Liquid Electrode Research Articles

Flexible Bridged Thermoelectric Device with an Optimized Heatsink for Personal Thermal Management.

A wearable thermoelectric cooler (TEC) for personal thermal management exhibits significant growth in numerous applications in personal thermal comfort and saving the energy consumed by space cooling. Most TECs provide a large cooling performance with the assistance of rigid heatsinks and electrodes, limiting wearability and practical implementation. Here, we design and propose a flexible bridged personal TEC with a high thermal management heatsink and spray-printed liquid metal electrodes. The system combines a bendable heatsink, a thermally insulative TE layer, and a bottom thermally conductive layer. Especially, the flexible heatsink composed of metal foam, phase change material, and fin structure greatly enhances the thermal conduction, storage, and diffusion capacities. Our TEC exhibits the desired comfortability and obtains an ideal temperature drop of 3 °C on human skin. Also, it could work as a self-generator providing 45 mV with a ΔT of 5 °C, which improves the generation efficiency by more than 3 times due to the stable temperature difference between the two sides. This work provides an effective way to develop wearable TEC devices and paves the way for achieving practical, personalized cooling applications.

CaviPlasma: parametric study of discharge parameters of high-throughput water plasma treatment technology in glow-like discharge regime

Abstract AC discharge in a dense hydrodynamic cavitation cloud in water, called CaviPlasma, has been studied at different discharge parameters. CaviPlasma stands for cavitation and plasma, which are two coupled basic phenomena of the novel technology enabling very high throughput of plasma water processing compared to other current technologies. In this article, the diagnostics and the properties of CaviPlasma discharge are discussed based on optical and electric characterization of the discharge phenomena together with the physico-chemical characterization of the plasma-treated water. The so-called unbridged mode of CaviPlasma operation is described, where the discharge propagates from a metal electrode towards a liquid electrode at the collapsing end of the cavitation cloud. The production of H, O and OH species in the discharge was proven by optical emission spectroscopy. The formation of hydrogen peroxide (H2O2) in water was determined by chemical methods. The energy yield for H2O2 generation is as high as 9.6 g kWh−1 and the generation rate is up to 2.4 g h−1. The degradation of phenol admixture in water was also studied. The article covers a parametric study enabling the development of tailored applications.

Secondary electron emission measurements from imidazolium-based ionic liquids

Abstract The electron-induced secondary electron emission (SEE) yields of imidazolium-based ionic liquids are presented for primary electron beam energies between 30 and 1000 eV. These results are important for understanding plasma synthesis of nanoparticles in plasma discharges with an ionic liquid electrode. Due to their low vapor pressure and high conductivity, ionic liquids can produce metal nanoparticles in low-pressure plasmas through reduction of dissolved metal salts. In this work, the low vapor pressure of ionic liquids is exploited to directly measure SEE yields by bombarding the liquid with electrons and measuring the resulting currents. The ionic liquids studied are [BMIM][Ac], [EMIM][Ac], and [BMIM][BF4]. The SEE yields vary significantly over the energy range, with maximum yields of around 2 at 200 eV for [BMIM][Ac] and [EMIM][Ac], and 1.8 at 250 eV for [BMIM][BF4]. Molecular orbital calculations indicate that the acetate anion is the likely electron donor for [BMIM][Ac] and [EMIM][Ac], while in [BMIM][BF4], the electrons likely originate from the [BMIM]$^+$ cation. The differences in SEE yields are attributed to varying ionization potentials and molecular structures of the ionic liquids. These findings are essential for accurate modeling of plasma discharges and understanding SEE mechanisms in ionic liquids.

Liquid Bi-Sb-Sn Electrodes with Synergistic Stabilization Mechanism for Long-Lifespan Sodium-Based Liquid Metal Batteries.

Sodium-based liquid metal batteries are well suited for stationary energy storage due to their long life, intrinsic safety, and ease of scale-up. However, the irreversible alloying reaction between the positive current collector (PCC) and the cathodes at high temperatures leads to severe capacity degradation of the battery, severely limiting its scale-up application. In this work, a Bi-Sb-Sn alloy cathode based on a synergistic stabilization mechanism was designed for the first time. Due to the density difference of Bi, Sb, and Sn and the compatibility difference of Bi and Sn with the PCC, a part of Bi and Sn is spontaneously distributed in the region close to the PCC. The protection of Sb is realized by blocking the contact of Sb with the PCC as well as removing the PCC material dissolved in the cathode to prevent the loss of active material. Based on such protection, the Na||Bi36Sb24Sn40 cell maintained 99% Coulombic efficiency for 450 cycles at a rate of 0.75 C, with a capacity retention of 99.56% and a capacity decay rate of 0.001% per cycle. In addition, the interaction of Bi, Sb, and Sn during discharge also promotes capacity release and energy efficiency. At 0.3 C, the Na||Bi36Sb24Sn40 cell achieved 89% capacity utilization and 82% energy efficiency. These results provide an idea for the design of other batteries based on liquid metal electrodes.

Tough and temperature-resistant mask-based separator realized by K-β”-Al2O3 protective layer for stabilizing NaK liquid metal batteries

The development of low-cost, high-temperature-resistant separators is crucial for optimizing the reaction interface and improving the safety performance of liquid NaK metal batteries. This paper presents a novel separator with a solid electrolyte layer, Mask@40 %β-Al2O3, primarily composed of K-β”-Al2O3 known for its exceptional ionic conductivity and high-temperature resistance. Specifically designed for room-temperature liquid NaK metal batteries, the Mask@40 %β-Al2O3 separator effectively transforms the unstable liquid–liquid interface between liquid NaK metal electrodes and traditional organic electrolytes into a stable solid–liquid interface. This transformation prevents short-circuiting caused by area collapse under high-temperature conditions. Moreover, the Bare Mask component can adsorb a conventional organic electrolyte to construct a stable solid–liquid interface on the cathode side, thereby reducing the typically observed high interfacial resistance associated with conventional solid electrolytes. The cost-effective nature and simple preparation process of the Mask@40 %β-Al2O3 separator address cost concerns while presenting an encouraging new direction for applying room-temperature liquid NaK metal batteries in extreme conditions.

Analysis of electrode performance on amplitude integrated electroencephalography in neonates: evaluation of a new electrode aCUP-E vs. liquid gel electrodes.

Neonatologists and clinical neurophysiologists face challenges with the current electrodes used for long-duration amplitude-integrated electroencephalography (aEEG) in neonatal intensive care units (NICU), limiting the capacity to diagnose brain damage. The objectives of this study were to develop methods for comparing the performance of different electrodes to be used in aEEG. The comparison was done between a newly designed neonate-specific electrode, aCUP-E, with commercial liquid gel electrodes used in amplitude-integrated electroencephalography (aEEG). The comparison included impedance stability, electrode survival, recording quality, usability, and satisfaction of NICU staff. aEEG recordings with bipolar montage was used, with one hemisphere fitted with commercial electrodes and the other with aCUP-E electrodes, alternated among subjects. Continuous impedance and raw EEG data were collected over a minimum of 24 h, and signal processing was performed using Python and MATLAB. aCUP-E electrodes demonstrated superior performance, including: Increased impedance stability and electrode survival, enhanced recording quality with fewer artifacts, high correlation in signal capture between electrodes during optimal brain activity segments, higher signal-to-noise ratio (SNR) across varying impedance levels, greater staff satisfaction and ease of use. Moreover, Kaplan-Meier curves indicated a higher survival rate for aCUP-E electrodes over 24 h compared to commercial electrodes. Impedance variability analysis showed statistically significant stability improvements for aCUP-E. aCUP-E electrodes outperform commercial liquid gel electrodes in impedance stability, electrode survival, and recording quality. These results suggest that aCUP-E electrodes could significantly enhance aEEG utilization in diagnosing and treating neonatal brain conditions in NICUs. Future improvements to the aCUP-E electrode may further reduce artifacts and increase electrode longevity, potentially leading to a significant improvement in neonatal brain monitoring by means of aEEG.

Temperature-induced phase transition of liquid metal for shape-adaptive triboelectric nanogenerator

Flexible wearable electronics are expected to fit different parts of the human body. However, existing energy harvester and sensor still face the difficulties of adhering to complex surfaces and spontaneously fixing to the human body. In this work, a shape-adaptive triboelectric nanogenerator (SA-TENG) based on the phase transition of liquid metal (Cd-In-Sn-Pb-Bi eutectic alloy, LM) has been constructed to achieve efficient wearable energy collection and sensitivity-tunable pressure sensing. The shape-adaptive energy harvester (SA-EH) prepared by constructing hole arrays on the electrode could be directly fixed on different parts of the human body to harvest mechanical energy for driving wearable electronics. It can generate a transferred charge density of 90.5 μC/m2 and an average power density of 45.1 mW/m2. The natural oxide layer of LM suppresses the loss of liquid electrode and increases the output by 18 % with charge trapping-blocking effect. Furthermore, a sensitivity-tunable pressure sensor (ST-PS) fabricated with microstructures on the surface of SA-TENG can realize the sensitivity of over 2.48 kPa−1 as well as the ultra-wide pressure detection range from 0.42 kPa to 113.17 kPa, and the LM-based shielding layer can weaken external interference. This novel electrode design has greatly expanded the applications of TENGs in wearable electronics.

Effect of Hydrogen Pressure on The Mass Transfer Characteristics of Hydrogen-Bromine Flow Battery Electrodes

The mass transfer characteristics of porous carbon electrodes in the liquid side of a hydrogen bromine redox flow battery (H2-Br2 RFB) were investigated under compressive deformation caused by operation at elevated hydrogen pressure. Here, flow cell measurements of permeability and micro-particle image velocimetry (μPIV), alongside electrochemical measurements of capacitance and battery discharge were used to characterize changes in the liquid side electrode compression, in-plane liquid flow, accessible surface area, polarization, and mass transfer scaling brought by hydrogen pressure. We studied two electrode types with different structures, carbon paper and carbon cloth, in untreated well as heat-treated forms in the pressure range 0–8 bar H2. It was found that pressure-induced compression of the liquid side electrode increases the accessible area of untreated electrodes, with little effect on heat-treated electrodes, but decreases the electrochemical performance of the battery in all cases by increasing the ohmic resistance of the cell and decreasing the mass transfer coefficient of the porous electrode. Overall, heat treatment is shown to affect the rigidity, saturation behavior, and generalized mass transfer of paper electrodes but not of cloth electrodes. Our findings will guide the selection of electrode materials and operation parameters for the H2-Br2 RFB.

Ionic liquid–electrode interface: Classification of ions, saturation of layers, and structure-determined potentials

Progress in electrochemical applications of ionic liquids builds on an understanding of electrical double layer. This computational study focuses on structure-determined quantities – maximum packing density, potentials, and capacitances – evaluated using a one-electrode electrical double layer model. Interfaces of the 40 studied ions are grouped into four distinct classes according to their characteristic packing at the model surface. The simulations suggest that the exact screening by a monolayer of counter-ions (preceding the crowding of ions) is unlikely for ions in known air- and water-stable ionic liquids within their electrochemical stability window. This work discusses how the assessed structure-determined quantities can guide the experimental tuning of (electro/mechano)chemical properties and characterize the structure of ionic liquid–electrode interfaces.

Electrodeposition of Crystalline Si Using a Liquid Ga Electrode in Molten KF–KCl–K2SiF6

In this study, the electrodeposition of silicon (Si) using a liquid gallium (Ga) electrode in molten KF–KCl was further investigated. Electrochemical measurements and electrolysis were conducted at 923 K in a KF–KCl–K2SiF6 melt. Cyclic voltammograms at liquid Ga electrodes revealed that the reduction current at 0.6–0.9 V vs K+/K was due to the formation of Si–Ga liquid alloys. Si was deposited via potentiostatic electrolysis at 0.80 V using liquid Ga held in a crucible as an electrode. The Si grains were primarily located at the boundary of the Ga and the crucible, indicating that they were deposited from the Si–Ga liquid alloy. X-ray diffraction confirmed the crystallinity of the deposited Si, with a maximum grain size of approximately 6 mm. Potentiostatic electrolysis at varying charges showed that the Si grain size increased with increased charge, confirming the growth of crystalline Si. The Si grains obtained using the liquid Ga electrode were larger than those obtained using a liquid Zn electrode. Finally, the differences in Si crystal growth rates between the Ga and Zn electrodes were discussed.

Study of plasma activated water effect on heavy metal bioaccumulation by Cannabis sativa Using Laser-Induced Breakdown Spectroscopy

Contamination of the environment with toxic metals such as cadmium or lead is a worldwide issue. The accumulator of metals Cannabis sativa L. has potential to be utilized in phytoremediation, which is an environmentally friendly way of soil decontamination. Novel non-thermal plasma-based technologies may be a helpful tool in this process. Plasma activated water (PAW), prepared by contact of gaseous plasma with water, contains reactive oxygen and nitrogen species, which enhance the growth of plants. In this study, C. sativa was grown in a short-term toxicity test in a medium which consisted of plasma activated water prepared by dielectric barrier discharge with liquid electrode and different concentrations of cadmium or lead. Application of PAW on heavy metal contaminated C. sativa resulted in increased growth under Pb contamination as was determined by ecotoxicology tests. Furthermore, the PAW influence on the bioaccumulation of these metals as well as the influence on the nutrient composition of plants was studied primarily by applying Laser-induced breakdown spectroscopy (LIBS). The LIBS elemental maps show that C. sativa accumulates heavy metals mainly in the roots. The results present a new proof-of-concept in which PAW could be used to improve the growth of plants in heavy metal contaminated environment, while LIBS can be implemented to study the phytoremediation efficiency.

Electrochemical Synthesis of Urea from Carbon Dioxide and Nitrite at Cobalt Phthalocyanine-Ion Liquid Electrodes

Electrochemical coreduction of carbon dioxide and nitrogen oxyanion/oxide pollutants are attractive processes for simultaneous environmental remediation and sustainable production of urea. The development of suitable technology requires catalysts and electrodes that provide higher efficiencies by decreasing the overpotential required and increasing the faradaic efficiency. Electrode design is a key element in this process through which the environment of the catalyst can be manipulated to optimize activity and selectivity. Here, ionic liquids have been used to control the coreduction of carbon dioxide and nitrite at a cobalt phthalocyanine catalyst. Increasing the hydrophobicity of the catalyst layer with a mixture of 1-butylpyridinium hexafluorophosphate and trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide was found to increase the faradaic efficiency for urea formation to 27% at the lowest overpotential (−0.064 V vs RHE), from 3% for a Nafion binder. Modulation of the electronic structure, arrangement (aggregation vs adsorption on the carbon support) and/or mobility (via solubilization) of the CoPc catalyst appear to play a role in determining the rate and faradaic efficiency of urea production. Combining the CoPc catalyst with a carbon supported Cu cocatalyst increased the rate of urea production by 195% at –0.064 V.

Electrically Driven Deterministic Plasmon Light Sources Based on Arrays of Molecular Tunnel Junctions.

Surface plasmons excited via inelastic tunnelling have led to plasmon light sources with small footprints and ultrafast response speeds, which are favored by integrated optical circuits. Self-assembled monolayers of organic molecules function as highly tunable tunnel barriers with novel functions. However, limited by the low effective contact between the liquid metal electrode and the self-assembled monolayers, it is quite challenging to obtain molecular plasmon light sources with high density and uniform emission. Here, by combining lithographic patterning with a solvent treatment method, we have demonstrated electrically driven deterministic plasmon emission from arrays of molecular tunnel junctions. The solvent treatment could largely improve the effective contact from 9.6% to 48% and simultaneously allow the liquid metal to fill into lithographically patterned micropore structures toward deterministic plasmon emission with desired patterns. Our findings open up new possibilities for tunnel junction-based plasmon light sources, laying the foundation for electrically driven light-emitting metasurfaces.

A room-temperature liquid eutectic GaSn anode with regulated wettability for lithium ion batteries

The alloy-type anodes in lithium ion batteries (LIBs) often suffer from the pulverization/failure of active materials caused by the drastic volume variations during cycling. Liquid Ga-based materials with low melting points and intrinsic self-healing feature are one of the best candidates for enhancing the Li storage property. Herein, a liquid eutectic GaSn (EGaSn) electrode was fabricated based upon a simple painting method and directly used as the anode for LIBs at room temperature. Furthermore, the wettability of liquid EGaSn alloy on the current collector in the Ar atmosphere was greatly improved through the construction of Ag3Ga modified layer on the stainless steel mesh (ssm) surface. And the Ag3Ga-EGaSn anode displays the much better Li storage performance (specific capacity, rate performance and cycling stability) than the untreated EGaSn anode. More importantly, operando XRD measurement clearly clarified the electrochemical reaction mechanism of Ag3Ga-EGaSn in LIBs. This work indicates a potential strategy to directly use liquid Ga-based electrode with regulated wettability for LIBs.

Fabrication of graphitic carbon nitride and black phosphorene composite based electrochemical sensor and application for sensitive determination of quercetin

A novel electrochemical method for sensitive detection quercetin (QU) was constructed with graphitic carbon nitride (g-C3N4) and black phosphorene (BP) composite (g-C3N4@BP) modified carbon ionic liquid electrode (CILE) as signal amplified interface. g-C3N4@BP was synthesized by a hydrothermal method with the characteristics investigated by SEM, XPS, FT-IR, XRD and electrochemical methods. Electrochemical behaviors of QU on the modified electrode (g-C3N4@BP/CILE) was investigated with the electrochemical parameters calculated and the experimental conditions optimized. The excellent electroanalytical result of QU was realized with the linear concentration range from 5.0 nmol/L to 90.0 µmol/L and a lower detection limit of 1.7 nmol/L (3σ). It was proved that the composite exhibited the synergistic effect of BP and g-C3N4 with more active sites, porous structure, large specific surface area, good electrical conductivity and strong electrocatalytic activity. The g-C3N4@BP/CILE was successfully used to detect the practical drug and food samples with satisfactory recoveries.

Halide solid-state electrolyte achieving high ionic conductivity by engineering nanocrystals

Lithium-ion battery (LIB) technologies utilize liquid electrolytes, which can cause safety issues due to electrolyte leakage, uncontrolled side reactions between the liquid electrolyte and electrode, dendrite formation, and flammability of the liquid components with air. These problems can be minimized using solid-state electrolytes (SSEs) containing the functionality of an electrolyte. Our research discovery meets the urgent requirement of developing rapid ionic conductive solid-state electrolytes for lithium metal battery applications, emphasizing safe operation and high energy density. The breakthrough lies in the functionalization and tunability of monoclinic doped Li3InCl6-based solid electrolytes to achieve desirable structural and high ionic conductivity (> 0.15 S cm−1). We report four formulations of solid-state electrolytes obtained using modified sol–gel synthesis and used to assemble symmetrical half cells for electrochemical impedance spectroscopic (EIS) analyses in the frequency ranging from 10–2 to 106 Hz under five different temperatures (15–55 °C). The EIS data of non-doped, F-, Ce-, and Mo-doped electrolytes showed R1 (solid-electrolyte) ranging from 0.05 to 0.10 Ohm and R2 (interfacial) resistance varying from 0.05 to 1.25 Ohm, resulting in superionic conductivity (0.15–0.45 S cm−1), equivalent to the commercially available liquid electrolyte and evidenced two magnitudes increase compared to the published data.Graphical abstract

Colloidal formation process based on electrophoretic phenomena of charged particles in liquid media and electrode reactions

Colloidal formation process based on electrophoretic phenomena of charged particles in liquid media and electrode reactions

Electrochemical Liquid‐Liquid‐Solid Growth of Ag‐In Crystals with Liquid Indium Alloy Electrodes

AbstractSynthesis of intermetallic crystals by electrodeposition of Ag from alkaline aqueous electrolytes containing AgCN onto liquid metal electrodes via an electrochemical liquid‐liquid‐solid (ec‐LLS) process has been performed. X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy were performed to identify crystalline products. Ec‐LLS experiments performed with pure liquid Hg and Ga electrodes resulted in the formation of polycrystalline Ag2Ga and Ag2Hg3. Experiments performed with In‐containing liquid metals preferentially yielded Ag9In4 and AgIn2 products with liquid Hg0.35In0.65 and Ga0.86In0.14, respectively. The product distribution with liquid Hg0.35In0.65 depended on the level of Ag supersaturation during the electrodeposition. A mechanism that accounts for the aforementioned observations is presented and discussed. This work described the formation of Ag−In intermetallic phases by the isothermal electroreduction of Ag into different liquid metal solvents via ec‐LLS. Electrodeposition of Ag into a pure Ga or pure Hg liquid metal pool yielded precisely the compounds predicted from isothermal cross‐sections of the respective binary phase diagrams. These compounds were not found when using liquid Hg or Ga containing appreciable In. The smaller enthalpy of formation for AgIn2 was consistent with its synthesis in Ga0.86In0.14. However, the observed product of Ag9In4 in Hg‐containing liquid metals could not be rationalized solely from thermodynamic factors. Instead, this observation was consistent with a kinetic pathway based on the lability of Hg‐metal bonds and nearly identical crystal structures of Ag9In4 and Ag2Hg3. Site exchange of Hg for In is consistent with our prior observations[23] of In exchange into Hg−Pd structures during Pd electrodeposition. This mechanism is not based on any direct role of electrochemistry other than aspects that dictate the operative supersaturation of the metal solute.

Highly flexible liquid metal/photocurable polymer electrodes via direct laser patterning

A highly flexible electrode was fabricated using eutectic gallium-indium (eGaIn) liquid metal combined with an ultraviolet (UV)-curable polyurethane acrylate (PUA) polymer. The eGaIn liquid metal electrodes prepared by a negative-type direct patterning technique using a UV pulse laser can eliminate the need for complex photolithography masks. The optimal UV pulsed laser peak fluence was ∼1.43 J/cm2 to pattern and sinter the eGaIn/PUA composite electrode simultaneously. The laser-patterned eGaIn/PUA composite electrode under the optimal laser condition exhibited a remarkable electrical conductivity of 6.33 × 105 S/m with a patterning resolution of ∼40 μm. Moreover, the resistance of the electrode only deteriorated by 0.95% after 50,000 cycles of severe cyclic folding at a peak strain of 2.5% with a bending radius of 1 mm, demonstrating its exceptional flexibility and durability. These easily patterned eGaIn flexible electrodes via direct laser patterning techniques hold great promise for applications in wearable and flexible electronic devices that require extreme flexibility.

93‐2: Highly Stretchable Liquid Metal‐based Deformable Micro‐LED Displays

Stretchable displays represent a cutting‐edge technology for creating novel freeform deformable displays. In this study, we developed a highly stretchable liquid metal‐based stretchable backplane technology for deformable micro‐LED displays. We developed a fine liquid metal patterning process and highly stretchable backplane fabrication technology to implement micro‐LED stretchable displays utilizing liquid metal electrodes. The developed stretchable display demonstrated exceptional flexibility allowing it to transition from planar to hemispherical shapes with up to 50% stretchability without disconnection of lines. Even when subjected to dome‐shaped deformation under 50% strain, the developed stretchable display utilizing liquid metal electrodes exhibited stable electrical characteristics, showcasing its practical applicability.