Stable Double Layer Research Articles

Demulsification of W/O emulsions induced by terahertz pulse electric fields-driven hydrogen bond disruption of water molecules

Demulsifying highly stable W/O emulsions, composed of heavy oil and water, is crucial for simplifying crude oil processing, reducing production costs, and mitigating environmental pollution. In these emulsions, aromatic components in the oil phase stack via π-π interactions, while hydrogen bonds stabilize the water phase. This leads to the creation of a strong oil-water interface through electrostatic attraction, ultimately hindering water droplet coalescence and oil-water separation. In this study, a 1.0 THz pulse electric field is introduced to effectively disrupt the hydrogen bond network among water molecules by inducing hydrogen bond resonance. This disruption contributes to increased water mobility in the oil phase, weakened stability of the oil-water interface film, and facilitates efficient water droplet coalescence in the oil phase. The results show that throughout the demulsification process, the average number of hydrogen bonds per water molecule rapidly decreases from 1.41 to 1.08 within 100 ps. The upper and lower limits of hydrogen bond lifetimes decrease by 8.12 ps and 3.24 ps, respectively. This indicates a significant disruption in the stability of hydrogen bonds between water molecules. Concurrently, the terahertz pulse electric field disrupts the initially stable oil-water interface film of the emulsion system, leading to a noteworthy reduction in the oil-water interface tension from 54.3 to 39.2 mN·m−1. The self-diffusion coefficient of water molecules increases from 1.33 to 2.62 Å2·ps−1, signifying that water molecules are more inclined to penetrate the interfacial region between the two phases. Additionally, the terahertz pulse electric field induces alterations in the arrangement of water molecules, resulting in the rearrangement of electrons in the water phase and disrupting the originally stable electrical double layer structure of the oil-water interface. This study provides novel insights into the development of efficient and environmentally friendly electric demulsification technologies, holding significant potential for widespread industrial applications.

Enhanced electrostatic shielding effect through incorporation of trace amounts of highly chelating anions for establishing a more stable electric double layer

IDHA anions with strong chelating capabilities participate in the solvation shell of Zn2+ and Na+. This interaction between IDHA anions and Na+ serves to stabilize the solvated sheath, thereby enhancing the electrostatic shielding effect of Na+.

Microwave-exfoliated Graphene Oxide for High Voltage “Water-in-Salt” Electrolyte-based Supercapacitor

Abstract Exfoliated and reduced graphene oxide (MEGO) was fabricated by rapid microwave irradiation. When MEGO was used as the electrode of 17 m NaClO4 “water-in-salt” (WIS) electrolyte-based supercapacitors, the cell exhibited stable double layer capacitant behavior up to 2.5 V, much higher than the electrochemical stable window of water. The MEGO exhibited high energy density of 22 Wh/kg at a power density of 12.5 kW/kg, attributable to fast motion of ion clusters in the large space of exfoliated nanosheets in MEGO.

High conducting PVDF-HFP + PTA polymer electrolyte for supercapacitor application

Herein, we reported the synthesis of polymer electrolyte prepared using polymer PVDF-HFP and PTA doped using well known solution cast technique method. There was a huge hike in the conductivity recorded while incorporating of PTA with polymer PVDF-HFP which was scrutinized by complex impedance spectroscopy. Fourier transform infrared spectroscopy was done to check the complexity of blended polymer PVDF-HFP with PTA. Polarized optical microscopy was also done to check the amorphousity of the polymer electrolyte. A good stable Electric double layer capacitor was fabricated using optimized polymer electrolyte film which shows reasonable efficiency.

The preparation of porous carbon materials derived from bio-protic ionic liquid with application in flexible solid-state supercapacitors

Ionic liquids have attracted much more attentions for its wide application in catalyst, green solvents and carbon precursors. Herein, N/P co-doped porous carbon materials with developed pore structure were facilely prepared from the phosphoric acid protic ionic liquid of arginine (Arg[H2PO4]2) and (NH4)2HPO4. The former acted as the carbon precursor, heteroatom source and mesopore generator, while the latter worked as the activator which had great impact on the pore distribution and microstructure. The porous carbon materials were characterized by SEM, XRD, Raman and N2 adsorption analysis in system, indicating that Arg-2–900 was promising electrode materials for supercapacitors. It exhibited high specific capacitance retention of 94% after 10000 cycles with stable electric double layer capacitors. The assembled symmetrical supercapacitors exhibited a wide voltage window in alkaline electrolyte and neutral aqueous electrolyte, displaying high energy density and power density, respectively. In addition, the solid-state supercapacitors were prepared and showed good flexibility after bending the flexible supercapacitor cell at different angles. The results demonstrated the successful synthesis of N/P co-doped porous carbon materials form Arg[H2PO4]2 and broad application in wearable storage device.

Novel flexible solid-state pseudo-parallel pseudocapacitor with manganese oxide active material synthesized using electrodeposition

Flexible and light-weight energy storage device is required for soft electronics. Novel flexible solid-state pseudo-parallel pseudocapacitor (SPP) with three electrodes is firstly proposed to achieve light-weight and excellent energy storage ability. SPP is assembled using only three electrodes without outer circuit. Active material of δ-MnO2 is fabricated on carbon cloth (CC) using electrodeposition with different currents. Highest specific capacitance of 9.41 F/cm2 is obtained for MnO2/CC electrode prepared using 30 mA, due to high surface area, large pore volume and suitable pore structure of nanosheet array. Normal-type pseudocapacitor (NP), two normal-type pseudocapacitor connected in parallel (NP in parallel), and two types of SPP are assembled using optimized MnO2/CC positive electrode and activated carbon negative electrode. The SPP composed of two positive electrodes and one negative electrode (PNP) shows best energy storage ability with energy density of 97.09 Wh/kg at power density of 0.65 W/kg, owing to more MnO2 pseudocapacitor electrode and better device configuration. However, worse charge/discharge stability is observed for PNP owing to lacking sufficient carbon material for providing stable electric double layer capacitor energy storage mechanism. This work greatly opens new blueprint for designing device configurations to achieve light-weight and efficient energy storage ability for flexible solid-state pseudocapacitors.

The Formation Mechanism of the Double Gas Layer in Gas-Assisted Extrusion and Its Influence on Plastic Micro-Tube Formation.

The diameter of a micro-tube is very small and its wall thickness is very thin. Thus, when applying double-layer gas-assisted extrusion technology to process a micro-tube, it is necessary to find the suitable inlet gas pressure and a method for forming a stable double gas layer. In this study, a double-layer gas-assisted extrusion experiment is conducted and combined with a numerical simulation made by POLYFLOW to analyze the effect of inlet gas pressure on micro-tube extrusion molding and the rheological properties of the melt under different inlet gas pressures. A method of forming a stable double gas layer is proposed, and its formation mechanism is analyzed. The research shows that when the inlet gas pressure is large, the viscosity on the inner and outer wall surfaces of the melt is very low due to the effects of shear thinning, viscous dissipation, and the compression effect of the melt, so the melt does not easily adhere to the wall surface of the die, and a double gas layer can be formed. When the inlet gas pressure slowly decreases, the effects of shear thinning and viscous dissipation are weakened, but the gas and the melt were constantly displacing each other and reaching a new balanced state and the gas and melt changed rapidly and steadily in the process without sudden changes, so the melt still does not easily adhere to the wall of the die. Thus, in this experiment, we adjusted the inlet gas pressure to 5000 Pa first to ensure that the melt do not adhere to the wall surface and then slowly increased the inlet gas pressure to 10,000 Pa to reduce the viscosity of the melt. Lastly, we slowly decreased the inlet gas pressure to 1000 Pa to form a stable double gas layer. Using this method will not only facilitate the formation of a stable double gas layer, but can also accurately control the diameter of the micro-tube.

Electrostabilized homogeneous dispersion of boron nitride nanotubes in wide-range of solvents achieved by surface polarity modulation through pyridine attachment

Boron nitride nanotubes (BNNTs) show exceptional physical properties including high mechanical strength and thermal conductivity; however, their applications have been restricted due to limited dispersibility in processing solvents. Here, a novel BNNT dispersion method with exceptional dispersibility in a wide range of solvents has been demonstrated by surface polarity modulation through short-molecule pyridine attachment. Nitrogen atoms in pyridine are selectively bonded to electron-deficient boron atoms of the BNNT surface through Lewis acid-base reaction, which changes the surface polarity of BNNTs from neutral to negative. Re-dispersing pyridine-attached BNNTs (Py-BNNTs) create a thick and stable electronic double layer (EDL), resulting in uniform dispersion of BNNTs in solvents with an exceptional solubility parameter range of 18.5–48 MPa1/2. The uniform dispersion of BNNTs is maintained even after the mixing with diverse polymers. Finally, composites incorporating uniformly-distributed BNNTs have been realized, and extraordinary property enhancements have been observed. The thermal conductivity of 20 wt.% Py-BNNT/epoxy composite has been significantly improved by 69.6% and the tensile strength of 2 wt.% Py-BNNT/PVA has been dramatically improved by 75.3%. Our work demonstrates a simple and facile route to dispersing BNNTs in diverse solvents, consequently leading to selective utilization of BNNT dispersed solvents in various application fields.

A discussion on the leaching process of the ion-adsorption type rare earth ore with the electrical double layer model

The practice of in-situ leaching of the ion-adsorption type rare earth ore using (NH4)2SO4 had revealed serious ammonia-nitrogen pollution. Therefore, a discussion on the leaching process of the ion-adsorption type rare earth ore with the electrical double layer model was presented in this paper, so as to screen out the green and efficient leaching agent and the appropriate leaching measures to improve the rare earth leaching efficiency and reduce or even eliminate ammonia-nitrogen emissions. It was determined that the leaching process could be described as the formation of a new stable electric double layer (EDL). The potential φ(x) with the distance x from clay surface to bulk solution in the diffusion layer was obtained, it showed that the potential φ(x) would decrease with the increase of the cationic charge of leaching agent, the leaching temperature and the concentration of leaching agent, leading to a higher rare earth leaching efficiency. The theoretical analysis was verified by soak leaching experiments. The results showed that the law of rare earth leaching efficiency was in agreement with the theoretical analysis. And the rare earths partition in the leaching liquor under different conditions was substantially constant except cerium element. Therefore, the cation and anion of leaching agent should have a large electric density and be environmental friendly, of which magnesium sulfate could be preferred. Moreover, chemical substances, which could form a more stable coordination with rare earth ions, could be used as an assistant to promote the leaching equilibrium to move toward a favorable direction. This paper had provided a theoretical foundation and application basis for the leaching of rare earth from the ion-adsorption type rare earth ore, and show the direction on reducing or even eliminate ammonia-nitrogen emissions.

In-Situ Solid-State Electrochemistry of Well-Defined Electrode-Electrolyte Interfaces Using Ion Soft Landing

Molecular-level understanding of electrochemical processes at electrode-electrolyte interfaces (EEI) is key to the development of high-performance electrochemical technologies such as batteries, supercapacitors, and fuel cells. Soft landing of mass-selected ions is ideally suited for controlled preparation of well-defined surfaces necessary for understanding processes at EEI. Specifically, ion soft landing enables deposition of uniform layers of redox-active species onto electrode surfaces with precise control over the charge state, composition, and kinetic energy.(1-3) Herein, we report the development and first demonstration of the capabilities of an in-situ solid-state three electrode electrochemical cell for studying the electrochemical activity of mass- and charge- selected ionic clusters deposited onto electrode surfaces using ion soft landing. In-situ electrochemical cells were fabricated using carefully designed nanoporous ionic liquid membranes with excellent mass transfer properties compared to liquid electrolyte.(4) The in-situ electrochemical cell enables (i) characterization of both intrinsic redox and reactive processes with control over the stoichiometry and distribution of analyte species at EEIs using soft landing onto nanostructured solid-state electrolyte and (ii) understanding of the effect of diffusion of ions of interest through pores on their electrochemical activity. The in-situ electrochemical cell was fabricated by depositing a ~10 µm thick room temperature ionic liquid - polymer electrolyte membrane on a screen printed electrode. The cell showed a stable rectangular double layer capacitive behavior both in high vacuum (10-5 Torr) and reactive gaseous environments. We demonstrate the performance of the in-situ electrochemical cell for studying both the intrinsic redox activity and reactive electrochemistry of well-defined ions at EEI. Specifically, we examined the intrinsic redox activity of mixed-addenda Keggin PMoxW12-xO40 3- (x=0,1,2,3,6,9,12) polyoxometalates. Multi-electron redox activity of stable anionic Keggin POMs that enable transfer of up to 24 electrons while retaining the structure of the cluster makes them attractive systems for studies in catalysis and energy storage.(5, 6) In addition, we examined the oxygen reduction reactivity of bare Pt cluster ions ∼1 nm in diameter produced using magnetron sputtering combined with gas aggregation. Soft landing of bare metal clusters directly onto the cell eliminates the need to use stabilizing ligands or solvent and, therefore, provides a direct route for studying intrinsic electrocatalytic activity. In summary, the in-situ electrochemical cell combined with mass-selected ion deposition is a powerful approach for studying processes both at model and technologically-relevant EEIs during operating conditions.

Investigation of Reduced Graphene Oxide with F-Doped SnO2 as Catalyst Support in Fuel Cells

Degradation of commonly used platinum on carbon black results into performance losses of proton exchange membrane fuel cells (PEMFC). A nanocomposite of fluorine-doped SnO2 (FTO) and reduced graphene oxide (rGO) is used as Pt support and studied on electrochemical stability by potential cycling between 0.05–1.47 VR HE. Highly dispersed Pt with anchoring at FTO–rGO interfaces is observed by use of high resolution transmission electron microscopy (HR-TEM). Stripping voltammetry shows weaker CO binding on Pt/FTO–rGO than on Pt/C, indicating higher CO tolerances. During potential cycling, the catalyst shows a loss of electrochemical active surface and a reduced activity for oxygen reduction, whereas the support exhibits unchanged amounts of hydroquinone/quinone functionalities and stable double layer capacitance. Additionally, identical location TEM shows unchanged FTO particles on rGO surface, demonstrating electrochemical stability of FTO–rGO substrate. Thus, this composite material meets the stability criteria for catalyst support in PEM fuel cells.

Investigation of self-assembly properties and the effect of tween series co-surfactants on the stability of nonionic branched-chain glycolipid hexosomes

Sugar-based surfactants have recently drawn much attention due to their nonionic and bio-friendly properties. These glycolipids are also popular because they can be found in nature or synthesized (e.g. alkyl polyglucosides) from cheap natural resources. In this research, the liquid crystalline and self-assembly properties of a novel branch alkylated glycolipid, namely 2-hexyldecyl-β(/α)-d-glucoside (αβ-Glu-OC10C6), were studied using differential scanning calorimetry (DSC), optical polarizing microscopy (OPM) and small-angle X-ray scattering (SAXS). The αβ-Glu-OC10C6 in anhydrous condition formed a columnar phase with focal conic texture, whereas in the binary aqueous system, αβ-Glu-OC10C6 formed inverse hexagonal dispersions known as hexosomes. The critical aggregation concentrations (CACs) were studied for the branched-chain glycolipid when this was mixed with nonionic co-surfactants (Tween series). The addition of co-surfactants to the glycolipid dispersions reduced the CAC value of αβ-Glu-OC10C6, thus making the system more stable. The formation of mixed surfactant hexosomes was further investigated in terms of their particle size and morphology by using a particle sizer and a transmission electron microscope (TEM), respectively. Furthermore, the particle size variations and particle migration were investigated using light backscattering measurements for 24h. In the previous study, αβ-Glu-OC10C6 hexosomes produced were unstable because the balance between hydrophilic and lipophilic was not optimum to stabilize the formation of a stable double layer. Therefore, the addition of co-surfactant Tween series reduced the particle size and enhanced the stability of αβ-Glu-OC10C6. Thus, branched-chain glycolipid provided an alternative nonionic surfactant with interesting phase behaviour as a drug carrier system for various applications.

Molecular Response of 1-Butyl-3-Methylimidazolium Dicyanamide Ionic Liquid at the Graphene Electrode Interface Investigated by Sum Frequency Generation Spectroscopy and Molecular Dynamics Simulations

The ion distribution at the charged three layer graphene–ionic liquid (1-butyl-3-methylimidazolium dicyanamide, [BMIM][DCA]) interface is probed by sum frequency generation spectroscopy (SFG), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The SFG results show the presence of both [BMIM]+ cations and [DCA]− anions at the charged graphene surface, where the anion signal increased with the increasing external potential and the cation signal was little influenced by the external potential. The CV and EIS results suggest that ions form an electrically stable double layer at the charged graphene surface. Molecular dynamics simulations of [BMIM][DCA] near the charged graphene surface suggest that the interface consists of alternating layers of cations and anions that restructure with external potential variation. The experimental data can be interpreted by a double-layer model where the anionic and cationic layers interchange position with each other at the surface depending on the a...

Highly Efficient Electrohydrodynamic Pumping: Molecular Isomer Effect of Dielectric Liquids, and Surface States of Electrodes.

Highly efficient electrohydrodynamic (EHD) pumping was obtained by a combination of a dielectric liquid having a molecular isomer and electrodes with a smooth surface. Four kinds of surface states of Cu electrodes were processed by conventional mechanical polishing, fine diamond paste polishing, chemical etching and Au vapor deposition. A series of hydrofluoroether liquids (HFEs) were used as dielectric liquids: C3F7OCH3 (HFE-7000), C4F9OCH3 (HFE-7100), C4F9OC2H5 (HFE-7200), C6F13OCH3 (HFE-7300), and C5H5F6OC3HF6 (HFE-7600). The coexistence of normal (n-) and isomer (i-) HFEs and their molar fractions were examined by NMR spectroscopy. Among the dielectric liquids, the hybrid n- and i-HFE-7600 showed highly efficient EHD pumping, where the electric current, I, was sufficiently suppressed by the smooth surface of the electrodes. The maximum hydrostatic pressure Δpmax was ∼7500 Pa with 12 kV and I = 19 μA. The smooth surface of the electrodes contributes not only to the formation of a stable electric double layer (EDL) but also to the prevention of charge injection from the electrodes. Polarization pumping derived from the stable EDL enables highly efficient energy transfer without discharging, or damage to the sample and electrodes. The dipole moments of the HFEs were estimated by density functional theory calculations. The hydrostatic pressure was found to be proportional to the difference in the calculated dipole moment between n- and i-HFEs. Numerical simulations were carried out to examine the experimentally obtained electrode gap dependence of the hydrostatic pressure.

Sound field measurement in a double layer cavitation cluster by rugged miniature needle hydrophones

During multi-bubble cavitation the bubbles tend to organize themselves into clusters and thus the understanding of properties and dynamics of clustering is essential for controlling technical applications of cavitation. Sound field measurements are a potential technique to provide valuable experimental information about the status of cavitation clouds. Using purpose-made, rugged, wide band, and small-sized needle hydrophones, sound field measurements in bubble clusters were performed and time-dependent sound pressure waveforms were acquired and analyzed in the frequency domain up to 20MHz. The cavitation clusters were synchronously observed by an electron multiplying charge-coupled device (EMCCD) camera and the relation between the sound field measurements and cluster behaviour was investigated. Depending on the driving power, three ranges could be identified and characteristic properties were assigned. At low power settings no transient and no or very low stable cavitation activity can be observed. The medium range is characterized by strong pressure peaks and various bubble cluster forms. At high power a stable double layer was observed which grew with further increasing power and became quite dynamic. The sound field was irregular and the fundamental at driving frequency decreased. Between the bubble clouds completely different sound field properties were found in comparison to those in the cloud where the cavitation activity is high. In between the sound field pressure amplitude was quite small and no collapses were detected.

Stability of single and double layer fibrillar amyloid-β oligomers

Alzheimer's disease (AD) is the most common form of dementia world-wide. The causative agent in this protein misfolding disease is the 39 to 42-residues long amyloid-β (Aβ) peptide, that aggregates into oligomers, filaments, and fibrils found in plaque deposits in the brain of AD patients [1]. Up to now a viable cure for this disease is still not available. One reason for this is Aβ's conformational flexibility and structural heterogeneity in solution paired with its aggregation tendency. This renders the determination and isolation of distinct Aβ structures experimentally challenging. Especially the soluble oligomers, that are thought to be the neurotoxic species in AD, may adopt a plethora of conformations in vivo [1]. It is known from experiment, that there exist toxic fibrillar oligomers, but the details of their topology are not yet known [2]. Thus, we used molecular dynamics simulations to investigate the structural stability of fibrillar single and ouble layer Aβ42 oligomers of different size (4-mer to 48-mer), that we constructed from the experimental structure [3] (cf Figure ​Figure11). Figure 1 Double layer Aβ 48-mer (Met35 in the interface in sticks representation). We found that there is a clear correlation between oligomer size and preference for double layer structure: Large oligomers display an enhanced stability in double layer conformation, whereas small oligomers prefer the single layer structure. On the other hand, large single layer oligomers dissociate into smaller oligomers, while small double layer oligomers collapse or are energetically unfavorable. From our simulations we deduce that the critical number of oligomers to construct a stable Aβ double layer is in the range of 10 to 12. In a more general picture, longitudinal growth along a single layer is limited by the increasing structural instability. Lateral growth, i.e. forming a double layer, creates stable mini-fibrils. These may act as seeds for further stable fibril growth.

Matrix circuit model for an electric double layer capacitor

A mathematical model of an electric double layer capacitor is developed treating the capacitance as a matrix instead of a scalar. Model explicitly demonstrates that when two electrodes are immersed an electrolyte and a potential difference applied, a stable double layer that store energy is created. It is suggested that supercapacitors could be modeled on the basis of capacitance matrices whose elements parameterize the geometry of the porous electrode.

Threshold for formation of a stable double layer in an expanding helicon plasma

We report detailed studies of a threshold antenna frequency for the creation of an ion beam due to the formation of a stable electric double layer (DL) in an expanding, low pressure, argon helicon plasma. Mutually consistent measurements of ion beam energy and density obtained with a retarding field energy analyzer and laser-induced-fluorescence indicate that a stable ion beam of approximately 15 eV appears for antenna frequencies above 11.5 MHz. At lower antenna frequencies, for which the rf coupling to the plasma improves, large electrostatic instabilities appear downstream of the expansion region and a well-formed ion beam is not observed. Further studies of the low frequency (∼17.5 kHz) electrostatic fluctuations suggest that they arise from beam-driven, ion acoustic instabilities. We also observe a sharp increase in the upstream density at the same threshold antenna frequency, confirming a theoretical model that predicts an increase in the upstream density due to enhanced ionization resulting from electrons accelerated upstream by the DL.

Laser acceleration of monoenergetic protons via a double layer emerging from an ultra-thin foil

We present theoretical and numerical studies of the acceleration of monoenergetic protons in a double layer formed by the laser irradiation of an ultra-thin film. The ponderomotive force of the laser light pushes the electrons forward, and the induced space charge electric field pulls the ions and makes the thin foil accelerate as a whole. The ions trapped by the combined electric field and inertial force in the accelerated frame, together with the electrons trapped in the well of the ponderomotive and ion electric field, form a stable double layer. The trapped ions are accelerated to monoenergetic energies up to 100 MeV and beyond, making them suitable for cancer treatment. We present an analytic theory for the laser-accelerated ion energy and for the amount of trapped ions as functions of the laser intensity, foil thickness and the plasma number density. We also discuss the underlying physics of the trapped and untrapped ions in a double layer. The analytical results are compared with those obtained from direct Vlasov simulations of the fully nonlinear electron and ion dynamics that is controlled by the laser light.

Effects of ionic interactions between clay and waterborne polyurethanes on the structure and physical properties of their nanocomposite dispersions

A waterborne polyurethane (WPU)/clay dispersion is electrostatically stabilized by COO− ions of WPU. Meanwhile, a stable electrical double layer is formed around each WPU/clay particle. The cations of clay platelets interact with COO− ions and interfere with the double layer of a pristine WPU dispersion. The WPU/clay dispersion, disturbed by ionic clay platelets, has fewer effective hydrophilic groups for stabilization in water. This leads to a larger particle size. Moreover, a WPU/clay dispersion with a higher clay concentration exhibits a higher viscosity. This is due to the stronger electrostatic interactions among a larger quantity of clay ions.