bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Microwave Drying on Electrochemical Performance and Morphology of Cathode Catalyst Layers for PEM Fuel Cells
Authors: Heider Emanuel Albert , Bayer Michael , Oesterlein Moritz , Joerissen Ludwig
Published: December 2024

Due to an increasing demand for sustainable energy, the polymer electrolyte membrane fuel cell (PEMFC) and electrolyzer (PEMEL) are considered as a key technology in energy conversion transformation towards climate neutral energy economy. The performance characteristics of a PEMFC is significantly influenced by the microstructure of the catalyst layer, which is formed predominantly during the drying step in the manufacturing process.

In order to improve the performance of PEMFC and hence reducing production costs, research effort has increasingly focused on the drying process. Moreover, energy efficiency of the drying step is considered one of the key driver for manufacturing cost reduction during the mass-market introduction of PEM fuel cells and electrolyzers due to increasing energy costs and the need for reduction of environmental impact.

In the presented work, a drying process for thin-film catalyst layers by making use of microwave radiation is addressed. Drying is performed by exposing the wet film to microwave radiation, leading to a more energy-efficient heat transfer into the wet film compared to conventional convective or infrared-based drying techniques. The dried catalyst layer is subsequently transferred to a polymer electrolyte membrane in a hot-pressing step and is completed with gas diffusion layers to a membrane electrode assembly (MEA). Electrochemical performance of the MEA is characterized on a fuel cell test bench in single cell configuration. The morphology of the structure obtained from microwave drying is analyzed and compared to samples dried in a conventional convective oven.

Although in the microwave drying process at lab scale, an increased tendency to crack formation due to faster drying rate was found , electrochemical performance of the MEAs are comparable to conventionally dried samples. A significant influence of applied pressure during the hot-pressing transfer step on cathode morphology was observed and is discussed with regard to electrochemical performance of the cathode catalyst layers, with a focus on performance in the high current density range.

A Systematic investigation of the electrochemical behavior of the MEA is performed by application of protonic conduction measurements and electrochemical impedance spectroscopy. The pore morphology of cathode catalyst layers, investigated by mercury intrusion porosimetry, is discussed with regard to preparation conditions and electrochemical performance.
First-Principles Studies on the Design of Tungsten-Based Platinum Electrocatalyst for Hydrogen Evolution Reaction in Alkaline Environment
Authors: Lee Haeshik , Park Jinwoo , Myoung Jae-Min , Han Byungchan
Published: December 2024

Hydrogen production has gained prominence as a clean and sustainable energy source, with water electrolysis emerging as a key method for generating hydrogen gas. Platinum (Pt), although extensively used as a cathode electrocatalyst in both acidic and alkaline media electrolyzers due to its moderate hydrogen binding energy, utilization in the Anion Exchange Membrane (AEM) system suffers from low catalytic activity. OH and H2O adsorption energy must be strong enough for facile water dissociation while H binding must be ideal to prevent H desorption from being the bottleneck. In this work, first-principles calculations were used to design Tungsten (W)-based Pt catalyst to effectively control the adsorption energies and aim for a superior alkaline HER catalyst compared to the bulk Pt catalyst. Owing to the weak OH and H2O binding energy on the conventional Pt slab, two methodologies were employed to precisely control adsorption strength of each intermediate. Nanoscale engineering of catalysts, modelled as Pt55 icosahedral nanocluster, was employed where the interaction of all the adsorbates with the surface was increased, lowering the activation barrier for water decomposition. Another approach is through monolayer deposition of Pt on the W simulated as Pt/W(110) slab where the heterogeneous surface induced strain effect and ligand effect. With the discrepancy of the crystal structures of two metals, strain effect was seen more dominant, where adsorbate-induced strain effect also played a significant role in fine-tuning the the adsorption energies of each adsorbate in a favorable direction. Lastly, pursuing the synergistic effect of both methods, W@Pt core-shell nanoparticle structure was formed which did not show enhanced catalytic activity. Since such fine-tuning of adsorption energies of varied intermediates is normally done by engineering a complex heterogeneous surface to execute for bifunctional active sites, this work will provide insights to control the adsorption energies with a simple metal monolayer surface.

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Space Charge Effects on the Reaction Kinetics of Metal Exsolution and the Coalescence of Exsolved Nanoparticles
Authors: Weber Moritz Lukas , Jennings Dylan , Šmíd Břetislav , Kindelmann Moritz , Fearn Sarah , Cavallaro Andrea , Gutsche Alexander , Heymann Lisa , Yasin Liam , Cooper Samuel J. , Skinner Stephen J , Dittmann Regina , Aguadero Ainara , Fang Xufei , Lenser Christian , Nemšák Slavomír , Gunkel Felix
Published: December 2024

Metal exsolution reactions can be driven in fuel electrode materials under the reducing operation conditions of solid oxide cells. The process enables the synthesis of nanostructured catalysts based on the release of a fraction of reducible dopants from a perovskite host to its’ surface and the subsequent nucleation of finely dispersed oxide-supported metal nanoparticles. The performance of such catalysts strongly depends on the nanoparticle characteristics, such as the nanoparticle size and nanoparticle density.

Consequently, dynamic structural and chemical changes of catalyst materials under operation conditions, oftentimes particularly affecting the catalyst surface i.e. the electrochemical interface, play a crucial role for the activity and stability of electrocatalysts. It is essential to understand the mechanistic processes that govern the material response to improve the lifetime of energy conversion devices such as water splitting catalysts or solid oxide cells.

We employ epitaxial thin films with atomically defined surface morphologies to study the exsolution kinetics with respect to the mass transport of Ni dopants from the bulk to the perovskite surface. In addition, we investigate the subsequent growth and coalescence behavior of the exsolved nanoparticles during thermal reduction of the thin film samples. For this purpose, different approaches of defect-engineering are explored to investigate the role of donor-type and acceptor-type defect chemistry as well as the role of dislocations for exsolution reactions.

We demonstrate that the electrostatic interactions of exsolution-active dopants with the surface potential that is correlated to the inherent surface space charge region of perovskite oxides determines the kinetics of metal exsolution in our material system. Moreover, we reveal that defects that form under the reducing reaction conditions at the surface of the perovskite support can accelerate nanoparticle clustering and hence degradation of metal exsolution catalysts. In addition, we show that dislocations may serve as preferential nucleation sites for nanoparticles during metal exsolution. Based on our findings, we derive strategies for the control of the metal exsolution dynamics and for the stabilization of exsolved nanoparticles.
(Invited) Unraveling the Impact of Different Thermal Quenching Routes on Luminescence Efficiency of Y3Al5O12:Ce3+ Phosphor: Insights from Mode-Selective Vibrational Excitation Experiments
Authors: Karlsson Maths
Published: December 2024

Cerium doped yttrium aluminium garnet, Y3Al5O12:Ce3+, is the prototype material for solid-state white lighting and it still is an important white LED phosphor. However, fundamental understanding of the thermal quenching of luminescence, which leads to a pronounced reduction of the emission intensity under high-power light-emitting diode operation, remains to be obtained. Here we show, through a multi-technique approach based on photoluminescence, thermoluminescence and mode-selective vibrational excitation experiments that thermal quenching of luminescence in Y3Al5O12:Ce3+ is caused by a combined effect of thermal ionization, thermally activated concentration quenching, and thermally activated 5d - 4f crossover relaxation via electron-phonon coupling, and establish the general trends upon variation of the Ce3+ concentration and temperature. Thermal quenching below 600 K is primarily the result of concentration quenching and crossover relaxation, which can be suppressed by keeping the Ce3+ dopant concentration far below 0.7 mol%, whereas for temperatures above 600 K thermal ionization is the predominating quenching process. This new insight into the interplay between different thermal quenching processes provides design principles for optimizing the light emittance and colour stability of new phosphor materials used in white lighting devices characterized by certain operating temperatures.
Exploring the Luminescent Properties of Transition Metal Ions in Solids through Theoretical Insights and the Prospects of Machine Learning
Authors: Novita Mega , Ma Chong-Geng , Piasecki Michal , Brik Mikhail G.
Published: December 2024

This work delineates over a decade of rigorous first-principles computational investigations into compounds doped with transition metal (TM) ions, such as Sc3+, Ti3+, V2+, V3+, Cr3+, Mn3+, Mn4+, Fe3+, Co3+, Ni3+, and Cu3+, within host matrices including α-Al2O3, MgTiO3, and various fluorides, devoid of empirical parameters. Our methodological framework employs discrete variational Xα (DV-Xα) and discrete variational multielectron (DVME) techniques, enhanced by configuration-dependent and correlation corrections to refine accuracy. Notably, our analysis integrates lattice-relaxation estimations through the use of Shannon crystal radii and the Cambridge Serial Total Energy Package (CASTEP), facilitating the examination of pressure-induced effects on lattice structures.

Our comprehensive studies, particularly on α-Al2O3 doped with TM 3d3 ions, have not only successfully replicated known optical characteristics but have also provided new insights into the variation of transition energies across different TM ion charges, alongside pressure-dependent behavior of multiplet energies in alignment with experimental findings. These endeavors highlight the complex interplay of dopant characteristics, including charge states and ionic radii, on the optical properties of host crystals, with precise attention to colorimetry within the International Commission on Illumination (abbreviated CIE) color space framework to evaluate the quality and perception of emitted light.

Furthermore, this work will introduce a discussion on the emerging potential of machine learning (ML) in advancing our understanding and predictive capabilities concerning the luminescence of materials. ML approaches promise to revolutionize the identification of optimal dopant-host combinations, predict novel luminescent materials, and enhance the accuracy of theoretical predictions through data-driven insights. By bridging traditional computational methods with ML, we aim to pave new pathways in the exploration of luminescent materials, potentially leading to innovative applications in lighting, display technologies, and beyond.
(Invited) Self-Recovery of Photodegraded CsPbBr3 Perovskite Nanocrystals and Problems By Irreversible Damage
Authors: Iso Yoshiki , Isobe Tetsuhiko
Published: December 2024

CsPbBr3 perovskite nanocrystals (NCs) synthesized by a typical hot injection method are adsorbed with surface modifiers. The authors have investigated photodegradation and self-recovery phenomena due to photo-induced desorption by excitation light irradiation and re-adsorption of the surface modifiers in the dark, respectively [1-4]. These phenomena occurred when a dry solid sample of NCs was placed in a sample holder covered with a glass plate to shut out the atmosphere. On the other hand, the dried NCs exposed to the air did not show the self-recovery after photodegradation. This was due to irreversible degradation caused by surface oxidation by atmospheric oxygen. When the dried NCs were covered with a resin film instead of a glass plate, the resin with lower gas barrier properties did not prevent oxidation. However, the use of a resin with higher gas barrier properties confirmed the occurrence of photodegradation and subsequent self-recovery. The authors will present recent results including experiments on nanocomposite films of the NCs dispersed in resin.

References

K. Kidokoro, Y. Iso, T. Isobe, J. Mater. Chem. C, 7, 8546 (2019).

K. Miyashita, K. Kidokoro, Y. Iso, T. Isobe, ACS Appl. Nano Mater., 4, 12600 (2021).

I. Enomoto, Y. Iso, T. Isobe, J. Mater. Chem. C, 10, 102 (2021).

K. Kano, Y. Iso, T. Isobe, ECS J. Solid State Sci. Technol., 12, 056003 (2023).

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Composition of Quantum Dot Color Conversion Layer with ZnS Nanoparticle for Facile Ink Formulation and Uniform Inkjet Printing
Authors: Chin Byung Doo
Published: December 2024

Quantum dot (QD) is excellent material for next-generation displays because of their superior optical properties, such as high quantum efficiency, narrow full width at half maximum, high color purity, and photoluminescence quantum yield. QD demonstrated efficient absorption of blue light, coupled with high color-conversion efficiency, fabricated them suitable for use as color-conversion layers (CCLs). However, robustness in pixel patterning uniformity and a printing resolution should be further studied. Light emission via conversion through QD films or converter pixels still need to be improved because the blue light can directly transmit the QD layers, sometimes leading to insufficient energy to excite the QDs. Thus, many studies on QD CCLs have focused on improving the absorption and emission properties of QDs, formulating CCL resins with enhanced color conversion efficiency. Scattering can alter the optical path and incident angle of the emitted light to increase internal reflection so that light emission of the optical film can be enhanced for excitation of photons. Thus, light scattering particles, such as titanium dioxide (TiO2), silicon dioxide (SiO2), zinc oxide (ZnO), and zirconium oxide (ZrO2) were carefully tuned to achieve outstanding properties as QD CCLs, increasing color conversion efficiency.

In this work, zinc sulfide (ZnS) light diffusers with hydrophobic properties and various size distribution were synthesized. ZnS and QD were mixed in acrylic resin, isobornyl acrylate, with proper composition of initiator and photocrosslinker. The recipe of mixing was considered for a fabrication of QD CCL ink with optimum viscosity, dispersion stability and uniformity, and printability. For the QD-CCL ink with relatively high viscosity, evaluation of jetting profile and pixel-patterning was conducted with commercial ink cartridge, Sapphire QE-256/30AAA (Fujifilm), combined with the custom-built inkjet printer and high-speed camera. With the scale up to 200ppi QD-CCL pattern, the color spectrum, printability, dispersion, optical properties (evaluation of color-emitting image), and surface uniformity were evaluated. Overall, this work will demonstrates the enhanced light converion behavior of QD-CCL layer fabricated by inkjet-printing process and provide a novel evaluation prorocol of uniformity for QD-CCL layer and color conversion device using blue micro-LED.
Scintillation Properties of LaMgAl11O19:Er Crystals with NIR Luminescence
Authors: Nakauchi Daisuke , Kato Takumi , Kawaguchi Noriaki , Yanagida Takayuki
Published: December 2024

A scintillator is a phosphor that emits photons with several eV when irradiated by ionizing radiations and has been used in applications such as medical diagnostic, security, resource exploration etc. A scintillation detector consists of a scintillator that converts ionizing radiations into photons and a photodetector such as a photomultiplier tube or photodiode that converts photons into electrical signals. Since the conversion efficiency from photon to electrical signal depends on the quantum efficiency of the photodetector, phosphors that emit in the UV–visible region, where the above photodetectors have high sensitivity, have been investigated.

Since the nuclear accident in Fukushima, various countermeasures using materials have been studied for reconstruction. In recent years, scintillators which exhibit luminescence in the near-infrared (NIR) region have attracted attention for remote monitoring applications in high-dose fields. Remote monitoring using scintillators and optical fibers has been proposed to avoid radiation damage to semiconductors and electrical circuits of signal amplifiers involved in measurements. Since the method uses a long optical fiber, the transmission efficiency of scintillation photons in an optical fiber is important. In the NIR region of 800–1700 nm, the transmittance of a quartz fiber is higher than that in the UV–visible region, and the transmission loss can be suppressed. So far, there have been sporadic studies on NIR-scintillators. In the past studies, only emission wavelengths shorter than 1000 nm were monitored because a Si-photodiode was used as the photodetector. On the other hand, InGaAs-based photodiodes enable stable measurement of NIR scintillation photons with wavelengths longer than 1000 nm. In our previous works, various scintillators doped with Nd as an emission center in the NIR region have been developed as candidate materials.

LaMgAl11O19 has been extensively studied in various phosphor fields such as laser and white LED applications. Since LaMgAl11O19 has La3+ sites that can be easily substituted with doped rare-earth ions as an emission center, LaMgAl11O19 doped with various trivalent rare-earth ions such as Ce, Nd, Sm, Eu, Dy, Tm, Yb etc. has been investigated. In addition, compared with conventional oxide scintillators such as rare-earth-based silicate and aluminate compounds, the composition ratio of rare-earth elements is relatively low, and the main component is Al2O3, so the cost of raw materials can be suppressed. However, no research on the scintillation properties for measuring ionizing radiations has been reported so far. In this study, the rare-earth-doped LaMgAl11O19 single crystals were synthesized, and the photoluminescence and scintillation properties were investigated to evaluate the potential applicability for high-dose monitoring applications.
Radioluminescence Properties of Tb-Doped PbF2 Crystals Obtained By Spontaneous Melt Crystallization
Authors: Kawaguchi Noriaki , Kunikata Toshiaki , Kato Takumi , Nakauchi Daisuke , Yanagida Takayuki
Published: December 2024

Radiation detectors equipped with scintillators are used in a variety of fields such as medicine, security, and radiation protection, and as there is no material that satisfies all required characteristics, research is still being conducted to find materials with higher performance. In addition, single crystal materials are widely used as scintillators, but the production methods such as the Czochralski method and Bridgman–Stockbarger method require a long period of time for crystal growth. Our group is aiming to develop new high-performance scintillators by a simple preparation method. We are studying spontaneous melt crystallization as a simple preparation method of samples. In this simple method, raw materials are melted and solidified in a crucible without moving a crucible or a seed crystal. It is possible to obtain transparent materials in the case of highly symmetrical crystalline materials by this method. So far, we have investigated CaF2-based and BaF2-based materials. In this study, we focused on PbF2, which contains heavy elements. Materials containing heavy elements are particularly important target because they have a high probability of interaction with X-rays and gamma rays. Tb3+ ions were selected as the luminescent center, which can show highly efficient emissions. The samples were prepared by the procedure described below. High-purity powders of PbF2 and TbF3 were used as raw materials, and after being weighed at a predetermined molar ratio, they were filled into a carbon crucible, placed in an electric furnace equipped with a vacuum chamber, and heated to approximately 300℃ in vacuum. Then, the raw material powders were melted at 850℃ in an Ar and CF4 mixed gas atmosphere, and the temperature was decreased to room temperature. The XRD patterns of obtained crystals were ascribed to that of β-PbF2. The X-ray induced scintillation spectra of the obtained samples were measured, and radioluminescence associated with 4f-4f transitions of Tb3+ ions was observed in each sample.
Electrocatalytic Hydrogenation of Nitrogen-Containing Compounds Using a Proton-Exchange Membrane Reactor
Authors: Suga Seiji , Mitsudo Koichi , Osaki Atsushi , Inoue Haruka
Published: December 2024

Proton-exchange membrane (PEM) reactors, including a membrane electrode assembly (MEA) consisting of a proton exchange membrane and an electro-catalyst supported on carbon, has attracted attention as an useful device for electrocatalytic hydrogenation [1,2]. With this reactor, a continuous flow system can be constructed without the need for a supporting electrolyte, making hydrogenation reactions very ubiquitous. Although there have been several reports on the reductive transformations using PEM reactors, its application for nitrogen-containing organic compounds is still limited.

We herein report the reduction of nitrogen-containing compounds having a cyano or nitro group by using a PEM reactor. We will also report on the reduction of quinoline and other nitrogen-containing aromatic compounds.

[1] Takano, K.; Tateno, H.; Matsumura, Y.; Fukazawa, A.; Kashiwagi, T.; Nakabayashi, K.; Nagasawa, K.; Mitsushima, S.; Atobe, M. Bull. Chem. Soc. Jpn. 2016, 89, 1178–1183.

[2] Mitsudo, K.; Inoue, H.; Niki, Y.; Sato, E.; Suga, S. Beilstein J. Org. Chem. 2022, 18, 1055–1061.
All in One Ionic Liquid. Acts As Catalyst, Electrolyte, and Solvent in Electrochemical Hydrogen Generation
Authors: Shimakoshi Hisashi , Sato Aya
Published: December 2024

A redox active ionic liquid (RIL), 1-ethyl-4-(methoxycarbonyl)pyridinium bis(fluorosulfonyl)amide with a half unit of methyl viologen, was synthesized from its iodide form by anion exchange reaction and were characterized by NMR, UV-VIS, IR and elemental analysis. The compound exhibited redox waves in CH3CN with or without n-Bu4NPF6 electrolyte at -0.76 and -1.55 V vs. Ag/AgCl attributed to RIL to its radical form (RIL
•) and RIL
• to its anion form (RIL-
), respectively. The redox behavior indicates the dual role of the ionic liquid as a solvent and electrolyte. The redox wave RILs was also observed in neat condition without any additional solvent and electrolyte using micro-electrode. The cyclic voltammogram (CV) of RILs changed dramatically in the presence of acetic acid to show proton-coupled electron transfer (PCET) process for proton reduction at -1.33 V vs. Ag/AgCl in CH3CN. The change in CV indicates that RIL could act as a catalyst for hydrogen (H2) production via RIL-H as shown in Scheme 1. The bulk electrolysis of acetic acid with RILproduced H2 with 13.4 turnover number based on RIL and current yield of 37.8 %. In addition, the electrolysis for H2generation proceeded in complete ionic liquid system of RIL. The RIL could work as catalyst, electrolyte, and solvent for H2 production.

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Electrochemical Evaluation of Phenylenediamine/Quinonediimine Redox Systems As Organic Electroactive Materials
Authors: Miyakoshi Kaori , Tajima Toshiki
Published: December 2024

Quinones are one of the most promising and widely investigated classes of redox active materials for organic aqueous redox flow batteries, because they have advantages such as low cost, excellent reaction rate, and wide variety. However, they have a serious problem of the limited solubility in water. In order to solve the problem, there have been many reports on the introduction of polar functional groups into quinones. On the other hand, quinonediimines are quinone equivalents, which allow the introduction of polar functional groups on the nitrogen atoms. Therefore, quinonediimines are easier to introduce polar functional groups than quinones. With these facts in mind, we evaluated the electrochemical properties of phenylenediamine/quinonediimine redox systems in this work.

First, cyclic voltammetry of 1,2-phenylenediamine (1) and 1,4-phenylenediamine (2) was performed to evaluate their electrochemical reversibility in aqueous (0.1 M KCl/water) and non-aqueous (0.1 M Bu4NBF4/MeCN) solutions. As a result, 2 was reversible, but 1 was irreversible in both solutions. However, the reversibility of 2 was lost on the second scan in the aqueous solution, suggesting that water makes a nucleophilic attack on the oxidized form of 2.

In order to suppress the nucleophilic attack of water, we used and measured the cyclic voltammograms of 2, 2,5-dimethyl-1,4-phenylenediamine (3), and 2,3,5,6-tetramethyl-1,4-phenylenediamine (4) in aqueous and non-aqueous solutions. Their reversibility improved with increasing the number of methyl groups in both solutions. This seems to be due to the steric hindrance of the methyl group, which suppressed the nucleophilic attack of water. In addition, as the number of electron-donating methyl groups increased, the redox potential shifted to the lower potential side.

Finally, in order to verify the electrochemical cycling stability, cyclic voltammetry of 4 was performed with 1000 consecutive scans in aqueous and non-aqueous solutions. In aqueous solution, the redox wave of 4 changed from two waves to one wave. In contrast, the redox wave was maintained after 1000 scans in non-aqueous solution. These suggest that the oxidized form of 4 is stable in non-aqueous solution even under multiple scans, whereas it is unstable in aqueous solution.

We will present the electrochemical properties of various phenylenediamine/quinonediimine redox systems and also introduce the introduction of polar functional groups into them in this presentation.

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Synthetic Organic Electrochemistry: From Bulk to Nano Chitin
Authors: Tran Thang Hong , Phan Thu Pham Anh , Kraglund Mikkel Rykær , Tran David , Jacobsen Charlotte , Hjelm Johan
Published: December 2024

Negatively charged nano chitin with carboxylic groups on the surface are traditionally synthesized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) mediated oxidation of α-chitin in water at pH 10 with the use of sodium hypochlorite (NaClO) or laccase enzyme as a co-oxidant. However, the use of NaClO leads to environmental concerns, while the laccase-mediated process suffers from notable deceleration due to undesired enzyme adsorption onto the chitin substrate. Therefore, we propose an alternative methodology for the fabrication of nano chitin using an environmentally friendly electrochemical approach.

The properties of surface chemistry, crystal structure, and morphology of nano chitin were comprehensively assessed using Zeta analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The size distribution of nano chitin ranged from 700 to 900 nm, with a negative surface charge of approximately -40 mV. Furthermore, new peak appearance at 1730 cm-1 in the FTIR spectrum attributes to the formation of carboxylic groups on the surface of nano chitin.

In conclusion, the application of electrochemical methods shows significant potential for the efficient production of nano chitin through TEMPO-mediated oxidation, offering promising avenues for future research and application. Following synthesis, the resultant product undergoes examination to evaluate its emulsification efficacy, particularly in the context of food applications.
Electrogeneration of Oxygen-Centered Radicals from N-Alkoxyphthalimides and Their Use in a Remote C-H Functionalization for 5,5-Spirocycles Construction
Authors: Romero Ibañez Julio , Chicas-Banos Diego Francisco , Colindres-Díaz Edgar Alan , Sartillo-Piscil Fernando , Frontana-Uribe Bernardo Antonio
Published: December 2024

Oxygen-centered radicals, also known as alkoxyl radicals, are highly reactive species that have been considered useful synthetic intermediates.[1] Considering their synthetic accessibility, stability, and particular reactivity, N-alkoxyphthalimides (NAPIs) offer a practical avenue for generating these radicals under mild conditions, such as via electrochemical means.[2] Recent studies have demonstrated the effectiveness of N-benzyloxyphthalimides in accessing benzylic-carbonyl compounds through electrochemical reduction.[3] To modulate the conversion of NAPIs to O-centered radicals under electroreductive conditions, it was studied and transferred the reported mechanistic insights of photocatalytic redox conditions to an electrochemical approach by employing the Hantzsch ester and rapid alternating polarity electrolysis.[4,5] The electrogenerated O-centered radicals from NAPIs were then explored for their utility in remote C-H allylation and the synthesis of 5,5-spirocycles which represent important structural motifs of diverse natural products, including Cephalosporolides.

[1] A.S. Budnikov, I.B. Krylov, A.V. Lastovko, B. Yu, A.O. Terent’ev, Nalkoxyphtalimides as versatile alkoxy radical precursors in modern organic Synthesis, Asian J. Org. Chem. 11 (2022), https://doi.org/10.1002/ ajoc.202200262.

[2] M.A. Syroeshkin, I.B. Krylov, A.M. Hughes, I.V. Alabugin, D.V. Nasybullina, M. Y. Sharipov, V.P. Gultyai, A.O. Terent’ev, Electrochemical behavior of Noxyphthalimides: cascades initiating self-sustaining catalytic reductive N–O bond cleavage, J. Phys. Org. Chem. 30 (2017) 1–15, https://doi.org/10.1002/poc.3744.

[3] D.F. Chicas-Baños, M. Lopez-Rivas, F.J. Gonzalez, F. Sartillo-Piscil, B.A. Frontana-Uribe, Access to carbonyl compounds via the electroreduction of Nbenzyloxyphthalimides: mechanism confirmation and preparative applications, Heliyon 10 (2024) e23808, https://doi.org/10.1016/j.heliyon.2023.e23808.

[4] J. Zhang, Y. Li, F. Zhang, C. Hu, Y. Chen, Generation of alkoxyl radicals by photoredox catalysis enables selective C(sp3 )-H functionalization under mild reaction conditions, Angew. Chem. Int. Ed. 55 (2016) 1872–1875, https://doi.org/ 10.1002/anie.201510014.

[5] J. Romero-Ibañez, D.F. Chicas-Baños, F. Sartillo-Piscil, B.A. Frontana-Uribe, Highly efficient electrogeneration of oxygen centered radicals from N-alkoxyphthalimides employing rapid alternating polarity (RAP) electrolysis. Transferring the photoredox catalytic conditions to organic electrosynthesis, Curr. Res. Green Sustain. Chem. 8 (2024) 100404, https://doi.org/10.1016/j.crgsc.2024.100404.

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Electrodes, Mediators, and New Opportunities for Selectivity in Chemical Reactions
Authors: Moeller Kevin D
Published: December 2024

Recently, we showed that it is possible to take advantage of confinement strategies developed on microelectrode arrays to introduce selectivity into a solution phase chemical reaction. This was accomplished by controlling where in a reaction flask the reaction occurred and then manipulating that environment. This discovery opens up a series of new opportunities for synthesis where the course of a chemical reaction is controlled not by the reaction itself but rather by a remote binding event. In the talk to be given we will begin to explore these ideas along two pathways.

In the first, we will examine how an electrode surface can be used to control the course of a transition metal catalyzed cross coupling reaction by its interaction with remote functionality in a substrate. Specifically, we will look at how the overall shape and charge of a molecule can be used to introduce selectivity into the reactions in a manner not possible through reagent control alone.

Second, we will talk about “platform” reactions that are allowing us to begin examining routes for introducing absolute stereochemistry into electrochemical cyclization reactions. This discussion will focus on the reactions themselves, mechanistic details that allow for their optimization, and new ways to mediate the cyclization reactions so that new handles for controlling stereochemistry can be utilized.

In both stories, we will focus on how the unique attributes of electrochemistry can be utilized to influence reactions of interest to the larger synthetic community.
Bioengineering of Cyanobacteria for Electrosynthesis
Authors: Minteer Shelley D.
Published: December 2024

Market analysis has shown that one of the challenges with using enzymes for electrosynthesis is the need for cofactor regeneration of non-redox cofactors (i.e. ATP, GTP, coenzyme A, etc.). Moving from enzymatic bioelectrocatalysis to microbial bioelectrocatalysis is one way to address this problem, but many microorganizations are not designed for the synthesis chemistry your desire and extracellular electron transport is slow. This paper will discuss the use of bioengineering techniques to overexpress synthetic oxidoreductase enzymes in microorganisms simulataneously with outer membrane cytochromes to improve extracellular electron transport. The example system shown will be for nitrogen reduction to ammonia with cyanobacteria.
(Invited) Photosynthetic Microbial Current Generation; The Correlation with Calvin-Cycle Activity
Authors: Nakanishi Shuji
Published: December 2024

When light is applied to an electrochemical cell containing living cyanobacterial cells, a photosynthetic microorganism, the reducing equivalents generated from photosynthetic electron transfer within the cells is transferred to the anode, producing a microbaial photocurrent. This process, termed extracellular electron transfer, is intriguing for its applications in environmental power generation, the study of photosynthetic physiology, and the exploration of the photosynthetic ecosystem. We have focused on elucidating the photocurrent generation mechanism in the cyanobacterium Synechocystis sp. PCC 6803. We have enhanced our understanding of how photocurrent values significantly increase following outer membrane deprivation, its association with the respiratory and photosynthetic electron transfer chains, and its connection with iron reduction capacity [1-4]. In this presentation, we will discuss our recent discovery of spontaneous periodic oscillations in microbial photocurrent and their relationship with Calvin cycle activity. Specifically, we conducted systematic investigations into (1) the quantity of reducing equivalents stored within the cell, (2) the influence of inhibitors on the photosynthetic electron transfer chain and the Calvin cycle, and (3) the effect of environmental temperature on oscillation period. Additionally, we measured changes over time in intracellular metabolite levels to clarify the critical processes behind photocurrent oscillation patterns.

S. Kusama, et al., Nature Communications, 13, 3067 (2022).

S. Kusama, et al., J. Plant Research, 135, 555 (2022).

J. Hatano, et al., Photosynthesis Research, 153, 113, (2022).

K. Tanaka, et al., Front. Microbiol., 12, 650832, (2021).

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Electrochemical Synthesis of Novel Ylide Compounds through N-N Bond Formation from Hydrazones
Authors: Chang Yongju , Park Jin Kyoon
Published: December 2024

Ylides are well-known reactive intermediates in organic synthesis, playing pivotal roles in a variety of transformations, including Wittig and related reactions. However, due to challenges such as insufficient nucleophilicity, the synthesis of pentagonal ylides has been rarely reported, with even fewer examples of ylide synthesis. We have developed a general electrochemical oxidative radical N-N bond cyclization strategy, enabling the efficient synthesis of a new type of ylide-like compound. This method is particularly exciting as it allows for the creation of complex molecules without the use of harsh chemicals, relying instead on electricity to drive the reaction. The N-iminoindazolium ylide was obtained in moderate to excellent yields and with a rapid reaction time, demonstrating the effectiveness of this approach. Additionally, the scale-up of the reaction to a half-gram scale under the same conditions yielded the N-iminoindazolium ylide in excellent yields, showcasing the robustness and scalability of our method.

Figure 1
Granule-Design Technology of Electrode-Composite for Reducing Electric Resistance of Lithium-Ion Battery
Authors: Yokota Maria , Tuerxun Feilure , Akimoto Yusuke , Matsunaga Takuro
Published: December 2024

We are facing a problem of global warming due to emission of greenhouse gases such as carbon dioxide. That promote people’s preference for electric vehicles causing increase of demand for batteries. Development of high-performance batteries for automotive applications is underway around the world. There, important issues to be solved include increasing speed of batteries’ production, improving the batteries’ performance, reducing greenhouse-gas emissions in the production processes. Here, we discuss our idea to achieve all three missions.

Our approach to the problems is dry processing of electrode sheeting and electrode-structure control. We used granulation by spray drying as a means of controlling the electrode structure. During granulation by spray-drying, we controlled the arrangement of conductive aid and binder particles to create a localized (phase-separated) structure. The core is active-material-rich, and the shell is conductive-aid-rich. When the particles packed as electrodes, the shells of the granules were automatically connected to each other, then the conductive aid formed network structure in the electrodes. The electrode achieved reducing the electric resistance.

Another reason for preparing granules using spray drying prior to electrode sheeting is to improve the flowability of the powder. Since the granules are large and their shapes are rounded, fluidity as a granular bulk be much high like sand on a beach. Then we spread them on metallic foil by doctor blade like slurry coating. That makes the production speed be high. In addition, our granules include polymer as binder, the granular-spread sheet can be stuck on the foil by heated roll press without solvent. Details of the deposition method and electrochemical evaluation results will be discussed on the day of the presentation.
(Invited) Comprehensive Microstructural Design and Fabrication Techniques for High-Energy-Density Solid-State Batteries
Authors: Kim Jinsoo , Jo Hyoi
Published: December 2024

Solid-state batteries (SSBs) represent a transformative advancement in energy storage technology, offering significant safety and energy density improvements over conventional lithium-ion batteries. This work introduces a comprehensive set of design principles and fabrication techniques explicitly aimed at maximizing the energy density of SSBs using solid polymer electrolytes. We explore the critical microstructural and architectural parameters influencing battery performance, such as electrode composition, loading, and density. Our methodology integrates numerical calculation with practical experimentation, leading to the successful construction of both 10-layer and 4-layer stacked solid-state pouch cells. These cells achieved energy densities of 280 Wh/kg and 310 Wh/kg, respectively. Our results demonstrate the practical applicability of our design principles and provide a scalable framework for the future development of high-performance SSBs.
Parameter Identification of Pseudo-Two-Dimensional Model for Lithium-Ion Batteries with Silicon/Graphite Composite Electrodes
Authors: Ha Jinho , Kim Sanghyun , Jun Gwang Hoon , Koh Dong-Wook , Choi Jung-Il
Published: December 2024

In this study, we assess the performance of lithium-ion batteries (LIBs) equipped with silicon/graphite composite electrodes and estimate the electrochemical properties of each constituent material. We employ a composite electrode model integrated into the conventional pseudo-two-dimensional (P2D) model to simulate the electrochemical dynamics of the battery. First, the accuracy of the numerical model is validated by comparing its voltage predictions with existing experimental data. The model successfully captures the voltage characteristics of LIBs across various C-rates. Additionally, the interaction effects between silicon and graphite within the composite electrode are validated by comparing them to previous simulation results. Specifically, the reactivity of silicon and graphite, which varies with the operating voltage range, is accurately assessed under various operating conditions.

Parameter estimation for the electrochemical model is performed using a genetic algorithm. Ten parameters significant to the electrochemical performance of each material are selected, considering their physical significance and the feasibility of experimental validation. These parameters are optimized by minimizing a fitness function defined by the relative errors between the experimental and simulated voltage, utilizing 1/3C discharge and pulse data from different states of charge (SOCs). The simulated voltages with the optimized parameters align well with the experimental data, accurately representing both the constant-current discharging voltage and the voltage dynamics during pulse application and removal. This alignment confirms that the estimated parameters effectively characterize the electrochemical behavior of LIBs with the composite electrode.

A comparative analysis of parameter identification using only constant-current discharging data versus a combination of constant-current and pulse data reveals significant variations in the distribution of estimated values. Parameters derived solely from constant-current data inadequately fit the pulse data, highlighting the necessity of incorporating diverse data types for reliable parameter estimation.

The methodology proposed in this work provides a robust framework for evaluating the electrochemical properties and performance of LIBs featuring silicon/graphite composite electrodes. This approach offers a detailed assessment of the material-level properties by identifying critical electrochemical parameters. Future work will focus on developing an efficient experimental protocol for parameter estimation, employing sensitivity analysis and case studies across different voltage profiles to ensure reliable parameter determination.

Figure 1
Fluorinated Azide Enables Fully Crosslinked Ceramic-Coated Separators for Advanced Li-Ion Batteries
Authors: Choi Seungyeop , Hassan Syed Zahid , Roh Youngjoon , Seo Jun Pyo , Chung Dae Sung , Lee Yong Min
Published: December 2024

Lithium-ion batteries (LIBs) have become widely adopted for energy storage due to their high energy density and long cycle life. However, the safety of LIBs under severe operating conditions remains a pressing issue. In this context, ceramic-coated separators (CCSs) are critical in enhancing LIB safety by reducing the risk of internal short circuits. Conventional methods for improving the thermal stability of CCSs have relied on combining ceramic particles with polymer binders. These techniques, however, face limitations in significantly enhancing the thermal stability of the ceramic coating layer (CCL), particularly as efforts to minimize the thickness and areal mass of the CCL aim to elevate the energy density and power performance of LIBs.

For this purpose, several strategies have been investigated to enhance the thermal stability of ceramic-coated separators (CCSs). One promising approach involves the incorporation of polymer binder with high melting points within the CCL, ensuring improved resilience to high temperatures [1]. In addition, our research group reported the effect of crosslinking structures between ceramic particles and polymer binder on the adhesive strength and thermal stability of the CCL [2]. Nevertheless, as the energy density of LIB increases, more comprehensive strategies must be developed.

Herein, we introduce a photo-crosslinking strategy employing a novel fluorinated azide crosslinker, capable of reacting with C-H groups in polymer chains under UV irradiation. After coating the CCL slurry composed of ceramic particles, polymer binder, and fluorinated azide crosslinker on the separator, short UV irradiation forms comprehensive crosslinking structures within the CCL. Crosslinking points occur not only within the separator substrate but also between the substrate and the polymer binder, as well as among the polymer binders present in the CCL. As a result, the thermal stability and adhesive strength of the CCS are significantly improved when compared to those of the non-crosslinked one. Moreover, a LiNi0.6Co0.2Mn0.2O2/graphite full cell incorporating the crosslinked CCS demonstrates a cycle life comparable to that of the non-crosslinked one.

References

A high-temperature stable ceramic-coated separator prepared with polyimide binder/Al2O3 particles for lithium-ion batteries,
J. Memb. Sci.
, 517 (2016) 91-99

Highly improved thermal stability of the ceramic coating layer on the polyethylene separator via chemical crosslinking between ceramic particles and polymeric binders,
Chem. Eng. J.
, 433 (2022) 134501
Enhancing High-Performance for the Lithium-Ion Battery of Si/G Anode Via an Effective Additive Strategy
Authors: Jeong Woojin , Yang Subi , Lee Seungho , Lee Juhyun , Han Seungmin , Chun Jinyoung , Choi Junghyun
Published: December 2024

Since the first commercialization of lithium-ion batteries (LIBs), LIBs have become an important power source for wireless electronics, electric vehicles (EVs), and other renewable energy storage systems due to their high energy density and operating voltage. The higher energy density of LIBs indicates that the electrode material can store more energy per unit mass or volume. Currently, with the high capacity demands of EV batteries and the use of high-capacity LIBs in a variety of devices, anode material capacity requirements are also rising rapidly. However, graphite, the most widely used anode material in commercial LIBs, has challenges in enhancing the energy and power density of LIBs due to its limited theoretical specific capacity (372 mAh g-1) and restricted rate capability. Hence, most battery industries have focused on forming graphite-silicon composites through the blending of silicon (Si) and graphite.

Si has an ultrahigh theoretical specific capacity of 3579 mAh g-1 (Li15Si4), which is roughly 10 times higher than the specific capacity of graphite, and has a low redox potential (0.4 V vs Li/Li+). However its excellent properties, the Si-based anode undergoes a severe volume expansion (up to 300 %) during the repetitive lithiation/delithiation process. The resulting physical change causes the breakdown/restoration of the solid electrolyte interphase (SEI) layer over the surface of the Si. This phenomenon causes electrolyte decomposition, degradation of Coulombic efficiency, the loss of active lithium ions, and the formation of an unstable SEI layer.

To address the inherent problems of Si, countless researches have been conducted to improve the electrochemical performance and long-term cycle stability of graphite-Si composite electrodes through nanostructure engineering, composite optimization, and surface modification. Nevertheless, graphite-Si composite electrodes continue to encounter challenges (e.g., electrode pulverization and delamination), constraining the incorporation of Si active materials into the composite. Therefore, it is imperative to devise a new graphite-Si composite for high-performance LIBs.

In this work, we used polyvinylpyrrolidone (PVP) as an electrode additive and investigated how it affects SEI components and volume expansion issues. PVP, a component of LiF and Li3N, can produce high-quality SEI in the field. We verified this via X-ray photoelectron spectroscopy(XPS). In addition, when we evaluated Li metal cells, we discovered that the electrode with PVP had better capacity retention and battery performance than the electrode without PVP, and when we reviewed full cells, we discovered that the rate characteristics were improved and volume expansion was reduced. This work explores a simple strategy for employing electrode additives to improve long-term cycle stability and high-rate performance.