Increase In Current Density Research Articles

Realizing the dendrite-free sulfide-based all-solid-state Li metal battery by surface design

Although the ultrahigh ionic conductivity of sulfide-type solid electrolytes is comparable to that of liquid electrolytes, the low critical current density (CCD) limits the practical application of solid-state lithium (Li) metal batteries. The insufficient Li0 self-diffusion in solid Li leads to the voids that form at the interface at a large stripping current density, which results in interface contact loss and the increase of local current density. Herein, an artificial hybrid interphase layer dominated by Li3Sb and LiF was constructed on the Li surface to explore the Li plating/stripping behavior at the Li/Li6PS5Cl interface. The Li3Sb alloy provides a fast Li0 diffusion channel to avoid the interfacial voids formation and current focusing, while the electrically insulated LiF acts an electron blocking shield at the Li/Li6PS5Cl interface. Consequently, the symmetric cells reveal a significantly increased CCD of 1.8 mA cm−2 and a stable Li plating/stripping for 1472 h with a high current density of 2 mA cm−2 at 50 °C. Moreover, the all-solid-state Li-SPAN cell with Li3Sb/LiF interphase exhibits good capacity retention of 83.2 % after 120 cycles at 0.5 C, and it also delivers a superior rate performance of 400 mAh g−1 at 5C. The construction of lithium-alloy interphase is a promising alternative to solid-state lithium battery applications.

Analysis of the influence and mechanism of the pollution condensation environment on the electrochemical migration behaviour of printed circuit board with immersion silver

A refrigeration device was developed to induce condensation on printed circuit board with immersion silver (PCB-ImAg). Results show that in a condensation environment with low relative humidity, an electrolyte film can still be formed that allows conduction between the two poles of PCB-ImAg, allowing the thermodynamic conditions for electrochemical migration (ECM) to be reached and creating the risk of short-circuit failure. Under high relative humidity, the main body of ions that underwent ECM on the surface of PCB-ImAg was Cu2+ and as the relative humidity of the environment increases, the short-circuit failure time shortens, and the initial current density increases.

Electric-field-assisted proton coupling enhanced oxygen evolution reaction.

The discovery of Mn-Ca complex in photosystem II stimulates research of manganese-based catalysts for oxygen evolution reaction (OER). However, conventional chemical strategies face challenges in regulating the four electron-proton processes of OER. Herein, we investigate alpha-manganese dioxide (α-MnO2) with typical MnIV-O-MnIII-HxO motifs as a model for adjusting proton coupling. We reveal that pre-equilibrium proton-coupled redox transition provides an adjustable energy profile for OER, paving the way for in-situ enhancing proton coupling through a new "reagent"- external electric field. Based on the α-MnO2 single-nanowire device, gate voltage induces a 4-fold increase in OER current density at 1.7 V versus reversible hydrogen electrode. Moreover, the proof-of-principle external electric field-assisted flow cell for water splitting demonstrates a 34% increase in current density and a 44.7 mW/cm² increase in net output power. These findings indicate an in-depth understanding of the role of proton-incorporated redox transition and develop practical approach for high-efficiency electrocatalysis.

Distribution of relaxation times used for analyzing the electrochemical impedance spectroscopy of polymer electrolyte membrane fuel cell

In this paper, a 25 cm2 polymer electrolyte membrane single cell is prepared by ultrasonic spraying coating method. The polarization curves and Electrochemical Impedance Spectroscopies (EIS) data of this cell are collected under different conditions, such as cell temperature, humidity, back pressure and pure O2. EIS data are analyzed by Distribution of Relaxation Time (DRT), and some results are concluded: (i) with the increase of current density, the Oxygen Reduction Reaction (ORR) time constant became lower, and the ORR reaction resistance and oxygen diffusion resistance both increases. (ii) With the increase of back pressure, the DRT peak assigned to oxygen diffusion process in cathode moves to low frequencies, the peak area decreases simultaneously. (iii) the proportion of the ORR polarization resistance gradually increases from 77 % to 84 % with the cell temperature increase from 65 °C to 80 °C. (iv) With the increase of humidity, the performance of the cell is decreased. (v) The oxygen diffusion resistance is negligible in pure oxygen working condition analyzed by DRT method.

Frequency Spectrum of Radiation Flux Generated by Beam-Plasma System with Ten Joules Energy Content in Microsecond Pulse

The work reports the achievement of an energy content of 10 J per microsecond pulse in a directed flux of electromagnetic radiation in the frequency range of ~ 0.2–0.3 THz. The flux is generated by a fundamentally new method, which is realized through the pumping of upper-hybrid plasma oscillations in a magnetized plasma column with a relativistic electron beam (REB) and their subsequent transformation into a flux of electromagnetic radiation. In the described experiments at the GOL-PET facility, this method to generate THz radiation is implemented in the following way a beam of electrons with energy E ~ 0.5 MeV with a current density of (1–2) kA/cm2 is passing through a magnetized (4 T) plasma column with a density of 1014–1015 cm–3. By comparing the experimentally measured spectral composition of the radiation flux with the calculated spectrum, it is proved that this process is realized through resonant pumping of the branch of upper-hybrid plasma waves by such beam. A coordinated increase in plasma density and beam current density opens up the prospect of advancement in the generation of multi-megawatt radiation fluxes in the region of one terahertz.

Effects of residual stress and microstructure on extremely anisotropic grain growth in nanotwinned Cu films

In this study, the thermal stability and microstructural evolutions of nanotwinned copper (NT-Cu) films under thermal cycling are investigated. The microstructures and residual stresses were tuned by the electroplating current density. It was found that the thermal stability of the NT-Cu films decreased with an increase in current density. The texture transition from (111) to (100) suggests that the extremely anisotropic grain growth (EAGG) was driven by the minimization of strain energy. Bending beam technic was employed to measure the residual stress in the NT-Cu films. Large residual stress in the NT-Cu films is also considered a main driving force for the transition to the (100)-oriented texture. Additionally, strain energy, surface/interface energy, grain boundary energy, and twin boundary energy were calculated, and the results supported the experimental results.

Theoretical Investigation and Improvement of Characteristics of InAs/GaAs Quantum Dot Intermediate Band Solar Cells by Optimizing Quantum Dot Dimensions

Quantum dot (QD)-based solar cells have been the focus of extensive research. One of the critical challenges in this field is optimizing the size and placement of QDs within the cells to enhance light absorption and overall efficiency. This paper theoretically investigates InAs/GaAs QD intermediate band solar cells (QD-IBSC) employing cylindrical QDs. The goal is to explore factors affecting light absorption and efficiency in QD-IBSC, such as the positioning of QDs, their dimensions, and the spacing (pitch) between the centers of adjacent dots. Achieving optimal values to enhance cell efficiency involves modifying and optimizing these QD parameters. This study involves an analysis of more than 500 frequency points to optimize parameters and evaluate efficiency under three distinct conditions: output power optimization, short-circuit current optimization, and generation rate optimization. The results indicate that optimizing the short-circuit current leads to the highest efficiency compared to the other conditions. Under optimized conditions, the efficiency and current density increase to 34.3% and 38.42 mA/cm2, respectively, representing a remarkable improvement of 15% and 22% compared to the reference cell.

Investigation of the effect of conformal pinning array on critical current density in infinitely long superconductors

In this study, the influence of conformal pinning centers on enhancing the critical current density in superconductors has been investigated. To increase the critical current density, a square-pinned array with dimensions of 10λ by 10λ under two appropriate conformal transformations is considered. Initially, by specifying the forces acting on the vortices, the relevant Langevin equation for the vortices is solved. By solving this equation, the vortex positions versus time are determined, and using this information, the critical current density is calculated as a function of the magnetic field. Then, the critical current density is calculated for various conformal function parameters in a superconductor tape. The results indicate that after applying two conformal transformations with appropriate parameters, the critical current density could be increased at higher magnetic fields. Simulations demonstrate a 25% increase in critical current density in the optimal case.

Experimental and Modeling Analyses of the Correlation between Local 3D Heterogeneities and the Macroscopic Observers of a Proton Exchange Membrane Fuel Cell Stack

In this study, we offer a complete investigation of a high-performing Proton Exchange Membrane Fuel Cell stack customized for automotive use. Our approach goes beyond traditional global electrochemical performance metrics such as polarization curves, ohmic resistance. Instead, we utilize specialized segmented high-surface sensors to measure current density and temperature in the active area plane, along with neutron imaging to determine liquid water distributions. Employing a pseudo three-dimensional two-phase flow model that integrates electrochemical and transport phenomena, we gain insight into the intricate relationships among these observables. The model proves particularly valuable in elucidating the operation of the anode and cathode sides, aspects challenging to capture solely through experimental mean. Our findings emphasize the substantial impact of fluid flow directions and current density on the distribution of liquid water. It is noteworthy that despite fluid flow direction, there is a consistent decrease in overall liquid water content with an increase in current density. This results in voltage instability within the cell, attributed to flooding phenomena, especially at low current densities. However, this is not observed in conditions representative of those encountered in on-field systems. We conduct a thorough analysis of this failure scenario to improve the fuel cell system’s control mechanisms.

Introduction of Co atoms into CdS thin films for improving photovoltaic properties

This paper represents a systematic work on the fabrication of chemical bath-grown CdS films with and without Co atoms and their photovoltaic performances in hybrid solar cells. Structural properties showed 1% Co-doping promoted crystal quality of CdS films. However, a poor crystal quality was developed above 3% Co concentrations. A reduction in sphere size of CdS samples was observed for 1% Co-doping which was ascribed to slow growth of film. Optical examination demonstrated CdS films with 1% Co-doping displayed the highest transparency of 85% in the visible and near-infrared regions, which were explained by the improvement of crystal quality. A maximum band gap of 2.43 eV was found for 1% Co-doped CdS films, whereas an increase in Co concentration to 7% led to a decline in the band gap of CdS that was attributed to sp-d exchange interaction. Photoluminescence data showed Co-doped CdS films had lower PL peak intensity than that of CdS, demonstrating a decrease in the number of intrinsic defects. Photovoltaic measurements displayed that the best efficiency of 0.488% was achieved for CdS-based device including 1% Co atoms, which were almost a seven-fold boost in overall efficiency compared to bare CdS-based device. The enhancement in power conversion efficiency originated from an increase in short-circuit current density of 1% Co-doped CdS-based photovoltaic cell.

Sulfur loads under high temperature on the surface of C/SnO2 to enhance first platform capacity of lithium-sulfur batteries

Polysulfides are easily dissolved during the redox reaction process of Li-S batteries, which may be severe when current density and cycle number increase. Increasing capacity of the first platform effectively is beneficial for improving cycling stability. Physical sulfur loads are benefit for achieving high-capacity storage. However, the influence of composite electrodes with sulfur loads under high temperature on cycling stability of the first platform capacity has not been studied. Sulfur particles are loaded on the surface of C/SnO2 under high temperature in this work. C/SnO2/S and C/SnS/S composite electrodes are obtained by controlling sulfur contents. Results show that C/SnS/S composite electrodes display better cycling stability (1161 mAh⋅g−1) than C/SnO2/S composite electrodes at 1C after 100 cycles, especially in P1 platforms (724 mAh⋅g−1). When cycling number increases to 1000, C/SnS/S composite electrodes still possess good cycling stability (274.8 mAh⋅g−1) at 1C. Good cycling stability is ascribed to strong surface activities of sulfur in SnS and rapid electron transportation abilities during the cycling process. Studying sulfur-loading methods under high temperature is beneficial for obtaining high cycling performance composite electrodes for lithium-sulfur batteries.

Стойкость против питтинговой коррозии как критерий безопасности эксплуатации металлического оборудования

Pitting corrosion is hazardous for personnel of chemical plants operating with tanks, reactors, and pipelines. Pitting is a pinpointed corrosive damage rapidly penetrating a metal and causing its through-perforation. Chemical and thermal burns and poisoning of personnel are also potential. When designing the equipment, it is required to select materials able to resist pitting corrosion in the operational medium. Quick methods of pitting resistance of material include the comparison of critical potentials determined by potentiodynamic polarization curves. The potential of the studied sample is given a value equal to the corrosion value that is increased at the rate of 0.2–2 mV/s. At the same time, values of current density are registered. The gradual increase of current density is followed by its decrease, and the metal turns to a passive state. With a certain value of pitting formation potential, the current density increases acutely; and pittings are formed on the metal surface. When the potential is decreased, current density within a certain range of values remains relevant to the current density at the pitting formation potential but then decreases to the values relevant to dissolution in a passive state. This occurs at the re-passivation potential. Earlier, values of potentials of pitting formation and corrosion were compared. Later, it was proved that the evaluation of the pitting resistance of metals based on the comparison was not correct as pittings could also be formed at the potentials lower than the pitting formation potential. The correct evaluation of metal pitting resistance can be obtained based on the comparison of re-passivation and corrosion potentials. Until now, however, the pitting formation potential has been used for the evaluation. Based on the experimental potentiodynamic polarization curve of stainless steel Х20Н6Г11 and the results of corrosion tests, it has been established that metal corrodes at potentials above the re-passivation potential but lower than the pitting formation potential. When potentials are lower than the re-passivation potential, pittings are not formed.

The role of lithium in hydrogen trapping and embrittlement of Al-Cu-Li alloys: Experimental study and DFT calculations

The role of lithium in hydrogen embrittlement (HE) and trapping of Al-Cu-Li alloys were investigated in experimental and density functional theory (DFT) calculations. The tensile curves and fracture morphology show that the Li-contained samples are more sensitive to HE than the Li-free samples and the HE sensitivity increases with the aging time expansion. The Transmission Electron Microscope (TEM) analyses reveal that the number density of T1 (Al2CuLi) precipitates increases about 66.8% with aging process, suggesting that HE sensitivity is exacerbated by T1 precipitates. In addition, the lithium in T1 precipitates, solid solution matrix and solute segregation grain boundaries (GBs) always has a high affinity to hydrogen according to DFT calculations, where T1 precipitates have the highest hydrogen trapping energy with 0.736 eV/H atom. Moreover, the influence of hydrogen on Al-Cu-Li alloys was investigated using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and electrochemical corrosion analysis. These analyses indicate that hydrogen exists in the form of hydrogen atoms, which results in a reduction in corrosion potential (Ecorr) from −676.3 mV to −699.3 mV by approximately 20 mV and an increase in corrosion current density (icorr) from 2.1×10−6 A/cm2 to 10.8×10−6 A/cm2 by an order of magnitude. The accumulated hydrogen atoms eventually lead to corrosion pits and blisters on the surface of alloys.

Separation of Chloride and Sulfate Ions from Desulfurization Wastewater Using Monovalent Anions Selective Electrodialysis.

The high concentration of chloride ions in desulphurization wastewater is the primary limiting factor for its reusability. Monovalent anion selective electrodialysis (S-ED) enables the selective removal of chloride ions, thereby facilitating the reuse of desulfurization wastewater. In this study, different concentrations of NaCl and Na2SO4 were used to simulate different softened desulfurization wastewater. The effects of current density and NaCl and Na2SO4 concentration on ion flux, permselectivity (PSO42-Cl-) and specific energy consumption were studied. The results show that Selemion ASA membrane exhibits excellent permselectivity for Cl- and SO42-, with a significantly lower flux observed for SO42- compared to Cl-. Current density exerts a significant influence on ion flux; as the current density increases, the flux of SO42- also increases but at a lower rate than that of Cl-, resulting in an increase in permselectivity. When the current density reaches 25 mA/cm2, the permselectivity reaches a maximum of 50.4. The increase in NaCl concentration leads to a decrease in the SO42- flux; however, the permselectivity is reduced due to the elevated Cl-/SO42- ratio. The SO42- flux increases with the increase in Na2SO4 concentration, while the permselectivity increases with the decrease in Cl-/SO42- ratio.

Influence of Mg concentration in Zn1-xMgxO buffer layers for enhanced Cu2(Sn,Ge)S3 solar cells performance

This study is focused on the influence of band alignment at the buffer/absorber interface of Cu2(Sn,Ge)S3 (CTGS) thin film solar cells fabricated on soda-lime glass substrates with an Al/Ni/Zn0.92Mg0.08O:Al/Zn1-xMgxO − 2nd buffer/CdS − 1st buffer/CTGS/Mo/glass structure. Here, Zn1-xMgxO 2nd buffers are used to minimize the energy losses and prevent direct contact between the Zn0.92Mg0.08O:Al and CTGS absorber. The study found that the conduction band offset between Zn1-xMgxO and CTGS changed from −0.68 eV (i.e., cliff-like, negative band offset) to +0.60 eV (i.e., spike-like, positive band offset) as the Mg content x increased in Zn1-xMgxO from 0 (i.e., pure ZnO) to 0.52. Optimization of the conduction band offset via tuning the Mg content in Zn1-xMgxO 2nd buffer reduced carrier recombination in the CTGS devices, improving band bending and enhancing the power conversion efficiency up to 3.1%. This was primarily attributed to an increase in short-circuit current density and fill factor.

CdS/CdSe/PbS quantum dots sensitized TiO2 eggshell hollow microspheres photoanode to boost photocurrent and power conversion efficiency of QDSSC

Light harvesting plays crucial role for high photovoltaic performance of quantum dots sensitized solar cell (QDSSC). However, there are still issues need to be tackled, such as enlarging light response range and enhancing light scattering capability. In this work, TiO2 eggshell hollow microspheres (EHMS) were synthesized by carbonaceous microspheres (CMS) template method and co-sensitized by CdS/CdSe/PbS quantum dots (QDs) for application in QDSSC. Compared with QDSSC based on TiO2 nanoparticles (NP) and TiO2 hollow microspheres (HMS), the TiO2 EHMS based QDSSC showed a remarkable increase of short-circuit current density (Jsc) to 24.81 mA cm−2 with a power conversion efficiency (PCE) of 4.07 %. Photoelectrochemical analysis of QDSSC indicate that CdS/CdSe/PbS QDs can enlarge the light response range, and the TiO2 EHMS improve the light scattering, leading to the improvement of light harvesting efficiency. Charges dynamics tests results proved that a larger charges recombination resistance at photoanode/electrolyte interface and longer electron lifetime can be achieved with TiO2 EHMS, contributing to the boost of Jsc. The presented study introduces a simple strategy for researchers interested in designing photoanode for various photoelectrochemical applications.

Atomic layer deposition for tuning the surface chemical composition of nickel iron phosphates for oxygen evolution reaction in alkaline electrolyzers

Transition metal phosphates are promising catalysts for the oxygen evolution reaction (OER) in alkaline medium. Herein, Fe-doped Ni phosphates are deposited using plasma-enhanced atomic layer deposition (PE-ALD) at 300 °C. A sequence of f Fe phosphate PE-ALD cycles and n Ni phosphate PE-ALD cycles is repeated x times. The Fe to Ni ratio can be controlled by the cycle ratio (f/n), while the film thickness can be controlled by the number of cycles (x times (n+f )). 30 nm films with an Fe/Ni ratio of ∼10% and ∼37%, respectively, are evaluated in 1.0 M KOH solution. Remarkably, a significant difference in OER activity is found when the order of the Ni and Fe phosphate PE-ALD cycles in the deposition sequence is reversed. A 20%–45% larger current density is obtained for catalysts grown with an Fe phosphate PE-ALD cycle at the end compared to the Ni phosphate-terminated flavour. We attribute this to a higher concentration of Fe centers on the surface, as a consequence of the specific PE-ALD approach. Secondly, increasing the thickness of the catalyst films up to 160 nm results in an increase of the OER current density and active surface area, suggesting that the as-deposited smooth and continuous films are converted into electrolyte-permeable structures during catalyst activation and operation. This work demonstrates the ability of PE-ALD to control both the surface and bulk composition of thin film electrocatalysts, offering valuable opportunities to understand their impact on performance.

Impact of the gate work function on the experimental I-V characteristics of MOS solar cells simulated with the Sentaurus TCAD software

In this work, the influence of gate work function on the experimental J-VG characteristics of MOS solar cells was investigated with the aid of the Sentaurus TCAD for 2D numer-ical simulations of TiN/SiOxNy/Si Al/SiOxNy/Si and Al/MgO/Mg/SiOxNy/Si structures aiming at solar cells for en-ergy harvesting applications. The increase of the gate work function led to the increase of the reverse current density as pointed out by the Sentaurus TCAD simulations and by the ex-perimental J-VG characteristics. The work functions of Mg, Al, and un-annealed TiN used in the TCAD simulations were 3.7 eV, 4.1 eV, and 4.4 eV, respectively. It was observed that the onset voltage at 0.5 mA/cm2 in the forward-biasing region was at a lower voltage for TiN (~ - 0.06 V) compared to Al (~ - 0.42 V) and the Al/MgO/Mg stack (~ - 0.47 V). On the other hand, the current density increased steeply in the forward biasing for TiN and Al compared to the Al/ MgO/Mg stack gate and the thin MgO layer between Al and Mg worked as a potential barrier in an opposite direction to the potential barrier of the Mg/Si-OxNy/Si structure, which meant an onset voltage lowering for the Al/MgO/Mg/SiOxNy/Si solar cell. For the Al/MgO/Mg stack, the barrier effect of the MgO layer was fitted as a series re-sistance RS = 100 Ω and an equivalent Al/MgO/Mg work func-tion of 4.15 eV considering a substrate doping NA = 1.2x1016 cm-3 and parallel conductance GP = 0. Also, the experimental JxVG characteristic of the Al/SiOxNy/Si cell was fitted for Al work function of 4.10 eV, a series resistance RS = 100 Ω, a parallel resistance RP = 0.02 Ω (GP = 50 S) and a substrate doping NA = 5.5x1015 cm-3. In this case, the high parallel conductance fitted was attributed to the tunneling through the dielectrics as a pre-dominant effect possibly caused by a high concentration of de-fects in the SiOxNy layer. Finally, the MOS solar cell parameters were relatively lower compared to those of commercial outdoor solar cells, but the power generated by the MOS cells reached the mW range, and the conversion efficiency from light energy into electrical energy was higher (12.7%) than the typical values found for energy-harvesting solar cells.

CO2-Promoted Electrocatalytic Reduction of Chlorinated Hydrocarbons.

Electrochemical reactions and their catalysis are important for energy and environmental applications, such as carbon neutralization and water purification. However, the synergy in electrocatalysis between CO2 utilization and wastewater treatment has not been explored. In this study, we find that the electrochemical reduction of chlorinated organic compounds such as 1,2-dichloroethane, trichloroethylene, and tetrachloroethylene into ethylene in aqueous media, which is a category of challenging reactions due to the competition of H2 evolution, can be substantially enhanced by simultaneously carrying out the reduction of CO2 on an easily prepared and cost-effective Cu metal catalyst. In the case of 1,2-dichloroethane dechlorination, a 6-fold improvement in Faradaic efficiency and a 19-fold increase in partial current density are demonstrated. Through electrochemical kinetic studies, in situ Raman spectroscopy, and computational simulations, we further find that CO2 reduction reduces hydrogen coverage on the Cu catalyst, which not only exposes more active sites for the dechlorination reaction but also enhances the effective reductive potential on the catalyst surface and reduces the kinetic barrier of the rate-determining step.

Phosphorus Removal Rate and Efficiency in an Electrochemical Sequencing Reactor for the Treatment of Wastewater with Low Organic Carbon Content

Energy is essential for the operation of wastewater treatment systems. Simultaneously, it can be a factor facilitating the electrochemical purification processes. Previous studies have shown that under specific conditions, there is no technological justification for using bio-electrochemical reactors designed for the simultaneous removal of both phosphorus and nitrogen compounds. This is because similar dephosphatation process effects can be achieved in an electrochemical reactor. Additionally, in a bio-electrochemical reactor, a portion of the organic substrate introduced for biological treatment is lost due to the electrocoagulation process. The aim of the research was to determine the influence of low direct current densities (0.4–2.0 A/m2) on the rate and efficiency of phosphorus and other compound removal in a sequencing electrochemical reactor treating real wastewater from a greenhouse with low organic compound content. In the conducted studies, an increase in electric current density resulted in an increase in the removal rates of phosphorus from 26.45 to 34.79 mg/L·h, nitrogen from 2.07 to 6.58 mg/L·h, and organic compounds from 0.44 to 1.50 mg/L·h. This corresponded to maximum removal efficiencies of 88.6 ± 2.5% for phosphorus, 7.4 ± 2.5% for nitrogen, and 51.1 ± 8.3% for organic compounds. As a result of electrocoagulation, sludge rich in phosphorus was obtained, ranging from 347 ± 38 mg/L (18.1% P) to 665 ± 36 mg/L (11.7% P). The obtained results can be utilized in the future for the development of two-stage systems for wastewater treatment with a low content of organic compounds, aiming at the removal of phosphorus and nitrogen.