Bulk Transfer Research Articles

Insight into Charge Transport Behaviors in Hematite Photoanodes via Potential-Dependent Impedance Spectroscopy and Machine Learning.

We employed machine learning (ML) techniques combined with potential-dependent photoelectrochemical impedance spectroscopy (pot-PEIS) to gain deeper insights into the charge transport mechanisms of hematite (α-Fe2O3) photoanodes. By the Shapley Additive exPlanations (SHAP) analysis from the ML model constructed from a small data set (dozens of samples) of electrical parameters obtained from pot-PEIS and the PEC performance, we identified the dominant factors influencing the electron transport to the back contact in the bulk and hole transfer to a solution at the hematite/electrolyte interface. The results revealed that shallow defect states significantly enhance electron transport, while deep defect states impede it, and also one of the surface states enhances the hole transfer to the electrolyte solution. The incorporation of a titanium dioxide underlayer had an effect to increase shallow defect states to promote electron transport and induce a new surface state to promote hole transfer. Cobalt phosphate cocatalyst improved charge separation, leading to enhance electron transport in the bulk, and the cocatalyst surface state promotes the hole transfer at the interface. The understanding of the band diagram based on the selected dominant descriptors provided critical insights into the electronic structure, elucidating the role of defect states and surface states in influencing the overall photoanode performance. This study showcases the potential of combining ML and pot-PEIS for material optimization.

Enhanced bulk and interfacial charge transfer in Fe:VOPO4 modified Mo:BiVO4 photoanodes for photoelectrochemical water splitting

Enhanced bulk and interfacial charge transfer in Fe:VOPO4 modified Mo:BiVO4 photoanodes for photoelectrochemical water splitting

Characteristics of Energy Fluxes and Cold Frontal Effects on Energy Exchange over a Boreal Lake

Understanding the characteristics and variations of heat exchange and evaporation of lakes is important for regional water resource management and sustainable development. Based on eddy covariance measurements over Lake Vanajavesi in southern Finland, characteristics of energy fluxes and cold frontal effects on energy exchange were investigated. The lake acted as a heat sink in spring and summer and a heat source in winter. The latent heat flux reached its minimum value in the morning and peaked in the afternoon. The diurnal variation of sensible heat flux was opposite to that of latent heat flux. Impact factors for the sensible heat flux were mainly the lake-air temperature difference and the product of lake-air temperature difference and wind speed. The latent heat flux was mainly affected by the vapor pressure deficit and the product of vapor pressure deficit and wind speed. The annual mean values of bulk transfer coefficients for momentum, heat, and water vapor were 1.98 × 10−3, 1.62 × 10−3, and 1.31 × 10−3, respectively. Bulk transfer coefficients for heat and water vapor were not equal, indicating that the parameterization of energy exchange in numerical models, where the assumption that the heat coefficient equals the water vapor coefficient needs improvement. During the ice-free season, cold fronts resulted in 28 sensible heat pulses and 17 latent heat pulses, contributing to 50.59% and 34.89% of sensible and latent heat exchange in Lake Vanajavesi. These results indicate that cold fronts significantly impact the surface energy budget and evaporation over lakes.

3D Structured Lithium Metal Anodes: A Comprehensive Analysis of Existing Work and Assessment of Performance Under Practical High Energy Density Cell Design

Lithium metal batteries (LMBs) are highly attractive for weight-limited applications due to their high theoretical gravimetric energy density. Advancements in recent years have yielded huge improvements in their cycle life and safety. However, LMBs still show capacity degradation and premature cell death due to the formation of dead lithium and electrolyte dry out in realistic cell design and testing. Current collectors with 3-dimensional structures have been proposed and studied extensively in recent years as an attempt to alleviate these issues. Three dimensional structures are claimed to improve performance by reducing local current density, restricting lithium volume expansion, stabilizing the solid-electrolyte interphase (SEI), improving the kinetics of lithium nucleation by providing additional lithium nucleation sites, and other justifications. However, despite the expansive literature published on the topic, no consensus has been reached as to what physical, chemical, and electrochemical properties of a 3D current collector are most likely to result in improved performance. This presentation focuses on two studies of 3D current collectors: (1) a meta-study reviewing literature data and analyzing the impact of key anode properties on the cycle life and Coulombic efficiency (CE); and (2) an experimental study on the electrochemical performance of four commercially available anode in combination with four different electrolytes.Analysis of published data using statistical methods and data science approaches (linear correlation coefficient calculations, self-organizing maps) show almost no consistent improvements of CE or cycle life based on frequently utilized strategies. Preliminary results suggest that there is no significant improvement with increasing surface area, altering pore diameter size, use of a lithiophilic coating or additive, nor any particular morphology. The only significant increase in CE noted is seen when a conductive coating or additive is utilized in the 3D structure compared to when an insulative coating is applied, though cycle life does not show a similar increase.Based on these insights, an experimental study is presented that compares four commercially available copper current collectors with different structures (foil, foam, punched foil, and layered punched foil on unaltered foil). These structures were chosen and left unaltered due to the lack of evidence in the literature data review of benefits arising from alterations. In addition to varying anode structure, four electrolytes are utilized, one conventional electrolyte and three state-of-the-art electrolytes, to determine if performance trends hold regardless of electrolyte used. Average CE values are determined over the course of a cycling protocol consisting of plating/stripping from a lithium reservoir, mimicking cycling in high energy density pouch cells. Changes in cell impedance are evaluated at multiple stages of cycling using electrochemical impedance spectroscopy (EIS), and the morphology of the SEI and the plated lithium metal is examined using cryo-focused ion beam scanning electron microscopy (cryo-FIB SEM) to give further insight into the behavior of lithium on the current collectors. Average CEs calculated from this testing show no statistically significant differences between any of the structures. Significant differences in CE are observed, however, when the varied electrolytes are employed. Evaluation of cell impedance changes during cycling shows similar bulk and interfacial charge transfer resistances between structures with consistent electrolyte. The conventional electrolyte demonstrates lower bulk resistance due to a slightly higher ionic conductivity than the state-of-the-art electrolyte yet greater charge transfer resistance, predicting worse long term performance. Morphological changes demonstrated increased lithium thickness, resulting in greater percentages of mossy lithium growth and more SEI formation over cycling for the conventional electrolyte, aligning with the observed charge transfer resistance. Differences in plated lithium density are also observed between substrates regardless of electrolyte, informing on their application for lean electrolyte conditions.In all, the experimental study indicates that electrolyte chemistry has a greater effect on the efficiency and morphology of lithium plating and stripping than current collector architecture when excess lithium is used in cell design. Based on the results presented, punched copper foil is proposed to be the ideal current collector for quick scale-up practical high energy density LMBs due to high CE in newer generation electrolytes and lower mass than the other tests substrates.

Electrochemical Analyses of the Li-Ion Transfer Resistances at the Chloride Solid Electrolyte | Sulfide Solid Electrolyte Interfaces

Introduction The all-solid-state Li-ion battery is expected to be a next-generation battery owing to its enhanced safety and high rate-capability ascribed to sulfide solid electrolytes (SEs) having incombustibility and high ionic conductivity. However, low cyclability hinders their practical application. Since the oxidative decomposition of the sulfide SE in the positive electrode is known as one of the main degradation modes, bilayer SE cells are promising to suppress the degradation where the chloride SE having relatively high stability against oxidation is placed on the positive electrode side and the reduction-resistive sulfide SE is placed on the negative electrode side. [1]. While it is reported that the interface between the sulfide and chloride SEs is not chemically stable and interphases are formed between the SEs [1], the effect of the interphase on the Li-ion transport between the sulfide and chloride SEs has not been investigated. As a way to analyze the resistance between two SEs, we have recently established an all-solid-state electrochemical four-electrode cell using a partially reduced lithium titanate (R-LTO) reference electrode (RE) [2,3]. Experimental In this study, we apply the electrochemical four-electrode cell to the sulfide SE | chloride SE interfaces to analyze the Li-ion transport resistance. The glass-ceramic Li2S-P2S5-LiI (LPSI) was synthesized by the method reported by X. Feng et al. [4]. The chloride SEs, Li3InCl6 (LIC), Li3SrCl6 (LSC), and Li3YCl6 (LYC) were synthesized following the previous report [1]. The ionic conductivities and activation energies of the LPSI, LIC, LSC, and LYC were measured to be 2.1, 0.36, 0.5 and 0.28 mS cm–1 at 25 °C, and 29.8, 33.5, 38.5 and 38.6 kJ mol–1, respectively. The R-LTO REs were fabricated by the previously reported method [2]. All-solid-state four-electrode cells (Fig. 1(a)) were fabricated in the following way. First, the LPSI pellet incorporating the R-LTO was fabricated by hand pressing in a mold. Then, the chloride SE powder was sandwiched with the LPSI layers followed by cold pressing at ca. 290 MPa. Finally, Li-In foil synthesized with a chemical lithiation of the In foil was put on the outer sides of the stacked pellet as the counter electrodes (CEs) [2]. Electrochemical impedance spectroscopy (EIS) was conducted between 50 mHz and 7 MHz with an AC amplitude of 10 mV at OCV using an electrochemical measurement system (VSP-300, BioLogic). Results and Discussion Fig. 1(b) shows the impedance spectrum obtained by EIS using a pristine LIC | LPSI cell at 25 °C. Two semicircles P 1 and P 2 are found in higher and lower frequency regions and assigned as bulk and interfacial Li-ion transfer from the frequency response [2]. The interfacial resistance of the LPSI | LIC | LPSI cell shows a continuous increase at 25 °C, though it does not change significantly at –5 °C. This result indicates that the resistive interphase is formed by a chemical reaction. The growth ratios of the interfacial resistances of the LPSI | LIC | LPSI, LPSI | LYC | LPSI, and LPSI | LSC | LPSI cells for 50 h are 2.2,1.6 and 1.4 respectively. References 1) M. Chandrappa et al., J. Am. Chem. Soc., 144, 18009 (2022).2) K. Yoshida et al., submitted to Electrochim. Acta (2024).3) A. Ikezawa et al., Electrochem. Commun., 116, 1067433 (2020).4) X. Feng et al., Energy Storage Mater., 22, 397 (2019). Acknowledgment This work was supported by JSPS KAKENHI Grant Number JP22H04608. Figure 1

Adsorption potential of spherical ZnO particles for sufficient antibiotic removal: isotherm, kinetic and thermodynamics

Due to the improvements of pharmaceutical industry, tetracycline (TC) is commonly detected in natural water environments, resulting in significant adverse impacts on living species. In this study, the TC adsorption over commercial spherical zinc oxide (ZnO) samples was systematically examined by considering adsorption isotherm models, kinetic model and thermodynamic behavior. The Langmuir kinetic model displayed the highest correlation coefficient (R2 = 0.97) with a maximum adsorption capacity of 86.35 mg/g. According to the results of the kinetic studies, the adsorption could be driven by both the bulk transfer of adsorbate molecules towards the adsorbent surface within the solution and chemisorption on the surface and inside the pores. In addition, the TC adsorption on the ZnO particles promoted by increasing temperature. The commercial spherical zinc oxide can be considered as a sustainable strategy to eliminate the emerging toxic contaminant of tetracycline.

Fully Flexible All‐in‐One Electronic Display Skin with Seamless Integration of MicroLED and Hydrogel Battery

AbstractVisualization is a cornerstone in human–computer interaction, evolving from large screens to mobile devices and now to wearable display technology. However, conventional batteries and displays lack the softness and stretchability inherent to human skin. Here, a fully flexible, all‐in‐one electronic display skin by integrating a flexible microLED display, a stretchable circuit, and a Zn|PAM|V2O5 hydrogel battery pack is developed. Vapor‐phase bulk transfer is used to efficiently and accurately transfer 10 000 microLEDs onto a flexible substrate, ensuring high flexibility and ultra‐thin (240 µm). The flexible hydrogel battery pack provides sustainable energy, with a high specific capacity of 331.3 mAh g−1. Additionally, a transparent stretchable circuit board (maximum stretch 40%) is made by 3D printing technology. The skin display exhibited exceptional stretchability and biocompatibility, conforming to movements while maintaining high‐resolution dynamic visual outputs. These innovations pave the way for advanced skin‐implanted displays, promising transformative applications in information interaction, healthcare, and artificial intelligence.

Boosting bulk photocharge separation and transfer in heterojunctions for antibiotics removal: Enhanced internal electric field and interfacial electric field

Boosting bulk photocharge separation and transfer in heterojunctions for antibiotics removal: Enhanced internal electric field and interfacial electric field

Control of Interface Migration in Nonequilibrium Crystallization of Li2SiO3 from Li2O-SiO2 Melt by Spatiotemporal Temperature and Concentration Fields.

During liquid-solid transformation, bulk mass and thermal diffusion, along with the evolved interfacial latent heat, work in tandem to generate interfacial thermodynamic and kinetic forces, the interplay of which decides the solidification velocity and consequently the solidified phase attributes. Hence, access to interface dynamics information in dependence of bulk transfer processes is pivotal to tailor the desired quantity of solid phases of unique compositions. It finds particular application for engineering concentrated Lithium (Li) phases out of Li-ion battery slags, thus generating a high value-added product from a conventional waste process stream. However, considerable challenge exists to predict the impact of the diverse external cooling rates on the evolving internal transfer processes and thus tuning solidification routes for achieving phases of interest. Hence, in this work, a thermodynamically consistent nonequilibrium model, by considering spatiotemporal temperature and concentration fields, is developed and applied to study solidification of Li2SiO3 from a Li2O-SiO2 melt that constitutes an important subsystem of the Li containing battery-recycling slags. The approach treats the sharp solid/liquid interface as a moving heat source. In the presence of different heat extraction profiles, it evaluates the spatial temperature heterogeneity and its implicit correlation to internal material fluxes resulting from maximization of dissipation and consequently the interrelation to interface velocities. Model calculations revealed that irrespective of the external cooling rate, for an initial short time duration, the magnitude of which increased with decreasing cooling rates, the interface velocities show a reducing trajectory directly relatable to the reducing thermodynamic forces due to localized interfacial temperature rise from the generated latent heat of fusion from the initial solidification. This is followed by a thermodynamically controlled regime, whereby for each cooling rate, the interface velocities increase until a maxima, the magnitude of which decreases with decreasing cooling rates. Finally, the interface propagation speeds decrease as controlled by the kinetic regime.

Solvation structure dependent ion transport and desolvation mechanism for fast-charging Li-ion batteries.

The solvation structures of Li+ in electrolytes play prominent roles in determining the fast-charging capabilities of lithium-ion batteries (LIBs), which are in urgent demand for smart electronic devices and electric vehicles. Nevertheless, a comprehensive understanding of how solvation structures affect ion transport through the electrolyte bulk and interfacial charge transfer reactions remains elusive. We report that the charge transfer reaction involving the desolvation process is the rate-determining step of the fast charging when ion conductivity reaches a certain value as determined by investigating electrolytes with eight conventional solvents (linear/cyclic carbonate/ether). The physicochemical characteristics of solvent molecules can result in strong ion-ion, moderate ion-dipole, strong ion-dipole, and weak ion-dipole/ion-ion interactions, respectively, in which the speed of the charge transfer reaction follows the above order of interactions. Among all solvents, dioxolane (DOL) is found to enable strong ion-ion interactions in electrolytes and thus exhibits exceptional fast-charging performance and it can still retain 60% of the initial capacity at 20C (1C = 170 mA g-1) with a polarization of merely 0.35 V. Further experimental characterization and theoretical calculation reveal that the aggregates in DOL electrolytes contribute to hopping assisted ion transport and facilitate the desolvation process of Li+. Our results deepen the fundamental understanding of the behavior of Li+ solvation and provide an effective guiding principle for electrolyte design for fast-charging batteries.

Enhancing photocatalytic efficiency with hematite photoanodes: principles, properties, and strategies for surface, bulk, and interface charge transfer improvement

This review systematically explores various strategies aimed at enhancing charge transfer at different levels—bulk, surface, and interfaces of hematite. The examination encompasses diverse approaches, and assesses their impact on mitigating the identified issues.

An approach to substitute costly-commercial capattery electrodes by activated carbon@Co with advanced retention: Detailed device study supported by DFT investigation

An approach to substitute costly-commercial capattery electrodes by activated carbon@Co with advanced retention: Detailed device study supported by DFT investigation

Chimie Douce Derived K-Based P2-Type Transition Metal(s) Layered Oxides for Secondary K-Ion Batteries

Owing to great societal and technological benefits, there has been a remarkable growth in the industrial demand for enhanced energy storage for many target applications including electric vehicles, aerospace applications, and portable electronics. Secondary K-ion batteries (KIBs) are among the potentially inexpensive candidates for energy storage systems beyond state-of-the-art Li-ion batteries (LIBs). Electrochemical cells based on mobile carrier K+ can provide efficient energy storage because of comparative ionic diffusion in bulk and swift charge transfer at the interface due to weak Lewis’s acidity.1,2 Despite various advantages over LIBs and NIBs, the roadblock of practical KIB implementation lies in identifying suitable cathodes that reversibly (de)intercalate K+ at optimum voltage, swift rate, and with prolonged cycle life.Despite constant efforts to develop new cathodes for K+ -ion batteries, several challenges such as low concentrations of K-ions due to strong electrostatic repulsions between the K+ - K+ ions and difficulty in preparation from direct synthesis routes3 limit its practical application. In this scenario, we have adopted the chimie douce (soft chemistry) method to design the novel layered transition metal oxide cathode from the parent P2 type Na-based system. In addition, we have probed the ion exchange mechanism using X-ray diffraction and transmission electron microscopy (TEM) techniques. Rietveld analysis confirmed the structure having a P2-type stacking sequence with hexagonal symmetry and P6/3mmc space group. Further, we have successfully examined the chemical ion-exchanged novel layered P2- K2/3Co1/3Mn2/3O2 as a cathode for KIB at ambient and high temperatures. It delivered a good capacity (~70 mAh/g) with an average redox potential of 3.0 V along with good cycling stability and coulombic efficiency (CE) in temperature ranging from 25-50 ºC. Ex-situ X-ray diffraction analysis and potentio/galvanostatic titration techniques were used to analyse the K+ insertion mechanism. This study can assist in developing new insertion K+ host materials for viable and reliable practical applications.

Bifunctional Co-TiO2 co-promoted bulk and interfacial charge transfer of BiVO4 photoanodes for solar water oxidation

Bifunctional Co-TiO2 co-promoted bulk and interfacial charge transfer of BiVO4 photoanodes for solar water oxidation

Swelling of lignin-based gel in salt-containing organic solvents and its application as gel electrolyte

Abstract A lignin-based gel prepared by the chemical crosslinking of hardwood acetic acid lignin (AL) with poly(ethylene glycol) diglycidyl ether has been reported to shrink in water and organic solvents but swell specifically in aqueous binary solutions. In this study, the AL-based gel was also found to swell in lithium-salt-containing organic solvents, namely, liquid electrolytes. The uptake of salt solutions reached five times the dry weight of the gel. The ionic conductivity of the gel swollen with 1 M LiBF4 in propylene carbonate or a mixed solution (1:1, v/v) of ethylene carbonate and dimethyl carbonate exceeded 1 mS cm−1 at room temperature (25 °C), suggesting that this gel can be applied as a gel electrolyte for lithium-ion batteries (LIBs). A prototype LIB was assembled with the AL-based gel electrolyte and LiCoO2/graphite-based electrodes and exhibited low bulk and charge transfer resistances of 4.1 and 9.7 Ω, respectively. Moreover, its initial specific capacity reached 104 mAh g−1 at a current density of 28 mA g−1, which is comparable to that of a reference LIB assembled using a commercial polyethylene separator. These results indicate the significant potential of this lignin-based gel for application in energy storage devices.

Upstream–Downstream Asymmetry in Multiscale Interaction Underlying the Northern Hemisphere Atmospheric Blockings

Abstract The typical blockings over the Pacific, Atlantic, and Ural Mountain regions are investigated for an understanding of their dynamical interactions in a unified treatment with their respective basic flows and high-frequency processes, respectively. Thanks to the localized nature of the new methodology as used in this study, for the first time we identify a dipolar structure (for each of the three regions) in the map of the interscale energy transfer from the basic flow to the composite blocking, with a positive center upstream and a negative center downstream. This indicates the crucial role of the instability of the basic flow in the maintenance of blockings, which has been overlooked due to the bulk nature of the spatially integrated energetics (by summing the transfer over the whole blocking, the two centers essentially cancel out, leaving an insignificant bulk transfer). For the interaction between the blocking and the high-frequency storms, the well-known critical role of the upscale forcing in blocking development is confirmed. But, unexpectedly, except for that over the Atlantic where the forcing exists throughout, over the other two regions the forcing is found to occur mainly downstream. This is quite different from what the classical theory, e.g., the famous eddy strain mechanism of Shutts, would predict.

Enhancing HTTP Web Protocol Performance with Updated Transport Layer Techniques

Popular Internet applications such as web browsing, and web video download use HTTP protocol as application over the standard Transport Control Protocol (TCP). Traditional TCP behavior is unsuitable for this style of application because their transmission rate and traffic pattern are different from conventional bulk transfer applications. Previous works have analyzed the interaction of these applications with the congestion control algorithms in TCP and the proposed Congestion Window Validation (CWV) as a solution. However, this method was incomplete and has been shown to present drawbacks. This paper focuses on the ‘newCWV’ which was designed to address these drawbacks. NewCWV provides a practical mechanism to estimate the available path capacity and suggests a more appropriate congestion control behavior. This paper describes how this algorithm was implemented in the Linux TCP/IP stack and tested by experiments, where results indicate that, with newCWV, the browsing can get 50% faster in an uncongested network.

Fine-tuning Li+ solvation structure enabled by steric effect and solvating chemistry of the anion for practical electrolyte engineering

Fine-tuning Li+ solvation structure enabled by steric effect and solvating chemistry of the anion for practical electrolyte engineering

Parameterization and Remote Sensing Retrieval of Land Surface Processes in the Gurbantunggut Desert, China

The exchange of energy between the land surface and atmosphere is dependent upon crucial parameters, including surface roughness, emissivity, bulk transfer coefficients for momentum (CD) and heat (CH). These parameters are calculated through site observation data and remote sensing data. The following conclusions are drawn: (1) the aerodynamic roughness of the Gurbantunggut Desert measures 1.1 × 10−2 m, which is influenced by the varying conditions of the underlying surface. The roughness decreases as wind speed increases and is seen to be directly proportional to the growth of vegetation. From April to June, the aerodynamic roughness increases with increasing vegetation cover, but begins to gradually decrease after July. Spatially, the middle regions show higher roughness values than the eastern and western areas. In the central part of the desert, the roughness is between 2.37 × 10−2 m and 2.46 × 10−2 m from April to November. The northwest and northeast regions measure 1.41 × 10−2 m–2.04 × 10−2 m and 1.53 × 10−2 m–2.39 × 10−2 m, respectively. (2) The surface emissivity is 0.93, and it varies depending on the snow and vegetation present in the underlying area. (3) CD and CH exhibit an inverse relationship with wind speed. When wind speed falls below 6 m/s, the CD declines rapidly as wind speed increases. In contrast, once wind speed surpasses 6 m/s, the propensity for the CD to decrease with increasing wind speed slows down and approaches stability.

An Application of the Maximum Entropy Production Method in the WRF Noah Land Surface Model

AbstractThe calculation of surface sensible heat (SH) and latent heat (LE) fluxes using the bulk transfer models for complex terrains, tall vegetation regions, and morning and evening transition periods remains a challenging problem in numerical weather and climate models. The maximum entropy production (MEP) model, a new method of calculating surface heat fluxes, is coupled with the Noah land surface model (LSM) in the Weather Research and Forecasting (WRF) model. Surface heat fluxes and meteorological variables including air temperature, relative humidity, soil temperature, and precipitation data at nine intensive observation stations and 453 routine meteorological operational observation stations in the Tibetan Plateau (TP) from 1 June to 31 August 2015 are used to evaluate the coupled model. The results show that the MEP method improves the nonclosure of the surface energy balance in the WRF (with an energy residual from 24.3 to 1.9 W m−2), reducing the overestimations of SH and LE and the underestimation of the surface ground heat flux over the complex terrain of TP (with the bias decreases of 50.6% and 117.1% for SH and LE in turn), especially during the daytime. The improved SH and LE reduce the cold and wet biases in the TP by 29.4% and 51.7%, respectively. The MEP model also reduces the overestimated soil temperature by 63%. Moreover, the overestimated daily precipitation is reduced by 3% over the TP. The successful application of the MEP method demonstrates its advantage over the bulk transfer method, providing a new approach for reducing the overestimation of surface heat fluxes and wet and cold biases in numerical forecast models in complex terrains.