| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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