bluuebunny/crossref_metadata_2025 huggingface dataset:
Molybdenum Disulfide As an Efficient Catalyst for Hydrogen Evolution Reaction
Authors: Alarawi Abeer
Published: December 2024

Hydrogen is a carrier energy gas that can be utilized as a clean energy source instead of oil and natural gas. Splitting the water into hydrogen and oxygen is one of the most favorable methods to generate hydrogen. The catalytic properties of molybdenum disulfide (MoS2) could be valuable in this role, particularly due to its unique structure and ability to be chemically modified, enabling its catalytic activity to be further enhanced or made comparable to that of Pt-based materials. In general, these modification strategies may involve either structural engineering of MoS2 or enhancing the kinetics of charge transfer, including by confining to single metal atoms and clusters or integrating with a conductive substrate. We present the results of synergetic integration of MoS2 films with a Si-heterojunction solar cell for generating H2 via the photochemical water splitting approach. The results of the photochemical measurements demonstrated an efficient photocurrent of 36. 3 mA cm-2 at 0 V vs. RHE and an onset potential of 0.56 V vs. RHE. In addition to 25 hours of continuous photon conversion to H2 generation, this study points out that the integration of the Si-HJ with MoS2 is an effective strategy for enhancing the internal conductivity of MoS2 towards efficient and stable hydrogen production. Moreover, we studied the effect of doping an atomic scale of Pt on the catalytic activity of MoS2. The electrochemical results indicated that the optimum single Pt atoms loading amount demonstrated a distinct enhancement in the hydrogen generating, in which the overpotential was minimized to -0.0505 V to reach a current density of 10 mA cm−2 using only 10 ALD cycles of Pt. The Tafel slopes of the ALD Pt/ML-MoS2 electrodes were in the range of 55–120 mV/decade, which indicates a fast improvement in the HER velocity as a result of the increased potential. Stability is another important parameter for evaluating a catalyst. The same (10 ALD cycles) Pt/ML-MoS2 electrode was able to continuously generate hydrogen molecules at for 150 hours. These superior results demonstrate that the low conductivity of semiconductive MoS2 can be enhanced by anchoring the film with Pt SAs and clusters, leading to sufficient charge transport and a decrease in the overpotential.
Enhanced Near-Infrared Electrochemiluminescence of Glutathione-Stabilized Au Nanoclusters in Water
Authors: Kim Joohoon
Published: December 2024

In this presentation, a unique generation of near-infrared electrochemiluminescence (ECL) from water-soluble Au nanoclusters is discussed. Specifically, we report the near-infrared ECL of glutathione-stabilized Au nanoclusters, of which the photoluminescence is primarily within the visible wavelength region. Detailed experimental studies, including spooling ECL spectroscopy and time-resolved optical measurements, suggested that the near-infrared ECL is ascribed to the Au(0)-glutathione motif in the Au nanoclusters. Further studies of individual Au nanoclusters fractionated by gel electrophoresis of as-synthesized Au nanoclusters also revealed that the individual Au nanoclusters exhibited near-infrared ECL that became dominant when the ratio of Au(0) to Au(I) increased in the individual nanoclusters. These indicated that the oxidation states of Au nanoclusters primarily affected the ECL wavelengths of the nanoclusters because the Au(0)-glutathione motif in the nanoclusters was responsible for the near-infrared ECL emission.
Analysis of the Origin of the Centroid Shift in 4f-5d Transition Energies of Eu2+ in Oxide and Fluoride Crystals Using First-Principles Calculations
Authors: Honda Mamoru , Ogasawara Kazuyoshi
Published: December 2024

There are many applications that utilize the 4f-5d transitions of lanthanide ions, including (Sr,Ca)AlSiN3:Eu2+ (SCASN), which is widely used as a red phosphor for white LEDs. Also, research on the f-d transitions of Eu2+ in such compounds has been actively conducted both experimentally and theoretically. Dorenbos systematically analyzed the red shift of the 4f-5d transitions of lanthanide ions in crystals from those of the free ions based on large amount of literature data. He indicated that the red shift is a property unique to each host crystal and almost independent of the species of the lanthanide ions. Based on this fact, he created the energy level diagrams of lanthanide ions in various crystals. The red shift is mainly determined by two factors, the crystal field splitting and the centroid shift which is a shift of the barycenter of the 5d levels relative to the lowest 4f level. Therefore, prediction of these parameters for a given host crystal is important for theoretical design of novel lanthanide-doped phosphors. In this work, we aimed to analyze the electronic and structural origin of the centroid shift in 4f-5d transition energies of Eu2+ in oxides and fluorides. Small clusters consisting of the substituted Eu2+ ions and first-neighbor anions were constructed and the first-principles multiplet calculations using the relativistic DVME method were performed. In order to clarify the origin of the centroid shift, the correlations between the centroid shift and the various electronic and structural parameters were investigated in detail.
Fabrication of a Laser Using Aggregation-Induced Emission Dyes Combined with Cholesteric Liquid Crystal Networks
Authors: Moon tae-Woong , Choi Suk-Won
Published: December 2024

Cholesteric liquid crystals (CLCs) reflect light at specific wavelengths due to their helical structure, creating a photonic bandgap (PBG) that can serve as a laser cavity when light emitted from a dye is confined within it. In this work, we fabricate a laser using aggregation-induced emission (AIE) dyes as gain materials, combined with a CLC templating technique. First, we produce polymer-stabilized CLCs. Next, the low-molecular-weight components are removed, leaving behind CLC polymer networks (CLC templates). AIE dyes are then introduced into the CLC template. This method prevents disruption of the CLC structure and PBG caused by high concentrations of AIE dye. The technique enables the fabrication of flexible, free-standing CLC lasers, offering high durability and expanding the potential for advanced optical devices.
Regioselective Electrocatalytic Deuteration Reactions in PEM Reactor
Authors: Ashikari Yosuke , Yao Yiyuye , Mandai Kyoko , Nagaki Aiichiro
Published: December 2024

Although organic chemistry has brought significant benefits to humanity by providing a wide range of chemicals, conventional production methods often generate a significant amount of chemical waste. As the need for sustainability increases, there is a growing demand for organic reactions that utilize fewer chemical reagents, resulting in reduced waste generation. In this context, electrochemical synthetic methods have garnered great attention in recent decades. Unlike general redox reactions in organic synthesis, which require stoichiometric amounts of oxidants and reductants, electrochemical oxidation and reduction utilize electricity as a substitute for these chemicals, leading to a reduction in chemical usage and waste production.

In industrial-scale synthesis, the characteristics of electro-organic synthesis, particularly its applicability in waste reduction, become increasingly important. However, scaling up electrochemical reactions presents a hurdle, as the reaction occurs on the surface of the electrodes, necessitating larger electrode surface areas. According to the square-cube law, as the reaction scale increases, the ratio of the electrode's surface area to the reaction volume decreases proportionally. This implies a physical limitation to scaling up electro-organic reactions.

To circumvent this limitation and enable scalable and sustainable synthesis, flow reactors offer a viable solution. Flow synthesis offers numerous benefits over conventional batch reactions and proves advantageous for scaling up. Flow reactors allow for the successive insertion of reactants into the reactor and subsequent passage outside, eliminating the need to enlarge the reactor to increase the reaction scale.

Herein, we report a flow electrosynthesis using a proton-exchange membrane (PEM) reactor. With the PEM reactor, water serves as the proton source for the hydrogenation and semi-hydrogenation of unsaturated compounds, as well as bis-deuterated alkenes via the semi-hydrogenation of alkynes using heavy water as a deuterium source. Additionally, we found that reductive deuteration reactions could be applicable to the dehalogenation of (hetero)aryl halides, thereby producing mono-deuterated compounds.
Electrochemical One-Pot Synthesis of Cyclic Oligoglucosamines
Authors: Endo Hirofumi , Rahman Azadur MD , Masaharu Ochi , Hamada Tomoaki , Kawano Takahiro , Sasaki Norihiko , Nokami Toshiki
Published: December 2024

Carbohydrates are known as the third chain of life, following DNA and proteins, and their roles extend beyond energy and structural materials to function as pharmaceuticals and cell recognition molecules (1. Among carbohydrates, sugar chains that undergo intramolecular glycosylation are called cyclic oligosaccharides; for example, cyclodextrins are a well-known example composed of six or more D-glucose unit. By utilizing the inclusion ability and molecular recognition ability of the cavities within cyclodextrins, applications such as drug delivery systems, functional materials, and pharmaceuticals have been developed (2. These functional developments are achieved through functional group transformations, although the adaptability of these transformations is partially challenging from the perspective of identifying the reactivity of hydroxyl groups. Therefore, for further functional development, a bottom-up synthesis starting from the monosaccharide is required.

We have been focusing on the synthesis of cyclic oligosaccharides using D-glucosamine, which has an amino group at the 2-position of the pyranose ring (3. Although cyclic oligosaccharides are essentially repetitions of the same monosaccharide, sequential synthesis is required to distinguish between elongation and cyclization, leading to redundancy in the synthetic process. Therefore, we have focused on an organic electrochemical method (4, where we can control the initiation and termination of reactions by passing electric currents. To control both elongation and cyclization in one-pot, we synthesized building blocks containing 2,3-oxazolidinone, known to change its structure from the β-form to the α-form through thermodynamically controlled isomerization using acid (5. Using this building block, we achieved the synthesis of cyclic oligosaccharides containing α-1,4-glycosidic bonds from D-glucosamine in one-pot through a combination of two-stage electrolysis and acid-induced isomerization (6 (Figure a.). We will also present the α-selective synthesis of disaccharides containing oxazolidinone protecting groups, which significantly affect the formation of the cyclic structure, and their one-pot synthesis aiming to expand the substrate scope of cyclic oligosaccharides.

We are also conducting research on establishing an electrochemical one-pot synthesis for β-1,6-cyclic oligoglucosamine, in addition to cyclic oligosaccharides containing α-1,4-glycosidic bonds. By introducing different protecting groups to the amino group of glucosamine and its hydroxyl groups, we have achieved control over the cyclic structure and polymerization degree of the products (Figure b.).

1) Varki, A. Glycobiology, 2017, 27, 3.

2) Szejtli, J. Chem. Rev., 1998, 98, 1743.

3) Nokami, T. et al., Chem. Rec., 2021, 21, 2389.

4) Baran, P. S. et al., Chem. Rev., 2017, 117, 13230.

5) Kerns, R. J. et al., J. Am. Chem. Soc., 2001, 123, 9461.

6) Nokami, T. et al., Chem. Commun., 2022, 58, 7948.

Figure 1
Development of Electrochemical Reductive C-O/C-N Bond Forming Reactions
Authors: Nokami Toshiki , Ghosh Titli , Kaizawa Hazuki , Sasaki Norihiko , Abe Manabu , Nishikata Takashi
Published: December 2024

Development of sterically congested C-O/C-N bond forming reactions are highly desired because these bonds are difficult to construct using conventional methods. Initially we have found that cesium carbonate mediates coupling reactions between α-bromocarboxyamide and alcohols and this method is useful to synthesize sterically congested C-O bonds.1 Based on our proposal of the reaction mechanism we envisioned that this reaction might proceed under electrochemical conditions. Here we report an electrochemical approach to form C-O/C-N bonds of alkyl halides and alcohols/amines under electrochemical reductive conditions.2

1T. Nishikata, et al. Angew. Chem. Int. Ed.
2021, 60, 4329-4335.

2T. Nishikata, et al. ChemElectroChem
2024, 11, e202300636.
Reductive Electrosynthesis Initiated By Mediated Oxalate Oxidation
Authors: Beeler Joshua A. , White Henry S.
Published: December 2024

Reductive electrosynthesis often requires large negative potentials, air-sensitive electrocatalysts, precious metal electrode surfaces, dry solvent, and/or a sacrificial anode. As a result, electroorganic reduction reactions remain relatively underdeveloped compared to oxidative electroorganic methods. This work introduces a novel reductive electrosynthetic method, wherein the mediated oxidation of oxalate (C2O4
2–) at a carbon electrode facilitates the homogeneous reduction of aryl halides. Specifically, the homogeneous oxidation of C2O4
2– in mixed organic/aqueous solutions by electrochemically generated 1,1-dimethylferrocenium (E
0 (DiMeFc+/DiMeFc) = 0.35 V vs Ag/AgCl) produces the strongly reducing CO2
·– (E
0 (CO2/ CO2
·–) = –2.17 V vs Ag/AgCl), capable of reducing species whose reduction potential exceeds –2.0 V. Thus, strongly reducing conditions are achieved under mild applied potentials (0.4 V vs Ag/AgCl) at a carbon electrode, thereby eliminating the need for large negative potentials, air-sensitive homogeneous electrocatalysts, and precious metal heterogeneous electrocatalysts. Additionally, the hydrogen evolution reaction serves as a convenient counter-electrode reaction eliminating the need for a sacrificial anode/oxidant. Furthermore, additions of H2O can be used to tune the reaction efficiency. Overall, this method demonstrates that reduction reactions that typically require potentials of approximately –2.0 V vs Ag/AgCl can be carried out at 0.4 V vs Ag/AgCl using an inexpensive, commercially available iron-based electrocatalyst at a carbon electrode.

Figure 1
Detection of Antibody-Antigen Interactions with Electrochemical Biosensor Based on Bipolar Phenomenon
Authors: Tochigi Arisa , Takahashi Joh , Kondo Mizuki , Kuwahara Takashi
Published: December 2024

Introduction

We propose a new biosensor based on the bipolar phenomenon. The bipolar phenomenon polarizes a conductor (bipolar electrode, BPE) inserted into an electric field formed between driving electrodes (DEs) connected to an external power source. Electrochemical biosensing using the bipolar phenomenon for detecting biomolecules has recently been reported. In biosensing, BPE separates the molecular recognition site from the detection site. This feature is scalable and enables the exploration of new detection reactions. Therefore, the bipolar phenomenon shows potential as a new tool for biosensors. Here, we demonstrate the electrochemical biosensor with a simple design using an open BPE. The biosensor detects C-reactive protein (CRP) by electrochemical impedance measurement under non-faradic conditions.

Experimental

Gold electrodes (10 mm × 10 mm) were immersed in 10 mM 3-mercaptopropionic acid (MPA) solution for 1 h to form an MPA self-assembled monolayer. The carboxyl groups of the MPA monolayer were treated with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (0.2 M/0.1 M). Subsequently, the electrodes were incubated with 10 µg/mL of anti-CRP antibody in 0.1 M phosphate buffer (PB, pH 7.0) to immobilize the antibody. Following the blocking treatment, the electrodes were exposed to 10 μg/mL CRP in 0.1 M PB at 37°C for 0-2 h to react with CRP. For impedance measurements, Pt-black-coated gold wires were used as the DEs and connected to an impedance analyzer. The BPE was placed at the bottom of an electrochemical cell filled with 0.1 M PB (pH 7.0), and the DE was positioned directly above the BPE (refer to Fig. 1A). The measurements were performed in a frequency range from 1 Hz to 8 MHz, with an amplitude of 0.1 V and a DC bias voltage of 0 V.

Results and Discussion

Figure 1B shows the relationship between CRP immobilization time and impedance value at 1 kHz. A linear decrease in impedance was observed during the immobilization time of 0-1 h, which caused the increased in capacitance of the BPE surface resulting from the increased amount of immobilized CRP. Over 1 h of immobilization, the impedance change slowed down, indicating the saturation of CRP immobilization. These results suggest that the sensor developed in this study detects the antigen-antibody reaction on the BPE through impedance change.

Figure 1
Whole-Cell Controlled Living Polymerization By Electrochemically-Active Bacteria
Authors: Fan Gang
Published: December 2024

Bacteria produce a variety of soft materials, but they are limited in their structure and function. A synthetic system in which the power of bacterial engineering is combined with traditional organometallic catalysis could pave new avenues to polymer synthesis. Here we demonstrate that the electroactive bacteria Shewanella oneidensis can control the activity of a transitional-metal catalyst in atom-transfer radical polymerization (ATRP) through extracellular electron transport (EET) machinery. This polymerization features characteristics of controlled radical polymerization, such as first-order kinetics, narrow molecular weight distribution and block-polymer synthesis. Catalyst performance and polymer microstructure were a strong function of bacterial metabolism, specific electron transport machinery, and catalyst design. Moreover, different bio-renewable and bio-friendly energy sources, such as lactate, glucose, pyruvate and xylose, could be utilized to control the rate of polymerization process. Overall, our results demonstrate that targeting biological electron transport pathways may combine the advantages of metabolic engineering with traditional polymer synthesis.
(Invited) Bi-Functionalized Extinguishable Separator with Non-Flammable Microcapsules for Highly Safe Lithium Ion Batteries
Authors: Kim Ki Jae , Kim Ki Jae
Published: December 2024

Although the lithium ion batteries (LIBs) is a most prospective energy storage system, poor safety characteristics of LIBs is considered as one of challengeable issue for successful expansion of applications in the near future. In this work, microcapsule functionalized with non-flammable additive is investigated to prevent thermal runaway during electrochemical process through utilization of extinguishable additive. The microcapsule is prepared by optimized reaction condition and they are characterized by a various spectroscopy tools including SEM, TEM, 19F-NMR spectroscopy. The microcapsule showed much improved thermal stability in terms of onset temperature and heat generations and it does not significantly affect electrochemical performance analyzed by LSV and evaluation of cycle performances. In addition, the effect of microcapsule is clearly probed by nail-tests of 200 mAh full-cell (graphite/NCM52) – the cell cycled with microcapsule showed less maximum temperature and potential drop compared to its corresponding analogues. With these results, it can be concluded that the microcapsule is greatly effective in increasing safety of LIBs and we believe that these insights will help to construct more efficient LIBs.
(Invited) Key Factors of Ni-Rich Materials from the Perspective of Crystal Structure for Realizing High-Performance Electric Vehicles
Authors: Lee Wontae , Yoon Won-Sub
Published: December 2024

The advancement of Ni-rich layered cathode materials has accelerated the growth of the electric vehicle market. Yet, achieving the requisite rate-performance and thermal stability poses ongoing challenges, critical for meeting the demands of modern electric vehicles. Addressing these challenges requires a deep understanding of the structural behavior during high-rate cycling and thermal decomposition reactions. We demonstrate that Ni-rich layered materials exhibit different lattice strain depending on charge and discharge during high-rate cycling, which is confirmed by discontinuous XRD patterns during de-intercalation and intercalation reactions. This intrinsic property necessitates various perspectives for charge and discharge to optimize rate performance. Additionally, we investigate the structural behaviors of Ni-based layered materials across three different states-of-charge during heating. Notably, thermal decomposition reactions are not solely contingent upon the state-of-charge. The onset temperature for disordered spinel structure formation is influenced by the size of intermediate tetrahedrons, while completion temperature depends on the Li contents of the Li layer. Furthermore, a highly charged state accelerates Ni ion reduction, causing sudden expansion of the crystal structure during thermal decomposition, exacerbating thermal runaway risks. From this structural analysis, we underscore the importance of understanding factors that enhance rate characteristics and thermal stability in Ni-rich materials for realizing high-performance electric vehicles.
(Invited) New Form-Factor Li-Ion Batteries for Electric Vehicles
Authors: Lee Jung Tae
Published: December 2024

The advent of innovative form factor batteries represents a transformative milestone within the energy storage sector, owing to their capacity for enhanced energy density. This advancement is poised to substantially elevate the range of electric vehicles, marking a significant leap forward in sustainable transportation technology. Lithium-ion battery fibers, serving as the foundational components for arbitrarily-shaped 3D objects, offer unique prospects for the creation of pervasive, multidimensional power systems. A principal challenge within the field of fiber-shaped batteries is achieving lengths akin to those of conventional textile fibers, which is essential for extending energy capacity and scaling up for practical applications. This talk will present an innovative approach to creating Li-ion batteries that are integrated within system-level fibers. This strategy enables the production of long fibers that exhibit high functionality, flexibility, printability. Moreover, the talk will cover various challenges encountered throughout the different phases of development, along with the corresponding solutions implemented to overcome these obstacles.
A New Approach to Synthesis of Porous Si Anode for Li-Ion Batteries Via Organic-Solvent Assisted Etching
Authors: Jin Dahee , Kim Ju-Myung , Yi Ran , Zhang Ji-Guang
Published: December 2024

Silicon (Si) has been regarded as a promising anode for Li-ion batteries due to its high theoretical capacity (4200 mAh/g) compared to graphite anode (372 mAh/g). However, it undergoes significant volume changes (~ 300%) during lithiation and delithiation, leading to particle pulverization and continuous electrolyte decomposition on Si surface, which hinders its practical application. The porous silicon obtained by wet etching method using hydrogen fluoride (HF) can accommodate the volume changes and improve the overall performance of silicon anodes. However, HF etching is highly corrosive, leading to the generation of excess heat and bubbling, lower yields, and difficult to scale-up. Furthermore, the water in etchant oxidizes the newly exposed Si, generating more SiOx, which also cause over-etching of Si and worsen electrochemical performance.

Herein, we report an organic-solvent assistant etching process for Si anode. In this process, selected organic solvent were mixed with the HF etchant. When micron sized Si/SiOx powder was added to the solution, the organic solvent in the mixed solution will preferentially be absorbed on the surface of Si/SiOx powder and form a shield which can enable controlled etching of silicon oxide (SiOx) and prevent direct contact between water and newly etched Si surface. This method leads to controllable etching of Si and avoids bubbling/overheating, results in a higher Si yield. The maximum temperature during the etching process is less than ~30°C. The various process parameters, including etchant composition, stirring speed, and time have been optimized to maximize the yield and electrochemical performance of the Si anode. A Si-based anode with organic-solvent assisted etching process has demonstrated improved cycling performance in a Si||Li(Ni0.6Co0.2Mn0.2)O2 (NMC622) full cell. It also leads to low swelling in both particle and electrode levels required for the next generation of high-energy LIBs. Similar organic-solvent assisted etching process can also be used in safe-etching of a broad range of materials.
(Invited) Unveiling Olivine Cathodes for High-Energy-Density Lithium-Ion Batteries: Engineering from the Atomic Level to the Electrode Scale
Authors: Hwang Wonchan , Kim Jaehwan , Park Jungjin
Published: December 2024

The pursuit of high energy density has spurred significant interest in layered cathodes such as lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminium oxide (NCA), renowned for their excellent energy storage capabilities. However, Ni- and Co-based layered cathodes face significant thermal instability, resulting in thermal runaway in the case of short circuits, high temperature exposure, and so forth. Recently, lithium iron phosphate (LFP) has emerged as an alternative due to its enhanced structural and thermal stability, despite the absence of expensive metals such as Co and Ni. However, LFP encounters significant challenges, notably its inherently low redox potential and capacity (energy density), which undermines its competitiveness in electric device applications such as electric vehicles (EVs) and energy storage systems (ESSs). Boosting energy density can now be accomplished through the engineering of active materials and electrode configurations. It has been noticed that new strategies, such as increasing the working voltage through fine-tuning of active materials and/or using thick electrodes to augment the ratio of active materials per unit area, can make a breakthrough for elevating energy density within the existing battery volume dimension. However, transitioning to thick electrodes poses challenges related to electron and ionic conductivity, as well as the structural stability of the electrode.

Herein, I will present integrating strategies for enhancing the high-energy density of olivine cathodes. This includes atomic modifications such as substitutional doping with manganese to achieve a high redox voltage, and particle/electrode engineering techniques like optimizing tap and press density. In addition, I will briefly show key technologies involving conducting agents and binders used to construct thick electrodes for olivine cathodes through eco-friendly processes. A comprehensive understanding will provide insights into how to conduct research on olivine-based cathodes and contribute to the impacts of secondary batteries in both academia and industry.
Engineering Surface Oxidation States in Co-Free, High-Ni Core/Shell Cathode Precursors: Impact on Physicochemical Properties and Lithium-Ion Battery Performance
Authors: Shim Jinha , Bang Jin Ho
Published: December 2024

This work explores the core/shell structure (Ni-rich core, Mn-rich shell) as a promising approach to improve interfacial stability in high-nickel cathode materials. This structure reduces surface reactivity without sacrificing capacity. Traditionally, co-precipitation is used to synthesize these materials. Here, we investigate the impact of manganese (Mn) oxidation state during drying on the physicochemical and electrochemical properties. We focus on how this state depends on the sintering temperature. Our findings reveal that the presence of oxidized Mn in the precursor lattice can mitigate further transition metal (TM) oxidation at lower sintering temperatures. This also induces oxygen vacancies on the particle surface. However, this leads to poor electrochemical performance due to two factors: the magnetic frustration effect and the “cross-talk effect” caused by TM dissolution and deposition on the graphite anode. In contrast, higher sintering temperatures promote complete Mn oxidation in the precursors. This kinetically suppresses Mn diffusion, preserving the core/shell structure and minimizing surface defects. This approach also demonstrably suppresses the cross-talk effect.

This study highlights the profound influence of surface Mn oxidation state in core/shell high-nickel cathode material precursors. The oxidation state impacts surface properties, intrinsic characteristics, and reaction kinetics during heat treatment. Consequently, this research emphasizes the critical role of precursor surface chemistry and offers valuable insights for developing strategies to enhance cathode material interface stability.

Keywords: Ni-rich cathode / Core-Shell structure / Precursor surface oxidation / Transition metal dissolution / Magnetic Frustration
Improving the Electrochemical Performance of Sb-Modified Ni-rich NCM Cathode Materials for Lithium-Ion Batteries
Authors: Kim Hyun-Soo , Sim Seong-Joo , Jin Bong-Soo
Published: December 2024

Ni-rich layered LiNixCoyMn(1-x-y)O2 (Ni-rich NCM) (x≥0.8) cathode materials have recently attracted much attention for high energy density lithium ion batteries(LIBs) owing to their high reversible capacity (>200 mAh g-1), relatively high operating voltage (3.6 V vs Li/Li+) and low cost. However, the cycle life and safety become more serious with increasing Ni contents. It can be caused by various problems such as phase transitions during charge-discharge, surface side reaction and the reaction of Ni4+ and oxygen release resulting in destroy the crystal structure.

To overcome these problems, various strategies have been researched such as doping, coating, core-shell, concentration-gradient structure and single-crystal. Among these methods, doping method is a beneficial way to enhance the structural stability of the materials to prevent deterioration of the crystal structure. The dopants improve the Li+ transport and suppress the cation mixing by preventing the migration of Ni2+ to the Li layer and inhibit oxygen release by strengthening TM-O bond.

Various elements (such as Al, Ti, Zr, Mg, Fe, F, etc.) has been modified by substituting the transition metal sites. Antimony can be an attractive candidate as a dopant material because of similar ionic radius and bond strength compared with Ni ions. It indicates that Sb can be substituted for Ni sites.

In this work, Sb-modified Li[Ni0.91Co0.06Mn0.03]O2 (denoted as Sb-NCM) was synthesized by solid-state method to improve the structure stability resulting in cyclic stability during charge-discharge. The Sb-NCM exhibited improved cycling retention and rate capability compared to the pristine NCM. The effect of Sb-NCM on the structural characteristic, morphology and electrochemical properties was investigated. The results indicate that the doped Sb performs an important role for enhanced electrochemical performance.
Dry Battery Electrode Manufacturing for Graphite Anodes: Implications on Electrochemical Properties and Cell Manufacturing
Authors: Huber Korbinian , Scheidle Christian , Wichmann Moritz
Published: December 2024

Dry Coating of Lithium-Ion Battery electrodes is widely considered as a gamechanger technology to reduce the cost, energy demand and footprint of battery Gigafactories. By now, industrialization has primarily focused on the negative electrode using graphite and as active material, notably by Tesla.[1] Yet, the full scope of the implications and advancements brought by a dry coating process for graphite anodes on cell properties and downstream manufacturing processes remains unexplored.

Current dry coating technologies necessitate using a fibrillizable PTFE binder. While PTFE is very stable towards oxidation when used as a binder in Lithium-Ion Battery cathodes, a reduction of the fluoropolymer in battery anodes at low potentials < 1 V vs. Li/Li+ is reported.[2] We discuss the decomposition reaction of PTFE in graphite anodes during the formation process and the resulting irreversible consumption of Li. Our interest focuses on the decomposition mechanism of PTFE, examining the nature of the decomposition products through XPS analysis. We assess whether the reduction is quantitative and if the decomposition persists beyond the initial lithiation of graphite into subsequent cycles. We contemplate strategies to reduce the irreversible capacity loss and show that reducing the PTFE binder content while maintaining the mechanical integrity of the electrode is a promising approach to enhance the coulombic efficiency during formation.

Beyond the electrochemical implications, differences in microstructural properties and the processing conditions during electrode manufacturing between a wet and a dry coated graphite anode offer opportunities for adaptions in the downstream process of Lithium-Ion Battery manufacturing. We demonstrate that the electrolyte filling time of cylindrical cells in a 4695-format is strongly influenced by the coating method and the arising differences in pore size distribution and electrode tortuosity. Also, we show that a vacuum drying of the anodes might not be needed if the electrode is dry coated instead of using water as the solvent for a slurry-based coating.

[1] https://www.youtube.com/watch?v=8WPPBhqeekw

[2] Y. Suh, J. K. Koo, H. Im, Y.-J. Kim, Chemical Engineering Journal
2023, 476, 146299.
Green Energy Solutions: Metal-Free ORR Electrocatalysts from Mandarin Peel Waste
Authors: Lee Nayeon , Lim Sung Yul
Published: December 2024

To meet the growing energy demand, the use of fossil fuels has also increased with concerns for environment issues. Therefore, the need for research and development into replacing energy sources with renewable alternatives has become more prominent. Not only is it merely producing renewable energy but it is also crucial to develop energy conversion and storage systems. Zinc-Air-Batteries (ZABs) are considered one of the most promising, stable, efficient, and environmentally-friendly energy storage devices with high theoretical energy density (1,218 Wh kg-1). The sluggish kinetics of the 4-electron reaction at the air electrode is a key limiting factor in determining the performance of ZAB. Replacing the scarce and high-cost Pt-based ORR electrocatalysts is essential for the large-scale commercialization of ZABs. Therefore, metal-free carbon-based catalysts gained attention due to cost-effectiveness, environmental-friendliness, and high ORR performance. In this regard, we report a metal-free carbon-based catalyst obtained by mandarin-peel-waste(MPW) upcycling, doped with nitrogen. The optimized MPW catalyst indicated high porosity which facilitates the access of reactants to the N-doped active sites. Additionally, the catalyst exhibited high ORR activity and 4-electron reaction selectivity. Durability and stability were confirmed through accelerated stability test(AST) during consecutive 40,000 cycles. We expect that our catalyst can be effectively utilized as an ORR catalyst for ZABs in the future.
Tracking Water Dissociation on Well-Defined Ruthenium Oxide Surfaces
Authors: Reese Austin Jerad , Gelin Simon , Maalouf Maria , Wadehra Neha , Schlom Darrell , Dabo Ismaila , Suntivich Jin
Published: December 2024

The interaction between interfacial water and metal oxides represents an important first step in the oxygen evolution reaction (OER). RuO2 is a well-known OER electrocatalyst; however, its active state remains elusive. We will discuss an atomic force microscopy (AFM) investigation on the RuO2(110) surface held at various potentials. We use this result to study how RuO2 surfaces change during OER. We further image water dissociation into OH* (* denotes adsorbed species) and O* species. Starting from surface-bound water, which manifests as a row of surface-bound molecules, increasing the oxidative potential transforms these adsorbates into OH* and O*. This oxidative step also changes the pattern of the surface-bound molecules. We use these results to map the surface phase diagram of RuO2(110) and provide an interpretation of its cyclic voltammetry.
(Invited) Synthesis of Oxyhalides and Exploration of Their Photocurrent Response
Authors: Wei Wei
Published: December 2024

While energy needs constantly increase around the world, the depletion of fossil fuels and increased environmental impairment by classic energy production methods have turned the attention towards renewable energy sources. Hydrogen (H2), a very promising fuel with high energy capacity and no secondary pollution arising from its combustion, has attracted the interest of the research community, which is focused on green and reliable methods for its production and storage. Photocatalysis is an affordable and environmentally friendly technology for H2 production based on great sustainable sources. In this talk. four heteroanionic oxyhalides, CeClMoO4, CeBrMoO4, CeClWO4, and CeBrWO4, have been studied as multifunctional materials, which combine good second harmonic generation (SHG) response and photocurrent signals. Their potential as photocatalyst is also explored.
Developments in Nanostructuring for Enhanced Solar Water Splitting: Investigating Morphology Effects on Photoelectrode Performance
Authors: Jeong Hye Won , Park Hyunwoong , Janaky Csaba
Published: December 2024

The importance of developing efficient technologies for converting solar energy into chemical energy has drawn attention, particularly through solar water splitting using photocatalytic materials. It highlighted the complexity of factors affecting the performance of photoelectrodes in this process, including bandgap energy, carrier density, morphology, defects, and surface properties. Among them, nanostructuring in photoelectrodes offers the potential for improved efficiency due to their large specific surface area and accelerated charge transfer. Despite more than a decade of dedicated research into the impact of nanoscale morphology on the photoelectrochemical (PEC) performance of semiconductor materials, the literature still contains notable disparities and debates. This study aimed to provide clarifying comparisons of the effect of the shape and dimensions of particles in a photoelectrode. It explores various synthetic methods to control morphology, using titanium dioxide (TiO2) as a model material for testing. Surface analysis via XRD, Raman spectroscopy, XPS, etc. demonstrated that the chemical nature of the nanostructures is practically identical, and only morphology offers a difference in PEC performance. A comparison of morphology effects of PEC activities in sulfite and water oxidation gave insight into the dependence on particle morphology.

This research was supported by the National Research Foundation of Korea (NRF-2022R1I1A1A01053034 and RS-2023-00254645).
(Invited) Semi-Monolithic Integration of Dissimilar Material Classes into Efficient Water Splitting Devices
Authors: Gaillard Nicolas
Published: December 2024

Materials compatibility is an important issue in multi-junction (MJ) device integration, which has stifled innovation in photoelectrochemistry (PEC) for decades. Essentially, the deposition process of each layer must not damage the previously deposited layers and interfaces in any way. For example, with state-of-the-art chalcopyrite technology, it is impossible to fabricate high-efficiency monolithic MJ devices by directly depositing a wide-bandgap cell on top of a narrow-bandgap CIGSe device, because the required temperatures for high quality films (Tprocess = 500oC) destroy the underlying CdS/CIGSe heterojunction. As a result, the power conversion efficiency (PCE) of monolithically integrated chalcopyrite solid-state tandems has not exceeded 4.3%. The limitation of monolithic integration goes far beyond the chalcopyrite class, as it inherently restricts materials selection to a sub-set of compatible systems while limiting the adoption of emerging promising candidates. An integration scheme in which material classes can be combined, regardless of their nature, while preserving their intrinsic performance could revolutionize manufacturing technologies that rely on material stacking and lead to combinations of different material classes previously not considered for PEC water splitting.

In this communication, we report on our recent efforts to develop a novel and scalable integration scheme to combine promising material classes, regardless of their thermal, physical, or chemical compatibility, into low-cost MJ PEC devices. Such a scheme, pioneered by HNEI and known as semi-monolithic integration, relies on 2D layer-assisted exfoliation and room temperature bonding techniques to transfer fully processed cells from their original substrates onto new handles. With this integration scheme, sub-cells of different bandgaps can be successively transferred onto a new host substrate to create a fully functional MJ structure. By design, semi-monolithic integration allows to circumvent all material incompatibilities, enabling new MJ architectures otherwise not possible with conventional monolithic integration.
(Invited) Gallium Nitride: An Industry Ready Platform for Scalable Artificial Photosynthesis
Authors: Mi Zetian
Published: December 2024

In this talk, I will present recent advances of artificial photosynthesis utilizing gallium nitride (GaN), which is the second most produced semiconductors next only to silicon. Through nanoscale, quantum, and catalyst engineering, conventional GaN-based semiconductors can be transformed to be highly efficient and stable photocatalyst materials for a broad range of artificial photosynthesis reactions, including solar water splitting, carbon dioxide reduction, methane oxidation, and nitrogen reduction to ammonia. By growing GaN nanostructures under N-rich conditions, the nonpolar surfaces can be transformed to be gallium oxynitride during harsh photocatalysis reaction, which not only protects the surfaces of the light absorber but leads to significantly enhanced photocatalytic and photoelectrochemical performance. Moreover, we have developed unique photocatalytic processes wherein high efficiency solar hydrogen can be produced utilizing tap water, or seawater, without any wire connection, or electricity input. The demonstration of large-scale solar water splitting systems and the performance will be discussed and reported, together with advances in carbon dioxide and nitrogen reduction to clean chemicals and fuels.
(Invited) Photocatalytic and Photoelectrochemical Systems for Nitrogen Cycles
Authors: Choi Wonyong , Lee Shinbi , Zhao Shen , Pan Donglai
Published: December 2024

The chemical transformation of N species plays important roles in the global environmental systems and their interconversion involves key compounds such as nitrate, nitrite, and nitric oxide, which are major water and air pollutants. The photocatalytic and photoelectrocatalytic processes have been applied to denitrification, de-NOx, and nitrogen fixation reactions but the successful performance is limited. The direct conversion of nitrogenous pollutants to dinitrogen and dinitrogen to ammonia without using chemical reductants is an ideal solution but difficult to be realized. Here we introduce various engineered photo(electro)catalytic systems that selectively interconvert among NO3
−, NO2
−
,NO, NH4
+, and N2. Firstly, a ternary composite photocatalyst composed of TiO2, bimetals, and reduced graphene oxide (rGO) is developed and tested for chemical reductant-free solar denitrification. Direct transformation of nitrate to N2 occurs via using in-situ H2 generated from water splitting with achieving near 100% conversion and selectivity to N2 under both anoxic and oxic conditions. Secondly, a PEC system that converts NO to nitrate and ammonium on an anode and a cathode simultaneously is described. Finally, the direct NO conversion to N2 and O2 is successfully demonstrated by developing oxygen-deficient titania as a photocatalyst working under visible light.
(Invited) Exploring Electrochemical Methods to Enhance Catalytic Activity and Selectivity in Photoelectrochemical CO2 Reduction
Authors: Nam Ki Min , Ma Ahyeon , Seo Dongho
Published: December 2024

Various electrocatalysts have undergone extensive examination regarding their capacity to selectively produce desired products via the electrochemical CO2 reduction reaction (CO2RR). Nonetheless, the efficiency of a CO2RR electrocatalyst does not guarantee the effectiveness of a co-catalyst on the semiconductor surface for photoelectrochemical CO2RR. Herein, we synthesize Bi2S3 nanorods and electrochemically reduce them to Bi nanoplates that adhere to substrates for use in electrochemical and photoelectrochemical CO2RR applications. Compared with bare Bi, the Bi2S3-derived Bi (S-Bi) nanoplates on carbon paper exhibit superior electrocatalytic activity and selectivity for formate (HCOO-) in the electrochemical CO2RR, achieving a Faradaic efficiency exceeding 93%, with minimal H2 production over a wide potential range. This highly selective S-Bi catalyst is being employed on the Si photocathode to investigate the behavior of electrocatalysts during photoelectrochemical CO2RR. The strong adhesion of the S-Bi nanoplates to the Si nanowire substrate and their unique catalytic properties afford exceptional activity and selectivity for HCOO- under simulated solar irradiation. The selectivity observed in electrochemical CO2RR using the S-Bi catalyst correlates with that seen in the photoelectrochemical CO2RR system. Combined pulsed potential methods and theoretical analyses reveal stabilization of the OCHO* intermediate on the S-Bi catalyst under specific conditions, which is critical for developing efficient catalysts for CO2-to-HCOO- conversion. These results emphasize the potential of S-Bi as an effective catalyst for CO2 reduction reactions and provide valuable insights into optimizing the reaction mechanisms and enhancing the product selectivity, especially in conjunction with co-catalysts for Si photocathodes.
Visible-Light-Driven Oxygen Reduction By an Anisotropically Crystallized CuBi2O4 Photocathode Synthesized Using a Mixed Metal-Imidazole Casting Method
Authors: Yagi Masayuki , Zahran Zaki , Tsubonouchi Yuta , Chandra Debraj , Hoshino Norihisa
Published: December 2024

An anisotropically crystallized CuBi2O4 (CuBi2O4(w)) film adhering rigidly on a fluorine doped tin oxide (FTO) electrode was prepared by a mixed metal-imidazole casting (MiMIC) method using 1-methylimidazole (MeIm). MeIm acts as a binder among metal oxide nanoparticles to result in tightly-interconnected angular nanoparticles, as well as a structure-directing agent for growth of the anisotropically crystallized CuBi2O4 film. The photoelectrochemical (PEC) oxygen reduction reaction (ORR) at the CuBi2O4(w) electrode was investigated to compare with the electrode ((CuBi2O4(w/o)) prepared without MeIm in a similar manner. The photocurrent for ORR at the CuBi2O4(w) electrode under O2 in liner sweep voltammetry (LSV) was generated at an onset potential (E
on) of 0.96 V vs. RHE. The photocurrent decreased immediately for the CuBi2O4(w) electrode in chronoamperometry (CA) under Ar, being ascribable to reductive decomposition of the CuBi2O4(w) film. However, under O2, the photocurrent remained for 1 h (4% decrease) due to ORR proceeding stably at the CuBi2O4(w) film. The high selectivity of ORR to produce water was confirmed at the CuBi2O4(w) electrode, despite 8.0 % hydrogen peroxide production after the 1 h photoelectrolysis under O2. The IPCE value (21.0%) at 440 nm and 0.41 V vs. RHE for ORR at the CuBi2O4(w) electrode was 2.2-fold higher than that (9.6%) at the CuBi2O4(w/o) electrode. The photoelectrochemical impedance spectroscopic (PEIS) measurement suggested the faster ORR at the surface of the CuBi2O4(w) electrode, likely resulting from the anisotropic crystallization of tetragonal CuBi2O4, which is responsible for the high IPCE and stability for PEC ORR at the CuBi2O4(w) electrode.