| 1. |
- Mikheenkova, Anastasiia, et al.
(författare)
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Ageing of High Energy Density Automotive Li-Ion Batteries : The Effect of Temperature and State-of-Charge
- 2023
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 170:8
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Tidskriftsartikel (refereegranskat)abstract
- Lithium ion batteries (LIB) have become a cornerstone of the shift to electric transportation. In an attempt to decrease the production load and prolong battery life, understanding different degradation mechanisms in state-of-the-art LIBs is essential. Here, we analyze how operational temperature and state-of-charge (SoC) range in cycling influence the ageing of automotive grade 21700 batteries, extracted from a Tesla 3 long Range 2018 battery pack with positive electrode containing LiNixCoyAlzO2 (NCA) and negative electrode containing SiOx-C. In the given study we use a combination of electrochemical and material analysis to understand degradation sources in the cell. Herein we show that loss of lithium inventory is the main degradation mode in the cells, with loss of material on the negative electrode as there is a significant contributor when cycled in the low SoC range. Degradation of NCA dominates at elevated temperatures with combination of cycling to high SoC (beyond 50%).
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| 2. |
- Abbaszad Rafi, Abdolrahim, et al.
(författare)
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A facile route for concurrent fabrication and surface selective functionalization of cellulose nanofibers by lactic acid mediated catalysis
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322 .- 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Celulose nanofibers are lightweight, recycable, biodegradable, and renewable. Hence, there is a great interest of using them instead of fossil-based components in new materials and biocomposites. In this study, we disclose an environmentally benign (green) one-step reaction approach to fabricate lactic acid ester functionalized cellulose nanofibrils from wood-derived pulp fibers in high yields. This was accomplished by converting wood-derived pulp fibers to nanofibrillated “cellulose lactate” under mild conditions using lactic acid as both the reaction media and catalyst. Thus, in parallel to the cellulose nanofibril production, concurrent lactic acid-catalyzed esterification of lactic acid to the cellulose nanofibers surface occured. The direct lactic acid esterification, which is a surface selective functionalization and reversible (de-attaching the ester groups by cleavage of the ester bonds), of the cellulose nanofibrils was confirmed by low numbers of degree of substitution, and FT-IR analyses. Thus, autocatalytic esterification and cellulose hydrolysis occurred without the need of metal based or a harsh mineral acid catalysts, which has disadvantages such as acid corrosiveness and high recovery cost of acid. Moreover, adding a mineral acid as a co-catalyst significantly decreased the yield of the nanocellulose. The lactic acid media is successfully recycled in multiple reaction cycles producing the corresponding nanocellulose fibers in high yields. The disclosed green cellulose nanofibril production route is industrial relevant and gives direct access to nanocellulose for use in variety of applications such as sustainable filaments, composites, packaging and strengthening of recycled fibers.
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| 3. |
- Ali, Hasan, 1985-, et al.
(författare)
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Noise-dependent bias in quantitative STEM-EMCD experiments revealed by bootstrapping
- 2024
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Ingår i: Ultramicroscopy. - : Elsevier. - 0304-3991 .- 1879-2723. ; 257
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Tidskriftsartikel (refereegranskat)abstract
- Electron magnetic circular dichroism (EMCD) is a powerful technique for estimating element-specific magnetic moments of materials on nanoscale with the potential to reach atomic resolution in transmission electron microscopes. However, the fundamentally weak EMCD signal strength complicates quantification of magnetic moments, as this requires very high precision, especially in the denominator of the sum rules. Here, we employ a statistical resampling technique known as bootstrapping to an experimental EMCD dataset to produce an empirical estimate of the noise-dependent error distribution resulting from application of EMCD sum rules to bcc iron in a 3-beam orientation. We observe clear experimental evidence that noisy EMCD signals preferentially bias the estimation of magnetic moments, further supporting this with error distributions produced by Monte-Carlo simulations. Finally, we propose guidelines for the recognition and minimization of this bias in the estimation of magnetic moments.
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| 4. |
- Ali, Hasan, 1985-, et al.
(författare)
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Single scan STEM-EMCD in 3-beam orientation using a quadruple aperture
- 2023
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 251
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Tidskriftsartikel (refereegranskat)abstract
- The need to acquire multiple angle-resolved electron energy loss spectra (EELS) is one of the several critical challenges associated with electron magnetic circular dichroism (EMCD) experiments. If the experiments are performed by scanning a nanometer to atomic-sized electron probe on a specific region of a sample, the precision of the local magnetic information extracted from such data highly depends on the accuracy of the spatial registration between multiple scans. For an EMCD experiment in a 3-beam orientation, this means that the same specimen area must be scanned four times while keeping all the experimental conditions same. This is a non-trivial task as there is a high chance of morphological and chemical modification as well as non-systematic local orientation variations of the crystal between the different scans due to beam damage, contamination and spatial drift. In this work, we employ a custom-made quadruple aperture to acquire the four EELS spectra needed for the EMCD analysis in a single electron beam scan, thus removing the above-mentioned complexities. We demonstrate a quantitative EMCD result for a beam convergence angle corresponding to sub-nm probe size and compare the EMCD results for different detector geometries.
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| 5. |
- Alimohammadzadeh, Rana, et al.
(författare)
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Direct Organocatalytic Thioglycolic Acid Esterification of Cellulose Nanocrystals : A simple entry to click chemistry on the surface of nanocellulose
- 2022
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Ingår i: Carbohydrate Polymer Technologies and Applications. - : Elsevier BV. - 2666-8939. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- The mild and simple direct organocatalytic esterification of cellulose nanocrystals (CNC) and nanocellulose-based materials (e.g. foams and films) with thioglycolic acid (TGA) is disclosed. The transformation gives the corresponding thiol group (-SH) functionalized crystalline nanocellulose (CNC-SH) using simple, naturally occurring, and non-toxic organic acids (e.g. tartaric acid) as catalysts. We also discovered that the direct esterification of cellulose with TGA is autocatalytic (i.e. the TGA is catalyzing its own esterification). The introduction of the -SH functionality at the nanocellulose surface opens up for further selective applications. This was demonstrated by attaching organic catalysts and fluorescent molecules, which are useful as sensors, to the CNC-SH surface by thiol-ene click chemistry. Another application is to use the CNC-SH-based foam as a heterogeneous biomimetic reducing agent, which is stable during multiple recycles, for the copper-catalyzed alkyne-azide 1,3-dipolar cycloaddition (“click” reaction).
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| 6. |
- Asfaw, Habtom D., Dr. 1986-, et al.
(författare)
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Bio-derived hard carbon nanosheets with high rate sodium-ion storage characteristics
- 2022
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Ingår i: Sustainable Materials and Technologies. - : Elsevier. - 2214-9937. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Biomass is a sustainable precursor of hard carbons destined for use in sodium-ion batteries. This study explores the synthesis of hard carbon nanosheets (HCNS) from oxidized cork and impact of synthesis temperature on the hard carbon characteristics. An increase in the carbonization temperature from 1000 to 1500 °C generally leads to lower BET specific surface areas (~55 to 20 m2 g−1) and d002 interlayer spacing (~ 4.0 to 3.7 Å). The effect of synthesis temperature is reflected in the initial coulombic efficiency (iCE) which increases from 72% at 1000 °C to 88% at 1500 °C, as a result of the decrease in surface area, and structural defects in the hard carbon as verified using Raman scattering. The impact of cycling temperature (~25, 30 and 55 °C) on the rate capability and long-term cycling is investigated using high precision coulometry cycler. For a galvanostatic test at 20 mA g−1 and ~ 25 °C, a reversible capacity of 276 mAh g−1 is observed with an iCE of ~88%. Increasing cycling temperature enhances the rate performance, but slightly lowers the iCE (~86% at 30 °C and ~ 81% at 55 °C). At 20 mA g−1, the reversible capacities obtained at 30 °C and 55 °C are on average ~ 260 and ~ 270 mAh g−1, respectively. For constant-current constant-voltage (CCCV) tests conducted at 30 °C, reversible capacities ranging from 252 to 268, 247–252, and 237–242 mAh g−1 can be obtained at 10, 100, and 1000 mA g−1, respectively. The respective capacities obtained at 55 °C are about 272–290, 260–279, and 234–265 mAh g−1 at 10, 100 and 1000 mA g−1. The applicability of the HCNS electrodes is eventually evaluated in full-cells with Prussian white cathodes, for which a discharge capacity of 152 mAh g−1 is obtained with an iCE of ~90%.
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| 7. |
- Deiana, Luca, et al.
(författare)
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Artificial Arthropod Exoskeletons/Fungi Cell Walls Integrating Metal and Biocatalysts for Heterogeneous Synergistic Catalysis of Asymmetric Cascade Transformations
- 2023
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Ingår i: ChemCatChem. - : John Wiley & Sons. - 1867-3880 .- 1867-3899. ; 15:15
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Tidskriftsartikel (refereegranskat)abstract
- A novel and sustainable tandem-catalysis system for asymmetric synthesis is disclosed, which is fabricated by bio-inspired self-assembly of artificial arthropod exoskeletons (AAEs) or artificial fungi cell walls (AFCWs) containing two different types of catalysts (enzyme and metal nanoparticles). The heterogeneous integrated enzyme/metal nanoparticle AAE/AFCW systems, which contain chitosan as the main structural component, co-catalyze dynamic kinetic resolution of primary amines via a tandem racemization/enantioselective amidation reaction process to give the corresponding amides in high yields and excellent ee. The heterogeneous AAE/AFCW systems display successful heterogeneous synergistic catalysis at the surfaces since they can catalyze multiple reaction cycles without metal leaching. The use of natural-based and biocompatible structural components makes the AAE/AFCW systems fully biodegradable and renewable, thus fulfilling important green chemistry requirements.
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| 8. |
- Deiana, Luca, et al.
(författare)
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Cellulose-Supported Heterogeneous Gold-Catalyzed Cycloisomerization Reactions of Alkynoic Acids and Allenynamides
- 2023
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435 .- 2155-5435. ; 13:15, s. 10418-10424
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we describe efficient nanogold-catalyzed cycloisomerization reactions of alkynoic acids and allenynamides to enol lactones and dihydropyrroles, respectively (the latter via an Alder-ene reaction). The gold nanoparticles were immobilized on thiol-functionalized microcrystalline cellulose and characterized by electron microscopy (HAADF-STEM) and by XPS. The thiol-stabilized gold nanoparticles (Au-0) were obtained in the size range 1.5-6 nm at the cellulose surface. The robust and sustainable cellulose-supported gold nanocatalyst can be recycled for multiple cycles without losing activity.
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| 9. |
- Dürr, Robin N., et al.
(författare)
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Clearing Up Discrepancies in 2D and 3D Nickel Molybdate Hydrate Structures
- 2024
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 63:5
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Tidskriftsartikel (refereegranskat)abstract
- When electrocatalysts are prepared, modification of the morphology is a common strategy to enhance their electrocatalytic performance. In this work, we have examined and characterized nanorods (3D) and nanosheets (2D) of nickel molybdate hydrates, which previously have been treated as the same material with just a variation in morphology. We thoroughly investigated the materials and report that they contain fundamentally different compounds with different crystal structures, chemical compositions, and chemical stabilities. The 3D nanorod structure exhibits the chemical formula NiMoO4·0.6H2O and crystallizes in a triclinic system, whereas the 2D nanosheet structures can be rationalized with Ni3MoO5–0.5x(OH)x·(2.3 – 0.5x)H2O, with a mixed valence of both Ni and Mo, which enables a layered crystal structure. The difference in structure and composition is supported by X-ray photoelectron spectroscopy, ion beam analysis, thermogravimetric analysis, X-ray diffraction, electron diffraction, infrared spectroscopy, Raman spectroscopy, and magnetic measurements. The previously proposed crystal structure for the nickel molybdate hydrate nanorods from the literature needs to be reconsidered and is here refined by ab initio molecular dynamics on a quantum mechanical level using density functional theory calculations to reproduce the experimental findings. Because the material is frequently studied as an electrocatalyst or catalyst precursor and both structures can appear in the same synthesis, a clear distinction between the two compounds is necessary to assess the underlying structure-to-function relationship and targeted electrocatalytic properties.
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| 10. |
- Holm, Alexander, 1983-, et al.
(författare)
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A Water-Promoted Mars-van Krevelen Reaction Dominates Low-Temperature CO Oxidation over Au-Fe2O3 but Not over Au-TiO2
- 2024
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Ingår i: ACS Catalysis. - 2155-5435 .- 2155-5435. ; 14:5, s. 3191-3197
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Tidskriftsartikel (refereegranskat)abstract
- We provide experimental evidence that is inconsistent with often proposed Langmuir−Hinshelwood (LH) mechanistic hypotheses for water-promoted CO oxidation over Au–Fe2O3. Passing CO and H2O, but no O2, over Au-γ-Fe2O3 at 25 °C, we observe significant CO2 production, inconsistent with LH mechanistic hypotheses. Experiments with H218O further show that previous LH mechanistic proposals cannot account for water-promoted CO oxidation over Au-γ-Fe2O3. Guided by density functional theory, we instead postulate a water-promoted Mars–van Krevelen (w-MvK) reaction. Our proposed w-MvK mechanism is consistent both with observed CO2 production in the absence of O2 and with CO oxidation in the presence of H218O and 16O2. In contrast, for Au-TiO2, our data is consistent with previous LH mechanistic hypotheses.
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