bluuebunny/crossref_metadata_2025 huggingface dataset:
Cathode Reaction Studies in Lithium-Oxygen Battery through Operando XRD Measurements
Authors: Dilixiati Dilinigeer , Aoki Makoto , Maeda Kazuno , Kondo Toshihiro
Published: December 2024

Introduction

The lithium-Oxygen (Li-O2; LOB) battery has obtained significant attention as a promising candidate for next-generation storage batteries due to its higher specific energy density compared to conventional lithium-ion batteries [1]. However, the mechanism of the cathode reaction remains unclear, and the type of Li2O2 produced during cathode discharge is still uncertain, mainly because it's challenging to directly observe the compounds generated at the cathode during LOB operations. By newly designing observation cells and improving laboratory XRD system, we clarified the discharge products and investigated the discharging process using operando XRD measurements and Rietveld refinements[2]. In this study, the cathode reaction mechanism was discussed based on the results of the operando XRD measurements.

Experimental

A newly designed electrochemical cell, covered with a Kapton film dome to enable constant oxygen flow to the cathode side of the LOB, was set to the diffractomator of the Rigaku Ultima IV XRD measurement system. In the XRD system, Cu Kα was utilized as the incident X-ray, and high-speed one-dimensional detector served as the detector. In the electrochemical cell, Ketjen black self-standing films were employed as cathode materials, and tetraglyme solution containing 0.5 M LiTFSI + 0.5 M LiNO3 + 0.2 M LiBr was used as the electrolyte solution. The LOB was discharged and charged at a constant current density of 0.4 mA/cm2 for 10 hours each (4.0 mAh/cm2), in which XRD profiles were recorded every 20 minutes. Rigaku's SmartLab Studio II software was utilized for Rietveld analysis of each XRD profile to determine the detailed cathode product and its crystal structure.

Results and discussion

Upon conducting operando XRD measurements and Rietveld analyses, the cathode reactions of the Li-O2 battery were investigated. The discharging and charging reactions at the cathode of the Li-O2 battery, as well as the x values of the major product Li2-xO2 during discharging, have been investigated and determined. In the XRD profile measured during discharging, several peaks attributed to the cathode product were observed. Detailed Rietveld analysis of these peaks revealed that LiO2 with the same P63/mmc space group structure as Li2O2 was immediately formed after discharge initiation, followed by the deposition of Li2-xO2 accompanied by an increase in lithium occupancy. As discharging progressed, the lattice constant gradually extended towards the c-axis direction, leading to the formation of Li1.5O2 at a discharge capacity of 4.0 mAh/cm2. In this presentation, we will discuss the discharge and charge reactions of the Li-O2 battery cathode in detail, and we will also discuss the charge-discharge cycle characteristics.

References

[1] T. Liu, et al., Chem. Rev.
120, 6558 (2020).

[2] M. Aoki and T. Kondo, et al., J. Phys. Chem. C
127, 15051 (2023).
MOF-Derived Carbons Coupled CdSe Quantum Dots for Solar Hydrogen Production
Authors: Wang Chien-Yi , Hsu Yung-Jung
Published: December 2024

Metal-organic framework (MOF)-derived carbons have increasingly captivated the scientific community, owing to their remarkable attributes such as mesoporous configurations, enhanced electron conductivity, and robust chemical stability. This study introduces a novel low-temperature synthesis approach for ZIF-67-derived carbons, further augmented by integration with CdSe quantum dots to boost photocatalytic efficiency for solar hydrogen production. Through detailed analysis using time-resolved photoluminescence spectroscopy and in-situ X-ray absorption spectroscopy, the electronic synergies between ZIF-67-derived carbons and CdSe quantum dots were thoughtfully explored. The resultant composites demonstrated a photocatalytic hydrogen production rate of 10.4 mmol g-1 hr-1, showcasing significant apparent quantum yields of 8.1% at 300 nm and 6.4% at 420 nm. Recycling assays revealed a superior chemical durability, effectively mitigating the typical photocorrosion issue of CdSe when coupled with ZIF-67-derived carbons. This investigation presents a groundbreaking paradigm in photocatalyst design, merging MOF-derived carbons with semiconductor nanostructures to advance the field of photocatalytic applications.
(Invited) Unassisted Conversion of Carbon Dioxide and Water into Aliphatic Acids Using Copper and Iron Oxide Photocatalyst Film at Solar-to-Chemical Conversion Efficiency of ~5%
Authors: Park Hyunwoong
Published: December 2024

Harnessing and utilizing sunlight at high efficiency have represented an enormous challenge to the achievement of a carbon neutral society over the past four decades. Photocatalysis uniquely mimics natural photosynthesis in terms of light absorption and conversion, as well as storage of the absorbed photon energy into chemical bond energy. Despite this similarity, the development of low cost photocatalysts capable of selectively producing liquid chemicals from CO2 and water with efficiency and durability comparable to those in typical photosynthesis remains a great challenge. Most of the photocatalyst suspension systems produce mixtures of gas and liquid products at poor efficiencies, whereas electrically biased film systems exhibit a near-commercial gas production efficiency, albeit only for disappointingly short periods. Herein, we report the facile, environmentally benign synthesis of CuFeO2 and CuO binary films via electrodeposition, and demonstrate that these binary films produce only liquid aliphatic acid anions (C1-C6) from aqueous CO2 at energy efficiency exceeding natural photosynthesis, while driving O2 evolution from water on a wired Pt plate under continuous irradiation of simulated sunlight over 24 h. An as-synthesized photocatalyst film with a three-dimensional, double-layer configuration further shows the continued production of C1 for over 17 days. However, the crystalline structure and elemental state of the used photocatalysts undergo gradual chemical reduction. Such a deformation can be thermally healed by recycling the weekly used samples via oxidative annealing. Thus, a single photocatalyst sample produces formate continuously for 35 days. The photocatalyst components (Cu, Fe, and O) are earth-abundant, and the photocatalyst synthesis is straightforward, facile, environmentally benign, reproducible, and scalable. On achieving higher efficiencies in the future, the practical applicability of these photocatalysts will become enormous.
Nanoconfinement Enables Photoelectrochemical Selective Oxidation of Glycerol Via the Microscale Fluid Effect
Authors: Liu Tae-Kyung , LU Yuan , Park Jong Hyeok
Published: December 2024

The glycerol oxidation reaction (GOR) run with photoelectrochemical cells (PECs) is one of the most promising ways to upgrade biomass because it is thermodynamically favorable, while irreversible overoxidation leads to unsatisfactory product selectivities. Herein, a tunable one-dimensional nanoconfined environment was introduced into the GOR process, which accelerated mass transfer of glycerol via the microscale fluid effect and changed the main oxidation product from formic acid (FA) to glyceraldehyde (GLD), which led to retention of the heavier multicarbon products. The rate of glycerol diffusion in the nanochannels increased by a factor of 4.92 with decreasing inner diameters. The main product from the PEC-selective oxidation of glycerol changed from the C1 product FA to the C3 product GLD with a great selectivity of 60.7%. This work provides a favorable approach for inhibiting further oxidation of multicarbon products and illustrates the importance of microenvironmental regulation in biomass oxidation.
Growth and Photoelectrochemical Characterization of Epitaxial ZnTe Photocathodes for Carbon Dioxide Reduction
Authors: Shiau Lily , Lee Sola , Atwater Harry A.
Published: December 2024

We report on the growth and photoelectrochemical (PEC) characterization of single crystal, epitaxial zinc telluride (ZnTe) thin film photocathodes. ZnTe is a II-VI semiconductor that has promising photocathode characteristics, including its suitable band gap alignments to CO2 reduction potentials, chemical stability, strong p-type character, and is theorized to have surface sites suitable for CO2 reduction. To gain a deeper understanding of the fundamental charge transport of the reactivity mechanism for ZnTe, we utilized molecular beam epitaxy (MBE) to grow single crystal thin film photocathodes. This work focuses largely on the synthesis and characterization of degenerately-doped ZnTe films on three different gallium arsenide (GaAs) substrate orientations: (100), (110), and (111)A. ZnTe thin films with a thickness of 300 nm, grown in the temperature range of 340–360ºC, were doped with nitrogen via an in situ RF plasma source and characterized by RHEED, XRD, AFM, and Hall effect measurements. The epitaxial films exhibited p-type characteristics with doping concentrations of 1018 to 1020 cm-3. Photoelectrochemical stability and catalytic selectivity of the ZnTe photocathodes were investigated in a three-electrode compression cell in a CO2-saturated electrolyte (0.1 M KHCO3). Utilizing degenerately doped (100) ZnTe, we have demonstrated high (60%) selectivity for CO2 reduction to CO in the absence of cocatalysts. Overall, we showed the correlation between the CO2R selectivity and ZnTe orientation and this work can be leveraged for developing catalyst-free tandem ZnTe-based photocathodes for carbon dioxide reduction.
(Invited) Predicting Interfacial Ion Adsorption, Ion Solvation, and Correlated Ion Transport in Advanced Electrolytes
Authors: Son Chang Yun
Published: December 2024

Electrostatic interactions plays a dominant role in charged materials systems. Understanding the complex correlation between macroscopic properties with microscopic structures is of critical importance to develop rational design strategies for advanced materials. But the complexity of this challenging task is augmented by interfaces present in the system, requiring a multi-scale approach to incorporate the spatiotemporal resolution needed for molecular descriptors and the interfacial heterogeneity.

In this talk, I’ll present our ongoing efforts to enable predictive molecular simulations of these highly charged systems, especially focusing on the field of developing advanced electrolytes. A key advancement has been made with the development of predictive multi-scale force field for Li+ solvating electrolytes, ionic liquids (ILs), and polymers based entirely on first-principle calculation, as well as novel simulation algorithm to treat the complex surface polarization effect occurring at the conducting electrodes. New physical insights gained from the new simulation model and simulation algorithms will be discussed, which includes simulation study of lithium ion transport under nanoscale confinement formed by microphase separation, and controlling morphology and interfaces to enhance the mechanical and dynamic properties of novel polymer-IL mixture system for energy application.
(Invited) Towards AI2 Electrochemistry(AI2 = AI × ab initio)
Authors: Cheng Jun
Published: December 2024

It is known that electrode materials undergo dynamic structural changes at in-situ/in-operando conditions. Yet, the majority of computational studies only consider the static structures of electrode materials. When the materials are submerged in liquid solution, dynamic solvation effects are often completely ignored, or treated with dielectric continuum models, often lacking validation. The situations are about to change. Thanks to the latest development of in-situ experimental techniques and state-of-the-art computational methods, dynamics of electrode materials has recently drawn more and more attentions in many research areas. In this talk, I will present our recent progress on modeling dynamic catalysis and electrochemistry using ab initio molecular dynamics (AIMD). The high computational cost of AIMD however limits its application to small model systems consisting of hundreds of atoms at timescale of tens of ps. While, the latest development of AI accelerated AIMD (AI2MD) significantly increases the size and timescale, showing great promise for in situ modeling of realistic electrochemical systems.
(Invited) Double Layer Structure, Electric Fields, and Making and Breaking of Lewis Bonds at an Electrochemical Interface
Authors: Dawlaty Jahan M
Published: December 2024

Understanding breaking and formation of Lewis bonds at an electrified interface is broadly relevant to a large range of phenomena, including electrocatalysis, electroadsorption, and sensing. The complexities of interfacial environments, including the interfacial electric fields and the electric double layer structure often impede their systematic understanding. One of the impediments is the lack of clear signatures for the formation and dissociation of such bonds. To address this challenge, we report tethering of well-defined Lewis bases on the surface to receive Lewis acid molecules from the electrolyte. The important feature of our approach is that a clear vibrational signature of the surface-bound Lewis base will report on the formation or breaking of the bond. We will report two types of interfacial Lewis bonds – first a classic Lewis bond between pyridine as a base and BF3 as a Lewis acid, and second benzonitrile as a Lewis base and Zn2+ ion as a Lewis acid. The first system is a universal model for Lewis interaction. We will report on its behavior in response to potential and electrolyte types. Our unexpected discovery is that the breaking and formation of the Lewis adduct has the opposite behavior of what is normally expected from electro-induction, and is related to the complex ionic equilibria near the surface. The benzonitrile-Zn2+ Lewis pair was designed to understand desolvation of multivalent ions from an electrolyte, which is relevant to energy storage in batteries. The large blue shift of nitrile upon coordination with Zn2+ is used as a marker of the ion breaking from the bulk solvent shell and interacting with the surface. We found that this event is surprisingly slow, and in some solvents can take up to 10 minutes. We will propose possible desolvation barriers that govern this process. Finally, the generality and limitations of the surface vibrational probes for studying such processes will be discussed.
(Invited) Direct Observation of Nanoscale Heterogeneity in Ruthenium Oxide Rutile Nanocrystals for the Oxygen Evolution Reaction via Liquid Phase Transmission Electron Microscopy
Authors: Moreno-Hernandez Ivan A.
Published: December 2024

Oxygen-evolving electrocatalysts in acid undergo structural changes that result in a loss of activity, which necessitates high catalyst loadings of precious noble metal oxides. A fundamental understanding of the structural dynamics at the electrode/electrolyte interface that occur during oxygen evolution is necessary to design the next generation of electrocatalyst materials with improved performance. The Moreno-Hernandez Laboratory utilizes liquid phase transmission electron microscopy to directly observe the stability of single-nanocrystalline and highly faceted metal oxide nanocrystals under anodic conditions in acidic electrolytes. Our studies reveal the distribution of stability relationships between different crystallographic facets for nanocrystalline materials, and enable the direct determination of nanoscale heterogeneity at the single nanocrystal level. Substantial stability differences are observed across multiple nanocrystals, which are correlated to variability in the nanoscale strain present in individual nanocrystals. These studies suggest that nanoscale heterogeneity occluded in conventional bulk-scale analysis techniques substantially influences stability under relevant operation conditions, and provide crucial information for the design of resilient electrocatalyst materials.
Hydrogen Dopant Modulated Strain Control of Copper Electrocatalysis for Nitrate Reduction Reaction
Authors: Xiao Zhongcan , Li Zhao
Published: December 2024

The manipulation of the local atomic arrangement of electrode materials using lattice-distortion-induced strain represents a rational design strategy that can effectively modulate the electron structure configuration and catalytic activity. We employ first-principles methods to study the catalytic effect of Cu with interstitial H dopant on the reduction reaction of nitrite. We find that the H dopants induce a local strain field that significantly facilitated charge transfer, thereby reducing the energy barrier of and promoting the reaction process. Our work provides an appealing electrocatalytic approach for the degradation of NO2
- pollutants in wastewater and paves the way to Zinc-nitrite battery as a sustainable energy supply.
Operando X-Ray Tomography Measurements of a Membrane Electrode Assembly for Electrochemical CO2 Reduction
Authors: Lee Sola , Jang Myeong Je , Qi Zhiyuan , Paradis-Fortin Laura , Atwater Harry A. , Drisdell Walter S. , Xiang Chengxiang("CX")
Published: December 2024

The electrochemical reduction of carbon dioxide (eCO2R) holds great promise for producing valuable chemicals and fuels while mitigating carbon emissions. However, challenges arise from the need to enhance CO2 transport and operate at higher current densities. Despite the development of gas diffusion electrodes, operating at higher current densities generates hydroxide ions at the cathode, promoting the formation of carbonate ions, which can cause salt precipitation and flooding, hindering CO2 mass transport.

To investigate the potential degradation of eCO2R of copper gas diffusion electrode (Cu GDE), we utilize X-ray tomography, a nondestructive method for visualizing morphological changes. Through in-line gas chromatography, we track salt precipitation and flooding in the GDE, correlating these changes with shifts in product distribution during eCO2R. Our findings reveal that the degradation of membrane electrode assembly (MEA) cells is linked to the extent of precipitation and flooding. Furthermore, micro-CT imaging captures morphological changes, such as precipitation growth, dissolution, and regrowth from the Cu surface to the gas diffusion layer, during transient oscillatory voltage profiles and selectivity changes in Cu GDE. This study sheds light on the degradation mechanism of MEA cells and offers insights into strategies for enhancing device durability.
Attenuation of Electrochemical CO2 Reduction Via the Electric Double Layer
Authors: Raciti David
Published: December 2024

This abstract delves into the crucial role of interfacial phenomena, particularly the electric double layer (EDL), in CO2 electroreduction. Nano catalyst materials often incorporate additives such as polar organic functional groups and polymers, which significantly affect selectivity and activity by perturbing the EDL. Additionally, electrolyte choice and ionic strength can alter conditions adjacent to the electrode surface, further influencing performance. Recently, the electrocatalysis community has shown substantial interest in understanding and manipulating these factors to achieve desired performance. This presentation explores a variety of operando/in-situ measurement techniques aimed at better resolving EDL properties and their impact on catalytic active sites or system performance. By elucidating these complex interfacial phenomena, this research contributes to the advancement of sustainable CO2 utilization technologies and the realization of a closed carbon economy.
Micro-Electrochemical Sensor Array for Detection of Serotonin
Authors: Navaei Milad , Park Jinho , Heist Christopher A. , Swarts Matthew , Young Katherine T.
Published: December 2024

Chemical and biological threats pose a significant risk to national security, whether arising from natural outbreaks, accidental releases, warfare, or terrorism. Consequently, there's an urgent demand for innovative technologies capable of real-time screening, detection, and forensic analysis, especially concerning chemical warfare agents, explosives, and nuclear monitoring in field operations. Advancements in biosensing have revolutionized the detection of contaminants using diverse techniques. One notable breakthrough involves synthetic biology, which has led to the creation of biosensor devices capable of monitoring chemical and physical contaminants. These devices can conveniently display detected contaminants as visual signals, such as fluorescence and bioluminescence. However, due to lack of the advances in bio-electronics interfaces, these sensors are not ubiquitous for chemical and biological sensing electronic systems.

In this context, we present the development of a Bio engineered microfabricated electrochemical sensor to detect serotonin by producing hydrogen peroxide (H2O2). The study entails COMSOL simulations aimed at understanding the electrochemical behavior of the electrode for detection of H2O2 by identifying relevant physics, determining the necessary parameters for the simulation concerning the solution and materials, and conducting experiments to validate the electrochemical signal, particularly the charge transfer density. Three distinct electrode geometries are explored in this experiment: the unpatterned electrode, the interdigitated electrode, and the ring array electrode. The performance of the ring electrode is experimentally evaluated for its ability to detect H2O2 levels ranging from 0 to 250 parts per million (ppm).
FIPEX: Sensor Kinetics of Thin-Film Solid Electrolyte Atomic Oxygen Sensors for Space Applications
Authors: Hoerner Igor , Eberhart Martin , Loehle Stefan , Fasoulas Stefanos
Published: December 2024

Atomic oxygen (AOX) quantification in the upper atmosphere of the Earth is of fundamental interest for the understanding of weather and climate development. Solid electrolyte sensors are suitable instruments for this task since they qualify as payload on all common spaceflight systems due to their small size and low power consumption. The High Enthalpy Flow Diagnostics Group (HEFDiG) at the Institute of Space Systems (IRS) (University of Stuttgart, Germany) has been developing solid electrolyte sensors (FIPEX) for applications aboard sounding rockets in the past 12 years.

FIPEX sensors employ YSZ (yttria stabilized zirconia) as solid electrolyte. Together with platinum or gold electrodes they form an electrochemical cell that is operated in an amperometric mode of operation. At elevated temperatures and with a voltage applied between the electrodes this setup forces a migration of oxygen anions through the electrolyte. The corresponding electrical current is measured in an outer circuit and is a function of the AOX flux onto the surface of the sensor.

On sounding rockets, the measurement of atomic oxygen is particularly difficult because of the rocket’s high vertical speed yielding strong gradients in AOX number densities along the trajectory. Therefore, our research focuses on the measurement of sensor response times and their reduction. Initially, FIPEX sensors were manufactured with screen printed electrodes that are robust yet comparably thick. Surface diffusion of adsorbed oxygen atoms at the cathode was identified as the rate limiting step in this configuration. In order to reduce the diffusion length, the screen printed electrodes were replaced by porous thin-film electrodes leading to significantly improved response times.

This contribution focuses on the analysis of the sensor kinetics governing the behavior of the new thin-film FIPEX sensors. We demonstrate how porosity of the initially dense anode is triggered by high polarization. From this, we provide evidence that an increased porosity at the anode is sufficient to improve the response time of a FIPEX sensor. This is different from the conclusions drawn from the analysis of sensors with thicker screen printed electrodes. An experimental configuration to determine sensor step responses to sufficiently fast changes in oxygen particle flux is presented. Above that, we discuss cyclic voltammetry observations to develop a deeper understanding of the underlying kinetic processes.

In conclusion, the transient behavior of thin-film sensors is shown to be dictated by kinetic steps different from what was found for screen printed sensors. Impacts on the suitability and further application of FIPEX sensors in space are presented.

Fig. 1: a) Functional layers of a FIPEX sensor. b) Photography of a FIPEX sensor with thin film electrodes.

Figure 1
Virus Detection Using Functionalized Graphene Oxide Composites
Authors: Hwang Teajong , Hwang Yun Ji , LIU Tianci , Jun Seong Chan
Published: December 2024

In this study, we explore the optimization of Reduced Graphene Oxide (RGO)-based sensors for detecting respiratory viruses, employing an innovative thermal reduction process. Traditional methods of graphene oxide (GO) production often struggle with scalability and uniformity. Addressing these challenges, we utilize a common glass substrate within a controlled oven environment, achieving precise temperature regulation essential for consistent sensor properties. RGO produced at these specific conditions demonstrated significantly enhanced uniformity and electrical properties when compared to those produced under traditional, less controlled conditions. Expanding upon this base, we have now incorporated metals (such as Fe, Ag) into the graphene oxide matrix to create metal-graphene oxide composites. These composites were methodically synthesized and integrated into our existing Field-Effect Transistor (FET) sensors, allowing us to evaluate their enhanced responsiveness to Human Parainfluenza Virus types 2 and 3 (HPIV-2, HPIV-3), and Respiratory Syncytial Virus (RSV). Early experiments with these new composites show a marked improvement in sensor sensitivity and specificity, particularly against HPIV-3, suggesting a robust interaction between the virus and the sensor interface. The addition of metal composites not only fortifies the electrical and mechanical properties of the sensors but also significantly boosts their viral detection capabilities. This advancement confirms the reproducibility and reliability of the optimized RGO production process, reinforcing the importance of precise thermal control in producing not just stable and uniform RGO, but also highly effective biosensing platforms. These results pave the way for the potential mass production of RGO-based sensors, equipped with metal-graphene oxide composites, targeting high sensitivity and specificity in virus detection. This enhancement has profound implications for the broad applicability of RGO in diverse fields including electronics, chemical sensing, and gas sensing, contributing foundational knowledge for the advancement of graphene-based technologies. This research reaffirms the critical need for standardized production processes that ensure the consistency and efficiency of RGO and showcases the practical application of these processes in creating high-performance biosensors.
Peroxynitrite Sensing Using Glassy Carbon Electrods Decorated with Grafted Diaryl Selenides
Authors: Ibrahim Magdy , Kalil Haitham , Fouad Farid , Bayachou Mekki
Published: December 2024

Peroxynitrite (PON), a highly reactive species, poses challenges in accurately measuring its concentration due to its propensity to damage cells. Electrochemical techniques for detecting peroxynitrite are currently restricted, prompting ongoing research aimed at creating efficient electrochemical probes or catalytic materials to enhance peroxynitrite detection. In our previous work we developed and characterized a thin film material based on 4,4’ diaminodiphenyl selenide grafted onto glassy carbon electrodes to create a functional interface for peroxynitrite detection. This selenide-based peroxynitrite sensors demonstrated remarkable sensitivity and a low limit of detection, and we postulated an electrocatalytic catalytic mechanism whereby the grafted selenide moieties act as electroactive mediators that ultimately lead to the catalytic oxidation of peroxynitrite. The positive charge developed on the selenium atom of the diarylselenide upon electrochemical oxidation is crucial for a such electrocatalytic mechanism. To test the validity of the postulated mechanism, we designed other diarylselenides with different functional groups in the para position of the selenium atom. In this study, we decorated electrodes with diarylselenide moieties bearing various functional groups in the para position of the selenium atom of the diaryl selenide (See Scheme1; R=-H, -OMe, -CF3). We show that the electron-withdrawing -CF3 group significantly improves the sensitivity of the corresponding electrode towards PON. The opposite is observed with the methoxy group, which almost abolishes the mediated electrocatalytic oxidation of PON. We will present the results and analyze these findings in light of the electron-donating or withdrawing ability of the substituents placed in the para position from the selenium atom in the context of the postulated electrocatalytic mechanism mediated by the selenide moiety.
(Keynote) Elevating Supercapacitors with Ultrafast Materials: Vital Contributors to Sustainable Energy Solutions
Authors: Naoi Katsuhiko , Naoi Wako
Published: December 2024

Supercapacitors have emerged as pivotal energy conversion-storage systems in contemporary renewable and sustainable nanotechnology, offering a cost-effective and eco-friendly alternative. With material properties being paramount to their performance, supercapacitors stand out from conventional batteries due to their exceptional high-power capabilities and longevity, making them versatile for various applications. Their remarkable features, such as high-power capabilities and extended cycle-life, make them highly attractive for advanced hybrid configurations, serving both mobile and stationary purposes across diverse applications. The drive to shape the next generation of energy technologies fuels the development of composite materials, integrating elements like nanocarbon/graphene and metal oxides to enhance electrochemical performance.

Material selection plays a critical role in supercapacitors, as different materials used as electrodes and electrolytes significantly influence functionality and characteristics, particularly in determining thermal and electrical properties. Leveraging innovative techniques such as "Ultracentrifugation" and “Spray-Dry Synthesis,” nanoarchitecture electrode materials are engineered for improved performance and safety.

Collaborations with Li-predoping technology experts aim to develop groundbreaking Li-ion-based energy facilitators like the "iE7" SuperRedox Capacitor, capable of seamlessly balancing high power and energy demands. By integrating advancements in material science, pre-doping techniques, and cell design, the vision extends beyond innovation to lead the transition towards solar regeneration, driving electrification, and decarbonization across extensive mobility and heavy-duty sectors.

References:

K. Naoi et al., Adv. Mater.,
28, 6751 (2016); E. Iwama, K. Naoi et al., ACS Nano, 10, 5398 (2016); P. Simon, K. Naoi et al., Nat. Ener., 1, 16070 (2016); K. Naoi et al., Acc. Chem. Res., 46,1075 (2013); K. Naoi et al., Ener. Environ. Sci., 5, 9363 (2012).

K. Naoi et al., Chem. of Mater., 36, 2495 (2024); K. Naoi et al., J. Mater. Chem. A, 12, 2081 (2024); K. Naoi et al., J. Mater. Chem. A, 12, 1703 (2024); K. Fujii, K. Naoi et al., Phys.
Chem. Chem. Phys., 26, 3920 (2024); K. Naoi et al., J. Electrochem. Soc., 170, 010524 (2023); K. Naoi et al., ACS Appl. Ener. Mater., 6, 9, 4657 (2023); K. Naoi et al., J. Mater. Chem. A, 11, 1841 (2023).

Figure 1
(Invited) Synthesis of Structured Transition Metal Sulfide Electrodes Via a Highly Active Sulfur Activation Process for Fast Energy Storage Applications
Authors: Hong John
Published: December 2024

Transition metal sulfide (TMS) materials exhibit significant potential as high-performance supercapacitor electrodes for rapid charge-discharge cycles. Compared to their oxide counterparts, TMS materials generally show superior electrical conductivities, with the incorporation of sulfur atoms boosting their ionic conductivities.

The fabrication and control of the structure and morphology of TMS electrodes are crucial in determining their physical and electrochemical properties for energy storage applications. Typically, the electrochemical efficiency correlates with the interactions between the electrode materials and electrolyte ions at the electrode's surface. Hence, electrodes with an optimally structured morphology can demonstrate enhanced electrochemical performance due to their increased surface area, reduced ion transport distances, and structural integrity. These characteristics contribute to higher specific capacitance, enhanced ion diffusion kinetics, and extended cyclability.

Electrochemically active electrode materials are typically created with various micro/nanostructures using different synthetic methods, such as solvo-/hydrothermal synthesis, thermolysis, microwave irradiation, chemical vapor deposition, sputtering, and electrodeposition. These synthetic processes often require extended synthesis times (approximately 12–24 hours), electrochemical deposition and additional heat treatment to transform chemical reactants (above 400°C). Such methods impose significant high-temperature input, voltage damage, or mechanical strain on substrates, rendering them impractical for the industrialization of supercapacitors and likely degrading the practicalbility of diverse substrates. Consequently, identifying an effective method to fabricate electrochemically active electrode materials without thermal heat treatment is important. The low-temperature solution-based synthetic approach has been investigated as a viable alternative for depositing active materials on metal substrates.

In this study, we introduce a novel and efficient method for synthesizing hierarchically structured TMS electrodes using a direct exposure approach with a highly reactive sulfide solution. The essence of this synthesis technique lies in the swift interaction between the ammonium sulfide solution and transition metal, wherein the ammonium ions catalyze the liberation of transition metal ions. Subsequently, these released ions react with sulfur ions in the solution, resulting in the formation of TMS materials. By modulating the synthesis conditions, it is possible to engineer TMS electrodes with diverse structures, leading to varying electrochemical properties. This approach offers a simple yet effective pathway to fabricate scalable, hierarchical TMS structures, highlighting the innovative capabilities of the solution-based sulfur activation method for high performance and fast energy storage applications.
(Invited) Fast Proton Storage in Metal Oxide Electrodes for Aqueous Electrochemical Energy Storage
Authors: Okubo Masashi
Published: December 2024

Lithium-ion batteries (LIBs) dominate the battery market for portable electronics and electric vehicles owing to their long lifetime, high efficiency, and high energy densities. However, LIBs are comprised of flammable and costly organic electrolytes, which unexceptionally accompany both safety hazards and high fabrication costs. Electrochemical energy storage (EES) devices that utilize aqueous electrolytes are expected to provide more operational safety, affordability, high power, and environmental benignity. Although the intrinsically narrow electrochemical stability window for water as an electrolyte solvent (1.23 V) imposed severe limitations on any practical applications of aqueous EES devices, novel strategies involving highly concentrated aqueous electrolytes have achieved much wider electrochemical potential windows (>3 V), thereby paving a path for the development of more practical aqueous EES devices. Importantly, highly concentrated aqueous electrolytes can provide unexpected environments for electrode materials that have been considered ‘useless’ in conventional dilute aqueous electrolytes. I will show our recent attempts to achieve fast proton storage of oxide electrodes in aqueous media.

Reference

1. D. Sun, M. Okubo, A. Yamada, Chem. Sci., 2021, 12, 4450-4454.

2. Z. Ma, et al., M. Okubo, A. Yamada, Adv. Mater. 2022, 34, 2203335.

3. T. Shimada, et al., M. Okubo, A. Yamada, Chem. Mater. 2022, 34, 2069-2075.

4. Z. Ma, et al., M. Okubo, A. Yamada, Adv. Funct. Mater. 2023, 2214466.
水性レドックスフロー電池用アントラキノン系陽極液の機能化
Authors: Kawgauchi Momoka , Okazawa Atsushi , Kawai Kosuke , Okubo Masashi
Published: December 2024

Redox flow batteries (RFBs) are developed as grid-scale load-leveling technologies for renewable energy. Commercial RFBs use vanadium ions as active materials. However, their low energy density and high cost hinder wide deployment in electrical grids. To address these issues, 2,2′-(anthraquinone-2,6-diyldioxy)dipropionic acid (1Me) was reported as an aqueous anolyte to achieve two-electron redox capability, long cycle life, and high solubility.1 In this work, we improve the cycle stability by introducing a sterically bulkier substituent into the side chain of the anthraflavic acid derivative: 2,2′-(anthraquinone-2,6-diyldioxy)dibutyric acid (1Et; Figure 1).

1Et was synthesized by introducing methyl 2-bromobutyrate into anthraflavic acid, followed by saponification and subsequent neutralization with hydrochloric acid. Both 1Me and 1Et exhibit a redox potential of −0.68 V (vs. Ag/AgCl) in 1 mol L−1 KCl and 0.01 mol L−1 KOH aqueous solutions, indicating little influence of the substituent modification to a redox potential. Interestingly, 1Et shows higher solubility (1.73 mol L−1) than 1Me (1.54 mol L−1) despite an elongated hydrophobic alkyl side chain moiety. An ethyl group possesses a higher degree of freedom for rotation and vibration than a methyl group, resulting in larger dissolution entropy and hence higher solubility. Charge/discharge measurements using an H-type cell reveal that 1Et shows a higher capacity retention (0.029%/cycle) than that of 1Me (0.047%/cycle) (Figure 2) owing to a bulkier substituent preventing from nucleophilic attack on the side chain of anthraquinone. Levich analyses show comparable diffusion coefficients for 1Et (4.55×10−6 cm2 s−1) and 1Me (3.26×10−
6 cm2 s−1). These results demonstrate that introducing a bulkier substituent is an effective strategy to improve solubility in water and cycle stability without degrading other physical properties (e.g., redox potential and diffusivity).

Reference

[1] R. G. Godon, M. J. Aziz, et al., ACS Energy Lett.
2023, 8, 600.

Figure 1
Compositional Development and Characterization of Mixed Glass Former Oxy-Sulfide Materials for an Electrochemically Stable Glassy Solid Electrolyte
Authors: Wakefield Alec , Martin Madison , Riley Noah , Martin Steve W
Published: December 2024

Glassy solid electrolytes (GSE) for all-solid-state sodium-ion batteries have the potential to combine the low cost of sodium, the improved energy density and safety of solid-state batteries, and the excellent processability of glass in one system. The 0.54 Na2S + 0.33 SiS2 + 0.06 PS5/2 + 0.06 NaPO3 (NaPSiSO-15) GSE was shown to be a promising candidate for a thin-film glassy solid electrolyte, with a room temperature conductivity of 3.2 x 10-5 S/cm, a critical current density of 0.80 mA-hr/cm2, and the capability to be drawn into films thinner than 100 μm. However, this composition was found to have sulfur defect structures that proved problematic for use in cathode applications, reacting to form Na2S. To resolve this problem, new glass compositions with reduced sodium-to-glass former ratios (R-value) were developed, exploring compositions between R=2.0 and R=3.0. The structure of these compositions was explored using Raman, Fourier transformed infrared, and x-ray photoelectron spectroscopy. Their electrochemical behavior was also characterized using electrochemical impedance spectroscopy and cyclic voltammetry. These results were used to find a composition without the defects found at high R-values and avoid crystallization seen at lower R-values.
Development of Corrosion Diagnosis Method for Copper with Carbon Film by Potential Difference Measurement
Authors: Kito Kaito , Hoshi Yoshinao , Ikeda Itaru , Kuratani Motoki , Tanaka Noriyuki
Published: December 2024

Copper is widely used in the heat exchangers of air conditioning systems because of its high thermal conductivity and good workability. Although copper shows a good corrosion resistance in the fresh water, the occurrence of pitting corrosion is strongly related to the carbon films on copper 1,2. It has been reported that the pitting corrosion was observed in the inner surface of copper tubes due to the carbon films on copper 2,3. In this case, the carbon films were produced by the influence of undergoing an oil and heat treatment. Yamada et al.2 investigated the factor of the pitting corrosion on copper by field test of air conditioning systems in Japan. They indicated that the occurrence of type Ⅰ pitting corrosion was affected by the water quality and carbon films on copper. Iyasu et al.3 reported a method to estimate the residual amount of carbon on the inner surface of the carbon tube by electrochemical measurement. In this method, the corrosion potentials related to the inner and outer of copper tube were measured to estimate the corrosion potential difference from both corrosion potentials at arbitrary measurement time. They demonstrated that the residual amount of carbon on the inner surface of the carbon tube was correlated to the corrosion potential difference estimated from the corrosion potentials of the inner and outer of copper tube. Though they implied that their proposed method can be applied the corrosion diagnosis method for copper tubes, the dissolution mechanisms of copper with carbon films were still unclear.

In the present study, we investigated the dissolution behavior of copper with carbon films in the fresh water based on the air conditioning systems. To estimate the corrosion potential difference, the corrosion potentials related to the inner and outer of copper tube were measured in the different compositions of electrolyte solution. The inner surface of copper tube with different residual carbon contents was employed for the measurement. To develop the corrosion diagnosis method of copper, the suitable conditions involving compositions of electrolyte solution for the corrosion potential measurements were discussed.

References

F. J. Cornwell, G. Wildsmith, P. T. Gilbert, ASTM STP (1976).

Y. Yamada, K. Mizutani, and Y. Inoue, Zairyo-to-Kankyo, 63, 158-162 (2014).

T. Iyasu, M. Kuratani, I. Ikeda, N. Tanaka, Y. Yamada, O. Sakurada, Open J. Compos. Mater., 11, 12-22 (2021).
Simple Direct Alternating Current Battery Using Iron Electrodes
Authors: Sato Ryo , Kuge Terumasa , Nakanishi Shuji , Mukouyama Yoshiharu
Published: December 2024

Alternating current (AC) is currently used as a power source for a wide variety of electronic and electrical devices. Direct AC batteries, which generate AC without external devices, are expected to find a variety of applications. Despite the development of various chemical batteries, direct AC batteries with this capability have not been reported. To realize a direct AC battery, the current flow between the two electrodes needs to be spontaneously and repeatedly reversed. In other words, the electrodes of the battery need to alternately undergo oxidation and reduction reactions.

On the other hand, electrochemical oscillations are often observed during electrolysis. For example, various metals (e.g., Fe) exhibit current oscillations during dissolution. Typically, these oscillations are observed in anodic currents. Figure 1a shows the current (I)–potential (E) curve of a Fe electrode in a 1.0 M H2SO4 solution. The anode current due to Reaction 1 oscillated at approximately 0.45 V.

Fe→ Fe2+ + 2e- (1)

When a phosphoric acid solution containing hydrogen peroxide is used as the electrolyte, the oxidation reaction of Fe (Reaction 1) and the reduction reaction of hydrogen peroxide (Reaction 2) proceed alternately at approximately 0.3 V (Figure 1b) [1]. In other words, AC is spontaneously generated.

H2O2 + 2H+ + 2e- → 2H2O (2)

In this study, we developed a direct AC battery that utilizes the current oscillation. The battery has a simple structure with two Fe electrodes immersed in 0.5 M H3PO4 + 1.5 M H2O2, and an AC is generated by the alternating progression of Reactions 1 and 2 (Figure 2). The amplitude of the AC is approximately 0.05 mA though the amplitude of the current oscillation observed in the I−E curve reaches 10 mA (Fig. 1b). Figure 3 displays the relationship between current (I) and applied voltage (V
app) for the direct AC battery, demonstrating that AC behavior is observed over a wide voltage range. It is worth noting that the amplitude of the AC depends on V
app. This suggests that the battery can generate considerable amplitudes, possibly reaching several mA.

In general, current oscillations are attributed to negative differential resistance (NDR) [2]. In this presentation, the origin of AC will be explained based on the NDR characteristics. The necessary conditions for a direct AC battery will also be explained.

References

R. Sato and Y. Mukouyama, The 74th Annual Meeting of the ISE, S16-P-026 (2023).

M. Orlik, Self-Organization in Electrochemical Systems I, Springer-Verlag Berlin Heidelberg, Berlin (2012).

Figure 1
Evaluation of Phase Transition Behavior of Nonionic Surfactant Solutions Containing Electrolytes by Rheo-Impedance Measurement
Authors: Kotsubo Ryo , Loew Noya , Ogura Taku , Yamagata Yoshifumi , Miyamoto Keisuke , Watanabe Hikari , Shitanda Isao , Itagaki Masayuki
Published: December 2024

Aqueous nonionic surfactant solutions are known to undergo a phase transition from lamellar to vesicle when shear force is applied. It is also known that viscosity increases with the phase transition1). Our group has previously reported that the impedance decreases during the phase transition2). However, there are still many unknown aspects of the conduction mechanism in aqueous surfactant solutions of before, after, and during the phase transition. Therefore, in this study, we performed rheo-impedance measurements of aqueous surfactant solutions with different electrolyte concentrations. Furthermore, the dependency of the phase on the rheological parameters was verified using small-angle light scattering.

As surfactant, two types of polyoxyethylene lauryl ethers (BL4.2 and BL4SY) were used. As electrolyte, an aqueous Na2SO4 solution of 1.0 × 100 mol/L, 1.0 × 10-1 mol/L, 1.0 × 10-2 mol/L or 1.0 × 10-3 mol/L was prepared. The sample solution was a mixture of Na2SO4 solution, surfactant, and pure water with ratios of 5 wt%, 40 wt%, and 55 wt%, respectively. The sample solution was heated to 40°C, stirred, and allowed to settle until all bubbles disappeared completely. Samples without electrolyte (40 wt% surfactant, 60 wt% pure water) were prepared correspondingly. Rheology was measured with a gap of 1.0 mm over 30 min, at 35 °C, and a shear rate of 10 s-1. Simultaneously, electrochemical impedance was measured continuously with an initial potential of 0 V, in the frequency range of 500 kHz to 1 kHz (5 points per decade), with an amplitude 10 mV using a potentiogalvanostat with FRA (Hz-7000).

Phase transitions were observed in all solutions. Electrolyte concentration did not affect the time to phase transition. Capacitive semicircles were observed in all solutions. Curve fitting showed that the resistance of the solutions decreased after the phase transition. This is thought to be due to the difference in the orientation of the structure, which allows for easier transfer of protons and sodium ions in the vesicle than in the lamellar. When the electrolyte concentration was low, the resistance was greater than that of the solution without electrolyte. On the other hand, when the electrolyte concentration was high, the resistance decreased obviously. We are currently investigating the cause of this phenomenon. Details will be reported on the day.

1) Diat, D. Roux, F. Nallet, J. Phys. II France, 3, 1427 (1993).

2) Isao Shitanda et al., Proceedings of the 90th Annual Meeting of the Electrochemical Society of Japan (2023).