in both materials design and device performance.
11.	Kim, Nara, et al. (författare) Elastic conducting polymer composites in thermoelectric modules 2020 Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 11:1 Tidskriftsartikel (refereegranskat)abstract The rapid growth of wearables has created a demand for lightweight, elastic and conformal energy harvesting and storage devices. The conducting polymer poly(3,4-ethylenedioxythiophene) has shown great promise for thermoelectric generators, however, the thick layers of pristine poly(3,4-ethylenedioxythiophene) required for effective energy harvesting are too hard and brittle for seamless integration into wearables. Poly(3,4-ethylenedioxythiophene)-elastomer composites have been developed to improve its mechanical properties, although so far without simultaneously achieving softness, high electrical conductivity, and stretchability. Here we report an aqueously processed poly(3,4-ethylenedioxythiophene)-polyurethane-ionic liquid composite, which combines high conductivity (>140Scm(-1)) with superior stretchability (>600%), elasticity, and low Youngs modulus (<7MPa). The outstanding performance of this organic nanocomposite is the result of favorable percolation networks on the nano- and micro-scale and the plasticizing effect of the ionic liquid. The elastic thermoelectric material is implemented in the first reported intrinsically stretchable organic thermoelectric module. Though deformable thermoelectric materials are desirable for integrating thermoelectric devices into wearable electronics, typical thermoelectric materials are too brittle for practical application. Here, the authors report a high-performance elastic composite for stretchable thermoelectric modules.
12.	Kumar, Divyaratan, et al. (författare) Self-Discharge in Batteries Based on Lignin and Water-in-Polymer Salt Electrolyte 2022 Ingår i: Advanced Energy and Sustainability Research. - : Wiley. - 2699-9412. ; 3:10 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.
13.	Kumar, Divyaratan, et al. (författare) Water-in-Polymer Salt Electrolyte for Long-Life Rechargeable Aqueous Zinc-Lignin Battery 2024 Ingår i: Energy and Environmental Materials. - : WILEY. - 2575-0356 .- 2575-0348. ; In Press Tidskriftsartikel (refereegranskat)abstract Zinc metal batteries (ZnBs) are poised as the next-generation energy storage solution, complementing lithium-ion batteries, thanks to their cost-effectiveness and safety advantages. These benefits originate from the abundance of zinc and its compatibility with non-flammable aqueous electrolytes. However, the inherent instability of zinc in aqueous environments, manifested through hydrogen evolution reactions (HER) and dendritic growth, has hindered commercialization due to poor cycling stability. Enter potassium polyacrylate (PAAK)-based water-in-polymer salt electrolyte (WiPSE), a novel variant of water-in-salt electrolytes (WiSE), designed to mitigate side reactions associated with water redox processes, thereby enhancing the cyclic stability of ZnBs. In this study, WiPSE was employed in ZnBs featuring lignin and carbon composites as cathode materials. Our research highlights the crucial function of acrylate groups from WiPSE in stabilizing the ionic flux on the surface of the Zn electrode. This stabilization promotes the parallel deposition of Zn along the (002) plane, resulting in a significant reduction in dendritic growth. Notably, our sustainable Zn-lignin battery showcases remarkable cyclic stability, retaining 80% of its initial capacity after 8000 cycles at a high current rate (1 A g−1) and maintaining over 75% capacity retention up to 2000 cycles at a low current rate (0.2 A g−1). This study showcases the practical application of WiPSE for the development of low-cost, dendrite-free, and scalable ZnBs.
14.	Kumar, Divyaratan, et al. (författare) Water-in-Polymer Salt Electrolyte for Long-Life Rechargeable Aqueous Zinc-Lignin Battery 2024 Ingår i: Energy & Environmental Materials. - : John Wiley & Sons. - 2575-0356 .- 2575-0348. Tidskriftsartikel (refereegranskat)abstract Zinc metal batteries (ZnBs) are poised as the next-generation energy storage solution, complementing lithium-ion batteries, thanks to their cost-effectiveness and safety advantages. These benefits originate from the abundance of zinc and its compatibility with non-flammable aqueous electrolytes. However, the inherent instability of zinc in aqueous environments, manifested through hydrogen evolution reactions (HER) and dendritic growth, has hindered commercialization due to poor cycling stability. Enter potassium polyacrylate (PAAK)-based water-in-polymer salt electrolyte (WiPSE), a novel variant of water-in-salt electrolytes (WiSE), designed to mitigate side reactions associated with water redox processes, thereby enhancing the cyclic stability of ZnBs. In this study, WiPSE was employed in ZnBs featuring lignin and carbon composites as cathode materials. Our research highlights the crucial function of acrylate groups from WiPSE in stabilizing the ionic flux on the surface of the Zn electrode. This stabilization promotes the parallel deposition of Zn along the (002) plane, resulting in a significant reduction in dendritic growth. Notably, our sustainable Zn-lignin battery showcases remarkable cyclic stability, retaining 80% of its initial capacity after 8000 cycles at a high current rate (1 A g-1) and maintaining over 75% capacity retention up to 2000 cycles at a low current rate (0.2 A g-1). This study showcases the practical application of WiPSE for the development of low-cost, dendrite-free, and scalable ZnBs. A dendrite-free and long-life cycle Zn-lignin battery was demonstrated using water-in-polymer salt electrolyte.
15.	Kumar, Divyaratan, 1995-, et al. (författare) Zinc salt in "Water-in-Polymer Salt Electrolyte" for Zinc-Lignin Batteries: Electroactivity of the Lignin Cathode 2023 Ingår i: ADVANCED SUSTAINABLE SYSTEMS. - : WILEY-V C H VERLAG GMBH. - 2366-7486. ; 7:4 Tidskriftsartikel (refereegranskat)abstract Zn-ion batteries are one of the hot candidates for low-cost and sustainable secondary batteries. The hydrogen evolution and dendritic growth upon zinc deposition are todays challenges for that technology. One of the new strategies to cope with these issues is to use "water-in-salt" electrolyte (WISE), that is, super concentrated aqueous electrolytes, to broaden its electrochemical stability window (ESW), suppressing hydrogen evolution reaction (HER), and perturbing the dendritic growth. Herein, this work proposes to use "water-in-polymer salt" electrolyte (WIPSE) concept to mitigate the challenges with Zn ion batteries and bring this technology toward one of the cheapest, greenest, and most sustainable electrodes: Lignin-carbon (L-C) electrode. Potassium polyacrylate (PAAK) as WISE bears out as better electrolyte for L-C electrodes in terms of self-discharge, cyclic stability, and specific capacity compared to conventional electrolyte based on chemically cousin molecule potassium acetate. Zinc bis(trifluoromethanesulfonyl) imide (Zn(TFSI)(2)) added into WIPSE shows deposition and dissolution of Zn in Zn//Zn symmetric cell suggesting that Zn2+ are moving into the polyanionic network. Furthermore, the added bis (trifluor omethanesul fonyl) imide (TFSI-) metal salts trigger a approximate to 40% enhancement of the capacity of L-C electrode. These results show a new promising direction toward the development of cost-effective and sustainable Zn-lignin batteries.
16.	Lander, Sanna, et al. (författare) Controlling the rate of posolyte degradation in all-quinone aqueous organic redox flow batteries by sulfonated nanocellulose based membranes: The role of crossover and Michael addition 2024 Ingår i: Journal of Energy Storage. - : Elsevier BV. - 2352-152X .- 2352-1538. ; 83 Tidskriftsartikel (refereegranskat)abstract Aqueous organic redox flow battery (AORFB) is a technological route towards the large-scale sustainable energy storage. However, several factors need to be controlled to maintain the AORFB performance. Prevention of posolyte and negolyte cross-contamination in asymmetric AORFBs, one of the main causes of capacity decay, relies on their membranes' ability to prevent migration of the redox-active species between the two electrolytes. The barrier properties are often traded for a reduction in ionic conductivity which is crucial to enable the device operation. Another factor greatly affecting quinone-based AORFBs is the Michael addition reaction (MAR) on the charged posolyte, quinone, which has been identified as a major reason for all-quinone AORFBs performance deterioration. Herein, we investigate deterioration scenarios of an all-quinone AORFB using both experimental and computational methods. The study includes a series of membranes based on sulfonated cellulose nanofibrils and different membrane modifications. The layer-by-layer (LbL) surface modifications, i.e. the incorporation of inorganic materials and the reduction of the pore size of the sulfonated cellulose membranes, were all viable routes to reduce the passive diffusion permeability of membranes which correlated to an increased cycling stability of the battery. The kinetics of MAR on quinone was detected using NMR and its impact on the performance fading was modeled computationally. The localization of MAR close to the membrane, which can be assigned to the surface reactivity, affects the diffusion of MAR reagent and the deterioration dynamics of the present all-quinone AORFB.
17.	Lander, Sanna, 1990- (författare) Sulfonated Cellulose Membranes for Energy Storage Applications 2023 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.
18.	Lander, Sanna, 1990-, et al. (författare) Sulfonated Cellulose Membranes Improve the Stability of Aqueous Organic Redox Flow Batteries 2022 Ingår i: Advanced Energy and Sustainability Research. - : Wiley. - 2699-9412. ; 3:9 Tidskriftsartikel (refereegranskat)abstract The drawbacks of current state-of-the-art selective membranes, such as poor barrier properties, high cost, and poor recyclability, limit the large-scale deployment of electrochemical energy devices such as redox flow batteries (RFBs) and fuel cells. In recent years, cellulosic nanomaterials have been proposed as a low-cost and green raw material for such membranes, but their performance in RFBs and fuel cells is typically poorer than that of the sulfonated fluoropolymer ionomer membranes such as Nafion. Herein, sulfonated cellulose nanofibrils densely cross-linked to form a compact sulfonated cellulose membrane with limited swelling and good stability in water are used. The membranes possess low porosity and excellent ionic transport properties. A model aqueous organic redox flow battery (AORFB) with alizarin red S as negolyte and tiron as posolyte is assembled with the sulfonated cellulose membrane. The performance of the nanocellulose-based battery is superior in terms of cyclability in comparison to that displayed by the battery assembled with commercially available Nafion 115 due to the mitigation of crossover of the redox-active components. This finding paves the way to new green organic materials for fully sustainable AORFB solutions.
19.	Lander, Sanna, 1990-, et al. (författare) Sulfonated Cellulose Membranes: Physicochemical Properties and Ionic Transport versus Degree of Sulfonation 2022 Ingår i: Advanced Sustainable Systems. - : Wiley. - 2366-7486. ; 6:11 Tidskriftsartikel (refereegranskat)abstract The next generation of green ion selective membranes is foreseen to be based on cellulosic nanomaterials with controllable properties. The introduction of ionic groups into the cellulose structure via chemical modification is one strategy to obtain desired functionalities. In this work, bleached softwood fibers are oxidatively sulfonated and thereafter homogenized to liberate the cellulose nanofibrils (CNFs) from the fiber walls. The liberated CNFs are subsequently used to prepare and characterize novel cellulose membranes. It is found that the degree of sulfonation collectively affects several important properties of the membranes via the density of fixed charged groups on the surfaces of the CNFs, in particular the membrane morphology, water uptake and swelling, and correspondingly the ionic transport. Both ionic conductivity and cation transport increase with the increased level of sulfonation of the starting material. Thus, it is shown that the chemical modification of the CNFs can be used as a tool for precise and rational design of green ion selective membranes that can replace expensive conventional fluorinated ionomer membranes.
20.	Petsagkourakis, Ioannis, et al. (författare) Improved Performance of Organic Thermoelectric Generators Through Interfacial Energetics 2023 Ingår i: Advanced Science. - : WILEY. - 2198-3844. ; 10:20 Tidskriftsartikel (refereegranskat)abstract The interfacial energetics are known to play a crucial role in organic diodes, transistors, and sensors. Designing the metal-organic interface has been a tool to optimize the performance of organic (opto)electronic devices, but this is not reported for organic thermoelectrics. In this work, it is demonstrated that the electrical power of organic thermoelectric generators (OTEGs) is also strongly dependent on the metal-organic interfacial energetics. Without changing the thermoelectric figure of merit (ZT) of polythiophene-based conducting polymers, the generated power of an OTEG can vary by three orders of magnitude simply by tuning the work function of the metal contact to reach above 1000 mu W cm(-2). The effective Seebeck coefficient (S-eff) of a metal/polymer/metal single leg OTEG includes an interfacial contribution (V-inter/Delta T) in addition to the intrinsic bulk Seebeck coefficient of the polythiophenes, such that S-eff = S + V-inter/Delta T varies from 22.7 mu V K-1 [9.4 mu V K-1] with Al to 50.5 mu V K-1 [26.3 mu V K-1] with Pt for poly(3,4-ethylenedioxythiophene):p-toluenesulfonate [poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)]. Spectroscopic techniques are used to reveal a redox interfacial reaction affecting locally the doping level of the polymer at the vicinity of the metal-organic interface and conclude that the energetics at the metal-polymer interface provides a new strategy to enhance the performance of OTEGs.
21.	Sarrami, Farzaneh, et al. (författare) Electrochemical oxygen reduction reaction at conductive polymer PEDOT: Insight from ab initio molecular dynamics simulations 2021 Ingår i: Chemical Physics. - : ELSEVIER. - 0301-0104 .- 1873-4421. ; 551 Tidskriftsartikel (refereegranskat)abstract Conducting polymers such as poly (3,4-ethylenedioxythiophene) (PEDOT) have attracted research attention as promising effective electrocatalytic materials for Oxygen Reduction Reaction (ORR). However, the complete reaction pathways leading to the hydrogen peroxide, H2O2, formation still remained unexplored. In this study, ab initio Born-Oppenheimer molecular dynamics (MD) calculations with an explicit solvent, were carried out to investigate the detailed mechanisms of the ORR on PEDOT via monitoring MD trajectories and analysing electronic energies. We confirm the outer-sphere nature of the first electron transfer and describe the essentially concerted electron-proton transfer nature of both oxygen reduction steps. Proton transfer is found to be involved in the first and second reduction steps and the role of water as an explicit solvent is outlined. Formation of the hydrogen peroxide is observed via either the reduction of hydroperoxyl radical HO2 center dot or cleavage of its peroxoadduct with PEDOT. It is therefore theoretically validated that the O2 reduction on a PEDOT may proceed a series pathway occurring simultaneously in acidic media. This approach provides an efficient and reliable means to rationalize and predict reaction mechanisms in solvent environment.
22.	Vagin, Mikhail, et al. (författare) Ion-Selective Electrocatalysis on Conducting Polymer Electrodes - Improving the Performance of Redox Flow Batteries 2020 Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 30:52 Tidskriftsartikel (refereegranskat)abstract The selective ion transport characteristics of a conducting polymer electrode, based on poly(3,4-ethylenedioxythiophene) (PEDOT), is evaluated with respect to its electrocatalytic performance, specifically targeting redox switching of quinone couples. Employing model organic redox quinones, here, the novel phenomenon of ion-selective electrocatalysis (ISEC) is conceptualized. The effect of ISEC is studied and evaluated using two forms of PEDOT electrodes, which differ in their ion-exchange characteristics, by comparing the redox transformations of catechol and tiron. It is rationalized that the choice of the specific redox couple and the ion selectivity characteristics of the conducting polymer electrode impacts the activation losses in aqueous organic redox-flow batteries. By carefully selecting and designing the conducting polymer electrodes, high conversion efficiency on acid-resistant electrodes is obtained. As far as it is known, this is the first redox flow battery to include conducting polymer electrodes operating in both the posolyte and negolyte configurations, thus the first "all-organic" RFBs.
23.	Vagin, Mikhail, et al. (författare) Negatively-Doped Conducting Polymers for Oxygen Reduction Reaction 2021 Ingår i: Advanced Energy Materials. - : Wiley-VCH Verlagsgesellschaft. - 1614-6832 .- 1614-6840. ; 11:3 Tidskriftsartikel (refereegranskat)abstract The oxygen reduction reaction (ORR) limits the efficiency of oxygen-associated energy conversion in fuel cells and air-metal batteries. Today, expensive noble metal catalysts are often utilized to enhance the ORR and the resulting conversion efficiency in those devices. Hence, there is an intensive research to find efficient electrodes, exhibiting a favorable electronic structure, for ORR based on abundant materials that can be manufactured using low cost processes. In that context, metal-free carbon-based nanostructures and conducting polymers have been actively investigated. The negatively doped poly(benzimidazobenzophenanthroline) (BBL) as an efficient and stable oxygen cathode material is reported here. Compared to the benchmark p-doped conducting polymer poly(3,4-ethylendioxythiophene) (PEDOT), the BBL provides electrocatalysis that fully reduces dioxygen into water, via a (2 + 2)-electron transfer pathway with hydrogen peroxide (H2O2) as an intermediate; while PEDOT limits the ORR to H2O2. It is demonstrated that n-doped BBL is a promising air electrode material for low-cost and ecofriendly model fuel cells, without the need of any co-catalysts, and its performance is found to be superior to p-doped PEDOT air electrodes.
24.	Valiollahi Bisheh, Roudabeh, et al. (författare) Electrochemical hydrogen production on a metal-free polymer 2019 Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry. - 2398-4902. ; 3:12, s. 3387-3398 Tidskriftsartikel (refereegranskat)abstract The exploration for true electrocatalytic reactions at organic conducting polymer electrodes, including chemisorption of a reactant and desorption of a product, is receiving renewed interest due to the profound implications it could have on low-cost large area electrochemical energy technology. Here, we finalize the debate about the ability of an organic electrode, more specifically poly(3,4-ethylenedioxythiophene) (PEDOT), to be an electrocatalyst for hydrogen production. This paper proves and covers fundamental studies of the hydrogen evolution reaction (HER) on PEDOT films. Both theory based on DFT (Density Functional Theory) and experimental studies using electrochemical techniques and operando mass spectrometry suggest a Volmer-Heyrovsky mechanism for the actual HER on PEDOT. It is shown that PEDOT reaches an exchange current density comparable to that of metals (i.e. Cu, Ni, and Au) and in addition does not form passivating oxide layers or suffer from chemical corrosion in acidic media. Finally, an electrolyzer stack using the organic polymer electrode demonstrates HER performance in real applications.
25.	Wadnerkar, Nitin Shriram, 1983-, et al. (författare) Density Functional Theory Mechanistic Study on H2O2 Production Using an Organic Semiconductor Epindolidione 2020 Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 124:46, s. 9605-9610 Tidskriftsartikel (refereegranskat)abstract Organic semiconductors have recently emerged as promising catalytic materials for oxygen reduction to hydrogen peroxide, H2O2, a chemical of great importance in industry as well as biology. While examples of organic semiconductor-mediated photocatalytic and electrocatalytic processes for H2O2 production become more numerous and improve in performance, fundamental understanding of the reaction mechanisms at play have been explored far less. The aim of the present work is to computationally test hypotheses of how selective oxygen reduction to H2O2 generally occurs on carbonyl dyes and pigments. As an example material, we consider epindolidione (EPI), an industrial pigment with demonstrated semiconductor properties, which photocatalytic activity in oxygen reduction reaction (ORR) and thereby producing hydrogen peroxide (H2O2) in low pH environment has been recently experimentally demonstrated. In this work, the ability of the reduced form of EPI, viz. EPI-2H (which was formed after a photoinduced 2e(-)/2H(+) process), to reduce molecular triplet oxygen to peroxide and the possible mechanism of this reaction are computationally investigated using density functional theory. In the main reaction pathway, the reduction of O-2 to H2O2 reaction occurs via abstraction of one of the hydrogen atoms of EPI-2H by triplet dioxygen to produce an intermediate complex consisting of the radicals of hydrogen peroxide (HOW) and EPI-H at the initial stage. HOO center dot thus released can abstract another hydrogen atom from EPI-H-center dot to produce H2O2 and regenerates EPI; otherwise, it can enter another pathway to abstract hydrogen from a neighboring EPI-2H to form EPI-H-center dot and H2O2. EPI, after reduction, thus plays in ORR the role of hydrogen atom transfer (HAT) agent via its OH group, similar to anthraquinone in the industrial process, while HAT from its amino hydrogen is found unfavorable.
26.	Wu, Zhixing, 1990-, et al. (författare) Conducting Polymer‐Based e‐Refinery for Sustainable Hydrogen Peroxide Production 2023 Ingår i: Energy & Environmental Materials. - : Wiley-Blackwell. - 2575-0356. 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%.
27.	Yang, Hongli, 1992-, et al. (författare) Cross-Linked Nanocellulose Membranes for Nanofluidic Osmotic Energy Harvesting 2022 Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 5:12, s. 15740-15748 Tidskriftsartikel (refereegranskat)abstract Osmotic energy generated from the salinity gradient is a kind of clean and renewable energy source, where the ion-exchange membranes play a critical role in its operation. The nanofluidic technique is emerging to overcome the limitations of high resistance and low mass transport of traditional ion-exchange membranes and thus improve osmotic power conversion. However, the currently reported nanofluidic materials suffer from high cost and complicated fabrication processes, which limits their practical application. Here, we report low-cost nanocellulose membranes that can be facilely prepared by a chemical cross-linking approach. The obtained membranes exhibit excellent ion transport characteristics as high-performance nanofluidic osmotic power generators. The control of cross-linker dosage enables the simultaneous tunability of the surface charge density and size of nanofluidic channels created between the interwoven cellulose nanofibrils. The maximum osmotic power generated by the membrane is reached when the cross-linker weight content is 20 wt %. Furthermore, the cross-linked nanocellulose membranes exhibit long-term working stability in osmotic energy harvesting under a wide range of pH values (3.2-9.7). This nanocellulose membrane derived from green and sustainable natural materials demonstrates a promising potential for renewable osmotic energy harvesting.
28.	Yang, Hongli, et al. (författare) Study on the Rectification of Ionic Diode Based on Cross-Linked Nanocellulose Bipolar Membranes 2024 Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 25:3, s. 1933-1941 Tidskriftsartikel (refereegranskat)abstract Nanocellulose-based membranes have attracted intense attention in bioelectronic devices due to their low cost, flexibility, biocompatibility, degradability, and sustainability. Herein, we demonstrate a flexible ionic diode using a cross-linked bipolar membrane fabricated from positively and negatively charged cellulose nanofibrils (CNFs). The rectified current originates from the asymmetric charge distribution, which can selectively determine the direction of ion transport inside the bipolar membrane. The mechanism of rectification was demonstrated by electrochemical impedance spectroscopy with voltage biases. The rectifying behavior of this kind of ionic diode was studied by using linear sweep voltammetry to obtain current-voltage characteristics and the time dependence of the current. In addition, the performance of cross-linked CNF diodes was investigated while changing parameters such as the thickness of the bipolar membranes, the scanning voltage range, and the scanning rate. A good long-term stability due to the high density cross-linking of the diode was shown in both current-voltage characteristics and the time dependence of current.
29.	Yang, Hongli, et al. (författare) Study on the Rectification of Ionic Diode Based on Cross-Linked Nanocellulose Bipolar Membranes 2024 Ingår i: Biomacromolecules. - : American Chemical Society. - 1525-7797 .- 1526-4602. ; 25:3, s. 1933-1941 Tidskriftsartikel (refereegranskat)abstract Nanocellulose-based membranes have attracted intense attention in bioelectronic devices due to their low cost, flexibility, biocompatibility, degradability, and sustainability. Herein, we demonstrate a flexible ionic diode using a cross-linked bipolar membrane fabricated from positively and negatively charged cellulose nanofibrils (CNFs). The rectified current originates from the asymmetric charge distribution, which can selectively determine the direction of ion transport inside the bipolar membrane. The mechanism of rectification was demonstrated by electrochemical impedance spectroscopy with voltage biases. The rectifying behavior of this kind of ionic diode was studied by using linear sweep voltammetry to obtain current-voltage characteristics and the time dependence of the current. In addition, the performance of cross-linked CNF diodes was investigated while changing parameters such as the thickness of the bipolar membranes, the scanning voltage range, and the scanning rate. A good long-term stability due to the high density cross-linking of the diode was shown in both current-voltage characteristics and the time dependence of current.
30.	Yang, Hongli, et al. (författare) The effect of crosslinking on ion transport in nanocellulose-based membranes 2021 Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. Tidskriftsartikel (refereegranskat)abstract Ion selective membranes are at the heart of energy conversion and harvesting, water treatment, and biotechnologies. The currently available membranes are mostly based on expensive and non-biodegradable polymers. Here, we report a cation-selective and low-cost membrane prepared from renewable nanocellulose and 1,2,3,4-butanetetracarboxylic acid which simultaneously serves as crosslinker and source of anionic surface groups. Charge density and structure of the membranes are studied. By using different degrees of crosslinking, simultaneous control over both the nanochannel structure and surface charge concentration is achieved, which in turn determines the resulting ion transport properties. Increasing negative charge concentration via higher crosslinker content, the obtained ion conductivity reaches up to 8 mS/cm (0.1 M KCl). Optimal ion selectivity, also influenced by the solution pH, is achieved at 20 wt% crosslinker addition (with ion conductivity of 1.6 mS/cm). As regular ~1.4 nm nanochannels were formed at this composition, nanofluidic contribution to ion transport is likely. © 2021 The Authors
31.	Zozoulenko, Igor, et al. (författare) Electronic, Optical, Morphological, Transport, and Electrochemical Properties of PEDOT: A Theoretical Perspective 2021 Ingår i: Macromolecules. - : AMER CHEMICAL SOC. - 0024-9297 .- 1520-5835. ; 54:13, s. 5915-5934 Tidskriftsartikel (refereegranskat)abstract Among all conducting polymers, PEDOT or poly(3,4-ethylenedioxythiophene) has a special place within the field of organic electronics due to its outstanding conductivity, stability, and processability. Since PEDOT was first synthesized in the late 1980s, a massive amount of knowledge has been accumulated about its morphological, structural, electrical, and optical properties, along with its applications in various devices. Notably, however, is that the vast majority of the reports in the field are purely experimental, without any theoretical support from simulation and modeling. In many other fields of material science, molecular modeling has already become a standard tool for guiding the experimental work. For PEDOT, the lack of the theoretical understanding of many important aspects of the material properties and device functionality leads to misconceptions and controversial issues hindering the progress in the field. The purpose of this Perspective is to fill the knowledge gaps and to present the current state-of-the art of the theoretical understanding of PEDOT. As theoretical understanding is essential to correctly interpretate experimental results and for the design of materials and devices with better performance, this Perspective targets equally experimental and theoretical communities working on PEDOT and related materials. We also hope that this Perspective will attract further attention of the computational community, which would help to bring the theoretical understanding of PEDOT to the levels already achieved in many other fields of material science.
32.	Zozoulenko, Igor, et al. (författare) Polarons, Bipolarons, And Absorption Spectroscopy of PEDOT 2019 Ingår i: ACS APPLIED POLYMER MATERIALS. - : American Chemical Society (ACS). - 2637-6105. ; 1:1, s. 83-94 Tidskriftsartikel (refereegranskat)abstract Electronic structure and optical absorption spectra of poly(3,4-ethyl-enedioxythiophene) (PEDOT) for different oxidation levels were studied using density functional theory (DFT) and time-dependent DFT. It is shown, that the DFT-based predictions for the polaronic and bipolaronic states and the nature of corresponding optical transitions are qualitatively different from the widely used traditional picture based on semi-empirical pre-DFT approaches that still dominate the current literature. On the basis of the results of our calculations, the experimental Vis/NIR absorbance spectroscopy and the electron paramagnetic resonance spectroscopy are re-examined, and a new interpretation of the measured spectra and the spin signal, which is qualitatively different from the traditional interpretation, is provided. The findings and conclusions concerning the nature of polaronic and bipolaronic states, band structure and absorption spectra presented for PEDOT, are generic for a wide class of conducting polymers (such as polythiophenes and their derivatives) that have a similar structure of monomer units.

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