Water Electrolyte Research Articles

The effect of the load of bushes with shoots on the stress resistance of grapes of the varieties Vladimir, Dmitry, Kurchansky

Due to the currently observed global and local climate changes, there is an imbalance in the biological cycles of plants, a change in their resistance to biotic and abiotic stressors. The level of realization of the potential of economic productivity of grape varieties in the Krasnodar Territory is low and amounts to 60%. At the heart of its increase is the optimization of the placement of grape plantations, taking into account varietal characteristics and variety-oriented, zone-oriented technologies of grape cultivation. Varietal agrotechnology, which provides for the establishment of an optimal load of grape bushes with shoots, plays an important role in regulating the growth of the grape bush and its individual parts, the formation of plant resistance to stressors and the quality of viticulture products. Due to the more frequent manifestation of stressful weather conditions during the growing season of grapes, namely, insufficient soil moisture in combination with high temperature and low humidity, an urgent area of research is the study of stress resistance indicators under different loads of bushes with shoots. The purpose of the research is to study the effect of the load of bushes with shoots on the stress resistance of grape varieties of domestic selection Vladimir, Dmitry, Kurchansky. Indicators characterizing the stress resistance of plants, such as electrolyte yield, hydration, water deficiency and loss of water by leaves (water retention capacity), have been studied. A variety-specific reaction of grape plants to changes in the load of bushes with shoots under stressful conditions (insufficient precipitation and high air temperature) has been established. Increasing the load in Dmitry and Kurchansky grape varieties improves stress resistance indicators, such as tissue hydration, water deficiency and water retention capacity. The Vladimir variety had the best performance with a minimum and average load of bushes with shoots.

Aplicação exógena de melatonina mitiga o estresse salino em soja

ABSTRACT Salinity is an abiotic factor that impairs the growth and physiological, biochemical, and molecular mechanisms of plants. Among plants, soybeans are an important crop worldwide, so managing abiotic factors is essential to mitigate plant damage. However, biostimulants, such as melatonin, are being employed to alleviate the stress caused by these factors. Therefore, this study aimed to evaluate the growth, photosynthetic pigments, and water relations of soybean plants subjected to salinity levels and exogenous melatonin application. The research was conducted in experimental area belonging to the Federal Rural University of the Semi-Arid Region, Mossoró, RN, Brazil. The experimental design was randomized blocks, arranged in a 3 x 3 factorial scheme (three salinity levels in the irrigation water - 0.50, 3.00, and 5.00 dS m-1 and three melatonin concentrations - 0, 0.5, and 1 mM) with three replications. At 47 days after planting, plant height, stem diameter, number of leaves, root length, chlorophyll content (a, b, and total), relative water content, leaf moisture, and electrolyte leakage were evaluated. Soybean plants tolerated the effects of salinity on growth aspects, photosynthetic pigments, and water relations up to 3.00 dS m-1, regardless of melatonin concentration. Exogenous application of melatonin mitigated the effects of salt stress on chlorophyll b and relative water content at salinity level of 5.00 dS m-1 and concentration of 1 mM.

Dynamic Modulation of Ions Solvation Sheath by Butyramide as Molecular Additives in Aqueous Batteries.

The high activity of water in aqueous battery electrolytes can trigger side reactions, limiting their large-scale application. Additives that form contact pairs (CPs) with cations by coordinating with them can effectively reduce water's activity. However, due to the complex interactions between ions, additives, and solvent molecules and the fact that current strategies for additive screening primarily rely on static physical parameters, the dynamic mechanisms that govern the modulation of ion solvation sheaths are still poorly understood. In this study, we introduce butyramide (BUT) as a molecular additive and employ molecular simulations to demonstrate its regulatory effect on the hydration sheath of Ca2+, which is more pronounced than that for Na+. The dynamic process by which BUT replaces water molecules in the tight hydration sheath of Ca2+ is elucidated by forming a stable [BUT-Ca2+(H2O)7] complex that suppresses water molecule activity. At a 2 M concentration, the free energy barrier for the transition from contact pair (CP) to solvent-shared pair (SP) for Ca2+ is 11.7 kJ/mol higher than that for Na+ at 8.5 kJ/mol, consistent with the cationic Hofmeister series. Furthermore, the stability and dynamic fluctuations among solvent-separated pair (SSP), SP, and CP states are attributed to the balance between electrostatic attractive potential energy and hydration repulsive potential energy, supported by quantum chemical calculations of the ion desolvation process. Using BUT as an additive presents a promising strategy to enhance battery performance by modulating the solvation environment of metal ions, addressing the growing demand for safer and more sustainable energy storage solutions.

Molecular Micellar Aggregate Electrolytes Enable Durable Electrochemical Proton Storage.

Proton electrochemistry holds eminent potential for developing high capacity and rate energy storage devices in the post-lithium era. However, the decomposition of water in acidic aqueous electrolytes causes electrode corrosion, leading to capacity fading. Herein, we report a judicious design of molecular micellar aggregates as non-aqueous electrolytes for stable and high-voltage electrochemical proton storage. The key to our strategy lies in introducing cetyltrimethylammonium bromide (CTAB), forming micelles to improve the miscibility of acetonitrile (ACN) and H3PO4, afford channel for proton transport, and electrostatically interact with phosphate ions of H3PO4 to further promote proton transport. Such aggregates impart rapid and stable electrochemical proton storage with a widened operating voltage (1.8 V vs. 1.5 V in aqueous electrolyte). By optimizing CTAB content, proton transport can be enhanced. Asymmetric full proton battery using the optimal CTAB electrolyte achieves a maximum energy density of 102.8 Wh kg-1 and a maximum power density of 10.1 kW kg-1. Our simple yet robust route to micellar aggregate electrolytes enables stable proton storage, underscoring its potential for grid-scale energy storage, emergency power supplies, and portable electronics.

Molecular Micellar Aggregate Electrolytes Enable Durable Electrochemical Proton Storage

Proton electrochemistry holds eminent potential for developing high capacity and rate energy storage devices in the post‐lithium era. However, the decomposition of water in acidic aqueous electrolytes causes electrode corrosion, leading to capacity fading. Herein, we report a judicious design of molecular micellar aggregates as non‐aqueous electrolytes for stable and high‐voltage electrochemical proton storage. The key to our strategy lies in introducing cetyltrimethylammonium bromide (CTAB), forming micelles to improve the miscibility of acetonitrile (ACN) and H3PO4, afford channel for proton transport, and electrostatically interact with phosphate ions of H3PO4 to further promote proton transport. Such aggregates impart rapid and stable electrochemical proton storage with a widened operating voltage (1.8 V vs. 1.5 V in aqueous electrolyte). By optimizing CTAB content, proton transport can be enhanced. Asymmetric full proton battery using the optimal CTAB electrolyte achieves a maximum energy density of 102.8 Wh kg‐1 and a maximum power density of 10.1 kW kg‐1. Our simple yet robust route to micellar aggregate electrolytes enables stable proton storage, underscoring its potential for grid‐scale energy storage, emergency power supplies, and portable electronics.

Succinonitrile Electrolyte Additive for Stabilizing Aqueous Zinc Metal Batteries.

The utilization of water electrolytes in zinc-ion batteries offers the advantages of enhanced safety, reduced cost, and improved environmental friendliness, rendering them an optimal choice for replacing lithium-ion batteries. Nevertheless, the conventional zinc sulfate electrolyte fails to meet stringent requirements. Therefore, developing electrolytes is crucial for addressing the low cycle life of zinc ions and suppressing the growth of zinc dendrites. So we proposed a strategy for engineering dilution of aqueous Zn(OTf)2 solution with succinonitrile (SN) network electrolytes. The introduction of SN also disrupts the original hydrogen bonding network within the system and mitigates issues related to side reactions. Additionally, the inclusion of SN additives significantly diminishes the reactivity of water molecules and smoothing zinc deposition to form favorable two-component Zn3N2/ZnF2 SEI. The results indicate that symmetric cells exhibit a remarkable cycling performance (877 h at current density and capacity of 1 mA cm-2 and 1 mAh cm-2, respectively). Furthermore, after 2000 cycles at a current density of 5 A g-1, the full battery demonstrates an impressive capacity of 151.2 mAh g-1. These results show that the electrolyte structure project provides a promising direction for the design of aqueous zinc-metal batteries, aiming to achieve high reversibility and long cycle life.

Long term porosity of solid electrolyte interphase on model silicon anodes with liquid battery electrolytes

A stable solid electrolyte interphase (SEI) is of great importance for battery electrodes in terms of cycling as well as for its shelf life. While SEI formation on silicon anodes is generally only studied after the first charge and discharge of cells and initial reaction of electrolyte, we show the formation of a liquid/solid SEI in symmetric cells with silicon electrodes in contact with carbonate and glyme-based electrolytes under close to open circuit conditions and its behavior during long-term ageing. Activation energies of SEIs were measured via temperature-dependent electrochemical impedance spectroscopy (EIS) to study the contribution of liquid/solid phases to ion transport. The effect of different solvents, salts, their concentrations, and final water content of the glyme-electrolyte on the SEI was studied in detail. SEIs formed in cells with glyme-based electrolytes are generally more porous than the ones in cells with carbonate-based electrolytes. The addition of vinylene carbonate to glyme electrolyte is shown to be beneficial for its SEI, as it causes lower and more stable SEI resistances over time. A small amount of water in glyme electrolytes causes a denser SEI without much change in SEI resistance.

On the compatibility of the Madrid-2019 force field for electrolytes with the TIP4P/Ice water model.

The Madrid-2019 force field was recently developed to perform simulations of electrolytes in water. The model was specifically parameterized for TIP4P/2005 water and uses scaled charges for the ions. In this work, we test the compatibility of the Madrid-2019 force field with another water model: TIP4P/Ice. We shall denote this combination as Madrid-2019(TIP4P/Ice) force field. The key idea of this combination is to keep the ion-ion (Madrid-2019) and water-water (TIP4P/Ice) interactions unaltered with respect to the original models and taking the Lennard-Jones parameters for the ion-water interactions from the Madrid-2019 force field. By implementing this approach, we have maintained a reasonably good performance of the model regarding the densities and structural features of aqueous solutions, albeit yielding a moderately higher viscosity than the original model. However, the standout achievement of this new combination lies in its effective reproduction of the absolute values of the freezing temperatures of a number of ionic aqueous solutions, which could also be useful when studying hydrate formation from a two-phase system containing an aqueous solution in contact with a gas.

Triple Regulation of Water Molecules Behavior to Realize High Stability and Broad Temperature Tolerance in Aqueous Zinc Metal Batteries via a Novel Cost‐Effective Eutectic Electrolyte

AbstractThe high activity of water in aqueous electrolyte causes drastic side reactions on the Zn anodes, severely limiting the electrochemical performance of aqueous zinc metal batteries (AZMBs) under extreme conditions. Herein, levulinic acid is developed as the hydrated deep eutectic solvent (DES), to build a novel non‐flammable and cost‐effective ZnSO4‐based eutectic electrolyte with triple regulation of water molecules behavior, enabling highly stable AZMBs over a wide temperature. In situ experiments, molecular dynamics simulations, and spectroscopy analysis jointly reveal that the DES is capable of comprehensively lowering the water activity by simultaneously controlling the behavior of the free, solvated, and interfacial water molecules within the eutectic electrolyte system. Consequently, the Zn anodes exhibit ultralong cycling stability (4500 h at 1 mA cm−2/1 mA h cm−2), decent Coulombic efficiency of 99.39%, and excellent temperature tolerance (−20–50 °C). Notably, the designed 2.0 Ah Zn//VOX pouch cell exhibits a recorded actual energy density of 37.46 Wh Kg−1 and 95.38 Wh L−1 at the whole cell level, with a remarkable capacity retention of 81.01% after 150 cycles, demonstrating the potential for scale‐up into real AZMBs. This work provides an in‐depth understanding of the correlation between the water molecule behavior and electrochemical properties of AZMBs.

The influence of water polarization on slip friction at charged interfaces.

The present study employs equilibrium molecular dynamics simulations to explore the potential mechanism for controlling friction by applying electrostatic fields in nanoconfined aqueous electrolytes. The slip friction coefficient demonstrates a gradual increase corresponding to the surface charge density for pure water and aqueous electrolytes, exhibiting a similar trend across both nanochannel walls. An expression is formulated to rationalize the observed slip friction behavior, describing the effect of the electric field on the slip friction coefficient. According to this formulation, the slip friction coefficient increases proportionally to the square of the uniform electric field emanating from the charged electrode. This increase in slip friction results from the energy change due to the orientation polarization of interfacial water dipoles. The minimal variations in the empirically determined proportionality constant for pure water and aqueous electrolytes indicate that water polarization primarily governs slip friction at charged interfaces. These findings offer insights into the electrical effects on nanoscale lubrication of aqueous electrolytes, highlighting the significant role of water polarization in determining slip.

Combined application of biochar and silicon nanoparticles enhance soil and wheat productivity under drought: Insights into physiological and antioxidant defense mechanisms

Agricultural drought periods are enhanced by the change in global climate that threatens food security. One of the main factors affecting soil and wheat productivity worldwide is drought stress. Especially, in semi-arid climates, studies are not found about adding organic amendments may be a viable way to reduce the adverse impacts of drought on crops while enhancing soil qualities and water use efficiency. In this study, we aimed to explore the effects of combined application of biochar (BC = 5 %) and silicon nanoparticles (SiNP = 900 mg/L) on soil and wheat drought resistance. Drought stress was applied at the three most critical growth stages of wheat, tillering (DTS), flowering (DFS), and grain filling (DGFS) stages, then evaluated the soil nutrients and wheat drought physiological resistance under applied treatments (BC, SiNP, BC+SiNP). Results showed that combined treatment of BC and SiNP greatly reduced the adverse effects of drought by enhancing plant height (9.36 %), spike length (25.63 %), number of fertile tillers (29.26 %), grains per spike (10.86 %), thousand-grain weight (18.25 %), and biological yield (16.34 %) with comparison to the control application. Additionally, physiological measures like water use efficiency (20.58 %), stomatal conductance (29.26 %), chlorophyll a (16.25 %), chlorophyll b (18.96 %), transpiration rate (21.65 %), photosynthetic rate (22.94 %), electrolyte leakage (-17.77 %), MDA (29.25 %), hydrogen peroxide (-19.88 %), superoxide dismutase (11.19 %), catalase (9.26 %), peroxidase (18.59 %), nitrogen (14.81 %), phosphorus (13.89 %), and potassium (17.61 %) were also meaningfully improved by treated application. BC and SiNP also significantly amended the organic carbon, nitrogen, and minerals percentage in soil. In conclusion, using the synergistic application of BC and SiNP could be a successful strategy to promote the biological soil properties, plant growth, yield, and quality of wheat crops as compared to all other treatments via dropping the dangerous effects of drought stress.

Optimization of Proton Source for Li-Mediated Nitrogen Reduction with Water

IntroductionAmmonia has been used for diverse applications, and its worldwide demand is significantly high. Therefore, it is desirable to develop ammonia synthesis methods that do not emit carbon dioxide, unlike the Haber-Bosch process. In this context, lithium-mediated electrochemical nitrogen reduction reaction (Li-NRR) has received much attention as an alternative method. Previous research1) has shown that ethanol works as a good proton source for Li-NRR. However, there are some concerns about the use of ethanol, which is associated with its cost and sustainability. Alternatively, N2 reduction would be paired with water oxidation in full-cell operation. Hence, Li-NRR with water as a proton source is ultimately desired. Recently, our group revealed that the addition of a certain amount of water improves Faradaic efficiency (FE) to ammonia in Li-NRR, mainly due to the modification of the solid electrolyte interphase (SEI)2). On the other hand, previous reports3) show that other proton carriers could replace ethanol, and also proton carriers influence SEI composition and proton activity. Therefore, combining proton sources other than ethanol with water may tune the SEI composition and proton activity, making it suitable for operating in the presence of water. In this study, we evaluated the performance of Li-NRR in the presence of various amounts of water in electrolytes containing a variety of proton carriers. From this study, we aim to elucidate the factors that enable electrochemical ammonia synthesis in the presence of water, which is required to achieve Li-NRR using water as a proton source.Electrolytes were prepared by mixing (CF₃SO₂)₂NLi (LiTFSI) and tetrahydrofuran to make the 1 mol dm-3 electrolyte solution. Subsequently, various proton sources, such as ethanol, propanol, and phenol, as well as water were added to the electrolytes. The electrochemical measurements were conducted using electrolysis cells composed of a working electrode: Mo plate, counter electrode: Pt wire, and reference electrode: Li1-x FePO4. During chronoamperometry (CA) at -4.5 V vs. Li1-x FePO4, the applied charge was set at 10 C. After the electrolysis, the FE of ammonia formation was calculated using the quantification method reported elsewhere4). The FE obtained with water varied with the type of proton carrier used, indicating the importance of optimizing the proton source to enable the operation under the co-existence of water. In the presentation, we will show the results of Li-NRR with other proton carriers, and the correlation between FE and properties of proton source and/or SEI will be discussed.AcknowledgmentsA part of this work was supported by the NEDO Research and Development Program for Promoting Innovative Clean Energy Technologies Through International Collaboration (JPNP20005).(1) A. Tsuneto et al., J. Electroanal. Chem., 367, 183-188, (1994)(2) M. Spry et al., ACS Energy Lett, 8, 1230-1235, (2023)(3) H. Du et al., Energy Environ. Sci., 16, 1082, (2023)(4) R. Tort et al., ACS Energy Lett., 8, 1003-1009, (2023)

The Effects of Water and Ion Management for Modulate CO2 Reduction Selectivity Via Anode Control

The process of conversion ethylene through carbon dioxide reduction reaction (CO2RR) shows potential in catalysis by encouraging the formation of C-C bonds while reducing the occurrence of competing reactions(1). Despite their potential, a deeper understanding of membrane electrode assembly (MEA) systems is needed due to their low selectivity. The MEA configuration, which eliminates the need for a catholyte, delivers humidified CO2 to the cathode, enhancing CO2 solubility and minimizing overall ohmic resistance by maintaining a narrow electrode gap, thus boosting energy efficiency(2). However, in MEA, since protons and ions from the anolyte for reaction are supplied to the catalyst through a membrane, additional understanding of the electrolyte supply effect is needed to optimize the overall system(3). Ions and water of electrolytes are essential for CO2RR. Water serves as a proton source for CO2RR and facilitates ion transport. However, the delicate balance of water is crucial in CO2RR systems. While water is necessary for proton supply, an excess of water at the cathode can lead to complications, particularly in promoting the competing hydrogen evolution reaction (HER)(4). HER can occur alongside CO2RR and consume protons and electrons, thereby reducing the selectivity of CO2 conversion and diminishing overall efficiency. Balancing the concentrations of ions and water is crucial for optimizing cell voltage and overall performance, highlighting the necessity of effective water and ion management approaches. While much research on water management has focused on cathodes, electrolytes, and membranes, the properties of the anodes have been relatively neglected. This study proposes the hypothesis that modulation of the anode electrode can have a significant impact on CO2RR performance. When comparing Ti-mesh, which facilitates the passage of electrolyte, with carbon paper, which restricts electrolyte movement, localized pH changes and optimal ethylene production efficiency were observed. In particular, in situ/operando analysis shows that under conditions of insufficient water and ion supply, local pH effects are promoted and Cu valence increases during CO2RR, resulting in optimal ethylene production efficiency at low current densities. However, at high current densities, the reaction was not evenly distributed and catalytic activity decreased. On the other hand, when water and ions are supplied smoothly, the ethylene production efficiency increases as the current density increases, showing that the material is sufficiently transferred. In addition, it was confirmed through the backside image that water crossed over to the cathode at the same time. This shows that the anode can affect the catalytic activity of the cathode side.Therefore, this study highlights the importance of effective ion and water management in improving CO2RR efficiency in MEA and highlights the central role of the anode in this process.References Zhan C, Dattila F, Rettenmaier C, Bergmann A, Kuhl S, Garcia-Muelas R, et al. Revealing the CO Coverage-Driven C-C Coupling Mechanism for Electrochemical CO(2) Reduction on Cu(2)O Nanocubes via Operando Raman Spectroscopy. ACS Catal. 2021;11(13):7694-701.Lee WH, Lim C, Lee SY, Chae KH, Choi CH, Lee U, et al. Highly selective and stackable electrode design for gaseous CO2 electroreduction to ethylene in a zero-gap configuration. Nano Energy. 2021;84.Choi W, Park S, Jung W, Won DH, Na J, Hwang YJ. Origin of Hydrogen Incorporated into Ethylene during Electrochemical CO2 Reduction in Membrane Electrode Assembly. ACS Energy Letters. 2022;7(3):939-45.Marcandalli G, Monteiro MCO, Goyal A, Koper MTM. Electrolyte Effects on CO(2) Electrochemical Reduction to CO. Acc Chem Res. 2022;55(14):1900-11. Figure 1

Influence of Operating Conditions on the Mass Activity Characteristics and Performance of Carbon-Free Pt Black Electrodes for PEFC

In recent years, the development of polymer electrolyte fuel cells (PEFCs) has been progressing. To expand their application to heavy-duty vehicles (HDVs), enhancing the power density and heat dissipation efficiency of PEFCs through high-temperature operation has become essential. Therefore, there is a need for high durability to enable the high-temperature operation of electrodes. In this context, we focused on carbon-free ionomer-free electrodes utilizing unsupported catalysts such as Pt black and low-Pt yet highly durable platinum nanosheets (Pt-ns). These electrodes offer high durability by avoiding the use of carbon and ionomer, which are factors contributing to performance degradation. Moreover, these electrodes have a different proton conduction pathway compared to conventional electrodes, relying on water on the Pt surface. Therefore, water management becomes crucial, considering the characteristics of carbon-ionomer-free electrodes. This study aims to elucidate the characteristics of the performance in the low-current region of Pt black electrodes and the effect of operating conditions on power generation characteristics.The performance of ionomer-free Pt black electrodes and ionomer-added Pt black electrodes was compared in terms of their IV characteristics. In the high-current region (>1000 mA) where concentration overpotential dominates, ionomer-free Pt black electrodes exhibited a gentler slope, indicating superior gas diffusion compared to ionomer-added Pt black electrodes. Conversely, in the low-current region (<100 mA), ionomer-free Pt black electrodes showed higher power generation performance, attributed to ionomer-induced catalyst poisoning reported in literature.Additionally, the IV characteristics of ionomer-free electrodes using different types of unsupported Pt catalysts, Pt black, and Pt particles were examined. Ionomer-free Pt particle electrodes displayed lower performance across the entire current range compared to ionomer-free Pt black electrodes, with a convex curvature of the IV curve indicating concentration overpotential. Analysis of electrochemical surface area (ECSA) and mass activity (MA) showed that ionomer-free Pt particle electrodes exhibited lower ECSA and MA compared to ionomer-free Pt black electrodes, indicating a lack of effective reaction sites, likely due to limited proton conduction.The IV characteristics of ionomer-free and ionomer-added Pt black electrodes at different relative humidities were investigated. Ionomer-free Pt black electrodes demonstrated consistent performance across relative humidities in the range of 1 to 10 mA, but as humidity increased, the curvature of the IV curve steepened, indicating higher activation overpotential. In the region above 100 mA, the curvature of the IV curve became concave with increasing current under low humidity, suggesting localized current density distribution due to proton conduction resistance as electrolyte water increased.AcknowledgmentsPart of this paper is based on results obtained from a project, JPNP20003, subsidized by the New Energy and Industrial Technology Development Organization (NEDO).

Recent Progress in Liquid Water Visualization of Polymer Electrolyte Fuel Cells Elucidated By Synchrotron X-Ray and Pulsed Neutron Sources

The formation, accumulation, evaporation, and elimination of water in polymer electrolyte fuel cells (PEFCs) is one of the key features for achieving high power density. The oxygen reduction reaction at the cathode catalyst surface produces water as a by-product. Some of the produced water is discharged from the PEFC through the gas flow channels, while the rest accumulates in the catalyst layer (CL) and gas diffusion layer (GDL). The accumulated water in the porous media inhibits the oxygen supply to the cathode catalyst surface, leading to an increase in the concentration overpotential. Therefore, we have developed water visualization techniques using synchrotron X-rays and pulsed neutrons [1–9]. The three-dimensional water transport behavior in GDLs has been reported by operando X-ray computed tomography (CT) [1]. The water condensation behavior in GDLs has been demonstrated by ex-situ X-ray micro-CT [2] and nano-CT [4]. The dynamic water behavior in GDLs induced by water injection has been studied by ex-situ X-ray high-speed time-resolved X-ray micro-CT [3]. The complementary use of operando X-ray and neutron radiography revealed the water drainage mechanism of large-sized PEFCs [5]. The water accumulation behavior in GDLs has been studied by operando X-ray radiography [6–8]. The water behavior in large-sized PEFCs during cold start has been clarified by the water/ice identification technique using operando pulsed neutron imaging [9].In this talk, we will briefly introduce our previous achievements and present a recent progress in new results: water visualization in Pt-based CLs and thawing behavior in large-sized PEFCs during cold start. In the first topic, water visualization imaging was performed using operando synchrotron X-ray radiography. In general, the strong X-ray absorption of Pt results in low transmittance, which limits water visualization in Pt-based CLs. To overcome this problem, we reviewed our cell configuration and developed a new in-house cell dedicated to the observation of water distribution in cathode CLs. In the second topic, water visualization imaging was performed using operando pulsed neutron radiography. We focused on the current recovery behavior observed during cold start in short stacks. The temperature condition in short stacks during cold start was reproduced in a single cell by rapid heating with an in-house external heater.Reference1) Y. Nagai, J. Eller, T. Hatanaka, S. Yamaguchi, S. Kato, A. Kato, F. Marone, H. Xu and F. N. Büchi, J. Power Sources, 435 (2019) 226809.2) S. Kato, S. Yamaguchi, W. Yoshimune, Y. Matsuoka, A. Kato, Y. Nagai and T. Suzuki, Electrochem. Commun., 111 (2020) 106644.3) S. Yamaguchi, S. Kato, A. Kato, Y. Matsuoka, Y. Nagai and T. Suzuki, Electrochem. Commun., 128 (2021) 107059.4) S. Yamaguchi, S. Kato, W. Yoshimune, D. Setoyama, A. Kato, Y. Nagai, T. Suzuki, A. Takeuchi and K. Uesugi, J. Synchrotron Radiat., 29 (2022) 1258-1264.5) A. Kato, S. Kato, S. Yamaguchi, T. Suzuki and Y. Nagai, J. Power Sources, 521 (2022) 230951.6) W. Yoshimune, Y. Higuchi, A. Kato, S. Hibi, S. Yamaguchi, Y. Matsumoto, H. Hayashida, H. Nozaki, T. Shinohara and S. Kato, ACS Energy Lett., 8 (2023) 3485.7) T. Suzuki, A. Kato, S. Yamaguchi, Y. Nagai, D. Hayashi and S. Kato, J. Power Sources Adv., 22 (2023) 100119.8) A. Kato, S. Kato, S. Yamaguchi, T. Suzuki and Y. Nagai, Int. J. Hydro. Energy, 50 (2024) 1218.9) Y. Higuchi, W. Yoshimune, S. Kato, S. Hibi, D. Setoyama, K. Isegawa, Y. Matsumoto, H. Hayashida, H. Nozaki, M. Harada, N. Fukaya, T. Suzuki, T. Shinohara and Y. Nagai, Commun. Eng., 3 (2024) 33.

(Invited) Manipulating Water Using Aprotic Solvents for CO2 Electrochemical Reduction

Carbon dioxide (CO2) electrochemical conversion is vital because it provides a pathway to efficiently valorize CO2 and incentivize CO2 capture. Electrocatalytic CO2 reduction reaction (CO2RR) is of great interest because it is scalable and can be done at ambient temperature and pressure. However, these reactions are typically performed in water which suffers from undesired hydrogen evolution reaction (HER) from water breakdown. Aprotic nonaqueous electrolytes can suppress HER and enable a wider range of catalysts for CO2RR. However, water is still needed as a proton source and to stabilize charged intermediates. Here, we study the influence of aprotic electrolyte solvent on modulating the water microenvironment, solvation, and dynamics for CO2RR. Furthermore, we probe changes to the water chemical environment in different aprotic media and the ability of aprotic electrolytes to enhance CO2RR or suppress HER. Our work pushes the field in the understanding of electrolyte solvent and water effects for electrochemical transformations such as CO2RR and HER.

Understanding Benzophenone Degradation Pathways to Improve Non-Aqueous Redox Flow Battery Performance

The growing energy demand forces us to look for alternative sources of energy such as wind or solar. However, this type of intermittent energy must be stored for later use. In this sense, redox flow batteries (RFBs) are presented as an interesting tool for energy storage. Non-aqueous RFBs allow a wide electrochemical window for organic solvents such as acetonitrile, propylene carbonate or dimethylformamide. These solvents allow us to reach very positive and negative potentials, opening an electrochemical window greater than 5 V before observing degradation of the solvents.In the design of electrolytes for RFBs it is essential to address aspects such as charge density, stability, price, and the voltage that the redox couple allows us to achieve. In this sense, organic molecules have been widely used as anolytes due to their high charge density, great solubility and the possibility of reaching very negative and positive potentials that would provide RFBs with efficient performance. In our search for organic molecules with E1/2 potentials equal or more negative than -2.0 V, we begun investigating benzophenone and derivatives. The BP family of derivatives have attracted the attention of the anolyte development community due to their extremely negative reduction potentials. In these molecules it is possible to achieve the first reduction at E1/2 -2.25 V vs Ag/Ag+ and the second reduction process at E1/2 -2.8 V vs Ag/Ag+. Although this molecule presents very negative reduction potentials, our initial evaluations show that they are not stable for sufficient time to be used in RFBs. Herein, we detail the degradation mechanism of benzophenones, using product characterization obtained after cycling the anolytes in redox flow batteries. We observed the generation of benzocarbinol and benzopinacol after water and support electrolyte (TBAPF6) addition respectively to a dianion (BP-●●) chemically reduced. Based on the degradation mechanism, we propose a mitigation pathway to improve the performance of these carriers, including modification of ortho position with bulky groups to protect the carbonyl group.

Synthesis and rheological properties of carboxymethyl cellulose modified polyacrylic acid thickener with high electrolyte resistance

Herein, a method for preparing highly resistant electrolyte thickeners by introducing supramolecular interactions (multiple hydrogen bonds and electrostatic interactions) and chemical crosslinking during the polymerization of acrylic monomers has been proposed. The hydroxyl group on the carboxymethyl cellulose (CMC) unit provides multiple hydrogen bonds for the thickener structure, the carboxyl group on the polyacrylic acid (PAA) molecular chain provides electrostatic interactions for the thickener structure, and the crosslinking agent MBA forms a chemical network structure in the CMC-PAA molecular chain. The synergistic formation of multiple dynamic crosslinking points through the above effects is beneficial for improving the electrolyte resistance of CMC-PAA thickeners. The shift of the carbonyl characteristic peak on the FTIR spectrum confirms the existence of hydrogen bonding interactions between PAA and CMC. The viscosity retention rates of CMC-PAA thickener in tap water and saltwater electrolytes were 97.01% and 53.22%, respectively, exceeding our previously reported hydrophobic modified polyacrylic acid thickener, confirmed that the introduction of hydrogen bonds inhibits the contraction of molecular chains. The fitting analysis of the rheological properties of the color paste shows that the sisko model has high fitting accuracy of the color paste. In addition, CMC-PAA has excellent thermal stability and water-holding properties, which can ensure the contour clarity of subsequent inkjet printed fabrics. This study provides a new method for improving the electrolyte resistance of polyacrylic acid thickeners.

Oxygen Evolution Platinum Group Metal-Free Catalyst Loading Optimization for Anion Exchange Membrane Water Electrolysis with Low Concentration Electrolyte

Anion exchange membrane water electrolysis (AEMWE) is receiving tremendous attention by many researchers in the field of the electrochemistry as it shows the potential to make the electrolytic hydrogen production more cost-effective. This technological advance has been made possible by the progress in the polymer chemistry of anion exchange membranes (AEMs) [1]. These materials can conduct hydroxide anions without suffering from the chemical degradation induced by the hydroxide itself. Like alkaline water electrolysis (AWE), AEMWE can exploit low cost and abundant materials, for example nickel and its alloys, for plates and porous transport layers and as catalysts. Furthermore, catalyst coated membranes (CCMs) can be manufactured as in proton exchange membrane water electrolysis and higher current densities can be achieved compared to AWE [2].However, nickel-based catalysts suffer from low mass activity as many other platinum-group metals-free (PGM-free) catalysts [3]. This downside could be mitigated by employing thick and high loading catalyst layers. However, as the catalyst is placed further from the membrane, the ohmic loss induced by the thickness of the electrode increases and reduces the utilization of the catalyst [4]. As the cost of PGM-free catalysts is orders of magnitude lower than traditional platinum and iridium catalysts, the fabrication of high loading catalyst seems a viable solution. Nevertheless, as the catalyst layer thickness continues to increase, the utilization of the catalyst decreases further and eventually it limits the performance improvement [3]. This applies especially to water or low concentration electrolyte fed systems, as concentrated KOH solution has been shown to greatly reduce catalyst layer ionic resistance [5]. Furthermore, mass transport issue can also play a significant role limiting performance as thick electrode have higher diffusion resistance.To explore the fabrication and electrochemical behavior of high loading anode electrodes, catalyst coated membranes (CCMs) were manufactured via decal transfer method [6]. RaneyTM Nickel mixed with Co3O4and RaneyTM Nickel served as the anode and cathode catalyst and the anode catalyst layer thickness was adjusted to control the loading. Low concentration electrolyte (0.1 KOH) was fed to the anode and the cathode was left dry. As expected, the cell voltage decreased increasing the catalyst loading. Notably, the performance was improved even when the catalyst loading increased from 6 to 12 mg/cm2.This work aims to study the performance limitations of high loading catalyst layer with PGM-free catalysts. It was found that even high catalyst loadings (12 mg/cm2) can deliver a sensible improvement of overall performance. We explain this with our systematic approach in this study.

Dynamic Modeling of Polymer Electrolyte Membrane Water Electrolysis System and Dynamic Response

Water electrolysis to produce hydrogen using electric energy is classified into polymer electrolyte water electrolysis, alkaline water electrolysis, solid oxide water electrolysis, and anion exchange membrane water electrolysis according to the type of electrolyte applied. Among them, polymer electrolyte membrane water electrolysis has a lower operating temperature than other types of water electrolysis, and it is possible to operate high-efficiency, high-power density hydrogen production with high current density. In addition, polymer electrolyte water electrolysis has the advantage of fast response to changes in power supply, so empirical studies for green hydrogen production linked to renewable energy are being conducted most actively compared to other water electrolysis. However, research on coupling polymer electrolyte water electrolysis with renewable energy generation with intermittent and irregular power generation has mainly focused on materials, cells, and stacks. In order to keep the hydrogen production reaction of water electrolysis stack stable under the condition of supply power fluctuation, the peripheral devices should be optimally installed and controlled.In this study, a dynamic model of a polymer electrolyte water electrolysis system was developed using Aspen HYSYS®. To accurately predict the hydrogen production efficiency, a stack model considering electrochemical reactions and crossovers through the electrolyte was developed and internalized in a spread sheet. A heat exchanger model from the model library was used to simulate dynamic changes in the electrolyte temperature flowing through the water electrolysis stack. The developed stack model was extended to a system model by integrating the feed pump, separator, condenser, heater, and cooling system. The developed water electrolysis system model was simulated in connection with power ramp variations and renewable energy output, and the optimal operation strategy of each module unit was derived to ensure the stability of high-purity hydrogen production under transient conditions.