bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring Na-Based Oxides as Electrode Materials for Alkali Metal Thermal-to-Electric Converters
Authors: Kim Tae Woo , Lee Dae-Gyun , Yu Ji-Haeng , Lee Wook Hyun , Han In Sub
Published: December 2024

The alkali metal thermal-to-electric converter (AMTEC) is a technology that converts thermal energy into electrical energy. It can operate with various heat sources, does not require fuel injection, and produces no harmful emissions, making it an environmentally friendly technology. Currently, Mo-based metallic materials are mainly used as electrode materials for AMTEC. However, when operated at temperatures above 800°C, the coarsening of electrode particles and the formation of Na-Mo-based secondary phases have a negative impact on the durability of the cell. In this study, Na-based oxides, widely known as electrode materials for secondary batteries, were applied as electrode materials for AMTEC. The electrode materials were synthesized via a solid-state reaction method that involved grinding and heat treatment at 950°C. The crystal structure and microstructure of the materials were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. To facilitate effective coating of the electrode material onto the surface of the beta-alumina solid electrolyte (BASE), physical treatments (e.g., sandpapering) and chemical treatments (e.g., chemical etching) were employed to optimize the BASE surface. Through this process, it was confirmed that the interface contact between the electrode and the BASE was successfully formed after chemical treatment. For electrochemical performance evaluation, cells with small-area and large-area electrodes were prepared by coating the cylindrical BASE surface. At an operating temperature of 600°C, the small-area cell (electrode area: 3 cm²) exhibited a maximum power output of approximately 1.02W (0.34W/cm2). The large-area cell (electrode area: 4.2 cm²) achieved an excellent power output of 10.13W (0.23W/cm2). This study confirmed for the first time that Na-based oxide electrode materials show great potential as electrodes for AMTEC. The detailed findings of this research will be discussed further in the presentation.
(Invited) Laser Induced Generation of Emission and Photocurrent of GaN Nanoceramics
Authors: Strek Wieslaw , Musialek Agata , Tomala Robert , Stefanski Mariusz
Published: December 2024

The measurements of laser induced emission (LIWE) and photocurrent (LIPC) of GaN semiconductor nanoceramics are reported. It was found that an origin of both the processes is related to the multiphoton ionization. They occur in a spot of focused laser beam irradiating a surface of ceramics. The emission and photocurrent are characterized by the excitation threshold and exponential increase of intensity. It was observed the hysteresis behavior in forward and backward measurement cycle for emission and photocurrent. A coexistence of both the effects open a possibility for applications in memory devices.

The authors would like to thank the National Science Centre, Poland for financial support (grant no. NCN 2021/40/Q/ST5/00220)
Thermally Stimulated Luminescence and Photoluminescence Properties of Dy-Doped Al2O3-SiO2 Glasses
Authors: Nishikawa Akihiro , Shiratori Daiki , Kato Takumi , Nakauchi Daisuke , Kawaguchi Noriaki , Yanagida Takayuki
Published: December 2024

Storage-type phosphors absorb and temporarily store the energy of ionizing radiation and emit low-energy photons when an external stimulus such as heat or light is applied. Since the number of emitted photons is proportional to the energy of the absorbed ionizing radiation, it is possible to estimate the irradiated dose. For this reason, they are applied in various fields such as personal radiation dosimetry and medical imaging. Storage-type phosphors are classified according to the type of external stimulus applied: optically stimulated luminescence (OSL) and thermally stimulated luminescence (TSL) materials. The mechanisms of OSL and TSL can be explained below. When a storage-type phosphor is irradiated with ionizing radiation, a large number of carriers are generated, and these carriers are trapped in the trapping centers in the material, which assumes a metastable state. Subsequent stimulation with heat or light causes the carriers to be re-excited, resulting in luminescence. These storage-type phosphors are required to have high emission intensity, wide dynamic range, and low fading. In particular, when applied to personal dosimeters, the materials must have tissue equivalency.

Al2O3-SiO2 glasses focused on in this study have good characteristics such as high hardness, high melting point and elastic modulus, and low electric conductivity. Therefore, this glass composition has been considered for optical amplifiers and lasers. These properties are also advantageous in terms of material durability when used for dosimetry. In addition, the effective atomic number (Zeff = 11.8) of Al2O3-SiO2 glasses is close to that of human soft tissues, making it a promising storage-type phosphor for personal dosimeters. Therefore, the purpose of this study was to investigate the TSL properties of this glass system in detail and to evaluate the dose-response characteristics.

We prepared the Dy-doped 10Al2O3-90SiO2 glasses with various Dy concentrations (0.1, 0.3, 1.0, and 3.0%) by the melt-quenching method and investigated the photoluminescence (PL) and TSL properties. We measured the TSL glow curves of all samples to research the concentration dependence of Dy. As a result, all samples showed the TSL at around 200℃, and the 0.3% Dy-doped 10Al2O3-90SiO2 glass showed the highest TSL intensity. It was found that the TSL originated from the 4f–4f transition of Dy3+ by measuring the TSL spectrum. In addition, the lower detection limit of the 0.3% Dy-doped sample was at least 0.1 mGy. Other details on optical, TSL, and these characteristics changes due to Dy concentration in the glass will be presented in our presentation.
Luminescence Properties of Perovskites Doped with Lanthanides Under High-Power Excitation
Authors: Tomala Robert , Musialek Agata , Stefanski Mariusz , Goncalves J.M. , Strek Wieslaw
Published: December 2024

Laser-induced white emission (LIWE) occurs when a material is excited with a focused infrared laser and is characterized by the emission of warm white light. Emission have a broadband character and cover visible range. It increased with a simultaneous decreasing f-f transitions. In particular the effect of excitation power density and concentration of dopants ions were investigated. The intensity of white emission was characterized by exponential dependence on excitation power density. Moreover the white emission threshold decreased with excitation photon energy. The photocurrent accompanying white emission was measured. It increased exponentially with excitation power density. The mechanism of laser induced white emission is briefly discussed in terms of multi-photon ionization and intervalence charge transfer (IVCT) mechanism. Therefore, it can be used as a new source of indoor lighting. Light parameters are similar to sunlight.

The authors would like to acknowledge National Science Centre for financial support (Grant No. NCN-2020/37/B/ST5/02399).
Enhanced Stability and High-Efficiency Lighting with Perovskite Quantum Wires
Authors: Zhang Qianpeng , Zhang Daquan , Fan Zhiyong , Mo Xiaoliang
Published: December 2024

Perovskite quantum wires (QWRs) represent an innovative class of perovskite materials, distinguished by their minuscule radial dimensions, approximately 5nm, which give rise to pronounced quantum confinement effects. These structures eclipse traditional perovskite thin films in terms of stability, owing to the protective encapsulation and passivation afforded by porous alumina membranes (PAM). Moreover, the quantum confinement intrinsic to QWRs markedly augments their photoluminescence quantum yield (PLQY), outperforming standard nanowires in this regard. Leveraging the remarkable physical attributes of perovskite QWRs, we have adeptly harnessed them across a spectrum of applications encompassing optoelectronic sensing, expansive lighting on 4-inch wafers, omni-directional spherical lighting, and vibrant full-color RGB illumination. Within these domains, our innovations have culminated in lighting apparatuses that boast external quantum efficiencies (EQE) in excess of 20%.

D. Zhang, L. Gu, Q. Zhang et al., "Increasing Photoluminescence Quantum Yield by Nanophotonic Design of Quantum-Confined Halide Perovskite Nanowire Arrays," Nano Lett. 19, 2850-2857 (2019).

D. Zhang, Q. Zhang, B. Ren et al., "Large-scale planar and spherical light-emitting diodes based on arrays of perovskite quantum wires," Nat. Photon. 16, 284-290 (2022).

Y. B. Cao, D. Zhang, Q. Zhang et al., "High-efficiency, flexible and large-area red/green/blue all-inorganic metal halide perovskite quantum wires-based light-emitting diodes," Nature Communications 14, 4611 (2023).

Q. Zhang, D. Zhang, L. Gu et al., "Three-Dimensional Perovskite Nanophotonic Wire Array-Based Light-Emitting Diodes with Significantly Improved Efficiency and Stability," ACS Nano 14, 1577-1585 (2020).

Y. Fu, S. Poddar, B. Ren et al., "Strongly Quantum-Confined Perovskite Nanowire Arrays for Color-Tunable Blue-Light-Emitting Diodes," ACS Nano 16, 8388-8398 (2022).
Αlpha-Ray Detection Properties of Spinel Single Crystals
Authors: Takebuchi Yuma , Tezuka Keitaro , Kato Takumi , Nakauchi Daisuke , Kawaguchi Noriaki , Yanagida Takayuki
Published: December 2024

A scintillator is one of the phosphors for radiation detection. Typical application fields of scintillators are medical, security, and environmental dosimetry. In nuclear facilities, there are high doses of α-ray, and monitoring of α-ray is necessary. Up to now, Ag-doped ZnS is used for α-ray detection. Although Ag-doped ZnS has high light yield, the detection efficiency is limited because the material form is opaque polycrystal. Therefore, a novel scintillator with high transparency is required for α-ray detection. Spinel materials are one of the candidates for radiation detection because of their high radiation resistant. According to the previous study, scintillation properties of MgGa2O4 and ZnGa2O4 have been studied under γ-ray irradiation. On the other hand, these materials seem to be suitable for α-ray detection rather than γ-ray detection because of the low effective atomic number. In addition, other spinel materials also worth studying. In this study, we synthesized MgAl2O4, MgGa2O4, ZnAl2O4, and ZnGa2O4 single crystals and evaluated the optical and scintillation properties.

The starting powders were MgO, ZnO, Al2O3, Ga2O3. The powders were mixed into homogeneously and shaped into cylindrical rods by packing into balloon and applying hydrostatic pressure. Then, the rods were sintered 1400°C for 8 h in air to obtain ceramics precursor. Single crystalline samples were synthesized by the floating zone method using the ceramics precursor. For measurements, the synthesized crystals were processed to approximately 5 mm in diameter and 1 mm in thickness by cut and polishing.

The transparent and single-phase of the MgAl2O4, MgGa2O4, ZnAl2O4, and ZnGa2O4 single crystals were successfully obtained by the floating zone method. According to the total transmission spectra, the total transmittances of the crystals were 70−80% in visible region. In the X-ray-induced scintillation spectra, MgAl2O4, MgGa2O4, ZnAl2O4, and ZnGa2O4 single crystals showed a luminescence peak around 380, 400, 300, and 350 nm, respectively. The luminescence origin of each crystal was considered to be due to oxygen vacancies of the host materials. Figure 1 shows the pulse height spectra of the spinel crystals under 241Am α-ray irradiation. The spectra of a commercial Bi4Ge3O12 (BGO, 8000 ph/MeV) single crystal under 137Cs γ-ray irradiation is also shown as a reference. As shown in Figure 1, all the crystals showed a clear full energy peak. From the comparison with the peak position of BGO, the light yields of the MgAl2O4, MgGa2O4, ZnAl2O4, and ZnGa2O4 single crystals were 200, 4300, 700, 5700 ph/5.5MeV-α, respectively. The details will be discussed in the conference.

Figure 1
Electrolyte Cage Effects in Organic Electrosynthesis: Measuring and Driving Selectivity
Authors: Nguyen Zachary A , Boucher Dylan G. , McFadden Kevin , Minteer Shelley
Published: December 2024

Electrochemical organic synthesis shows promise for the sustainable synthesis of agrochemical and pharmaceutically relevant molecules. However, the complexity of integrating organic and electrochemical methods often leads to overlooked reaction parameters. For example, electrolyte salts are used to decrease resistivity of the electrochemical cell and are traditionally viewed as benign species in electrochemical systems. However, the electroorganic literature is filled with examples in which changing the identity of the electrolyte impacts the reaction selectivity significantly, implying that these ‘benign’ molecules have overlooked chemical contributions to reactivity, such as the stabilization of critical intermediates.

Here, we explore the impact of electrolyte species on an important class of organic reactions: organic bond homolysis. In this reaction, a cage-paired radical is formed through the homolytic cleavage of a carbon bond, which then exists in a shell of solvent and solvated salts. This solvent-ion shell can stabilize this intermediate and allow for reversible bond homolysis. Such caged species are well-studied phenomena in metal-hydrogen atom transfer reactions and have been demonstrated to directly influence product selectivity in various organic reactions such as hydrogenation, isomerization, and dimerization. Here, we focus on how the lifetimes of cage-paired metal alkyl radical species are affected by common organic electrolytes and how this lifetime informs product selectivity. The lifetimes of these caged intermediates in various electrolyte conditions were examined using cyclic voltammetry, where titration studies were conducted to determine the rate of escape from the solvent-ion cage. This study provides insight into the role of common electrolyte salts on the stability of caged metal alkyl species and subsequent selectivity in organic synthetic reactions.
Measuring Hydride Transfer Kinetics to Mhat Relevant Catalysts Using Cyclic Voltammetry
Authors: McFadden Kevin , Boucher Dylan G. , Minteer Shelley
Published: December 2024

The area of organic electrocatalysis has been growing in importance as many new transformations have been developed and previously known transformations are adapted to be accomplished electrochemically. As the field of synthetic organic electrochemistry emerges, it is becoming ever more important to study the mechanisms of these electrocatalytic reactions. Understanding the mechanics of the chemical processes and how they are coupled to the electrode is critical for continuing to expand the synthetic utility of electrocatalysis. Radical based hydrofunctionalization of alkenes through transition-metal catalyzed hydrogen atom transfer (MHAT) mechanisms is a proven, powerful mode of forming C−C, C−O, C−N and C−X bonds. In recent years, new asymmetric MHAT reactions have been enabled through electrocatalysis. The in situ generation of the key metal-hydride species plays a crucial role in both the kinetics and selectivity of the observed products. These high energy metal hydrides are too reactive and too short lived to be isolated, thus the oxidative mechanism leading to their formation is poorly understood. Here, we utilize a model catalytic cycle in which metal hydride formation is the rate determining step. Cyclic voltammetry enables us to extract the rate constant of hydride transfer. The differences in kinetic trends between catalysts and hydride donors indicate separate mechanisms of hydride transfer are operative for different classes of MHAT catalysts. Specific trends in ligand electronics, hydride donor sterics and hydricity for cobalt salen type catalysts allowed us to postulate a possible metal/ligand cooperative mechanism of hydride transfer. In summary, these studies represent a significant step towards understanding the homolytic reactivity of metal hydride species and will help enable the design of new electrosynthetic reactions involving radical intermediates.
Synthesis of Degradable Polymers Containing Phenylpropanoid Skeleton Via [2+2] Cycloaddition Polymerization Triggered By Electrochemical Oxidation and Photocatalysis
Authors: Nagaya Ryo , Seko Tatsuya , Ueno Kazuhide , Shida Naoki , Atobe Mahito
Published: December 2024

Due to the increasing concern about climate change in human society, research on the use of biomass as a renewable carbon resource has become more active. Phenylpropanoids, which are obtained from the degradation of lignin, are expected as renewable aromatic monomers for plastic materials due to their availability. Various strategies have been proposed for polymerization of phenylpropanoids, including homopolymerization [1] or copolymerization [2]. However, the former strategies face challenges due to their limited scope of applicable phenylpropanoid. Furthermore, since conventional methods have mostly focused on polymerization of vinyl moiety, there remains the challenge in the chemical recycling of polymers.

In this work, we demonstrate the synthesis of degradable polymers containing phenylpropanoid by [2+2] cycloaddition polymerization. Bifunctional monomers containing two-phenylpropanoid moieties were synthesized by introducing siloxy- and (thio)phosphonate-linkage, respectively. Various phenylpropanoids are applicable to this strategy and we successfully synthesized various bifunctional monomers. Monomers were then polymerized by cycloaddition reactions triggered by electrochemical oxidation or photocatalysis. Siloxy- and (thio)phosphonate-linkage are cleavable by the reaction with specific reagents, enabling facile and chemoselective polymer degradation. The degradation reaction afforded a dimeric compound with a bisphenol skeleton, which could be used for further chemical recycling and upcycling.

[1] K. Ute et al., Polymer
2022, 246, 124780.

[2] K. Sato, Polymer Journal
2015, 47, 527-536.

Figure 1
Electrochemical Synthesis of Diarylsultones and Dibenzothiophene Dioxide Via C–O/C–S Bond Formation
Authors: Okumura Yasuyuki , Mitsudo Koichi , Suga Seiji
Published: December 2024

Sultones and dibenzothiophene dioxides are widely used in the fields of pharmaceuticals, biologically active molecules, and material sciences [1][2]. While many synthetic methods have been reported, the synthesis of sultones and dibenzothiophene dioxides usually require stoichiometric amounts of oxidants, expensive transition metals, and harsh conditions. Therefore, the development of efficient and environmentally friendly methods for the synthesis of these compounds is in highly demand.

Meanwhile, electrochemical reactions have received considerable attention as an environmentally benign method in organic synthesis. In particular, electrochemical C–O and C–S bond formations have been a point of focus for the synthesis of useful compounds. However, there have been no reports on the electrochemical synthesis of sultones and dibenzothiophene dioxides.

Herein, we report the electrochemical synthesis of diaryl-fused sultones and dibenzothiophene dioxides through dehydrogenative C–O and C–S bond formations [3][4]. A variety of diaryl-fused sultones were obtained in moderate to good yields through hydrolysis of sulfonyl chlorides and constant current electrolysis. Control experiments suggested that the electrochemical oxidation of the sulfonates generated in situ would afford sulfo radical intermediates, and subsequent radical cyclization gave the products. For synthesizing dibenzothiophene dioxides, using Bu4NOTf as an electrolyte in HFIP/CH3NO2 was essential. On the other hand, biaryl sulfonyl hydrazides were applied to constant current electrolysis to afford the corresponding dibenzothiophene dioxides efficiently. Control experiments suggested that the electrooxidation of biaryl sulfonyl hydrazides would proceed via sulfonyl radical and cation intermediates.

References

[1] Mondal, S. Chem. Rev.
2012, 112, 5339.

[2] Dias, F. B.; Bourdakos, K. N.; Jankus, V.; Moss. K. C.; Kamtekar, K. Y.; Bhalla, V.; Santos, J.; Bryce, M. R.; Monkman, A. P. Adv. Mater.
2013, 25, 3707.

[3] Mitsudo, K.; Okumura, Y.; Yohena, K.; Kurimoto, Y.; Sato, E.; Suga, S. Org. Lett.
2023, 25, 3476.

[4] Okumura, Y.; Sato, E.; Mitsudo, K.; Suga, S. Electrochemistry
2023, 91, 112007.

Figure 1
Evaluation of Porcine Sperm Activity Using an Electrochemical Device
Authors: Terui Yuma , Kumagai Ryoma , Frubayashi Yoko , Sakuranaka Yuta , Matsuzawa Tamio , Matsuzawa Ryusuke , Kasai Shigenobu
Published: December 2024

[Introduction] In recent years, in vitro fertilization has become an important method in the field of infertility treatment. Research is progressing in the livestock industry to improve fertility and pregnancy rates. The motility of sperm can be evaluated through time-lapse microscopy. This method is cost-effective and requires little space for activity evaluation. In addition, methods for selecting motile sperm include those that utilize centrifugation, such as density gradient centrifugation. However, there is a concern that centrifugation may physically damage sperm due to the large gravitational force it receives. We previously measured the respiratory activity levels of sperm and somatic cells in raw cow milk using amperometry; however, we did not evaluate sperm motility [1]. Therefore, in this study, we developed an electrochemical device that collects motile spermatozoa using moving gravity sedimentation without adding centrifugation, and we reported the examined changes in the oxygen reduction current before and after sperm movement.

[Experiment] Porcine (Duroc) sperm (approximately 108 sperm/mL) was purchased from the Miyagi Prefecture Livestock Experiment Station for use. The device was filled with 5.7 mL of 11.4 mM glucose-containing phosphate buffer solution (pH = 7.4), and a three-electrode system was constructed. A platinum electrode (diameter = 1.6 mm) was installed in the middle tube and a platinum electrode was installed in the counter electrode (Fig. 1). The applied voltage was maintained at -0.5 V vs. Ag/AgCl, and the sampling time was 0.1 s. After the start of measurement, 300 µL of the sperm sample was dropped onto the bottom of the outer tube, and amperometry was performed for approximately 60 minutes.

[Results and discussion] Fig. 2 shows the amperogram from 40 to 55 minutes after dropping the sperm sample. After approximately 42 minutes, the oxygen reduction current started to decrease. After approximately 10 minutes, the current became constant, and a decrease of approximately 100 nA was observed. This result suggested that the pig sperm potentially consumed oxygen during movement from the bottom of the outer ring to the center of the well. The number of sperm that swam upward and moved to the center was approximately 4.4 × 106 sperm/mL in 60 minutes, and the recovery rate was approximately 15.0%. Compared to the literature value for human sperm (approximately 13.8%), the experimental results were considered reasonable, suggesting the possibility of capturing the real-time respiratory activity of moving sperm [2]. In this paper, we thoroughly discussed the relationship between the initiation of porcine sperm migration and the oxygen reduction current.

[References]

[1]S.Kasai, A.Prasad, R.Kumagai, K.Takanohashi, Biology,2022,11,549.https://doi.org/10.3390/biology11040549.

[2] K.Tatsumi, T.Tatsumi, T.Uchida, K.Saito, H.Saito, F&S Reports, 2020,1(2), 106-112.

Figure 1
(Invited) Protein Film Electrochemistry and Surface-Enhanced Infrared Absorption Spectroscopy of Transmembrane Metalloenzymes
Authors: Kato Masaru
Published: December 2024

Transmembrane metalloenzymes encapsulating transition metal complexes are involved in electron transfer and in material transformation in living organisms. Understanding their operating principles is not only important for identifying the origin of highly efficient enzymatic reactions but also for developing sensors and catalysts inspired by metalloenzymes [1]. Protein film electrochemistry (PFE) is a powerful technique to investigate the redox behavior and enzymatic activity of transmembrane metalloenzymes even with a submonolayer amount of the target protein (~10 pmol cm–2). The challenge of PFE of metalloenzymes is the interpretation of the results obtained in PFE: PFE provides current–potential curves like cyclic voltammograms and relatively large transmembrane metalloenzymes tend to have multiple redox active cofactors inside the protein, which makes the interpretation of cyclic voltammograms difficult.

We are using PFE coupled with surface-enhanced infrared absorption (SEIRA) spectroscopy, which is a surface-sensitive vibrational spectroscopy, to understand enzymatic mechanisms and protein–lipid or protein–protein interactions of transmembrane metalloenzymes at the electrode surface. In this talk, we will discuss PFE–SEIRA spectroscopy results about the determination of redox potential using a vibrational probe of carbon monoxide for heme proteins [2], the mechanistic insights into nitric oxide reduction to nitrous oxide at cytochrome c-dependent nitric oxide reductase (cNOR) using in situ PFE-SEIRA spectroscopy, and protein–lipid and protein–protein interactions with cNOR [3] and cytochrome c oxidase (CcO) [4].

References.

[1] M. Kato, N. Fujibayashi, D. Abe, N. Matsubara, S. Yasuda, I. Yagi, ACS Catal., 11, 2356–2365 (2021).

[2] M. Kato, S. Nakagawa, T. Tosha, Y. Shiro, Y. Masuda, K. Nakata, I. Yagi, J. Phys. Chem. Lett., 9, 5196 (2018).

[3] M. Kato, Y. Masuda, N. Yoshida, T. Tosha, Y. Shiro, I. Yagi, Electrochim. Acta, 373, 137888 (2021).

[4] M. Kato, R. Sano, N. Yoshida, M. Iwafuji, Y. Nishiyama, S. Oka, K. Shinzawa-Itoh, Y. Nishida, Y. Shintani, I. Yagi, J. Phys. Chem. Lett., 13, 9165-9170 (2022).
Voltage Hysteresis without Cation Migration in Li-Rich Layered Oxides: A Discrepancy in the Intermediate Crystal Phases
Authors: Calpa Marcela , Kubota Kei , Matsuda Shoichi , Takada Kazunori
Published: December 2024

Li-rich layered oxides are promising as next-generation cathode materials for Li-ion batteries because of their potential to provide high voltage and large capacities. However, these materials suffer from significant voltage hysteresis between charge and discharge, and the causes are not yet well understood.

In this work, a comprehensive in-situ X-ray diffraction analysis, conducted in Li2RuO3 as a model of Li-rich cathode materials, reveals that a discrepancy in the intermediate crystal phases formed during Li extraction and re-insertion gives rise to different electrochemical potentials between charge and discharge, which causes the undesired voltage hysteresis [1]. These findings enrich the understanding of voltage hysteresis in Li-rich materials.

Reference

[1] Calpa, M., et al. Energy Storage Materials 63 (2023) 103051
Electrocatalytic Direct Halogenation of Aromatic Compounds Using Green Halogen Source
Authors: Choi SuHyeok , Park Jin Kyoon , Nam Ki Min , Park Joon Yong , Cho Hyeon Beom
Published: December 2024

Chlorination reactions are important transformations in organic synthesis. Here, we introduce the electrochlorination of aromatic compounds using sodium chloride as both the chlorine source and electrolyte, with Ir/Ru/TiO₂ as the anode and RVC as the cathode. The process involves the oxidation of chloride ions at the dimensionally stable anode to produce chlorine radicals, which react with aromatic compounds to form chlorinated derivatives. The RVC cathode efficiently collects hydrogen gas and prevents its reaction with chlorine gas. This electrochlorination method offers improved selectivity, control, and safety compared to traditional chlorination methods. Our reaction conditions were applied to various substrates, resulting in yields ranging from moderate to excellent. Additionally, we produced bromine radicals and successfully applied this method for electrobromination. Application of our reaction conditions to known pharmaceutical and natural products led to halogenated products with high yields. Experiments utilizing seawater as the chlorine source also produced chlorinated products in high yields, providing us with an endless source for sustainable chlorine chemistry.
Improving the Thermal Stability of Lithium-Ion Batteries Using a Separator Protective Film Made By Novel Materials
Authors: Uto Daiki , Imai Masato , Yasui Shintaro , Yoshino Kenji
Published: December 2024

Lithium-ion batteries (LIBs) are widely used in the portable electronics, power tools, and electric vehicle power markets. As the demand for higher battery density and energy density increases, improving the safety of LIBs has become an important issue. The separator in a LIB maintains physical isolation between the cathode and anode and allows the movement of lithium ions through the electrolyte through the porous separator structure during cycling. Therefore, cycle life and energy density are important components for achieving high battery performance.

Generally, most separators are porous polyolefin films made of polyethylene or polypropylene. Polyolefin separators have excellent mechanical strength and chemical stability, but they shrink significantly at high temperatures, and internal short circuits occur under conditions such as abnormal heating. In order to improve the thermal stability of the separator, many methods have been reported for coating the surface of the separator with inorganic powder, and most of them use dip coating or simple bar coating. The coating layer formed on the surface of the separator has a porous structure and is several microns thick. Coated separators reduce thermal shrinkage while ensuring ion transport, but there are concerns that increased film thickness may reduce the battery's energy density.

In this study, the coating was carried out on porous membranes such as separators at 50 °C by spray pyrolysis using methylaluminoxane diluted with N-methylpyrrolidone. The solution penetrated the separator during spraying and deposited an ultrathin layer on the side walls of the internal pores. These layers were suggested to be fine polycrystalline Al2O3. In the obtained film, most of the pores were exposed on the surface, and there was almost no increase in film thickness. Furthermore, it has ionic conductivity equivalent to that of film and has improved thermal stability. This method was considered to be an effective technique for improving the functionality of separators used in LIB.
The Potential Use of Transition Metal Carbonitrides as Catalyst for Nitrogen Reduction Reaction
Authors: Iqbal Atef , Skulason Egill , Abghoui Younes
Published: December 2024

Rapid and facile nitrogen reduction holds a critical role in ensuring the sustainable and energy-efficient production of ammonia, serving not only as a medium for hydrogen preservation and chemical substrates but also as a vital component for generating essential inorganic fertilizers. To achieve catalytic ammonia synthesis, it becomes imperative to develop a nitrogen reduction apparatus that operates effectively under low temperatures and ambient pressure, utilizing a catalyst that possesses optimum stability, selectivity, and activity. Here, we describe the discovery of effective and cost-efficient catalysts, transition metal carbonitrides (TMCNs). These catalysts enable the electrochemical conversion of molecular nitrogen into NH3 at room temperature. We use density functional theory calculations to gain insight about the feasibility of different mechanisms, associative (AM), dissociative (DM), and Mars-van Krevelen (MVK), and subsequently conduct a comparative analysis of the resultant reaction pathways using these mechanisms. Our investigation identifies that these carbonitrides are more active in the reduction of nitrogen rather than hydrogen evolution reaction (HER), in comparison to pure metal catalysts. Additionally, their resistance to poisoning and potential breakdown under working circumstances are investigated. The most attractive candidates are VCN and NbCN, which are predicted to reduce nitrogen via the MvK mechanism at onset potentials of -0.52 V and -0.53 V vs reversible hydrogen electrode (RHE), respectively. This is a promising advancement in the pursuit of a technology capable of viable nitrogen reduction in order to produce nitrogenous chemicals from electricity, water, and air under ambient environments.
Transport Numbers Ion-Exchange Membranes with Mixed Solvent Electrolyte Mixtures Relevant for Electrodialysis and Battery Technology
Authors: Solberg Simon Birger B. , Wilhelmsen Øivind , Burheim Odne
Published: December 2024

In this study, we have analysed measurements of the electric potential and permselectivity in concentration cells with Selemion CMVN and AMVN membranes (cation- and anion-exchange membranes respectively) in electrolyte mixtures of KCl and H2O with and without ethanol (EtOH). The presence of EtOH induced a change in the measured electric potential and permselectivity of the Selemion CMVN and AMVN ion-exchange membranes, but the effect was not well explained by transference of EtOH. Instead, the regression analysis indicated that the measured permselectivities were well explained by EtOH transference coefficients of ta
= 0. The variation of the permselectivity could be wholly explained by a gradual decrease in the water transference coefficient proportional to the average EtOH activity, tw
∝ aa
, with tw
≈ 4 in the absence of EtOH. The analysis also indicated that the CEM and AEM were perfectly selective toward migration of K+ (tK+
= 1) and Cl- (tCl-

= 1), respectively. Relations and the analysis method are based on non-equilibrium thermodynamics, and may be extended to other electrochemical systems of interest.
Two-Dimensional Covalent Organic Framework Photoanode for High Capacity Solar Battery
Authors: Rath Bibhuti Bhusan , Lotsch Bettina Valeska
Published: December 2024

To mitigate our reliance on fossil fuels and facilitate energy transition, efficient conversion and storage of ubiquitous solar energy is a key strategy. Despite significant research progress in photovoltaics, energy storage in decentralized batteries requires the decoupling of energy conversion and storage, which causes major energy loss and higher cost. Seamless integration of a photoconversion system and an energy storage system in a single device can effectively store the excess energy. Materials that can demonstrate light harvesting, effective charge carrier separation for long-term charge storage, and on-demand charge retrieval as electrical energy, would be the most suitable choice. Such properties have been demonstrated in graphene-, carbon-nitride-, polyoxometalate-, and metal organic frameworks- based materials; however, the charge storage capacity remains uncompetitive. Driven by the need for earth-abundant and sustainable materials for solar energy storage, covalent organic frameworks (COFs) have emerged as a new generation of molecularly defined semiconductors with tunable optoelectronic properties. Herein, the rational integration of an electron reservoir in a polyimide two-dimensional COF unlocks the unique combination of light harvesting and electrical energy storage. When used as an aqueous solar battery anode, the COF demonstrated a capacity of ~40 mAh g-1 operating as a pseudocapacitor, which stores charge as long-lived radical anions for days. With photo-electrochemical measurements in conjunction with detailed spectroscopic studies and theoretical support, we attempt to unravel the mechanism of long-term charge stabilization. Furthermore, on-demand release of long-lived electrons with a suitable co-catalyst unlocks the prospects of dark photocatalysis, which will be investigated in the future.

References:

F. Podjaski, B. V. Lotsch, Adv. Energy Mater. 2021, 11, 2003049.

V. W. Lau, D. Klose, H. Kasap, F. Podjaski, M-C. Pignié, E. Reisner, G. Jeschke, B. V. Lotsch, Angew.
Chem. Int. Ed. 2017, 56, 510 –514.

S. Amthor, S. Knoll, M. Heiland, L. Zedler, C. Li, D. Nauroozi, W. Tobaschus, A. K. Mengele, M. Anjass, U. S. Schubert, B. Dietzek-Ivanšić, S. Rau, C. Streb, Nat.
Chem. 2022, 14, 321−327.

M. Stanley, F. Sixt, J. Warnan, Adv. Mater. 2023, 35, 2207280.
Photothermally Enhanced Urea-Assisted Hydrogen Production Using Cus/WO3 Direct Z-Scheme Electrocatalyst
Authors: Cha Yoolim , Kim Wonhyeong , Kim Dong-Joo
Published: December 2024

Fossil fuels, such as coal and petroleum, are currently the primary energy source for the world’s needs. However, their depletion and role in the development of greenhouse gases, which contribute to global warming and climate change, necessitate the exploration of alternative green energy sources to promote a cleaner environment. Hydrogen, in particular, has emerged as a promising renewable energy fuel for the future. One promising method for producing hydrogen is urea-assisted water splitting, which has the potential to improve both hydrogen production productivity and energy conversion efficiency. However, urea oxidation reaction (UOR) is a complex six-electron transfer process with slow reaction kinetics and unclear mechanisms, which requires a high overpotential. This has led to the need to enhance electrocatalytic reactions. In general, the majority of research has been directed towards the synthesis of robust, efficient, and economically viable catalysts. In recent years, light irradiation has been introduced into an electrochemical system with the aim of enhancing the activities of the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and carbon dioxide reduction reaction. Insights into the mechanism demonstrate that external excitation effectively accelerates charge and mass transfer and thus improves the reaction kinetics and thermodynamics. In contrast to previous catalyst modifications, the external field assistance approach allows for greater flexibility in engineering an electrochemical process with facile, continuous, reversible, dynamic, and universal control. However, the utilization of photothermal-assisted urea oxidation reaction has not been reported yet.

In this research, we report a CuS/WO3 composite electrocatalyst with a direct Z-scheme system for photothermally-assisted UOR. Upon irradiation with light, the CuS/WO3 electrode exhibited a reduced overpotential of 308.2 mV, resulting in a UOR current density of 50 mA cm-2. Additionally, the CuS/WO3 electrode achieved a current density of 10 mA cm-2 at a potential of 1.38 V vs. RHE under irradiation. The catalytic activity of the CuS/WO3 electrode was found to be significantly enhanced, exhibiting a 2.5- and 2.8-fold increase compared to that of CuS and WO3, respectively. This enhancement can be attributed to the enhanced redox abilities of charge carriers in the direct Z-scheme system. Our studies demonstrate the importance of direct Z-scheme formation in light utilization and the synergistic effect of photon and photothermal on UOR.

Figure 1
Redox-Active Amine for Electrochemical CO2 Capture and Release
Authors: Liang Liang , Firschke Frederik , Strasser Peter
Published: December 2024

The recent IPCC report highlights the importance of negative carbon dioxide emissions scenarios to achieve the 1.5°C Paris Agreement goal, emphasizing the crucial role of negative emission technologies (NETs) in complementing decarbonization efforts. Capturing CO2 from dilute sources, such as flue gas and the atmosphere, is essential for managing global emissions and advancing storage and utilization efforts downstream. Electrochemical carbon capture methods are notable for their high energy efficiency, decentralized operation, ambient reaction conditions, and compatibility with renewable electricity. [1, 2]

In this context, a robust electroDAC approach with switchable electroactive adsorption materials is urgently needed. Cu-based electrochemically mediated amine regeneration (EMAR) shows promise for controlled, reversible complexation with CO2 capture amines in aqueous solutions. However, uncertainties persist regarding Cu2+/Cu interfacial chemistry mechanisms, dynamic competitive interactions at the surface and in bulk, and potential degradation routes or parasitic faradaic currents. [3]

To address these uncertainties, we propose a reversible system using an electrostatic charge transfer mechanism at the electrode interface for energy-efficient CO2 capture and release. Our study focuses on investigating the stability and reactivity of various Cu-based catalysts under different conditions, employing spectroelectrochemical analysis to elucidate changes and interactions between adsorbed species and CO2 at the electrode interface.

Literature:

[1] S. Voskian, T. A. Hatton, Energy Environ. Sci., 2019,12, 3530-3547.

[2] M. Massen-Hane, K. M. Diederichsen, T. A. Hatton, Nat Chem Eng., 2024, 1, 35–44.

[3] S. E. Renfrew, D. E. Starr, P. Strasser, P. ACS Catal. 2020, 10, 21, 13058–13074.
Local Electrochemistry Based on Scanning Probe Technique with Gel Electrolyte
Authors: Hwang Seongpil
Published: December 2024

The local electrochemistry down to nanometer scale based on scanning probe technique with agarose as solid electrolyte will be presented. Boron-doped diamond conductive atomic force microscopy (BDD C-AFM) tip served as a working electrode which was brought into the surface of agarose gel electrolyte, forming the small electroactive area corresponding to nanoelectrode under the feedback by the current in a modified scanning ionic conductance microscopy mode along with a simple home-built Matlab software. Cyclic voltammograms show the controlled nanoelectrode predicted by COMSOL simulation. Moreover, this nanoelectrode enables the simultaneous imaging of both the topography and electrochemical activity of a polymeric microparticle embedded in a hydrogel, which may pave the new way to investigate the single entity electrochemistry of particles.
Cathodic Decomposition Reference Electrodes As a Generalized Approach for Thermodynamic Calculations in Complex Molten Salts
Authors: Lichtenstein Timothy , Hawthorne Krista
Published: December 2024

The rise of molten salt use in green energy applications has led to increased efforts to model and understand the underlying thermochemical properties of active species within molten salts. Molten salts can become increasingly complex during the operational lifetime through corrosion or generation of new species, resulting in changes to the thermophysical and thermodynamic properties. For example, next-generation molten salt nuclear reactors start with a binary or ternary fuel salt, but generation of fission products during operation can significantly change the behavior of active species in the salt and interactions with container materials. While processes in established molten salt electrolytes such as LiCl-KCl eutectic can use well-characterized reference electrodes such as Ag/AgCl to quantify thermochemical properties1, emerging salt systems do not have well-established reference electrode systems. Using standard reference electrodes based upon anodic electrolyte decomposition (e.g., chlorine or fluorine gas-based electrodes) introduces additional engineering and safety challenges during construction and measurement of thermochemical properties. These experimental barriers have previously limited investigation of the thermodynamics of novel molten salt systems.

Here, we use cathodic decomposition electrodes (CDEs) to measure the thermochemical properties of molten salt systems. The CDE defines 0 V as the cathodic decomposition of the pure solvent electrolyte at all temperatures. A CDE was used to make activity measurements in chloride and fluoride salts. Both steady-state emf measurements in concentration cells and transient measurements were made in an electrolyte containing active species such as GdCl3 or NiF2. The universal nature of a CDE reference can improve accuracy and repeatability of activity measurements in molten salt systems and fill the knowledge gaps that prevent prediction of thermochemical and thermophysical properties in molten salt systems.

L. YANG and R. G. HUDSON, “Some Investigations of the Ag∕AgCl in LiCl-KCl Eutectic Reference Electrode,” J. Electrochem. Soc. 106 11, 986 (1959); https://doi.org/10.1149/1.2427195.
Electrowinning of Light Metals from Molten Salts Electrolytes
Authors: Haarberg Geir Martin
Published: December 2024

Light metals such as lithium, sodium, potassium, magnesium and aluminium are produced by molten salts electrolysis. Aluminium is by far the largest in terms of production volumes. Magnesium is currently produced by silicothermic reduction of MgO according to the Pidgeon process. Titanium is also regarded as a very attractive light metal with excellent properties. The current Kroll process is energy intensive and requires lots of work as well as low productivity. Ongoing research focuses on developing a process based on electrolysis in molten salts.

The main reason for large carbon footprint during electrowinning of metals from molten salts is the source of electricity due to the fact that China is the largest producer where generation of electricity is based on coal. In the Hall-Heroult process for producing aluminium the use of carbon anodes is an additional important cause for increased CO2 emissions. The use of carbon anodes also leads to the formation of perfluoro carbon (PFC) gases CF4 and C2F6 which are powerful greenhouse gases. The search for an inert oxygen evolving anode has been going on for many decades and if successful it will improve the carbon footprint significantly. The possibility to use alloys with iron, nickel and copper has been popular recently. Magnesium is produced by the Pidgeon process which is based on silicothermic reduction of MgO. However, electrolysis in molten chloride electrolytes using MgCl2 as feedstock used to be the main process for producing magnesium for many years until around 2000. Electrowinning is better in terms of environmental issues and carbon footprint but the Pidgeon process is more profitable. The production processes for alkali metals by electrolysis in molten chloride electrolytes may be improved by using alkali metal oxides as raw materials and inert oxygen evolving anodes, where tin oxide is a strong candidate and is commercially available. Electrolysis to produce titanium is very challenging mainly because of the existence of several stable valencies of dissolved titanium species. Electrodeposition of titanium based alloys by co-deposition of alloying elements may be a new and interesting alternative.
An Electrochemically Promoted Approach to Graphitization Via Molten Salts
Authors: Yuan Yating , Prasad Thapaliya Bishnu , Luo Huimin , Dai Sheng
Published: December 2024

Graphite stands as a critical element, as recognized by the US Department of Energy, owing to its pivotal role as anodes in batteries. The demand for high-purity graphite in battery applications is poised to surge in the foreseeable future. Synthetic graphite, prized for its high purity, typically emerges as the preferred option for such applications. However, the current synthesis process for graphite is exceedingly energy-intensive, mandating heat treatment of carbon precursors at temperatures soaring up to 3300 K for successful graphitization. In this talk, a novel method for graphitization is presented, one that operates at significantly lower temperatures and harnesses an electrochemical approach. Through cathodic electrochemical polarization of amorphous carbon in molten salts, the transformation of amorphous carbon into a highly graphitic structure is achieved. This innovative process holds promise in conserving substantial energy compared to existing methodologies.