Increase In Current Density Research Articles

Constructing bimetallic heterostructure as anodes for sodium storage with superior stability and high capacity

Heterostructure materials hold promise as future-generation anodes for sodium-based energy storage. However, the complexity and time-intensity of heterojunction fabrication processes limit their large-scale application. This study utilizes an ultrafast, one-step microwave process to successfully design and fabricate bimetallic selenides heterojunction nanoparticles, anchored on a three-dimensional porous carbon substrate (NiSe2–SnSe2/C). The in-situ formation of NiSe2–SnSe2 heterostructure optimizes sodium ion adsorption and transfer, which facilitates reaction kinetics and subsequently improves both the rate capability and cycle life. The NiSe2–SnSe2/C electrodes demonstrate a high-rate capability (719.8 mAh g−1 at 0.1 A g−1, and 667.9 mAh g−1 after a 50-fold increase in current density to 5 A g−1), maintaining high stability even after 10,000 cycles at 5 A g−1. The impact of the NiSe2–SnSe2 heterostructure on reaction kinetics was examined using density functional theory. The NiSe2–SnSe2/C anode, when coupled with the Na3V2(PO4)3 cathode in a full battery, demonstrated an impressive energy density of 155 Wh kg−1. This work exemplifies an ultrafast synthetic method for constructing heterostructure materials having great rate, high capacity and strong stability for sodium storage, making them promising candidates for large-scale energy storage applications.

Composite Graphite Bipolar Plates Under Different Working Conditions

This study uses the molding method to prepare composite graphite bipolar plates to improve the corrosion resistance and electrical conductivity of fuel cell bipolar plates, improve the conversion efficiency and service life, and test their environmental adaptability under different working conditions. In this experiment, the fuel cell test system (850e) is used to test the voltage change curve and power density change curve of the proton exchange membrane fuel cell (PEMFC). Under 200 KPa, the voltage of the fuel cell at a current density of 1000 mA/cm2 is 0.719 V. The power density reaches the maximum at 1540 mA/cm2 current density, which is 911 mW/cm 2. The radii of the three curves from 0.1 A/cm2 to 0.5 A/cm2 decrease with the increase of current density. This indicates that at the beginning, the greater the current density is, the smaller the mass transfer resistance inside the fuel cell is, and the smaller the electron transfer resistance during the electrochemical reaction is. However, when the current density increases to 1 A/cm2, the power density of the fuel cell increases slowly. In the 12-hour constant current density test, it is found that the fuel cell voltage dropped from 0.641 V to 0.611 V, and the rate of decline was 2.5 mV/h, proving that the overall performance of the fuel cell is relatively stable. The graphite bipolar plate prepared by the molding method has good adaptability under different working conditions, and the comprehensive performance is stable under long-term testing.

Minor Ag inducedshear performance alternation in BGA structure Cu/SnBi/Cu solder joints under electric current stressing

In this work, the effect of minor Ag addition on shear performance of ball grid array (BGA) structure Cu/SnBi/Cu solder joints under electric current stressing was investigated. The results show that the shear strength of solder joints decreased with increasing current density, and the effect of Ag addition on shear strength changed from an elevating state to a deteriorating state. The elevating effect of Ag addition was due to the dominance of Sn/Bi phase refinement and Ag3Sn dispersion, which was weakened gradually with the increase in current density. The deteriorating effect of Ag addition was attributed to the more inhomogeneous distribution of current density and higher thermal gradient induced by the finer phase of the solder matrix as well as the consequent severer strain mismatch at the Sn/Bi phase interface. The finer Sn/Bi phase was also conductive to easier lattice atom migration under current stressing, resulting in a rapid decrease in shear strength. Moreover, the dominant factor on the shear strength reduction tended to change from Joule heating to athermal effect of current stressing. The fracture of solder joints indicated an insignificant influence by the Ag addition, which all occurred in the solder matrix in a ductile mode.

Improvement of MoS2 electrocatalytic activity for hydrogen evolution reaction by ion irradiation

Molybdenum disulfide (MoS2) is considered promising noble metal-free catalysts for the hydrogen evolution reaction (HER). Whereas the bulk MoS2 does not exhibit significant activity, the catalytic properties of various nanostructures are noticeable. Therefore we synthesized flower-like molybdenum disulfide with the simple, one-step hydrothermal method. To enhance the catalytic activity of the material, low-energy ion irradiation is employed. As-prepared MoS2 is irradiated with hydrogen and carbon ions of various energies (20–40 keV) and fluences (1014-1017 ion/cm2). Our results show that irradiation has beneficial influence on MoS2 catalytic activity toward hydrogen evolution reaction. By producing morphological changes and defects in the structure, ion irradiation also impacts the conductivity of the material, which shows predominant effect on hydrogen evolution. The increase of current density at an overpotential of 300 mV with hydrogen ion irradiation is even 6 times higher than for as-synthesized catalyst.

Electrochemical obtaining of rhenium-molybdenum alloys

Based on the study of current-voltage dependences during the co-deposition nt electrical reduction of rhenium and molybdenum from sulfuric acid on a Pt electrode, conditions for deposition of alloy nanocoatings of the Re-Mo system were established. The influence of various factors, such as the content of components in the electrolyte, current density, temperature, acidity of solutions, etc., on the composition and quality of coatings was studied. It was established that with an increase in the content of rhenium in the electrolyte and increase of current density, the content of rhenium in the alloy is increased. The composition and morphology of Re-Mo thin films electrodeposited on a platinum electrode were analyzed. The phase composition of the obtained films was determined by XRD using a diffractometer, and the study of the morphology of Re-Mo films on platinum and nickel substrates was performed using a scanning electron microscope. Based on this study, the optimal conditions for the deposition molybdenum with rhenium and the required composition of the electrolyte were selected. For the obtaining rhenium-molybdenum alloys containing 50-80 wt.% Re, the following electrolyte composition can be recommended: 0.0015M Na2MoO4 + 0.0035M KReO4 + 2M H2SO4, pH 0.4; t = 75°C, electrode - Pt.

Impact of fin aspect ratio on enhancement of external quantum efficiency in single AlGaN fin light-emitting diodes pixels

Previously, we showed within a sub-micron fin shape heterojunction, as current density increases, the non-radiative Auger recombination saturates mediated by the extension of the depletion region into the fin, resulting in a droop-free behavior. Here, we investigate the dependence of the fin aspect ratio (height to width ratio) on external quantum efficiency (EQE) of single n-AlGaN fin/p-GaN heterojunctions. Fins are arranged in an array format varying in width from 3000 to 200 nm. In this architecture, an n-metal contact is interfaced with the non-polar side facet of the fin. At a fixed current density, as the aspect ratio increases from 0.2 to 3 (the fin width reduces), we systematically observe an increase in the ultraviolet (UV) excitonic emission of the AlGaN fin and a 7× enhancement in the EQE. We explain this phenomenon by conserving the volume of the carrier depletion region within a fin. As the fin gets thinner, the base area of the depletion volume shrinks, whereas its height increases within the fin. This geometrical advantage allows a 200 nm wide fin to operate at 1/3rd the current density compared to a 3000 nm wide fin while generating a UV emission with a comparable power of 1 μW. These findings show additional parameters that can be used for developing brighter light sources, including the shape and aspect ratio of a heterojunction at the micro- or nano-scale.

Effect of MgO recombination barrier layer on the performance of monolithic-structured solid-state dye sensitized solar cells

ABSTRACT In this paper, the optical, structural and electrical properties of pure and magnesium-doped TiO2 nanoparticles (NPs) of different cycles (2, 4, 6 and 8 cycles) were explored systematically. The magnesium-doped TiO2 was synthesised through successive ionic layer adsorption and reaction (SILAR) and deployed into dye sensitised solar cells. The effects of the MgO barrier layer was evaluated . The results show enhanced optical properties with MgO coating with a diminished band gap energy. The X-ray diffraction studies show that the anatase phase was preserved after doping and the dopant does not change the crystalline phase of the TiO2. The SEM results show well-dispersed morphology. For the device with 4 SILAR cycles of MgO, gains in open-circuit voltage, current density and simultaneous increase in efficiency were observed which is attributed to improved charge collection efficiency as electrons diffusing through TiO2 have a better chance of reaching the electrode before recombining. At greater SILAR cycles (6 and 8), losses in photocurrent caused net decrease in efficiencies. The results presented in this report implies that the modification of TiO2 with a metal oxide (MgO) can result to good photon management.

Improving the Electromigration Life of Advanced Interconnects through Graphene Capping

Since the discovery of graphene, 2D materials are establishing a rapidly growing and promising field, with great potential for diverse applications given their excellent conductivity and high transparency. In particular, graphene can isolate external chemical reactions when applied to back-end-of-line (BEOL) interconnect metals, thereby preventing the oxidation of the interconnect metals. In addition, it can improve the conductivity and breakdown current density of interconnects. However, the thermal budget remains an important problem in BEOL interconnects. We demonstrate an advanced graphene deposition method using an in-house plasma plasma-enhanced chemical vapor deposition system, which offers low thermal budget and high stability. We also optimize carbon precursors to improve the quality of graphene on Ru and Co thin films. We show the improvement of electrical conductivity, electromigration lifetime, and maximum breakdown current density after capping Ru and Co interconnects with graphene. The electromigration lifetimes of the Ru and Co interconnects increase by 4 and 4.5 times, respectively, and their maximum breakdown current density increases by 17.6 and 10.6%, respectively. The results show that capping with graphene has a high potential in BEOL applications.

Photoenhanced Electrocatalytic Hydrogen Evolution Accelerated Dominantly by the Hot Electrons from Intraband Transition rather than Interband Transition.

Plasmonic materials enabling sunlight as an energy input to catalyze the hydrogen evolution reaction (HER) have become the research focus of artificial photosynthesis. Upon visible photoexcitation, there are both intraband transition and interband transition hot carriers generated, and which of them dominates the catalytic reaction remains elusive. Here, the contributions of hot electrons from intraband and interband transitions to the photoelectrocatalytic HER on plasmonic Au triangle nanoprisms (AuTNPs) have been studied. Compared with the dark reaction, the exchange current density increases by 9-fold and 3-fold under intraband and interband excitation, respectively, which is attributed to the higher energy level of intraband transition hot electrons. By calculation of the reaction activation energy with and without illumination, the contributions of the hot electrons from the two photoexcitation modes to the photoenhanced electroreduction reaction (PEER) are quantitatively analyzed, proposing the general standard to measure the effect of different hot electrons in different reactions.

Fluorescent Waveguide Lattices for Enhanced Light Harvesting and Solar Cell Performance.

We present the properties and performance of fluorescent waveguide lattices as coatings for solar cells, designed to address the significant mismatch between the solar cell's spectral response range and the solar spectrum. Using arrays of microscale visible light optical beams transmitted through photoreactive polymer resins comprising acrylate and silicone monomers and fluorescein o,o'-dimethacrylate comonomer, we photopolymerize well-structured films with single and multiple waveguide lattices. The materials exhibited bright green-yellow fluorescence emission through down-conversion of blue-UV excitation and light redirection from the dye emission and waveguide lattice structure. This enables the films to collect a broader spectrum of light, spanning UV-vis-NIR over an exceptionally wide angular range of ±70°. When employed as encapsulant coatings on commercial silicon solar cells, the polymer waveguide lattices exhibited significant enhancements in solar cell current density. Below 400 nm, the primary mode of enhancement is through down-conversion and light redirection from the dye emission and collection by the waveguides. Above 400 nm, the primary modes of enhancement were a combination of down-conversion, wide-angle light collection, and light redirection from the dye emission and collection by the waveguides. Waveguide lattices with higher dye concentrations produced more well-defined structures better suited for current generation in encapsulated solar cells. Under standard AM 1.5 G irradiation, we observed nominal average current density increases of 0.7 and 1.87 mA/cm2 for single waveguide lattices and two intersecting lattices, respectively, across the full ±70° range and reveal optimal dye concentrations and suitable lattice structures for solar cell performance. Our findings demonstrate the significant potential of incorporating down-converting fluorescent dyes in polymer waveguide lattices for improving the current spectral and angular response of solar cell technologies toward increasing clean energy in the energy grid.

Annealing effect on the magneto-electric properties of SOT-MTJs from micro to nano-sized dimensions

Spin–orbit torque magnetic random-access memory exhibits great potential for next-generation memory. Annealing is an essential process for SOT magnetic tunnel junctions (SOT-MTJs) thin films. To optimize the SOT-MTJ thin films, studying the different dimensions from micro-size to nano-size is very necessary. Here, we investigate the annealing effect on magneto-electric properties of micro-scaled and nano-scaled SOT-MTJs. The tunnel magnetoresistance (TMR) and critical current density (J c) increase after annealing, attributing to the improved crystallization of CoFeB layers and perpendicular magnetic anisotropy (PMA), respectively. However, the TMR increment of micro-scaled SOT-MTJ is larger than that in nano-scale, due to the reduced defects of micro-scaled SOT-MTJs by annealing. Additionally, the J c of nano-scaled SOT-MTJ is decoupled from that of micro-scaled SOT-MTJ because of the improved PMA and diminished thermal effect. This work assesses the different annealing effects in micro- and nano-sized dimensions and supplies experiment foundations to optimize the performance of SOT-MTJs.

Effect of dynamic formation of multiphase slag skin on heat transfer and magneto-hydrodynamic flow in electroslag remelting process

During the electroslag remelting (ESR) process, the effect of dynamic formation of slag skin on magneto-hydrodynamic multiphase flow and temperature field is studied using a 2-D axisymmetric model. The electromagnetic field is described by user-defined functions. The dynamic formation and distribution of multiphase slag skin, as well as the interface between slag and metal, are investigated by using the volume of fluid (VOF) model and the dynamic meshing method. Especially, the effect of slag skin/air gap on heat transfer characteristics is considered and developed by user-defined functions. The results show that the thickness of slag skin at the interface between slag and metal increases as the axial distance from free surface of slag rises, reaching a maximum of about 25 mm. With the height of ingot increasing, the thickness of slag skin drops to 17 mm. When the current changes from 2.0 kA to 3.0 KA in the ESR process, the current density, Joule heat, velocity and temperature increases. In the meanwhile, the slag skin becomes thinner and the melt pool becomes deeper. The vibration of electrode has a weak effect on the formation behavior of slag skin, and only has effects on formation of metal droplet and velocity field.

Improvements in the electrochemically assisted absorption of BTX with the application of ultrasound

In this work, it is evaluated the influence of the application of ultrasound (US) on the absorption and electrochemically assisted absorption of gaseous streams polluted with benzene, toluene, and xylene (BTX). The experimental device combines a jet mixer absorber and a single-compartment electrochemical flow cell equipped with boron-doped diamond (BDD) anode. Results show that application of US has a positive effect on the amount of the pollutants absorbed and oxidized. This is explained in terms of the promotion in the mass transfer processes and because of the activation of oxidising species. Intermediates produced in the oxidative degradation of BTX were principally carboxylic acids. When current density increases, the removal rate increases. However, the elimination efficiency (mmol A−1 h−1) and the synergy coefficient decrease. A simple model is formulated and applied, and it reproduced satisfactorily experimental results and help to understand the processes involved.

Alpha-lipoic acid modulates the diabetes mellitus-mediated neuropathic pain via inhibition of the TRPV1 channel, apoptosis, and oxidative stress in rats.

Diabetes mellitus (DM) is a chronic syndrome involving neuropathic pain. Increased oxidative stress in DM is assumed to increase free reactive oxygen radicals (ROS) and causes diabetic damage. The sciatic nerve (ScN) and dorsal root ganglion (DRG) both contain high levels of the TRPV1 channel, which is triggered by capsaicin and ROSs and results in increased Ca2+ entry into the neurons. Alpha-lipoic acid (ALA) is considered an important part of the antioxidant system. To better characterize the protective effects of ALA on the DM-induced neuronal through TRPV1 modulation, we investigated the role of ALA on DM-induced neuropathic pain, oxidative ScN, and DRG damage in diabetic rats. Forty adult Wistar albino female rats were divided into four groups as control, ALA (50mg/kg for 14 days), streptozotocin (STZ and 45mg/kg and single dose), and STZ + ALA. Rats were used for the pain tests. After obtaining the DRGs and ScN, they were used for plate reader, patch-clamp, and laser confocal microscope analyses. We observed the modulator role of ALA on the thresholds of mechanical withdrawal pain (von Frey test) and hot sensitivity pain (hot plate test) in the STZ + ALA group. The treatment of ALA decreased STZ-induced increase of TRPV1 current densities, intracellular free Ca2+ concentrations (Fura-2 and Fluo - 3/AM), ROS, caspase 3, caspase 9, mitochondrial membrane potential, and apoptosis values in the ScN and DRG neurons, although its treatment induced the increase of cell viability and body weight gain. The treatment of ALA acted a neuroprotective role on the TRPV1 channel stimulation-mediated Ca2+ influx, neuropathic pain, and neuronal damage in diabetic rats. The neuroprotective role of ALA treatment can be explained by its modulating the TRPV1 channel activity, intracellular Ca2+ increase-induced oxidative stress, and apoptosis.

Ni–La coatings as electrocatalysts for hydrogen evolution reaction deposited from electrolytes based on a deep eutectic solvent

Ni–La electrocatalytic coatings were electrodeposited from electrolytes based on a eutectic mixture of choline chloride and ethylene glycol (the so-called deep eutectic solvent "ethaline") containing dissolved NiCl2 and LaCl3 salts. It was shown that in this case, nickel alloys containing up to approximately 1.75 wt.% lanthanum were formed. An increase in the cathodic current density and the content of La(III) salt in the solution contributed to a higher content of lanthanum in the electrodeposits. The presence of a lanthanum(III) salt in the electrolyte led to a noticeable leveling of the surface microprofile. The electrocatalytic activity of the deposited coatings towards the hydrogen evolution reaction was evaluated by linear voltammetry in an aqueous solution of 1 M NaOH at a temperature of 298 K. It was found that the polarization of hydrogen evolution decreased, and the exchange current density increased with an increase in the lanthanum content in the coating. For example, the calculated hydrogen evolution exchange current density is 4.2610–5 A cm–2 and 1.0310–3 A cm–2 for a lanthanum-free nickel deposit and a nickel-based coating containing 1.75 wt.% La, respectively. The increased electrocatalytic activity observed when lanthanum was introduced into the nickel matrix can be attributed to both the synergistic interaction of the nickel and lanthanum components of the alloy (as previously described, the catalytic effect resulting from the hypo-hyper-d-electron interaction of transition metals) and the presence of surface active sites with lanthanum in different oxidation states (La(III)/La(II)), which can serve as electron carriers. The significant electrocatalytic effect observed when nickel is doped with lanthanum during deposition from an electrolyte based on DES allows us to consider such electrode materials as very promising for use in the electrolytic synthesis of "green" hydrogen.

Coupling covariance matrix adaptation with continuum modeling for determination of kinetic parameters associated with electrochemical CO2 reduction

Coupling covariance matrix adaptation with continuum modeling for determination of kinetic parameters associated with electrochemical CO2 reduction

Preparation and Characterization of Electrochemically Deposited Cu2O/ZnO Heterojunctions on Porous Silicon.

Cu2O/ZnO heterojunction was fabricated on porous silicon (PSi) by a two-step electrochemical deposition technique with changing current densities and deposition times, and then the PSi/Cu2O/ZnO nanostructure was systematically investigated. SEM investigation revealed that the morphologies of the ZnO nanostructures were significantly affected by the applied current density but not those of Cu2O nanostructures. It was observed that with the increase of current density from 0.1 to 0.9 mA/cm2, ZnO nanoparticles showed more intense deposition on the surface. In addition, when the deposition time increased from 10 to 80 min, at a constant current density, an intense ZnO accumulation occured on Cu2O structures. XRD analysis showed that both the polycrystallinity and the preferential orientation of ZnO nanostructures change with the deposition time. XRD analysis also revealed that Cu2O nanostructures are mostly in the polycrystalline structure. Several strong Cu2O peaks were observed for less deposition times, but those peaks diminish with increasing deposition time due to ZnO contents. According to XPS analysis, extending the deposition time from 10 to 80 min, the intensity of the Zn peaks increases, whereas the intensity of the Cu peaks decreases, which is verified by the XRD and SEM investigations. It was found from the I-V analysis that the PSi/Cu2O/ZnO samples exhibited rectifying junction and acted as a characteristical p-n heterojunction. Among the chosen experimental parameters, PSi/Cu2O/ZnO samples obtained at 0.5 mA current density and 80 min deposition times have the best junction quality and defect density.

Femtosecond laser-induced nano- and microstructuring of Cu electrodes for CO2 electroreduction in acetonitrile medium

The dependency of CO2 reduction rate in acetonitrile-Bu4NClO4 solution on cathodes, which were modified by laser induction of a copper surface, was studied. The topography of laser-induced periodic surface structures (LIPSS) → grooves → spikes was successively formed by a certain number of pulses. It was proved that for a higher number of laser pulses, the surface area of the copper cathode increases and preferred platy orientation of the copper surface on [022] crystallografic direction and larger fluence values increase. At the same time, the content of copper (I) oxide on the surface of the copper cathode increases. Also, the tendency to larger fluency values is observed. It promotes the increase of cathodic current density for CO2 reduction, which reaches values of 14 mA cm-2 for samples with spikes surface structures at E = − 3.0 V upon a stable process.

Regulating the dissolution of brittle nano-precipitated phase in FeCrAl alloy by pulse current to repair aging properties

Usually, heat treatment is required to elevate the entire material to a higher energy state, thereby eliminating harmful precipitates and repairing the mechanical properties of aged materials. However, the energy utilization rate of this high-temperature treatment method is low, and the regulation of precipitates dissolution is overly dependent on temperature. In this study, an efficient and energy-saving pulse current method was used to control the brittle Cr-rich α′ phase dissolution in aged Fe-25Cr-5Al grade alloy (Fe-24.32Cr-5.67Al-0.043C in wt.%). Compared with conventional heat treatment, pulse current treatment significantly reduces the dissolution temperature and activation energy of the precipitate, and as the current density increases, the non-thermal effect promoting brittle phase dissolution becomes more pronounced. This study is of great significance for the microstructure control and performance design of materials using pulsed current.

Microbial fuel cells in coral reef sediments as indicator tools for organic carbon eutrophication

Eutrophication with organic carbon (OC) can be harmful for corals and their reefs due to its stimulating effects on associated and sedimentary microbes, leading to oxygen deficits. Mitigation measures require real-time monitoring of wastewater pulses close to coral reefs, where biogenic carbonate sands act as biocatalytic filters for OC. Microbial fuel cells (MFCs) where the anode is deployed in sediments and the cathode is in contact with the overlying water can directly generate electricity from the microbial degradation of OC in sediments, but their application in coral reefs has not yet been tested. During a laboratory experiment, we thus investigated if MFCs, vertically deployed in coral reef sands, can be used as indicator tools for eutrophication with artificial wastewater (AW, prepared from organic compounds and chemicals) at OC concentrations of 20, 40, or 52 mg C L-1 higher than controls. AW pulses were repeated three times at every concentration, with five weeks between the first and second pulse, and six months between the second and third pulse. Results revealed significant increases in current densities in all AW treatments (means up to 11, 36, and 39 mA m−2, respectively), while controls remained stable and low (-1 to 3 mA m−2). Current densities and OC concentrations correlated significantly (rrm = 0.64), and the slope of the correlation increased with each consecutive AW pulse. This highlights the functionality of the MFC as a qualitative indicator tool for OC pulses even months after deployment. The response time of the MFCs was fast (<1 day) compared to other indicators for water quality (e.g., coral colony- or community measures that take weeks to years to respond), and they successfully detected OC concentrations expected for wastewater effluents. Measurements can be automated for continuous monitoring, and no laboratory facilities are required (as for OC analysis), making MFC sensors a suitable tool for remote locations. Overall, these findings emphasize the high potential of these low-cost (<20 € per MFC) MFCs as indicator tools for OC pulses in coral reef environments.