Electric Charge Separation Research Articles

Construction of Br-Cu2O@NiFe-LDHs Z-scheme heterojunction and photocatalytic degradation of catechol

Facet regulation and construction of heterojunctions are important means to enhance the photocatalytic performance of single-phase materials. In this paper, the facet index of Cu2O was changed through Br doping, and then a Br doped Cu2O@NiFe-LDHs Z-scheme heterojunction (BC@LDHs) was constructed for photocatalytic degradation of catechol. The optimal conditions for photocatalytic degradation reaction were explored; the kinetic and thermodynamic parameters of the reaction, as well as the stability and reusability of the material were studied. Under optimal reaction conditions, the photocatalytic degradation of catechol can reach up to 95.68 % by BC@LDHs, which is much higher than that of single-phase materials and Cu2O@LDHs. By combining experiments and theoretical calculations, the intrinsic reasons and mechanisms for Br doping to enhance the photocatalytic degradation performance of BC@LDHs Z-scheme heterojunctions were fully explored from the perspectives of band structure and oxygen adsorption, determination of built-in electric field in Z-scheme heterojunctions, calculation of built-in electric field strength and bulk charge separation efficiency. This work proposes the insights that using Br doping to alter exposed facets and regulate the strength of the built-in electric field in Br-Cu2O@NiFe-LDHs heterojunctions, thereby promoting its efficient photocatalytic degradation.

Evaluation of Industrial Poly(tert-butyl acrylate) insulated A p-channel Organic Field-Effect Transistor (PtBA-p-OFET)

Poly(tert-butyl acrylate) (PTB-p-A) has been investigated as a promising insulator layer for p-channel organic field effect transistors (p-OFETs) using the p-type semiconductor Poly(3-hexylthiophene-2,5-diyl (P3HT) due to its favorable insulating properties, good film-forming ability and electrical charge separation properties. Top-gate, bottom-contact PTBA-p-OFET devices are fabricated with Indium Thin Oxide (ITO) source/drain electrodes and a P3HT organic semiconductor layer. The frequency-dependent capacitance of the PTBA-p-OFETs was studied through a plot to determine the key parameters, including the threshold voltage (VTh), field-effect mobility (μFET), and the current on/off ratio (Ion/off) of the device. The PTB-p- OFETs exhibit field-effect mobility value of 6.13x10-4 (cm2/V.s), an on/off current ratio of 1.11x102, and a threshold voltage of -15.8 V. The capacitance-frequency characteristics of the capacitor structure were analyzed and found to have as 7.6 nF/cm2 per unit area. This work presents PTBA as a promising for high-performance p-OFET applications.

Control of spontaneous charging of sliding water drops by plasma-surface treatment

Slide electrification is the spontaneous separation of electric charges at the rear of water drops sliding over solid surfaces. This study delves into how surfaces treated with a low-pressure plasma impact water slide electrification. Ar, O2, and N2 plasma treatment reduced the drop charge and contact angles on glass, quartz, and SU-8 coated with 1H,1H,2H,2H-perfluoroctyltrichlorosilane (PFOTS), and polystyrene. Conversely, 64% higher drop charge was achieved using electrode-facing treatment in plasma chamber. Based on the zeta potential, Kelvin potential, and XPS measurements, the plasma effects were attributed to alterations of the topmost layer's chemistry, such as oxidation and etching, and superficially charge deposition. The surface top layer charges were less negative after electrode-facing and more negative after bulk plasma treatment. As a result, the zeta potential was less negative after electrode-facing and more negative after bulk plasma treatment. Although the fluorinated layer was applied after plasma activation, we observed a discernible impact of plasma-glass treatment on drop charging. Plasma surface modification offers a means to adjust drop charges: electrode-facing treatment of the fluorinated layer leads to an enhanced drop charge, while plasma treatment on the substrate prior to fluorination diminishes drop charges, all without affecting contact angles or surface roughness.

Probabilistic Forecasting of Lightning Strikes over the Continental USA and Alaska: Model Development and Verification

Lightning is responsible for the most area annually burned by wildfires in the extratropical region of the Northern Hemisphere. Hence, predicting the occurrence of wildfires requires reliable forecasting of the chance of cloud-to-ground lightning strikes during storms. Here, we describe the development and verification of a probabilistic lightning-strike algorithm running on a uniform 20 km grid over the continental USA and Alaska. This is the first and only high-resolution lightning forecasting model for North America derived from 29-year-long data records. The algorithm consists of a large set of regional logistic equations parameterized on the long-term data records of observed lightning strikes and meteorological reanalysis fields from NOAA. Principal Component Analysis was employed to extract 13 principal components from a list of 611 potential predictors. Our analysis revealed that the occurrence of cloud-to-ground lightning strikes primarily depends on three factors: the temperature and geopotential heights across vertical pressure levels, the amount of low-level atmospheric moisture, and wind vectors. These physical variables isolate the conditions that are favorable for the development of thunderstorms and impact the vertical separation of electric charges in the lower troposphere during storms, which causes the voltage potential between the ground and the cloud deck to increase to a level that triggers electrical discharges. The results from a forecast verification using independent data showed excellent model performance, thus making this algorithm suitable for incorporation into models designed to forecast the chance of wildfire ignitions.

Charge in non-thunderstorm clouds and fogs

The global atmospheric electric circuit links charge separation in thunderclouds with current flow throughout the atmosphere. This current flow causes charge accumulation on the upper and lower boundaries of clouds and fogs. Thunderclouds are therefore not the only charged clouds in the atmosphere, and other forms of clouds, especially extensive horizontal layer clouds (stratus) are much more abundant globally. To investigate possible effects of charging of natural droplets in clouds, experiments have been undertaken using corona ion emission into fogs, releasing from within and above the fog. During the corona ion release the droplet size distribution was modified, with an increase in small drops. Further, when the ions were released over the fog, the reflectivity of the fog increased by ∼2%, about 30s later.

Surfaces with Lowered Electron Work Function: Problems of Their Creation and Theoretical Description. A Review

Experimental studies devoted to the creation of the modern photocathodes or efficient field emission cathodes with lowered work function or low/negative electron affinity are reviewed. We present theoretical models, where the electron affinity lowering is associated with the influence of electrically charged layers at the semiconductor/insulator interface. Modern experimental techniques of measuring the work function or the electron affinity and technologies aimed at fabricating the surfaces with low work function/electron affinity are described. In the framework of a simple theoretical model developed by the authors, it has been demonstrated that the presence of a dipole layer (e.g., composed of negatively charged oxygen ions and positively charged rare earth ions) at the semiconductor surface can lower the electron affinity by up to 3 eV provided equal concentrations of oppositely charged adsorbate ions. It is also shown that if the surface concentration of negatively charged oxygen ions is higher than the surface concentration of positively charged metal ions, the lowering of the electron affinity becomes smaller due to the upward band bending in the space charge region in the semiconductor; otherwise, the lowering of the electron affinity becomes larger due to the downward band bending. This effect allows technological proposals to be formulated for obtaining surfaces with minimum work function values in modern field-emission-based electronic devices. In the framework of the proposed model, the work function was evaluated for the OH-functionalized MXene. The corresponding value for the unfunctionalized MXene equals about 4.5 eV, being practically independent of the number of Ti and C layers (from 1 to 9 layers). The OH-functionalization lowers it down to about 1.6 eV, and this value is also practically independent of the number of atomic layers in MXene. Experimental approaches to obtain cathodes with low work function/low electron affinity are described. They are aimed at creating a spatial separation of electric charges in the near-surface cathode region perpendicularly to the surface plane. The corresponding spatial distributions of positive and negative charges are characterized by their localization either in two different atomic planes or in one plane and an extended space region (the latter variant is typical of semiconductor substrates). The technologies for producing such surfaces are based on various methods of adsorbate deposition onto the metal or semiconductor substrate: physical vapor deposition, chemical vapor deposition, liquid phase deposition, diffusion from the substrate bulk, and so forth. Particular attention is paid to the experimental works dealing with the adsorbtion of rare earth metals (Ce, Gd, Eu) and the coadsorbtion of oxygen onto the Si, Ge, and Mo surfaces (in a nano-structured state as well), which results in the dipole layer formation and the work function reduction.

Generalized chiral kinetic equations

We derive the generalized chiral kinetic equations which are applicable to the fermions with arbitrary mass. We show how the dynamical magnetic-moment distribution function could lead to spin polarization and electric charge separation. We also show how the electric/magnetic moment distribution and pseudoscalar distribution could be induced by vorticity and electromagnetic field in global equilibrium.

FeOOH interlayer with storing holes applied to construct WO3/FeOOH/Cu2O ternary heterojunction photoanode with dual built-in electric filed for efficient PEC cell

Broader visible light response, higher carrier separation efficiency and injection efficiency are extremely important methods to enhance photoelectrochemical (PEC) performances of WO 3 . In this work, FeOOH with the property of storing holes is firstly applied to modify WO 3 /Cu 2 O heterojunction as an interlayer, and the WO 3 /FeOOH/Cu 2 O ternary heterojunction with excellent PEC performances is obtained. The separation efficiencies of photoinduced carrier in bulk is enhanced to 29.33% with the formation of dual built-in electric filed as well as the storage of photoinduced carriers transferred from WO 3 in FeOOH, which is 3.27 folds higher than that of bare WO 3 . With the synergistic effect of expanded light absorption and accelerated charges transfer, the photocurrent density of 2.14 mA/cm 2 at 1.23 V vs. RHE is achieved by WO 3 /FeOOH/Cu 2 O ternary heterojunction. This work can be applied for reference to improve the PEC performance of other photoelectrodes through adequate utilization of storing holes interlayer. • WO 3 /FeOOH/Cu 2 O ternary heterojunction is prepared with FeOOH as interlayer for PEC water splitting. • Photocurrent density of WO 3 /FeOOH/Cu 2 O is 2.14 mA/cm 2 , which is 10.19 folds higher than that of WO 3 . • Cu 2 O particles outer layer as the primary light absorber improves the light utilization efficiency. • Ternary heterojunction with formation of dual built-in electric filed facilitates charge separation and transfer. • The effect of extracting and storing holes for FeOOH further enhance carrier separation of the heterojunction.

Pair invariant mass to isolate background in the search for the chiral magnetic effect in Au + Au collisions at sNN=200 GeV

Quark interactions with topological gluon configurations can induce local chirality imbalance and parity violation in quantum chromodynamics, which can lead to the chiral magnetic effect (CME)—an electric charge separation along the strong magnetic field in relativistic heavy-ion collisions. The CME-sensitive azimuthal correlator observable (Δγ) is contaminated by background arising, in part, from resonance decays coupled with elliptic anisotropy (v2). We report here differential measurements of the correlator as a function of the pair invariant mass (minv) in 20–50% centrality Au+Au collisions at sNN=200 GeV by the STAR experiment at the BNL Relativistic Heavy Ion Collider. Strong resonance background contributions to Δγ are observed. At large minv where this background is significantly reduced, the Δγ value is found to be significantly smaller. An event-shape-engineering technique is deployed to determine the v2 background shape as a function of minv. We extract a v2-independent and minv-averaged signal Δγsig=(0.03±0.06±0.08)×10−4, or (2±4±5)% of the inclusive Δγ(minv>0.4 GeV/c2)=(1.58±0.02±0.02)×10−4, within pion pT=0.2–0.8 GeV/c and averaged over pseudorapidity ranges of −1<η<−0.05 and 0.05<η<1. This represents an upper limit of 0.23×10−4, or 15% of the inclusive result, at 95% confidence level for the minv-integrated CME contribution.Received 11 June 2020Revised 12 July 2022Accepted 12 August 2022DOI:https://doi.org/10.1103/PhysRevC.106.034908©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle correlations & fluctuationsRelativistic heavy-ion collisionsNuclear Physics

Electric Fields and Charge Separation for Solid Oxide Fuel Cell Electrodes.

Activation losses at solid oxide fuel cell (SOFC) electrodes have been widely attributed to charge transfer at the electrode surface. The electrostatic nature of electrode–gas interactions allows us to study these phenomena by simulating an electric field across the electrode–gas interface, where we are able to describe the activation overpotential using density functional theory (DFT). The electrostatic responses to the electric field are used to approximate the behavior of an electrode under electrical bias and have found a correlation with experimental data for three different reduction reactions at mixed ionic–electronic conducting (MIEC) electrode surfaces (H2O and CO2 on CeO2; O2 on LaFeO3). In this work, we demonstrate the importance of decoupled ion–electron transfer and charged adsorbates on the performance of electrodes under nonequilibrium conditions. Finally, our findings on MIEC–gas interactions have potential implications in the fields of energy storage and catalysis.

Концентрационный элемент на основе электрогенных процессов в корнеобитаемой среде

The experimental bioelectrochemical current source based on the concentration gradient of charge carriers in the root environment of plants has been created. A potential difference of about 70 mV is observed in the nutrient solution. It is gradually decreasing due to equalization of concentrations. The voltage increases to 200 mV when plant are placed in a cultivation system as the root system develops due to the intensification of diffusion processes. The potential-forming role of nitrate forms of nitrogen is shown on the example of lettuce grown according to the panoponics technology. The separation of electrical charges by the root system during the life of plants can become an alternative source of green energy.

Concentration cell based on electrogenic processes in the root environment

The experimental bioelectrochemical current source based on the concentration gradient of charge carriers in the root environment of plants has been created. A potential difference of about 70 mV is observed in the nutrient solution. It is gradually decreasing due to equalization of concentrations. The voltage increases to 200 mV when plant are placed in a cultivation system as the root system develops due to the intensification of diffusion processes. The potential-forming role of nitrate forms of nitrogen is shown on the example of lettuce grown according to the panoponics technology. The separation of electrical charges by the root system during the life of plants can become an alternative source of green energy. Keywords: rhizosphere, bioelectric potential, panoponics, green energy.

CME search at STAR

The hot and dense medium produced in relativistic heavy-ion collisions has been conjectured to be accompanied by an axial charge asymmetry that may lead to a separation of electric charges in the direction of the extremely strong magnetic field, also known as the Chiral Magnetic Effect (CME) [1–3]. The measurement of azimuthal correlator (∆γ) with respect to the spectator plane [5], gives us an opportunity to measure the possible CME fraction beyond the flow background. Preliminary results using this approach with combined Au+Au collisions at √SNN = 200 GeV and U+U at √SNN = 193 GeV show fCME at (8±4±8)%. Meanwhile, the observability of CME has been conjectured to be dependent on √SNN due to changes in the lifetime of the magnetic field, the strengths of CME signal and non-CME background. At lower energies, the Event Plane Detector (EPD) installed in the year 2018 provides a unique capability for CME search. The background scenario test at Au+Au √SNN = GeV by using ∆γ with respect to TPC and the new installed EPD shows a consistency with no-CME scenario in the current statistics. The method of the ongoing isobar blind analysis, and the latest sensitivity check with the eventby- event AVFD model on the different observables between Ru+Ru and Zr+Zr are also briefly discussed.

Radiation hardening and optical properties of materials based on SiO2

Preliminary studies have shown that the optical absorption spectra of radiation-colored glasses correspond to the spectral behavior of the scattering losses of an optically inhomogeneous medium. The reasons for the same optical changes in glasses of different compositions are the radiation-induced electric charge separation in the structurally nano-inhomogeneous glass volume, polarization and formation of nanometer optical inhomogeneities. The authors of this work prove that the radiation changes in the mechanical and optical properties of silicate glasses are of the same nature. The performed estimates indicate that the electric charge separation in the glasses occurs up to absorbed doses of about 1 MGy. The local electric charge separation due to the appearance of Coulomb forces leads to radiation hardening of the glasses. The estimated Coulomb hardening of the quartz glasses was ~ 107 Pa. The theoretical results were experimentally confirmed by measuring the mechanical properties of the glasses under high intensity proton irradiation as well as by testing the mechanical strength of a composite material based on quartz glass. Under proton irradiation with a dose rate of 5×103 Gy/s (energy of 8 MeV) up to threshold doses of ~ (1 – 5) ×106 Gy in the KU-1 quartz glasses, the decrement of acoustic vibrations decreased due to Coulomb hardening. After gamma irradiation with 1.34×105 Gy, the tensile strength of the composite material based on quartz glass increased by up to 20 MPa. This value is in the range of estimates of Coulomb hardening of quartz glasses. It is also shown that ionizing radiation does not affect the elastic modulus of materials based on SiO2.

Enhanced photocatalytic activity of TiO2/Ag2O heterostructures by optimizing the separation of electric charges

Photodegradation of organic pollutants is becoming a promising technique of remediating environment. In this work, TiO2/Ag2O heterostructured films were fabricated by a method of abnormally oxidizing Ag films through reactive magnetron sputtering deposition of TiO2. The substrate temperature and O2 pressure were found to have significant impacts on the oxidation of Ag films and the formation of Ag2O. The TiO2/Ag2O heterostructured films fabricated under the conditions of low temperature and low-oxygen pressure exhibited excellent photocatalytic activity under irradiation of ultraviolet and visible light. The thickness of TiO2 layer was substantiated to be important in optimizing photocatalytic activity of TiO2/Ag2O heterostructured films and the best result in degrading methylene blue was obtained at TiO2 thickness of 37 nm. The photocatalytic mechanism of TiO2/Ag2O heterostructured films was discussed and the enhanced photocatalytic activity was attributed to the separation of electron-hole pairs, which is basically determined by the band structure in the heterostructures. This work provides an effective method of fabricating TiO2/Ag2O heterostructured films and are easily scaled up in industry. The suggested photocatalytic mechanism is helpful for comprehensively understanding the enhancement of photocatalytic activity observed in various forms of metal-oxide heterostructures.

Electrogenic and hydrocarbonoclastic biofilm at the oil-water interface as microbial responses to oil spill

The oil-water interface formed during an oil spill represents a challenging environment for pelagic communities living in aquatic ecosystems. At this anoxic barrier, we report the formation of a microbial hydrocarbonoclastic biofilm capable of electron transfer along the water column. This biofilm generated a membrane of surface-active compounds that allowed the spontaneous separation of electrical charges, causing the establishment of an anodic and a cathodic region and, as a result, the spontaneous creation of a liquid microbial fuel cell. Such floating biofilm was connected to the water column underneath by floating filaments that could contribute to oxygen reduction at distance. The filaments revealed an unusual lipid content induced by anoxic conditions, with prominent ultrastructural features similar to myelin found in oligodendrocytes of the vertebrate nervous system. Furthermore, these filaments showed an interesting cross-reactivity towards different epitopes of the myelin basic protein (MBP) and Claudin 11 (O4) of human oligodendrocytes. The presence of a network of filaments similar to myelin suggests the probable existence of evolutionary connections between very distant organisms. Collectively these results suggest a possible mechanism for how lake microbial communities can adapt to oil spills while offering an interesting starting point for technological developments of liquid microbial fuel cells related to the study of hydrocarbon-water interfaces.The data that support the findings of this study are openly available in figshare at https://figshare.com/s/72bc73ae14011dc7920d.

Tribo-Electrostatic Separation Analysis of a Beneficial Solution in the Recycling of Mixed Poly(Ethylene Terephthalate) and High-Density Polyethylene

The aim of this study was to investigate and analyze the impact of selected parameters during the tribocharging process of shredded poly(ethylene terephthalate) (PET) and high-density polyethylene (PE-HD) plastics on accumulated electric charge and electrostatic separation effectiveness. The accumulation of electric charge on surfaces of polymer particles as a result of their circular motion forced by the airflow cyclone container was investigated. The impact of the container material, time of tribocharging and the airflow intensity were experimentally examined. A container in which the particles of the considered polymers are electrified with opposite charges was selected. A high ability to accumulate surface charge on small particles of both polymers was demonstrated. The electrified mixed PET/PE-HD was subjected to a separation process. An electrostatic separator designed and constructed by the authors was used for to the separation. In turn, to assess the effectiveness of this separation, a dedicated vision system was used. Based on the result of the carried out tests, it has been assumed that the proposed approach’s effectiveness has been demonstrated by means of empirical validation.

Strong piezocatalysis in barium titanate/carbon hybrid nanocomposites for dye wastewater decomposition

In this work, the strong piezocatalysis is found in the two-step hydrothermally-synthesized barium titanate/carbon hybrid nanocomposites and is used for rhodamine B dye decomposition. As the carbon content increases from 0 to 5 wt%, the catalytic performance of hybrid nanocomposites first increases and then slightly decreases. When the carbon content increases to 2 wt%, the barium titanate/carbon hybrid nanocomposites exhibit the optimal piezocatalytic performance, which have the ~75.5% dye decomposition ratio and the ~0.04901 min−1 reaction rate constant after the 40 min vibration stimulation, while that of the pure barium titanate are 48.4% and 0.01942 min−1, respectively. The improvement of piezocatalytic performance in barium titanate/carbon hybrid nanocomposites can be ascribed to the action of carbon's charge transfer which promotes the effective separation of the piezoelectrically-induced electric charges. After three runs recycle utilization tests, the barium titanate/carbon hybrid nanocomposites still exhibit ~70% decomposition ratio of rhodamine B dye. The strong piezocatalytic performance and the good reusability make the barium titanate/carbon hybrid nanocomposites potential in the field of wastewater treatment through utilizing natural vibration energy in future.

Current sources based on supercapacitors with β-active isotopes

In asymmetric supercapacitors, electric charges are separated and accumulated in conditions of neutron irradiation. The paper presents the results of studying current sources with radioactive isotopes (CSRI) based on supercapacitors of 100 F made by neutron activation of the elements of the substances (BN or SrO) introduced to the electrodes. Following the neutron irradiation with a dose of up to 400 Gy, the supercapacitors turn into CSRIs and have a charging rate of up to 7.8 μV/day. The CSRI charging rate increases in proportion to the activation with a neutron dose up to 14 kGy. This is explained by the production of β-active isotopes as a result of the 14N(n, p)14C and 88Sr(n, γ)89Sr reactions in the supercapacitor electrode materials. Estimation of the radiation-induced charge accumulation rate, with regard for the energy released during β-decay of 14C and 89Sr, excludes the known mechanisms of charge separation in a condensed environment due to the ionization and production of secondary electrons, the production of electron-hole pairs, etc. The electric charge separation and accumulation in CSRIs take place as a result of non-equilibrium thermoelectric phenomena in the near-electrode nanoregions. Nuclear reactions in nanoscale regions produce “temperature gradients” of up to 105 K/nm, this leading to up to 1013 electrons “evaporating” from nanocrystallites at times of ~ 10-11 s.

Background evaluations for the chiral magnetic effect with normalized correlators using a multiphase transport model

The chiral magnetic effect (CME) induces an electric charge separation in a chiral medium along the magnetic field that is mostly produced by spectator protons in heavy-ion collisions. The experimental searches for the CME, based on the charge-dependent angular correlations (gamma ), however, have remained inconclusive, because the non-CME background contributions are not well understood. Experimentally, the gamma correlators have been measured with respect to the second-order (Psi _{2}) and the third-order (Psi _{3}) symmetry planes, defined as gamma _{112} and gamma _{123}, respectively. The expectation was that with a proper normalization, gamma _{123} would provide a data-driven estimate for the background contributions in gamma _{112}. In this work, we calculate different harmonics of the gamma correlators using a charge-conserving version of a multiphase transport (AMPT) model to examine the validity of the said assumption. We find that the pure-background AMPT simulations do not yield an equality in the normalized gamma _{112} and gamma _{123}, quantified by kappa _{112} and kappa _{123}, respectively. Furthermore, we test another correlator, gamma _{132}, within AMPT, and discuss the relation between different gamma correlators.