Electric Double Layer Research Articles

Cuδ+ Site-Enhanced Adsorption and Crown Ether-Reconfigured Interfacial D2O Promote Electrocatalytic Dehalogenative Deuteration.

Electrocatalytic dehalogenative deuteration is a sustainable method for precise deuteration, whereas its Faradaic efficiency (FE) is limited by a high overpotential and severe D2 evolution reaction (DER). Here, Cuδ+ site-adjusted adsorption and crown ether-reconfigured interfacial D2O are reported to cooperatively increase the FE of dehalogenative deuteration up to 84% at -100 mA cm-2. Cuδ+ sites strengthen the adsorption of aryl iodides, promoting interfacial mass transfer and thus accelerating the kinetics toward dehalogenative deuteration. The crown ethers disrupt the hydration effect of K·D2O and reconstruct the hydrogen bond with the interfacial D2O, lowering the content K·D2O of the electric double layer and hindering the interaction between D2O and the cathode, thus inhibiting the kinetics of the competitive DER. A linear relationship between the matched sizes of crown ethers and alkali metal cations is demonstrated for universally increasing FEs. This method is also suitable for the deuteration of various halides with high easily reducible functional group compatibility and improved FEs at -100 mA cm-2.

Recent Progress of Chemical Reactions Induced by Contact Electrification

Contact electrification (CE) spans from atomic to macroscopic scales, facilitating charge transfer between materials upon contact. This interfacial charge exchange, occurring in solid–solid (S–S) or solid–liquid (S–L) systems, initiates radical generation and chemical reactions, collectively termed contact-electro-chemistry (CE-Chemistry). As an emerging platform for green chemistry, CE-Chemistry facilitates redox, luminescent, synthetic, and catalytic reactions without the need for external power sources as in traditional electrochemistry with noble metal catalysts, significantly reducing energy consumption and environmental impact. Despite its broad applicability, the mechanistic understanding of CE-Chemistry remains incomplete. In S–S systems, CE-Chemistry is primarily driven by surface charges, whether electrons, ions, or radicals, on charged solid interfaces. However, a comprehensive theoretical framework is yet to be established. While S–S CE offers a promising platform for exploring the interplay between chemical reactions and triboelectric charge via surface charge modulation, it faces significant challenges in achieving scalability and optimizing chemical efficiency. In contrast, S–L CE-Chemistry focuses on interfacial electron transfer as a critical step in radical generation and subsequent reactions. This approach is notably versatile, enabling bulk-phase reactions in solutions and offering the flexibility to choose various solvents and/or dielectrics to optimize reaction pathways, such as the degradation of organic pollutants and polymerization, etc. The formation of an interfacial electrical double layer (EDL), driven by surface ion adsorption following electron transfer, plays a pivotal role in CE-Chemical processes within aqueous S–L systems. However, the EDL can exert a screening effect on further electron transfer, thereby inhibiting reaction progress. A comprehensive understanding and optimization of charge transfer mechanisms are pivotal for elucidating reaction pathways and enabling precise control over CE-Chemical processes. As the foundation of CE-Chemistry, charge transfer underpins the development of energy-efficient and environmentally sustainable methodologies, holding transformative potential for advancing green innovation. This review consolidates recent advancements, systematically classifying progress based on interfacial configurations in S–S and S–L systems and the underlying charge transfer dynamics. To unlock the full potential of CE-Chemistry, future research should prioritize the strategic tuning of material electronegativity, the engineering of sophisticated surface architectures, and the enhancement of charge transport mechanisms, paving the way for sustainable chemical innovations.

Anion-Modulated Solvation Sheath and Electric Double Layer Enabling Lithium-Ion Storage From -60 to 80 °C.

Current lithium batteries experience significant performance degradation under extreme temperature conditions, both high and low. Traditional wide-temperature electrolyte designs typically addressed these challenges by manipulating the solvation sheath and selecting solvents with extreme melting/boiling points. However, these solvent-mediated solutions, while effective at one temperature extreme, invariably fail at the opposite end due to the inherent difficulties in maintaining solvent stability across wide temperatures. Herein, we report the use of the main lithium salt to simultaneously address interfacial challenges at both extremely high and low temperatures. This approach is different from the conventional solvent-mediated strategies. As a proof of concept, we utilized lithium nitrate (LiNO3) to establish an anion-controlled solvation structure and electric double layer. The formulated electrolytes exhibited remarkable performance across temperature extremes, retaining 56.1% capacity at -60 °C and sustaining 400 stable cycles at 80 °C. In contrast, electrolytes based on current solvent-mediated strategies failed to operate at -60 °C and could not exceed 50 cycles at 80 °C. By shifting the focus to the main salt rather than the solvent, our work offers the possibility of addressing the enduring challenges of electrolyte stability across a broad temperature range.

Molecular Processes That Control Organic Electrosynthesis in Near-Electrode Microenvironments.

Electrosynthesis at an industrial scale offers an opportunity to use renewable electricity in chemical manufacturing, accelerating the decarbonization of large-scale chemical processes. Organic electrosynthesis can improve product selectivity, reduce reaction steps, and minimize waste byproducts. Electrochemical synthesis of adiponitrile (ADN) via hydrodimerization of acrylonitrile (AN) is a prominent example of industrial organic electrochemical processes, with annual production reaching 0.3 MMT. It circumvents the drawbacks of thermochemical synthesis by reducing toxicity and leveraging clean electricity as an energy source. Despite its industrial importance, mechanistic understanding and experimental insights on the near-electrode molecular processes of AN electrohydrodimerization remain insufficient. Here we show, using in situ ATR-FTIR spectroscopy, that tetraalkylammonium ions populate the electrical double layer (EDL), creating a microenvironment that favors interactions with organic molecules and enhances AN concentration while expelling water molecules. Our results provide experimental evidence supporting long-standing mechanistic hypotheses. Kinetic isotope effect studies reveal that propionitrile (PN) formation is rate-limited by proton transfer, while ADN formation likely is not. Electron paramagnetic resonance spectroscopy confirms the presence of free radicals during AN electroreduction, suggesting that coupling of PN radicals occurs primarily in the electrolyte. These insights highlight the importance of carefully controlling the EDL composition for selective organic electrosynthesis and provide fundamental engineering guidance for designing high-performing electro-organic reactions. We anticipate these findings will guide the optimization of electrolyte formulations and electrode interfaces for ADN synthesis and other emerging electro-organic processes.

Understanding the Effects of Edge Planes in Porous Carbon: Quantum Capacitance and Electrolyte Behavior in Supercapacitor.

Electric double layer capacitors (EDLC) require large specific surface area to provide high power density. The generation of pores increases the electrochemical capacitance with more graphitic edge planes exposed to the electrolyte. Conventional theory believes this increasing in capacitance is owed to the increased specific surface area, but our work uncovers another mechanism. DFT calculations discover the commonly seen defect-free zigzag and armchair edges can increase the quantum capacitance (CQ) due to their high chemical activity. Meanwhile, high chemical activity makes defect-free edges interact with electrolyte molecules more easily, leading to the potential reduce of electrolyte stabilization and the change on the origin mechanism of double layer capacitance (CD). Additionally, edges with non-hexagonal defects show a better balance between high CQ and electrolyte stability. Therefore, our discovery proves the preservation of non-hexagonal defects in edge planes through possible temperature controlling in heat treatment is important in reaching high electrochemical properties for EDLC.

Selective Interface Engineering with Large π‐Conjugated Molecules Enables Durable Zn Anodes

Undesirable dendrite growth and side reactions at the electrical double layer (EDL) of Zn/electrolyte interface are critical challenges limiting the performance of aqueous zinc ion batteries. Through density functional theory calculations, we demonstrate that grafting large π‐conjugated molecules (e.g. bilirubin, biliverdin, lumirubin, and hemoglobin) onto Zn surface induces preferential adsorption on non‐(002) facets, leading to interfacial charge redistribution, upshifted Zn d‐band center, and enhanced H+ fixation capability. Among these, bilirubin (BR) is identified as the most effective, preferentially adsorbing onto non‐Zn(002) facets to inhibit hydrogen evolution reaction and promote Zn(002) planar growth during plating. This approach results in average Coulombic efficiency of 99.86% over 4000 cycles in Zn||BR‐1@Cu cells and prolonged lifespan exceeding 1600 h in BR‐1@Zn||BR‐1@Zn cells at 10 mA cm−2 and 1 mAh cm−2. Even under harsh condition of 25 mA cm−2 and 10 mAh cm−2, BR‐1@Zn||BR‐1@Zn cell maintains a lifespan of over 400 h. Furthermore, BR‐1@Zn||MnO2 and BR‐1@Zn||NVO full cells achieve 76.4% and 86.1% capacity retention after 800 and 1400 cycles at 1.0 A g−1, respectively. This study underscores the importance of grafting large π‐conjugated molecules to allow selective Zn(002) exposure, Zn d‐band center upshift, and EDL structure regulation, paving the way towards durable Zn anodes.

Selective Interface Engineering with Large π-Conjugated Molecules Enables Durable Zn Anodes.

Undesirable dendrite growth and side reactions at the electrical double layer (EDL) of Zn/electrolyte interface are critical challenges limiting the performance of aqueous zinc ion batteries. Through density functional theory calculations, we demonstrate that grafting large π-conjugated molecules (e.g. bilirubin, biliverdin, lumirubin, and hemoglobin) onto Zn surface induces preferential adsorption on non-(002) facets, leading to interfacial charge redistribution, upshifted Zn d-band center, and enhanced H+ fixation capability. Among these, bilirubin (BR) is identified as the most effective, preferentially adsorbing onto non-Zn(002) facets to inhibit hydrogen evolution reaction and promote Zn(002) planar growth during plating. This approach results in average Coulombic efficiency of 99.86% over 4000 cycles in Zn||BR-1@Cu cells and prolonged lifespan exceeding 1600 h in BR-1@Zn||BR-1@Zn cells at 10 mA cm-2 and 1 mAh cm-2. Even under harsh condition of 25 mA cm-2 and 10 mAh cm-2, BR-1@Zn||BR-1@Zn cell maintains a lifespan of over 400 h. Furthermore, BR-1@Zn||MnO2 and BR-1@Zn||NVO full cells achieve 76.4% and 86.1% capacity retention after 800 and 1400 cycles at 1.0 A g-1, respectively. This study underscores the importance of grafting large π-conjugated molecules to allow selective Zn(002) exposure, Zn d-band center upshift, and EDL structure regulation, paving the way towards durable Zn anodes.

Cation Effect on the Electrochemical Platinum Dissolution.

Ensuring the stability of electrocatalysts is paramount to the success of electrochemical energy conversion devices. Degradation is a fundamental process involving the release of positively charged metal ions into the electric double layer (EDL) and their subsequent diffusion into the bulk electrolyte. However, despite its vital importance in achieving prolonged electrocatalysis, the underlying causality of catalyst dissolution with the EDL structure remains largely unknown. Here, we show that electrochemical Pt dissolution is strongly influenced by the identity of the alkali metal cation (AM+) in the electrolyte. By monitoring Pt dissolution in real-time, we found a trend of reduced Pt leaching in the sequence Li+ > Na+ > K+ > Cs+. Our computational predictions suggest that interfacial OH- concentration plays a pivotal role in Pt dissolution, where OH- facilitates the outward diffusion of dissolved Pt ions into the bulk electrolyte by neutralizing the Ptz+ species, thereby screening the migration force for their redeposition. Combined with this theoretical result, we verify a strong correlation between the amount of dissolved Pt and the hydrolysis pKa or acidity of AM+, indicating that the AM+ identity determines the local OH- concentration and thereby modifies the amount of Pt dissolution. Our results underscore the need to tune the EDL structure to achieve durable electrocatalysis, a promising area for future research.

Advanced Morphological and Material Engineering for High-Performance Interfacial Iontronic Pressure Sensors.

High-performance flexible pressure sensors are crucial for applications such as wearable electronics, interactive systems, and healthcare technologies. Among these, iontronic pressure sensors have garnered particular attention due to their superior sensitivity, enabled by the giant capacitance variation of the electric double layer (EDL) at the ionic-electronic interface under deformation. Key advancements, such as incorporating microstructures into ionic layers and employing diverse materials, have significantly improved sensor properties like sensitivity, accuracy, stability, and response time. This review highlights advancements in flexible EDL pressure sensors, focusing on structural designs and material engineering. These strategies are tailored to optimize key metrics such as sensitivity, detection limit, linearity, stability, response speed, hysteresis, transparency, wearability, selectivity, and multifunctionality. Key fabrication techniques, including micropatterning and externally assisted methods, are reviewed, along with strategies for sensor comparison and guidelines for selecting appropriate sensors. Emerging applications in healthcare, environmental and aerodynamic sensing, human-machine interaction, robotics, and machine learning-assisted intelligent sensing are explored. Finally, this review discusses the challenges and future directions for advancing EDL-based pressure sensors.

Electrolyte Engineering with Asymmetric Spatial Shielding Effect for Aqueous Zinc Batteries

AbstractThe electrochemical instability of electrode/electrolyte interface and aqueous electrolyte collectively brings technical barriers, such as side reactions like hydrogen evolution and corrosion, as well as zinc dendrites, which hinder the practical application of aqueous zinc batteries. Here, an electrolyte engineering strategy is proposed with asymmetric spatial shielding effect by employing the molecules with asymmetric spatial structure as a cosolvent. Such molecule contains small methyl group and large cyclopentyl group to balance migration capability and shielding volume, which can not only promote the solvation structure of Zn2+ containing more anions and solid electrolyte interface derived from abundant anions but also rapidly and effectively adsorb on the surface of Zn anode to remodel the electric double layer. This strategy alleviates hydrogen evolution and corrosion while achieving dendrite‐free Zn deposition. Consequently, the Zn/I2 cell can operate stably at 2 A g−1 for 30 000 cycles over 180 days, with a capacity retention of 79.8%. Despite featuring a cathode areal capacity of 4.74 mAh cm−2 and an N/P ratio of 2.5, the Zn/NH4V4O10 cell still achieves an impressive capacity retention of 88.8% at 0.5 A g−1 for 200 cycles, demonstrating a significant potential for practical application.

Gas-Liquid Interface of Aqueous Solutions of Surface Active Aromatic Molecules Studied Using Extreme Ultraviolet Laser Photoelectron Spectroscopy and Molecular Dynamics Simulation.

We investigated the gas-liquid interface of aqueous solutions containing phenol and related aromatic compounds using extreme ultraviolet laser photoelectron spectroscopy and molecular dynamics simulations. The interfacial densities of protonated and deprotonated forms of phenol, aniline, and 4-nitrophenol were found to be primarily determined by their surface affinities and exhibit similar concentration dependences to their respective bulk densities. Despite the distinct interfacial orientations of their permanent dipole moments, these compounds monotonically decreased the surface potential at higher concentrations. The exception was sodium phenolate, whose surface potential first increased and then decreased with increasing concentration. This behavior is attributed to the opposing effects of the electric double layer formed by Na+ and phenolate ions at the gas-liquid interface and the induced electronic polarization of phenolate.

A Deep Insight into the Microscopic Dynamics of the Electrode-Electrolyte Interface under Extreme Operating Conditions.

Understanding the interfacial dynamics during operation is critical for electrochemistry to make great advancements. However, breakthroughs on this topic under extreme conditions are very scarce. Here, as an example, we employ operando Raman spectroscopy to decode the interfacial dynamics of titanium electrolysis using a tailored instrument. Direct spectral evidence not only confirms the two-step reduction pathway and the key intermediate (TiF52-) in molten fluorides with high-temperature and strong-corrosion conditions but also unravels the origins of the undesirable shuttling effect of TiF52-, which are the sluggish reduction kinetics and outward diffusion behavior of TiF52-. Moreover, an insightful atomic scenario of the electric double layer (EDL) under varied potentials has been established. These quantitative understandings guide us to design economical-feasible regulation protocols─the rational combination of a high-concentration, low-valence Ti-ion electrolyte with appropriate applied potential. Impressively, the current efficiency is greatly promoted from 27.7 to 81.8% using our proposed protocols. Finally, this work also demonstrates a bottom-up technological research paradigm for extreme electrochemistry based on mechanism insights rather than phenomenological findings, which will accelerate the advancement of extreme electrochemistry.

Alternative multivalent metal elements for aqueous hybrid supercapacitors

The growing importance of sustainable and clean energy sources is a direct consequence of the increasing scarcity of non‐renewable resources and the necessity for energy storage solutions that are safe, efficient, and adaptable. Aqueous hybrid supercapacitors (AHSCs) have garnered attention due to their advantageous characteristics, including low cost, safety, reliability, and high cyclic stability. Here, this review provides a brief overview of the energy storage mechanisms of double electric layer capacitors (EDLCs), pseudocapacitors, and hybrid supercapacitors (HSCs), which combine the features of both of these types of capacitors. The progress made in recent years in research on AHSCs using multivalent metal cations, including manganese, zinc, and chromium, is highlighted. Additionally, some examples of AHSCs assembled with the participation of metal ions are summarized based on the metal activity series. Furthermore, the potential use of other multivalent metals, including iron, cobalt, nickel, and copper, in AHSCs electrodes was explored, with a focus on their respective advantages and challenges. Finally, this review proposes future research directions to further advance this field.

Probing the Interaction Mechanisms of Dodecane and Mica/Calcite: Implications for Oil Recovery.

Understanding the interfacial interaction mechanisms between oil and minerals is of vital importance in the applications of petroleum production and environmental protection. In this work, the interactions of dodecane with mica and calcite in aqueous media were investigated by using the drop probe technique based on atomic force microscopy. For the dodecane-mica interactions, the electrical double layer (EDL) repulsion dominated in 10 mM NaCl solution, and a higher pH facilitated the detachment of dodecane. The EDL interaction was diminished with an elevated NaCl concentration, and the van der Waals (vdW) attraction triggered the oil attachment on the mica surface. In the presence of Ca2+ and Mg2+, the EDL repulsion was weakened leading to a thinner water film, and the oil attachment occurred. For the dodecane-calcite interactions, large adhesions were observed under all of the solution conditions, mainly attributed to the ionic bridging by Ca2+ formed during calcite dissolution. At pH 4, CO2 bubbles appeared on the calcite surface, resulting in a repulsive vdW interaction between dodecane and the surface, which hindered the adhesion. The calcite surface wettability was modified in high concentrations of NaCl, leading to a reduced adhesion with oil. The ionic bridging effect was promoted, and the adhesion was enhanced in 500 mM Ca2+ and Mg2+ solutions. At pH 10, the precipitates of Ca(OH)2(s) and Mg(OH)2(s) appeared on the calcite surface, which diminished the adhesion. Our results provided fundamental insights into the mechanisms of oil-water-mineral interactions, which contributed to the understanding and modulation of engineering processes in the enhancement of oil pollutant removal and oil recovery.

Reconstructing Electric Double Layer with β‐diketone Additive for Highly Invertible Zn Anode

Reconstructing Electric Double Layer with β‐diketone Additive for Highly Invertible Zn Anode

Measurement of resistivity of biofluids in the presence of an electrical double layer

Abstract Detecting alterations in the electrical response of human biofluids can provide valuable information in the early stages on pathological conditions in a patient. Developing techniques for obtaining rapid information on the electrical resistivity of common ionic biofluids by non-invasive techniques can improve medicare through a rapid and more precise diagnosis. In this work, we analyze the use of an electrical device consisting of a cell formed of flat parallel steel plates to measure the resistivity of these substances. When the electrical cell is filled with a biofluid an electrical double layer (EDL) is formed on the electrodes/biofluid interface. Then, we measure the electrical response and examine the general conditions under which the EDL does not interfere with the assesment of the biofluid’s resistivity. The electrical response is analyzed in terms of an equivalent circuit model. Also, a simplified theoretical model of a suspension of biological cells considering spherical particles with a membrane is discussed to validate measurements and theoretically exhibit the contribution of the cell’s membrane to the effective resistivity. We present measurements of the resistance of the electrical cell filled with electrolyte solutions, blood plasma, and diluted suspensions of erythrocytes in a hypotonic solution. Results show that the resistance of the electrical cell is sensitive to the volume density of biological cells suspended between the parallel plate electrodes, producing a signal with a high signal to noise ratio. From the measured resistance of a suspension of erythrocytes in a isotoinc solution and the simplified theoretical model, we estimate the value of the conductivity of the interior of the erythrocytes. The results show that measured resistance varies with blood samples and hemolysis progression. The device's sensitivity to the number of erythrocytes passing between the electrodes makes it useful for measuring sedimentation kinetics.

Interfacial Water Orientation in Neutral Oxygen Catalysis for Reversible Ampere-Scale Zinc-Air Batteries.

The neutral oxygen catalysis is an electrochemical reaction of the utmost importance in energy generation, storage application, and chemical synthesis. However, the restricted availability of protons poses a challenge to achieving kinetically favorable oxygen catalytic reactions. Here, we alter the interfacial water orientation by adjusting the Brønsted acidity at the catalyst surface, to break the proton transfer limitation of neutral oxygen electrocatalysis. An unexpected role of water molecules in improving the activity of neutral oxygen catalysis is revealed, namely, increasing the H-down configuration water in electric double layers rather than merely affecting the energy barriers for reaction limiting steps. The proposed porous nanofibers with atomically dispersed MnN3 exhibit record-breaking activity (EORR@1/2/EOER@10 mA = 0.85/1.65 V vs. RHE) and reversibility (2500 h), outperforming all previously reported neutral catalysts and rivaling conventional alkaline systems. In particular, practical ampere-scale zinc-air batteries (ZABs) stack are constructed with a capacity of 5.93 Ah and can stably operate under 1.0 A and 1.0 Ah conditions, demonstrating broad application prospects. This work provides a novel and feasible perspective for designing neutral oxygen electrocatalysts and reveals the future commercial potential in mobile power supply and large-scale energy storage.

Interfacial Water Orientation in Neutral Oxygen Catalysis for Reversible Ampere‐scale Zinc‐air Batteries

The neutral oxygen catalysis is an electrochemical reaction of the utmost importance in energy generation, storage application, and chemical synthesis. However, the restricted availability of protons poses a challenge to achieving kinetically favorable oxygen catalytic reactions. Here, we alter the interfacial water orientation by adjusting the Brønsted acidity at the catalyst surface, to break the proton transfer limitation of neutral oxygen electrocatalysis. An unexpected role of water molecules in improving the activity of neutral oxygen catalysis is revealed, namely, increasing the H‐down configuration water in electric double layers rather than merely affecting the energy barriers for reaction limiting steps. The proposed porous nanofibers with atomically dispersed MnN3 exhibit record‐breaking activity (EORR@1/2/EOER@10 mA = 0.85/1.65 V vs. RHE) and reversibility (2500 h), outperforming all previously reported neutral catalysts and rivaling conventional alkaline systems. In particular, practical ampere‐scale zinc‐air batteries (ZABs) stack are constructed with a capacity of 5.93 Ah and can stably operate under 1.0 A and 1.0 Ah conditions, demonstrating broad application prospects. This work provides a novel and feasible perspective for designing neutral oxygen electrocatalysts and reveals the future commercial potential in mobile power supply and large‐scale energy storage.

Moisture-Electric Generators Working in Subzero Environments Based on Laser-Engraved Hygroscopic Hydrogel Arrays.

Moisture-electric generators (MEGs) generate power by adsorbing water from the air. However, their performance at low temperatures is hindered due to icing. In the present work, MEG arrays are developed by laser engraving techniques and a modulated low-temperature hydrogel as the absorbent material. LTH effectively captures moisture and maintains ion dissociation and migration even at subzero temperatures. Based on the double electric layer pseudocapacitance model, the oscillating circuit theory is introduced to explain the effects of moisture absorption, evaporation, and ion migration on the output current of the MEG, and the circuit calculations are matched with the experimental results. Molecular dynamics simulations indicate that LTH's low-temperature stability results from preferential hydrogen bonding between glycerol molecules and H2O, which disrupts H2O-H2O hydrogen bonds and slows water crystallization. A single MEG unit (0.25 cm2) can produce up to ∼0.8 V and ∼21.2 μW/cm2 at room temperature, and at -35 °C with 16% RH, it generates ∼0.58 V and ∼14.35 μA. MEG realizes the following applications: MEG successfully drives electronic devices in snow; arrays of 16 MEGs can power portable electronics, and 384 MEGs can achieve up to 210 V; MEG absorbs moisture in water and drives LEDs by blowing up; MEG has a flexible wearable nature; MEG is used for respiratory monitoring and photoelectric sensors.

Combined Effects of the Electric Double Layer and Slip on the Permeability in Fractal Micro/Nano Dual-Porosity Media

Combined Effects of the Electric Double Layer and Slip on the Permeability in Fractal Micro/Nano Dual-Porosity Media