Structure Of Electrical Double Layer Research Articles

Multifunctional Amphoteric Additive Alanine Enables High-Performance Wide-pH Zn Metal Anodes.

Interfacial pH fluctuation is one of the primary reasons for issues related to Zn metal anodes. Herein, polar amphoteric alanine, as a multifunctional electrolyte additive, is designed to regulate the electric double layer (EDL) and solvation structure. Alanine with self-adaptation capability to pH can stabilize electrolyte pH. Due to more negative adsorption energy, alanine preferentially adsorbs on the Zn surface and repels water molecules within the EDL. Alanine-enriched EDL effectively shields the surface tips, homogenizes interfacial electric field distribution, and promotes preferential deposition of horizontal flaky Zn. Alanine-enriched EDL limits the contact between water and the Zn anode. Alanine additive decreases the quantity of water molecules in the Zn2+ solvation sheath and disrupts H-bond networks in the electrolyte. Consequently, a dense and textured Zn deposition is achieved. Corrosion and side reactions are suppressed. Cycling stability of symmetrical cells attains 2700h at 3mAcm-2/1mAhcm-2 and 2050h at 5mAcm-2/1mAhcm-2. Average coulombic efficiency reaches 99.8% over 4500 cycles at 5mAcm-2/1mAhcm-2. Even within KOH alkaline electrolytes, alanine additive still improves the cycling lifespan of symmetrical cells to 100h at 0.5mAcm-2/0.5mAhcm-2.

Electrolyte Effects in Electrocatalytic Kinetics†

Comprehensive SummaryTuning electrolyte properties is a widely recognized strategy to enhance activity and selectivity in electrocatalysis, drawing increasing attention in this domain. Despite extensive experimental and theoretical studies, debates persist about how various electrolyte components influence electrocatalytic reactions. We offer a concise review focusing on current discussions, especially the contentious roles of cations. This article further examines how different factors affect the interfacial solvent structure, particularly the hydrogen‐bonding network, and delves into the microscopic kinetics of electron and proton‐coupled electron transfer. We also discuss the overarching influence of solvents from a kinetic modeling perspective, aiming to develop a robust correlation between electrolyte structure and reactivity. Lastly, we summarize ongoing research challenges and suggest potential directions for future studies on electrolyte effects in electrocatalysis. Key ScientistsIn 1956, Marcus theory was developed to describe the mechanism of outer‐sphere electron transfer (OS‐ET). In 1992, Nocera et al. directly measured proton‐coupled electron transfer (PCET) kinetics for the first time, and their subsequent research in 1995 investigated the effects of proton motion on electron transfer (ET) kinetics. In 1999 and 2000, Hammes‐schiffer et al. developed the multistate continuum theory for multiple charge reactions and deduced the rate expressions for nonadiabatic PCET reactions in solution, laying the theoretical foundation for the analysis of PCET kinetics in electrochemical processes. In 2006, Saveant et al. verified the concerted proton and electron transfer (CPET) mechanism in the oxidation of phenols coupled with intramolecular amine‐driven proton transfer (PT). Their subsequent work in 2008 reported the pH‐dependent pathways of electrochemical oxidation of phenols.Electrolyte effects in electrocatalysis have gained emphasis in recent years. In 2009, Markovic's pioneering work proposed non‐covalent interactions between hydrated alkaline cations and adsorbed OH species in oxygen reduction reaction (ORR)/hydrogen oxidation reaction (HOR). In 2011, Markovic et al. significantly enhanced hydrogen evolution reaction (HER) activity in alkaline solution by improving water dissociation, which was assumed to dominate the sluggish HER kinetics in such media. In comparation, Yan et al. applied hydrogen binding energy (HBE) theory in 2015 to explain the pH‐dependent HER/HOR activity. Cations play a significant role in regulating the selectivity and activity of carbon dioxide reduction (CO2RR). In 2016 and 2017, Karen Chan et al. introduced the electric field generated by solvated cations to explain the cation effects on electrochemical CO2RR. Conversely, in 2021, Koper et al. suggested that short‐range electrostatic interactions between partially desolvated metal cations and CO2 stabilized CO2 and promoted CO2RR.Recent researches have combined the exploration of the electrical double layer (EDL) structure with theoretical analysis of PCET kinetics. In 2019, Huang et al. developed a microscopic Hamiltonian model to quantitatively understand the sluggish hydrogen electrocatalysis in alkaline media. In 2021, two meticulous studies from Shao‐Horn's group analyzed the effects of cations on reorganization energy and the impacts of hydrogen bonds between proton donors and acceptors on proton tunneling kinetics, respectively. Electrolyte effects on proton transport process were researched in recent years. In 2022, Hu et al. and Chen et al. proposed that the cation‐induced electric field distribution and pH‐dependent hydrogen bonding network connectivity played essential roles in proton transport, separately.

Electrical Double Layer Spillover Drives Coupled Electron- and Phase-Transfer Reactions at Electrode/Toluene/Water Three-Phase Interfaces.

A mechanism for the concerted pathway of coupled electron- and phase-transfer reactions (CEPhT) is proposed. CEPhT at three-phase interfaces formed by a solid electrode, an insulating organic solvent, and an aqueous electrolyte is driven by electric double layer (EDL) spillover, with significant electrostatic potential gradients extending a few nanometers into the insulating phase. This EDL spillover phenomenon is studied using scanning electrochemical cell microscopy to interrogate the oxidation of ferrocene in toluene to ferrocenium in water, (Fc)tol → (Fc+)aq + e-. Finite element method simulations of the electrostatic potential distribution and species concentration profiles enable the calculation of complete i-E curves that incorporate mass transport, electron transfer, phase transfer, and the EDL structure. Simulated and experimental i-E traces show good agreement in the current magnitude and the effect of the supporting electrolyte, identifying an unexpected dependence of overall reaction kinetics on the concentration of the supporting electrolyte in the aqueous phase due to EDL spillover. An interfacial toluene/water mixing region generates a unique electrochemical microenvironment where concerted electron transfer and solvent shell replacement facilitate CEPhT. Kinetic expressions for concerted and sequential CEPhT mechanisms highlight the role of this interfacial environment in controlling the rate of CEPhT. These combined experimental and simulated results are the first to support a concerted mechanism for CEPhT where (Fc)tol is transported to the interfacial mixing region at the three-phase interface, where it undergoes oxidation and phase transfer. EDL spillover can be leveraged for engineering sample geometries and electrostatic microenvironments to drive electrochemical reactivity in classically forbidden regions, e.g., insulating solvents and gases.

Hydroxyl-Binding Induced Hydrogen Bond Network Connectivity on Ru-based Catalysts for Efficient Alkaline Hydrogen Oxidation Electrocatalysis.

Understanding the role of adsorbed intermediates at the polarized catalyst-electrolyte interface on the structure of electrical double layer (EDL) is essential for developing highly efficient electrocatalysts. Here, we prepared a series of unconventional face-centered-cubic (fcc) phase Ru-based catalysts (i.e. fcc-Ru, fcc-RuCr, and fcc-RuCrW) by rational tuning the binding energetics of hydroxyl intermediate to engineer the electrochemical interface and boost the performance of alkaline hydrogen oxidation reaction (HOR). The introduction of oxyphilic metals Cr and W can regulate the orbital occupation of Ru, promote the adsorption of hydroxyl species, resulting in an anomalous behavior that HOR performance under alkaline media exceeds acidic media. Experimental results and theoretical calculations unravel that the modulated adsorption of hydroxyl species on the electrode surface are responsible for the reconstruction of interfacial water structure and dynamic evolution of free water molecules from nearest to the electrode surface to above the gap region in the EDL, thereby leading to significantly increased water connectivity and hydrogen bond network. Our work reveals a new understanding of the surface intermediates in controlling the dynamic process of interfacial water and hydrogen bonding network in HOR electrocatalysis, and will guide rational design of advanced electrocatalysts through electrochemical interfacial engineering.

Hydroxyl‐Binding Induced Hydrogen Bond Network Connectivity on Ru‐based Catalysts for Efficient Alkaline Hydrogen Oxidation Electrocatalysis

Understanding the role of adsorbed intermediates at the polarized catalyst‐electrolyte interface on the structure of electrical double layer (EDL) is essential for developing highly efficient electrocatalysts. Here, we prepared a series of unconventional face‐centered‐cubic (fcc) phase Ru‐based catalysts (i.e. fcc‐Ru, fcc‐RuCr, and fcc‐RuCrW) by rational tuning the binding energetics of hydroxyl intermediate to engineer the electrochemical interface and boost the performance of alkaline hydrogen oxidation reaction (HOR). The introduction of oxyphilic metals Cr and W can regulate the orbital occupation of Ru, promote the adsorption of hydroxyl species, resulting in an anomalous behavior that HOR performance under alkaline media exceeds acidic media. Experimental results and theoretical calculations unravel that the modulated adsorption of hydroxyl species on the electrode surface are responsible for the reconstruction of interfacial water structure and dynamic evolution of free water molecules from nearest to the electrode surface to above the gap region in the EDL, thereby leading to significantly increased water connectivity and hydrogen bond network. Our work reveals a new understanding of the surface intermediates in controlling the dynamic process of interfacial water and hydrogen bonding network in HOR electrocatalysis, and will guide rational design of advanced electrocatalysts through electrochemical interfacial engineering.

Anion Receptor-manipulated solvation chemistry and electric double layer enables high Zn-Utilization rate and lean Zn metal batteries

The practical application of aqueous Zn metal batteries (AZMBs) is impeded by inferior reversibility and stability of Zn metal anode (ZMA) originated from side reactions and dendrite growth. Herein, anion receptor l-Proline (LP) is selected to simultaneously manipulate solvation chemistry and electric double layer (EDL) for constructing dendrite-free and stable AZMBs with an ultra-high depth of discharge (DOD of 100 %) and low negative/positive capacity ratio (N/P of 1.1). Experimental and computational results demonstrate that the strong interaction between −SO32- group from OTf- anion and LP promotes the coordination effect of cation and solvent, which improves the stability of electrolyte and induces fine and uniform Zn nucleus formation. Meanwhile, the preferential reduction of OTf- and adsorption of LP establish an anion-derived ZnF2-rich solid electrolyte interface by altering EDL structure, which enhances the mechanical stability and Zn2+ diffusion kinetics of the interface and prevents the contact of H2O molecules. Consequently, ZMA in LP/Zn(OTf)2 electrolyte delivers a satisfactory cycling lifespan under DOD of 100 % and an outstanding Coulombic efficiency of 99.93 % for 10,000 cycles at 10 mA cm−2. Moreover, Zn||Od-NH4V4O10 full cells with LP/Zn(OTf)2 electrolyte demonstrate excellent cycle stability at high cathode loading (20.412 mg), low N/P (1.1), and high temperature (50 °C).

High-Entropy-Inspired Multicomponent Electrical Double Layer Structure Design for Stable Zinc Metal Anodes.

Regulating the electrical double layer (EDL) structure can enhance the cycling stability of Zn metal anodes, however, the effectiveness of this strategy is significantly limited by individual additives. Inspired by the high-entropy (HE) concept, we developed a multicomponent (MC) EDL structure composed of La3+, Cl-, and BBI anions by adding dibenzenesulfonimide (BBI) and LaCl3 additives into ZnSO4 electrolytes (BBI/LaCl3/ZnSO4). Specifically, La3+ ions accumulate within EDL to shield the net charges on the Zn surface, allowing more BBI anions and Cl- ions to enter this region. Consequently, this unique MC EDL enables Zn anodes to simultaneously achieve uniform electric field, robust SEI layer, and balanced reaction kinetics. Moreover, the synergistic parameter - a novel descriptor for quantifying collaborative improvement - was first proposed to demonstrates the synergistic effect between BBI and LaCl3 additives. Benefitting from these advantages, Zn metal anodes achieved a high reversibility of 99.5 % at a depth of discharge (DoD) of 51.3 %, and Zn|MnO2 pouch cells exhibited a stable cycle life of 100 cycles at a low N/P ratio of 2.9.

High‐Entropy‐Inspired Multicomponent Electrical Double Layer Structure Design for Stable Zinc Metal Anodes

AbstractRegulating the electrical double layer (EDL) structure can enhance the cycling stability of Zn metal anodes, however, the effectiveness of this strategy is significantly limited by individual additives. Inspired by the high‐entropy (HE) concept, we developed a multicomponent (MC) EDL structure composed of La3+, Cl−, and BBI anions by adding dibenzenesulfonimide (BBI) and LaCl3 additives into ZnSO4 electrolytes (BBI/LaCl3/ZnSO4). Specifically, La3+ ions accumulate within EDL to shield the net charges on the Zn surface, allowing more BBI anions and Cl− ions to enter this region. Consequently, this unique MC EDL enables Zn anodes to simultaneously achieve uniform electric field, robust SEI layer, and balanced reaction kinetics. Moreover, the synergistic parameter – a novel descriptor for quantifying collaborative improvement – was first proposed to demonstrates the synergistic effect between BBI and LaCl3 additives. Benefitting from these advantages, Zn metal anodes achieved a high reversibility of 99.5 % at a depth of discharge (DoD) of 51.3 %, and Zn|MnO2 pouch cells exhibited a stable cycle life of 100 cycles at a low N/P ratio of 2.9.

Interfacial space confinement engineering toward ultrastable all-climate aqueous zinc ion batteries

The interfacial instability, particularly uncontrollable Zn nucleation and deposition, significantly impeding the commercialization of aqueous zinc ion batteries (ZIBs). Herein, we propose an interfacial space confinement strategy to enable the dendrite-free anode, specifically through constructing a zincophilic buffer layer based on hollow Sn@C. The porous Sn@C contributes to modify the electrical double layer structure, which greatly alleviates the concentration polarization during high-rate plating. In-situ experimental results demonstrate the inhibited H2O-mediated parasitic side reactions and the absence of dendrite deposition morphology. Based on the improved thermodynamics and kinetics, zincophilic buffer layers can deliver low nucleation overpotential (20 mV), ultrastable cycle life (> 5000 h), and excellent zinc utilization rate (62.4%). Importantly, the full batteries with zincophilic buffer layer exhibit excellent electrochemical stability over -40 to 70 °C, pushing forward the construction of advanced all-climate ZIBs.

Strategically Modulating Proton Activity and Electric Double Layer Adsorption for Innovative All-Vanadium Aqueous Mn2+/Proton Hybrid Batteries.

Aqueous Mn-ion batteries (MIBs) exhibit a promising development potential due to their cost-effectiveness, high safety, and potential for high energy density. However, the development of MIBs is hindered by the lack of electrode materials capable of storing Mn2+ ions due to acidic manganese salt electrolytes and large ion radius. Herein, the tunnel-type structure of monoclinic VO2 nanorods to effectively store Mn2+ ions via a reversible (de)insertion chemistry for the first time is reported. Utilizing exhaustive in situ/ex situ multi-scale characterization techniques and theoretical calculations, the co-insertion process of Mn2+/proton is revealed, elucidating the capacity decay mechanism wherein high proton activity leads to irreversible dissolution loss of vanadium species. Further, the Grotthuss transfer mechanism of protons is broken via a hydrogen bond reconstruction strategy while achieving the modulation of the electric double-layer structure, which effectively suppresses the electrode interface proton activity. Consequently, the VO2 demonstrates excellent electrochemical performance at both ambient temperatures and -20°C, especially maintaining a high capacity of 162mAhg-1 at 5Ag-1 after a record-breaking 20000 cycles. Notably, the all-vanadium symmetric pouch cells are successfully assembled for the first time based on the "rocking-chair" Mn2+/proton hybrid mechanism, demonstrating the practical application potential.

Electrical Double Layer and In Situ Polymerization SEI Enables High Reversible Zinc Metal Anode.

Aqueous zinc-ion batteries (AZIBs) stand out among new energy storage devices due to their excellent safety and environmental friendliness. However, the formation of dendrites and side reactions on the zinc metal anode during cycling have become the major obstacles to their commercialization. This study innovatively selected Sodium 4-vinylbenzenesulfonate (VBS) as a multifunctional electrolyte additive to address the issues. The dissociated VBS- anions can not only significantly alter the hydrogen bond network structure of H2O in the electrolyte, but also preferentially adsorb on the surface of the zinc anode before H2O molecules, which will result in the development of organic anion-rich interface and alterations to the electrical double layer (EDL) structure. Furthermore, the ─C═C─ structure in VBS leads to the formation of an in situ polymerized organic anion solid electrolyte interface (SEI) layer that adheres to the surface of the zinc anode. The mechanisms work together to significantly improve the performance of Zn//Zn symmetric batteries, achieving a cycle life of over 1800h at 1mA cm-2 and 1 mAh cm-2. The introduction of VBS also enhances the cycling performance and capacity of Zn//δ-MnO2 full cells. This study provides a low-cost solution for the development of AZIBs.

Evaluation of the Solid-Electrolyte Interphase Formation in a Bis(fluorosulfonyl)amide Based Ionic Liquid in the Presence Lithium Ion Using Different Redox Probes

The SEI formation in 0.5 M LiFSA/BMPFSA was investigated using different redox probes. The redox reaction of a metallocene and organic compound on a Pt electrode were investigated by cyclic voltammetry in BMPFSA and 0.5 M LiFSA/BMPFSA. Cyclic voltammograms were taken after holding the electrode at different potentials for 1 h. The cyclic voltammograms were unchanged in BMPFSA, indicating that BMPFSA was stable in the measured potential range and that the redox reaction was not affected by a change in the electric double layer structure. On the other hand, peak shifts were observed in the presence of Li+ at potentials more negative than –1.1 V vs. Ag|Ag(I), attributed to a decrease in the electron transfer rates and indicating that the SEI formation promoted by the interaction between Li+ and FSA– affects the redox reactions not only of metallocene but also of organic compounds that undergo outer sphere electron transfer reactions.

Preferred crystal surface exposure and near-crystal surface desolvation construct efficient Zn plating/stripping reversibility

The Zn/electrolyte interface stability is related to HER, passivation, dendrites, corrosion and Zn2+ deposition orientation. Reducing the occupation of H2O dipoles in the inner layer of electrical double layer (EDL) is conducive to the inhibition of interfacial side reactions and directing the deposition of Zn2+ along the (002) crystalline surface, which are beneficial to the reduction of dendrites and the improvement of plating/stripping reversibility. A mechanism is elucidated by which Acetyl-L-carnitine Hydrochloride (A-L-CN) reconfigures the EDL structure and guides the selective deposition of Zn2+ in this paper. Theoretical calculations show that A-L-CN can cover the high-energy active sites on the Zn (101) crystal plane and control the specific crystal orientation of the deposits along the (002) crystal plane to produce faceted epitaxial growth. The electrochemical test results show that the Zn anode has excellent plating/stripping reversibility as well as good cumulative capacity (10 mA cm−2, 1 mA h cm−2, ACE of 99.80 %, CPC of 7,753 mA h cm−2). The assembled Zn2+ hybrid supercapacitor (ZHS) and Zn//PANI full cell show excellent performance (ZHS up to 60,000 cycles; the capacity retention ratio of Zn//PANI full cell is 76.7 % after 1,000 cycles). The work offers the possibility of achieving stabilized Zn/electrolyte interface performance.

Engineering of charge density at the anode/electrolyte interface for long-life Zn anode in aqueous zinc ion battery.

The aqueous zinc ion battery emerges as the promising candidate applied in large-scale energy storage system. However, Zn anode suffers from the issues including Zn dendrite, Hydrogen evolution reaction and corrosion. These challenges are primarily derived from the instability of anode/electrolyte interface, which is associated with the interfacial charge density distribution. In this context, the recent advancements concentrating on the strategies and mechanism to regulate charge density at the Zn anode/electrolyte interface are summarized. Different characterization techniques for charge density distribution have been analysed, which can be applied to assess the interfacial zinc ion transport. Additionally, the charge density regulations at the Zn anode/electrolyte interface are discussed, elucidating their roles in modulating electrostatic interactions, electric field, structure of solvated zinc ion and electric double layer, respectively. Finally, the perspectives and challenges on the further research are provided to establish the stable anode/electrolyte interface by focusing on charge density modifications, which is expected to facilitate the development of aqueous zinc ion battery.

The electric double layer structure and interface energy of uranium electrode in molten LiCl-KCl-UCl3 mixture: A molecular dynamics simulation study

The electric double layer structure and interface energy of uranium electrode in molten LiCl-KCl-UCl3 mixture, as well as the surface energies of metallic uranium and molten salts, were investigated using molecular dynamics simulations. The surface energies were calculated, respectively, from the pressure tensor and the energy difference for molten salt and uranium, and interface energy was evaluated from the Gibbs free energy difference between systems with and without interface. The surface energies of molten alkali halides are between 76.4 and 201.8 mJ·m−2 and decrease with the increase of radius of the halide anion or the alkali cation for molten salt with the same alkali cation or the same halide anion. The surface energy of uranium depends on the allotrope morphology and crystal facet, and the surface energies of α-U, β-U, and γ-U are 2.36, 1.45, and 1.69 J·m−2 in average for the seven low index crystal facets. The interface energy of uranium and molten LiCl-KCl-UCl3 mixture is about 2.71 J·m−2 and increases with the increase of charge density on the uranium slabs. The molten LiCl-KCl-UCl3 mixture in anodic zone has higher coordination number than that in cathodic zone but similar coordination distance.

Disentangling heterogeneous thermocatalytic formic acid dehydrogenation from an electrochemical perspective

Heterogeneous thermocatalysis of formic acid dehydrogenation by metals in solution is of great importance for chemical storage and production of hydrogen. Insightful understanding of the complicated formic acid dehydrogenation kinetics at the metal-solution interface is challenging and yet essential for the design of efficient heterogeneous formic acid dehydrogenation systems. In this work, formic acid dehydrogenation kinetics is initially studied from a perspective of electrochemistry by decoupling this reaction on Pd catalyst into two short-circuit half reactions, formic acid oxidation reaction and hydrogen evolution reaction and manipulating the electrical double layer impact from the solution side. The pH-dependences of formic acid dehydrogenation kinetics and the associated cation effect are attributed to the induced change of electric double layer structure and potential by means of electrochemical measurements involving kinetic isotope effect, in situ infrared spectroscopy as well as grand canonical quantum mechanics calculations. This work showcases how kinetic puzzles on some important heterogeneous catalytic reactions can be tackled by electrochemical theories and methodologies.

Characterizing preferential infiltration of loess using geostatistical electrical resistivity tomography

Preferential infiltration is prevalent in loess and is pivotal in disasters such as landslides. However, the inherent multi-scale heterogeneity of loess makes traditional in-situ monitoring techniques challenging for characterizing the preferential infiltration process. This study employed the Geostatistical Electrical Resistivity Tomography (GERT) to examine the spatial distribution of mass water content (ωs) in loess strata to understand the preferential infiltration processes in loess. This study improved stimulus-response data quality and used GERT to characterize the spatial-temporal distribution of electrical conductivity (σ) and estimate ωs through the σ-ωs relationship. This study indicates that the surface loess layer has higher ωs than deeper layers, rapidly declining as depth increases. Under preferential infiltration, early-stage water forms a spherical saturated zone, transforming into an ellipsoid as it descends. Using equivalent homogeneous parameters as prior information effectively improved σ estimation. This study found a 15.9% error in the total change in water content based on the GERT survey compared to the known amount of injected water. It explores the possible impacts of the uncertainty of the unknown relationship between σ and ωs, its spatial variability, and the accuracy of the survey on the error. The formation of an electric double-layer structure within the loess as the saturation increases, which reduces the sensitivity of GERT to changes in water content, is likely another cause. Finally, these areas are essential for advancing future studies on applying geophysical tools to accurately estimate water distributions in loess formations.

Selection of Negative Charged Acidic Polar Additives to Regulate Electric Double Layer for Stable Zinc Ion Battery

HighlightsNegative charged acidic polarity (NCAP) has been unveiled as the guideline for selecting additives to regulate electric double layer (EDL) for Zn-ion batteries.NCAP glutamate has been verified to regulate EDL structure with synergetic effects, including preferential adsorption on Zn anode and reconstruction of hydrated Zn-ion clusters.Adding NCAP additives, Zn|Cu half-cell achieves a high Coulombic efficiency of 99.83% for 2000 cycles, and NH4V4O10|Zn full cell realizes a high-capacity retention of 82.1% for 3000 cycles.

(Invited) Modeling of the Electric Double Layer (EDL) Structures of Localized High-Concentration Electrolytes (LHCE)

Various electrical double layer (EDL) models have been proposed but mainly for homogenous solutions. Recently, the so-called Localized high-concentration electrolytes (LHCE) have shown many benefits to high-capacity electrodes. Recently, we have proposed micelle-like structures to enable a complete understanding of microstructures in LHCE, which contains a salt, solvent, and non-ion-solvating diluent, analogical to the roles of oil, surfactant, and water as in micelles. [1] As the solid electrolyte interphase (SEI) formation is sensitive to the EDL structure, [2] it is critical to understand the EDL structures for LHCE with heterogeneous structures.Molecular dynamics simulations were performed in several electrolytes with heterogeneous structures on negatively charged surfaces. It was found the Stern model with an absorbed cation layer adsorption layer and a more diffused layer with cation, anion, solvent, and diluents, should be used to describe the EDL of this type of electrolyte.For the system consisting of LiFSI salt, DME solvent, and TFEO diluent at a concentration of LiFSI-1.2DME-2TFEO, the heterogeneous micelle-like structures in LHCE are maintained in the EDL, with the Li+-rich salt-solvent clusters and the Li+-poor diluent regions. The diluent region contains Li+ near the negatively charged surface but does not have any ions in the bulk of LHCE. This is because TFEO cannot form a complete solvation shell in the bulk electrolyte due to the steric effect, however, only a partial solvation shell is needed in the Stern layer in the EDL. The appearance of Li+ in the diluent is also necessary for the EDL, as TFEO alone cannot screen the charge.The chemical and concentration design space for the three components is very large. To obtain a more general picture, we also explored different salt-solvent ratios and different diluent-salt interactions. As the salt solvent ratio increases from low (LCE), to medium (MCE) to high concentration electrolytes (HCE), where all solvents are coordinated with ions, the salt-solvent structures evolve from fully solvated ions or ion pairs in LCE, 3D branched networks in MCE, to fully connected salt aggregates in HCE. The salt-diluent interactions and diluent concentration further modify the micelle-like structures. The EDL for both LHCE and LMCE are heterogenous. [1] Nature Materials 22, 1531–1539 (2023)[2] J. Am. Chem. Soc. 145, 4, 2473–2484 (2023)

(Invited) Changes in Electric Double-Layer Structures Under Localized Surface Plasmon Excitation

For the visible light energy conversion, the localized surface plasmon resonance (LSPR), which is the collective oscillations of free electrons, should be promising. With the excitation of LSPR, the highly localized electric field generates in the vicinity of metal nanostructures. It is interesting that various unique photo-response properties, such as chemical reactions or molecular excitations, can be observed due to the enhancement of light-matter interaction.[1] To understand and control such mediated chemical reactions or electrochemical reactions, the precise understanding about the electrified interfaces of plasmonic nanostructures should be required.Especially in the electrochemical system, the electric double layer is formed due to the difference in electrochemical potential between the metal interface and solution. The study of the surface potential is important for the design of chemical reactions because the surface potential at the liquid-solid interface is dependent on the physical properties of the systems. The zeta potential which is the potential of the slipping surface near the Stern layer of the diffusion layer could provide such information. From this point of view, in this study, we investigated the electric double-layer structures through the examination of the zeta potential under LSPR excitation condition. To obtain the zeta potential, we have performed the streaming potential method using Au nanoisland structures under visible light illuminations to excite the LSPR. It was interesting that the zeta potential was drastically changes under the visible light illumination conditions. This zeta potential change indicates the changes in the electric double layer structures through the excitation of LSPR. Through the investigations of incident wavelength dependence or the substrate dependences, the effects for the LSPR excitations on the electric double layer structure have been revealed. The present work would provide the fundamental knowledge about the effect on the LSPR excitation at solid-liquid interfaces.[1] H. Minamimoto et al., Acc. Chem. Res., 2022, 55(6), 809.