Formation Of Double Layer Research Articles

Ion expansion dynamics of laser induced multi-elemental plasmas

Ablation of multi-elemental materials by nanosecond lasers is often used to deposit oxide thin films. Understanding the ablation plume dynamics is of utmost importance to gain a detailed insight into thin film growth of materials with a complex composition. In this study, the plume expansion dynamics of several compound materials (AuCu, La0.33Ca0.67MnO3, and LiMn2O4) were characterized by measuring the angular-dependent kinetic energy (KE) distributions of ionic plasma species produced by KrF- and XeCl-excimer laser ablation in vacuum. The distributions of the lightest plume ions were found to differ fundamentally from those of other ions. The latter are similar to the energy distributions observed in single-component plumes and represent a low-energy peak and high-energy tail, while those for the lightest ions consist of at least two distinct peaks. These observations can be explained by assuming the formation of a dynamic double layer (DL) at the front of the plasma giving rise to different acceleration rates for light and heavier ions. As a consequence, heavier elements stay longer within the dynamic DL and gain larger KEs that leads to the observed ion separation. Extending these considerations into three dimensions yields an anisotropic acceleration concept for the plasma ions with high acceleration rates and longer presence within the DL normal to the target surface and lower acceleration rates and shorter time in the parallel direction.

Improved inclusive performance of bi-stacked NiO nanoflakes coated nano-Co3O4 for dual function: An electrochromic-supercapacitor

As technology progresses, electrochromic supercapacitors realize the need for active chromophores to reduce energy consumption and manufacture power-efficient devices. A simultaneous effect of chromic modulation and energy storage has been achieved in a bi-layer stacked film of two different metal oxides (NiO@Co3O4). Staking of the film changes their suppressed resultant energy levels thereby obtaining less charge transfer resistance in an electrochemical cell. The electrochemistry of the fabricated electrodes in an alkaline medium displays its dominant capacitive behavior and therefore leads to the formation of an electric double layer at the electrode/electrolyte interface. While charging, the intercalation/de-intercalation of ions changes the oxidation state of metals at the electrode surface and responds to a finite chromic modulation. A well-defined interplay between the chromic modulation (ηCE = 27.5 cm2/C) and its capacitive performance (158 F/g) has been identified. At last, with a good reversible redox activity, the electrode was also checked as a counter electrode to exhibit better electrochromic performance with small organic viologen material.

Interplay between electron and ion plasma waves

We report the observation of the interplay between the first kind of high-frequency electron-dominated plasma waves (EPWs) and the second kind of low-frequency ion-dominated plasma waves (IPWs) in a DC glow discharge plasma experiment. On application of positive DC voltage on a probe immersed in plasma when the drift velocity of the electrons (vd) ≈1.3× the thermal velocity of electrons (vte), it gives rise to an instability resulting in the formation of double layers (DL). Under DL conditions, the anode sheath extends deep into plasma. The DL represents a nonequilibrium plasma condition that is known for the instabilities and excitation of plasma waves. In this experiment, the effect of the monotonic increase of plasma density fluctuations (δn≈0.01%) on the evolution of DL has been studied. The interplay between EPWs and IPWs is observed in the course of this investigation. The overall plasma response on density fluctuations is recorded as floating potential fluctuations (FPFs) which vary with an increase of δn. The FPFs exhibit order-chaos-order transition with the evolution of DLs. Further analysis of the fluctuations using the wavelet method gives a spectrum in both the time and frequency domains simultaneously. Wavelet spectra reveal that the nonlinear evolution of FPFs is a consequence of the interplay between EPWs and IPWs due to the trapping and detrapping of electrons in the extended anode sheath region. These results explain that the ordered oscillation corresponds to dominant EPWs and the chaotic fluctuations are due to the coexistence of EPWs and IPWs. This new understanding may assist to study the complex plasma behaviour observed in laboratories as well as space plasmas.

Electro-osmotically modulated magneto hydrodynamic peristaltic flow of menthol based nanofluid in a uniform channel with shape factor

Current article is a study on peristaltic transport of menthol electrolytes altered utilizing an external electric field which contributes to the creation of a net surface charge attracting counter ions and repels co ions from the menthol based nanofluid, thus preceding the formation of an electrical double layer (EDL), a region of net charges at surface vicinity. Effects of electroosmotic body forces are studied on the base fluid with and without the presence of copper nanoparticles. Menthol-based fluid is chosen to owe to its utility in medicines and flavoring. Combine effects of electro-osmotically modulated magneto hydrodynamic peristaltic flow for Menthol based nanofluid in a uniform channel with shape factor is not discussed so far in literature. Streamlines are drawn to examine the collective influence of electroosmosis and peristalsis on trapping a fluid volume (e.g., bolus) inside the channel. Trapping is reported to be significantly influenced by an electric field rather than an electro-osmotic parameter. The present investigation may also be beneficial in the design of organs on chip-like devices for improved drug design and delivery.

Novel Polyepoxysuccinic Acid-Grafted Polyacrylamide as a Green Corrosion Inhibitor for Carbon Steel in Acidic Solution.

Utilizing green corrosion inhibitors has been classified among the most efficient and economical mitigation practices against metallic degradation and failure. This study aims to integrate the features of green and complementary properties of polyepoxysuccinic acid (PESA) and polyacrylamide (PAM) for steel corrosion inhibition. A novel PESA-grafted-PAM (PESAPAM) has been first-ever synthesized in this research study and deployed as a corrosion inhibitor for C-steel in 1.0 M HCl solution. Eco-toxicity prediction confirmed the environmentally friendly properties acquired by the synthesized inhibitor. Electrochemical, kinetics, and surface microscopic studies were carried out to gain a holistic view of C-steel corrosion behavior with the PESAPAM. Furthermore, the performance of PESAPAM was compared with that of the pure PESA under the same testing conditions. Results revealed predominant inhibitive properties of PESAPAM with an inhibition efficiency (IE) reaching 90% at 500 mg·L-1 at 25 °C. Grafting PAM onto the PESA chain showed an overall performance improvement of 109% from IE% of 43 to 90%. Electrochemical measurements revealed a charge transfer-controlled corrosion mechanism and the formation of a thick double layer on the steel surface. The potentiodynamic study classified PESAPAM as a mixed-type inhibitor. Furthermore, the investigation of C-steel corrosion kinetics with the presence of PESAPAM predicted an activation energy of 85 kJ·mol-1, correlated with a physical adsorption behavior. Finally, performed scanning electron microscopy and energy-dispersive X-ray analyses confirmed the adsorption of PESA and PESAPAM, with superior coverage of PESAPAM onto the steel surface.

A Critical Overview of the Impact of Nanoparticles in Ester Fluid for Power Transformers

This paper examines the impact of various nanoparticles on ester fluids with a special focus on their usage towards power transformers. The precautionary measures to be considered on the nanofluids such as preparation methodologies with an appropriate surfactant and its stability is well elucidated. The electrical double layer (EDL) formation around the nanoparticles on its diffusion in the insulating fluid is explained by its different layers away from the particle surface. The partial discharge of ester nanofluids with different detection methods is elaborated on its comparison with conventional IEC 60270 measurements. The field configurations on ester-nanofluids govern the breakdown mechanism with variations in the streamer patterns. The equation of relaxation time towards breakdown is valid only when it is lower than the initiation time for streamers. The flow charges induced at the solid/liquid interface inside transformers depends on the structure of the nanofluid and the condition of pressboard/paper insulation. The impact of different concentrations of nanoparticles on ester nanofluids observes a change in its flow behaviour affecting the streaming current. The permittivity of nanofluid depends on the polarization of nanoparticles where the Clausius-Mossotti equation governing this mechanism is explained towards ester-nanofluids. The viscosity of nanofluids observed no significant variation whereas the other physio-chemical properties such as flash point, interfacial tension, and oxidation stability improved depending on the type of nanoparticle. The addition of metal-oxide nanoparticles on ester fluids increases thermal conductivity with different models proposed based on the structure and shape of a nanoparticle. The impact of ageing on nanofluids observes an instability over a longer ageing duration with specific nanoparticles which should be better understood before implementing them in real-time power transformers.

The process of free radical generation in contact electrification at solid-liquid interface

Solid-liquid interfaces are ubiquitous in nature and widely used in various applications such as catalysis, sensing, batteries, etc. Recently, we found the existence of electron transfer at the interface in solid-liquid contacting, and proposed a “two-step” theory for the formation of solid-liquid electric double layer (EDL). In this work, we found that hydroxyl radical (·OH) was generated when the droplet contact with the tube inner wall without external interference, and the concentration of·OH was increased with increasing pH, demonstrating that the·OH was generated from hydroxide ions (OH-) by electron transfer during contact electrification. This can be further supported by the fact that capillaries made of materials with stronger electron-withdrawing ability could generate more·OH. Interestingly, superoxide anion radical (·O2-) was not generated at the solid-liquid interface if no external energy is provided. However, if ultrasonic was applied,·O2- could be generated at the solid-liquid interface, because ultrasonication provides transition energy for the electron to transfer from the solid to O2 at the interface. Based on the generation of reactive oxygen species (·OH and·O2-), we demonstrated a proof-of-concept for degradation of tetracycline pollution. This work provides an excellent strategy to study the solid-liquid interface and also provides a new insight into the free radical generation at the interface in solid-liquid contacting.

Liquid-solid contact electrification and its effect on the formation of electric double layer: An atomic-level investigation

Contact electrification at liquid-solid interface has aroused many research interests. Some recent researches suggest that the formation of electric double layer may be dominated by the charge transfer from liquid-solid contact electrification, which challenges the traditional electric double layer models. However, how the liquid-solid contact electrification affects the electrical double layer is still lacking of atomic-level mechanism details. In this work, an atomic-level investigation on the effect of contact electrification on the liquid-solid electric double layer are performed via first-principles and molecular dynamics simulations. The results suggest that the liquid-solid contact electrification can influence the ions distribution in the solution, thus influencing the formation of electric double layer and can even reversing its polarity under specific surface charge density. The mechanism is that the contact charges on the solid surface can affect the adsorption energy of anion/cation at the liquid-solid interface. The conclusion of this work can provide a more comprehensive understanding of the effect of contact electrification to the electric double layer.

Boosted energy harvesting in droplet electrochemical cell with non-equilibrium electrical double layer

Droplet energy harvesting technologies, such as droplet triboelectric nanogenerators (D-TENGs) and droplet-based electricity generators (DEGs), which are not restricted by geographical location, have been vigorously developed in recent years. However, achieving electricity generation with high performance is still challenging. Here, we demonstrate a new approach for droplet-based energy harvesting device named droplet electrochemical cell (DECC) which could enhance energy generation performance by utilizing the formation of non-equilibrium electrical double layers. The DECC is designed by drawing inspiration from the zinc-copper primary battery system and demonstrated remarkable results when tested with dynamically impinging water droplets. The peak current and transferred charge generated by a 100 μL droplet are found to be 400 μA and 3.2 μC, respectively. The short circuit current is also found to increase by approximately 30 times when the dynamic impinging frequency of the droplets is increased. This study provides valuable insights into the development of energy harvesting devices based on droplets.

Interfacial Charge Transfer of B‐doped g‐C3N4/ZnIn2S4p–n Heterojunction for Plasticizer Bisphenol‐A and Dye/Drug Intermediates, 2,4‐Dinitrophenol Degradation in Sunlight

AbstractFabricating an efficient photocatalyst for solving energy and environmental pollution is challenging, especially using sunlight. Herein, a photocatalyst was developed to degrade plasticizer (Bisphenol A, BPA) and an industrial‐pollutant 2,4‐dinitrophenol (DNP) found in water bodies with sunlight. Several ZnIn2S4/B‐doped g‐C3N4(ZIS@BCN) heterojunctions were prepared by an ultra‐sonochemical route followed by calcination. HRTEM, MS analysis, EIS, photocurrent, and synergic factor calculations were employed to confirm p‐n heterojunction. The phase purity and optical characteristics of the photocatalysts were determined by XRD, PL, and DRS UV‐Vis spectroscopy. A successful p‐n heterojunction 2 %ZIS@BCN showed better degradation efficiency than pristine ZIS (n‐type) and BCN (p‐type) semiconductors. Moreover, the best photocatalyst (2 % ZIS@BCN) exhibited maximum photo‐degradation of 83 % of BPA and 85 % of DNP under solar light illumination. The degradation pathways and involvement of reactive species were confirmed using LC–MS, trapping experiments, nitroblue‐tetrazolium, and terephthalic acid tests. The superior activity is ascribed to the successful formation of an electrical double layer (EDL) between p‐type BCN and n‐type ZIS, which minimizes the e−‐h+recombination and thereby increases the visible light utilization efficiency. The work validates the formation of ZIS@BCN p‐n heterojunction, showing solar light‐driven photocatalytic degradation of toxic effluents found in water bodies.

High-Performance Supercapacitors: A Comprehensive Review on Paradigm Shift of Conventional Energy Storage Devices

The enormous demand for energy due to rapid technological developments pushes mankind to the limits in the exploration of high-performance energy devices. Among the two major energy storage devices (capacitors and batteries), electrochemical capacitors (known as ‘Supercapacitors’) play a crucial role in the storage and supply of conserved energy from various sustainable sources. The high power density and the ultra-high cyclic stability are the attractive characteristics of supercapacitors. However, the low energy density is a major downside of them, which is also responsible for the extensive research in this field to help the charge storage capabilities thrive to their limits. Discoveries of electrical double-layer formation, pseudocapacitive and intercalation-type (battery-type) behaviors drastically improved the electrochemical performances of supercapacitors. The introduction of nanostructured active materials (carbon-/metal-/redox-active-polymer/metal-organic/covalent-organic framework-based electrode materials), electrolytes (conventional aqueous and unconventional systems) with superior electrochemical stability and unprecedented device architectures further boosted their charge storage characteristics. In addition, the detailed investigations of the various processes at the electrode–electrolyte interfaces enable us to reinforce the present techniques and the approaches toward high-performance and next-generation supercapacitors. In this review, the fundamental concepts of the supercapacitor device in terms of components, assembly, evaluation, charge storage mechanism, and advanced properties are comprehensively discussed with representative examples.

Surface charge induced bioelectricity generation from freshwater macroalgae Pithophora

A new concept of energy harvesting from the interaction of water molecule with macroalgal surface charges has been developed. The formation of electrical double layers on the charged surface of algae was utilized to generate the voltage and current between two aluminum electrodes along the length of the biofilm. In this study, a facile and efficient algal hydrovoltaic device based on the macroalgae Pithophora roettleri was demonstrated which can generate continuous electric power with a current of ∼4.4 μA and voltage ∼0.32 V. Seven series connected devices can glow an LED light, without any external energy. The superior performance of the device is attributed to the intrinsic properties of the Pithophora algal film, including its hydrophilicity, filamentous structure, conductivity and more. This study is providing a new way to research on hydrovoltaic power generation integrated with electrostatic charges present on algal cytoplasmic membrane or surface.

Depression of electro-oxidation of Ti3C2Tx MXene Joule heater by alternating current for Joule heating membrane distillation

Membrane distillation (MD) is a promising technology with great potential to mitigate the crisis of water shortage. However, it still suffers from the low productivity due to that water vaporization on the membrane would reduce the transmembrane temperature and hence the permeate flux. Herein, an electrothermal membrane that can heat the feed solution on the membrane and hence enables the MD operation under a low electrical input was developed. This was achieved by coating a commercial PET-PTFE membrane with MXene nanosheets through a filtration method. The resultant MXene/PET-PTFE composite membrane could heat the surroundings (both air and brine) efficiently, showing a conversion efficiency of 73% at 1 W. Furthermore, it was shown that the composite membrane, while degrades rapidly in highly ionizable brine under a direct current (d.c.) input, could work stably over a long duration at high potential under high-frequency alternating current (a.c.) input. Systematic electrochemical impedance spectroscopic investigation suggested that the reciprocal vibration of ions under a high-frequency a.c. could inhibit the formation of electrical double layer, and thus depresses the electrochemical oxidation of MXene and water splitting. Furthermore, the composite membrane enabled efficient in-situ heating in a Joule heating MD (JHMD) system, delivering a permeate flux of 1.8 kg m−2h−1 at an input power of 3 W, which is 333% higher than that based on the conventional MD process. Theoretical simulation of the temperature distribution by a finite element method (FEM) confirmed a higher transmembrane temperature in the JHMD system than in the conventional MD, which is responsible for the performance enhancement.

Flexible iontronic sensors with high-precision and high-sensitivity detection for pressure and temperature

Flexible sensor with high precision and sensitivity in detecting pressure and temperature is highly desired. Herein, we design a flexible iontronic sensor by sandwiching a sandpaper-like ionogel layer between two silver nanowires-loaded polymeric nanofiber films. The obtained sensor can serve as a flexible pressure sensor with high precision (1.18 Pa), high sensitivity (106.01 kPa−1), wide measuring range (0–77 kPa), fast response/recovery time (16 ms/25 ms), and good stability over 2000 cycles because of the continuous change in the contract between electrode and dielectric layer under pressure and the formation of electric double layer between them. Owing to these excellent merits in pressure sense, the as-prepared sensor can real-time monitor tiny pressure caused by pulse, facial movements, and swallowing. More interestingly, this sensor can also serve as a temperature sensor, which has outstanding integrated performance of high precision of 0.02 °C, high sensitivity of 28.1% °C−1 (20–40 °C), wide operating window from −40 °C to 80 °C, superb repeatability and reliability, attributing to the monotonous relationship between the dielectric constant of TPU/IL ionogel and temperature. The designed sensor has bright prospects in flexible electronics and electronic skins for monitoring human health and human motion.

Adaptive distributed observer-based predictive formation tracking control for autonomous underwater vehicles

Numerous existing autonomous underwater vehicles (AUVs) formation control works have focused on the observation of external time-varying disturbances in trajectory tracking control. However, external time-varying disturbance outliers cannot be ignored due to the complex marine environment. It is rarely considered in previous research. In this paper, a double-layer distributed formation prediction control scheme is designed, including an upper-level adaptive distributed observer and a lower-level predictive controller. Firstly, the velocity is observed and regarded as an unknown variable by the expectation maximization algorithm. The gain in the observer will be optimized by adaptive cubature Kalman to improve the anti-disturbance performance of the adaptive distributed observer. Then, the constraints of internal safety distance and input saturation are fully considered. The distributed cooperative cost function is constructed based on the virtual trajectory, which is further introduced into local rolling domain optimization to realize formation predictive control. The boundedness of innovation and Lyapunov stability are utilized to prove the reliability of the control system. Some comparative simulation experiments are designed to demonstrate the effectiveness and robustness of the proposed method.

Hybrid pseudocapacitive sodium titanate/rGO and MXene/rGO nanocomposite electrodes in capacitive deionization

Two hybrid pseudocapacitive materials Na8Ti5O14/rGO (NTO/rGO) and Ti3C2Tx/rGO (MXene/rGO) were successfully synthesized using two-step easy hydrothermal processes, respectively. In this carefully nano-engineered architecture, the dense structure of NTO synthesized firstly were intertwined with the rGO nanosheets framework; whereas the highly organized thoroughly exfoliated MXene nanosheet were deposited with rGO nanosheets. The electrochemical capacitances of both hybrid pseudocapacitive nanocomposites were increased by 99.7 % and 72.7 % compared to the nanocrystals only, the capacitance retention and impendence were also improved. In the CDI experiments, the high salt removal capacities of the hybrid nanocomposite NTO/rGO and MXene/rGO were obtained as 75.6 mg g−1 and 64.3 mg g−1, which exceeded other reported values using similar electrodes. A 100 % regeneration in multiple cycles was achieved. This high desalting performance was attributed to the synergistic effect of efficient ion intercalation along with enhanced electrical conductivity and structure accessibility. These hybrid mechanism of ion intercalation and electrical double layer formation in action opened up the possibility of using hybrid pseudocapacitive nanocomposite electrodes such as Na8Ti5O14/rGO and Ti3C2Tx/rGO for effective capacitive desalination. Their respective selectivity in aqueous ionic solution will be investigated in future studies.

A Review on Non-Invasive Magnetic and Electric Field Excited Methods for Flow Characterisation of Incompressible Newtonian Low Conductive Liquids

Monitoring the flow rate of low conductive fluid is critical in sectors such as waste, culinary, chemical, pharmaceutical, oil and gas, and power. The flow meter can be used to measure several parameters like flow rate range, fluid electrical conductivity, cost and the scenario of desired monitoring. The existing invasive flow sensors for monitoring the velocity of conductive fluid are often associated with undesirable attributes of being obstructive, prone to interference effects, corrosion, significant pressure reduction, and energy loss in pipe systems causing severe and long-term damage to pipes during installation. This paper presents a comprehensive survey of various non-invasive methods for characterizing low conductive fluid flow based on the sources of strong magnetic and electric fields. This review discusses fundamental insights for understanding the physical phenomenon in the generation of eddy currents, Lorentz force, and the formation of the electric double layer with pertinent illustrations and discussions. The review presented in this paper concludes that each non-invasive measurement technique has limitations based on the excitation source of either magnetic or electric fields. Different values of low conductivity of fluid flow and flow velocity have been considered in various studies to get an in-depth understanding of the capability of selected techniques so that their scope and versatility can be researched further. This paper also highlights that emerging technologies like cryostats with superconducting magnet systems, which unquestionably exceed the mass limitation, have become viable in applications such as Lorentz force velocimetry.

Mathematical modeling of electrodialysis of a dilute solution with accounting for water dissociation-recombination reactions

The paper explores the limitations of electrodialysis (ED) in the range of very dilute feed solutions. The results of first principles modeling of this process are presented, taking into account water dissociation-recombination reactions (without catalytic effects). A 1D and a 2D model are formulated and applied. Both models use the equation for the rate of chemical reactions, the Nernst-Planck and Poisson equations; additionally, the Navier-Stokes equation is used in the 2D model. We show that the dissociation-recombination reactions can cause the appearance of a space charge region (SCR) in the central part of the desalination chamber (DC). In electrochemistry and colloidal science, the formation of a SCR is associated with the formation of an electrical double layer (EDL) at a charged solid surface. Our modeling predicts that in conditions where the concentrations of H+/OH− ions and salt ions in solution are comparable, a SCR can appear in the bulk solution due to the recombination of H+ and OH− ions. The latter are generated at the membrane forming the DC (water splitting). Water splitting makes impossible total desalting of aqueous solutions by conventional ED. An inversion of the salt concentration profiles is observed: the salt ions are accumulated near the membranes; a depletion region occurs in the center of the DC. Interplay between the chemical reactions and space charge is discussed.

Triboelectric Nanogenerator Array as a Probe for In Situ Dynamic Mapping of Interface Charge Transfer at a Liquid-Solid Contacting.

Contact between water droplets with hydrophobic surfaces is a common phenomenon at functional interfaces, and it has been extensively studied. However, quantifying the charge transfer between the liquid-solid interfacial contacting, especially for the charge density distribution throughout the movement of liquid droplet on a dielectric surface, remains to be investigated. Here, we developed a pixeled droplet triboelectric nanogenerator (pixeled droplet-TENG) array with high-density electrode array as a probe for measuring the charge transfer at a liquid-solid interface when a water drop moves on the hydrophobic surface. To intuitively observe the charge transfer between the liquid-solid interface, we "imaged" the transferred charges along movement trajectory of a water droplet as it slides along a tilted solid surface at a spatial resolution of 0.4 mm and time sensitivity of 0.02 s. Our study shows that the transferred charges are not uniformly distributed along the path, which is possibly due to the two-step model of electron transfer and ion adsorbed on the solid surface, and thus the formation of an electric double layer will inevitably shield the net surface on the solid surface. Our study presents a probe technology with potential applications in surface chemistry, physics, material science, and cell biology.

Observation of double layer formation in low-temperature E × B plasma based negative ion sources

In this paper, formation of a double layer (DL) is studied in the background plasma (considering only electrons and ions) in the presence of a magnetic field in the context of the Rf operated beam source in India for negative ion research negative ion source by using 2D-3V particle-in-cell Monte Carlo collision kinetic simulations. A rectangular geometry to model the source, expansion, and magnetic filter regions in the negative ion source is considered in the XY plane. A Gaussian shaped magnetic field is applied in the Z-direction (perpendicular to the simulation plane), and a bias voltage is applied on the extraction boundary. Our simulations show the presence of instabilities as reported in the literature. We confirm the formation of a weak DL in the magnetic filter region under some specific combinations of the magnetic field and bias voltage. Initiation of DL leads to ion acceleration in the magnetic filter region. Split in ion velocities is also visible in the phase space plots due to the presence of free and trapped ions in the DL region. Our study highlights the effect of DL on plasma transport, which should be taken into account when interpreting the experimental observations associated with E × B plasma based negative ion sources.