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Tin oxide (SnO2) as an electron transport material was prepared by atomic layer deposition in dye-sensitized NiO films to fabricate solid-state p-type dye-sensitized solar cells using two organic dyes PB6 and TIP as photosensitizers. Due to the excellent electron mobility and satisfactory penetration of SnO2 material into the NiO film, a record photocurrent density over 1 mA cm–2 was achieved with a power conversion efficiency of 0.14%. The effect of an inserted Al2O3 layer between the dye-sensitized NiO and SnO2 layer on photovoltaic performance of the devices was also investigated. The results suggest that the charge recombination between NiO and SnO2 can be significantly suppressed, showing prolonged charge lifetime and enhanced photovoltage.

Given the global demand for green energy, the battery industry is positioned to be an important future technology. Lithium-ion batteries (LIBs), which are the most widely used battery in the market, are the focus of various research and development efforts, from materials to systems, that seek to improve their performance. The separator is one of the core materials in LIBs and is a significant factor in the lifespan of high-performance batteries. To improve the performance of present LIBs, electrochemical testing and related surface analyses of the separator is essential. In this paper, we prepared a ceramic (Boehmite, γ-AlOOH) coated polypropylene separator and a porous polyimide separator to compare their electrochemical properties with a commercialized polypropylene (PP) separator. The prepared separators were assembled into nickelmanganese-cobalt (NMC) cathode half-cell and full-cell lithium-ion batteries. Their cycling performances were evaluated using differential capacity and electrochemical impedance spectroscopy with ethylene carbonate:dimethylcarbonate (EC:DMC) electrolyte. The ceramic coated polypropylene separator exhibited the best cycle performance at a high 5 C rate, with high ionic conductivity and less resistive solid electrolyte interphase. Also, it was confirmed that a separator solid electrolyte interface (SSEI) layer formed on the separator with cycle repetition, and it was also confirmed that this phenomenon determined the cycle life of the battery depending on the electrolyte.

Application of transcranial alternating current stimulation (tACS) is thought to modulate ongoing brain oscillations in a frequency-dependent manner. However, recent studies report various and sometimes inconsistent results regarding its capacity to induce changes in cortical activity beyond the stimulation period. Here, thirty healthy volunteers participated in a randomized, cross-over, sham-controlled, double-blind study using EEG to measure the offline effects of tACS on alpha and beta power. Sham and high current density tACS (1 mA; 10 Hz and 20 Hz; 0.32 mA/cm2) were applied for 20 min over bilateral sensorimotor areas and EEG was recorded at rest before and after stimulation for 20 min. Bilateral tACS was not associated with significant changes in local alpha and beta power frequencies at stimulation sites (C3 and C4 electrodes). Overall, the present results fail to provide evidence that bilateral tACS with high current density applied over sensorimotor regions at 10 and 20 Hz reliably modulates offline brain oscillation power at the stimulation site. These results may have implications for the design and implementation of future protocols aiming to induce sustained changes in brain activity, including in clinical populations.

Developing high-performing oxygen evolution reaction (OER) electrocatalysts under high-current operation conditions is critical for future commercial applications of alkaline water electrolysis for clean energy generation. Herein, we prepared a three-dimensional (3D) bimetallic oxyhydroxide hybrid grown on a Ni foam (NiFeOOH/NF) prepared by immersing Ni foam (NF) into Fe(NO3)3 solution. In this unique 3D structure, the NiFeOOH/NF hybrid was composed of crystalline Ni(OH)2 and amorphous FeOOH evenly grown on the NF surface. As a bimetallic oxyhydroxide electrocatalyst, the NiFeOOH/NF hybrid exhibited excellent catalytic activity, surpassing not only the other reported Ni–Fe based electrocatalysts, but also the commercial Ir/C catalyst. In situ electrochemical Raman spectroscopy demonstrated the active FeOOH and NiOOH phases involved in the OER process. Profiting from the synergy of Fe and Ni catalytic sites, the NiFeOOH/NF hybrid delivered an outstanding OER performance under challenging industrial conditions in a 10.0 mol∙L−1 KOH electrolyte at 80 °C, requiring potentials as small as 1.47 and 1.51 V to achieve the super-high catalytic current densities of 100 and 500 mA∙cm−2, respectively.

The ability of HTS cable networks to provide a solution for the high power density requirements of electric transportation applications was explored. The high current density and the temperature-dependent critical current features of HTS cables were shown to allow resilient designs for power distribution in electric transportation applications. Heat loads at the terminations are shown to be the primary challenge. Appropriate designs in terms of ampacities of the current leads are essential in using the beneficial features of HTS cables. Thermal network models were used to understand the implications of using HTS cables to carry the necessary additional current to mitigate contingencies and to aid in the designs of effective HTS cable networks for electric aircraft and ships.

We have been developing a no-insulation (NI) coil technology to achieve high thermal stability and high current density. NI coils can continue to operate even if a part of the coils degrades; however, a charging delay occurs in the coils. Moreover, the turn-to-turn contact electrical resistance of the NI coils must be increased to shorten the charging delay; however, a large turn-to-turn contact electrical resistance reduces thermal stability. In this study, using turn-to-turn contact electrical resistance and IOP / IC ratios as parameters, we analyze thermal stability and consider the possibility that NI coils can continue to operate even if they have local defects. Furthermore, to establish an evaluation criterion for determining turn-to-turn contact electrical resistance that can shorten charging delay and ensure high thermal stability, we analyze and evaluate the relationship between turn-to-turn contact electrical resistance and thermal stability, focusing on three types of heat generation.

In this study, we studied the surface and mechanical properties of multiple additives as well as the initial plating properties of individual additives. With the individual additive groups, copper crystals tended to converge at a stage above the critical amount of additive. When chloride ions were added, large crystals formed at several places on the surface. Thereafter, small crystals were attached to and grew on the surface of the large crystals. When collagen and JGB (Janes Green B) were added individually, the crystals were more uniformly distributed on the surface as compared with the group with added chloride ions. In addition, starlike crystals were grown depending on the amount of addition. It was necessary to use multiple additives, which is why it is difficult to make a uniform surface layer with individual additives. Large crystals of more than 10 μm formed unevenly on the surface treated with multiple additives of chloride ions and MPSA (3-mercapto-1-propane sulfonic acid). Large crystals disappeared on the surface treated with additional collagen along with multiple additives. However, valley like shapes were observed on this surface, due to the large crystals. But, addition of JGB additives to this reduced the valley and formed a uniform plating layer. MPSA and 20 ppm of collagen were added as multiple additives, grain sizes increased by 93.5% (220 peak) and 172.3% (311 peak) compared with the non-additive group. As a result, tensile strength decreased by 24.5% and elongation increased by 17.8%. The crystal size was reduced 25.0% on average by the addition of 10 ppm JGB, which contributed to a 5.4% increase in tensile strength and a 16.0% decrease in elongation. The grain size and surface properties could be controlled by adding multiple combinations of additives. As a result, It was confirmed that mechanical properties could be controlled by the proper amount and the optimum combination of additives.

Development of practical rechargeable Mg batteries (RMBs) is impeded by their limited cycle life and rate performance of cathodes. As demonstrated herein, a copper‐porphyrin with meso‐functionalized ethynyl groups is capable of reversible two‐ and four‐electron storage at an extremely fast rate (tested up to 53 C). The reversible four‐electron redox process with cationic‐anionic contributions resulted in a specific discharge capacity of 155 mAh g−1 at the high current density of 1000 mA g−1. Even at 4000 mA g−1, it still delivered >70 mAh g−1 after 500 cycles, corresponding to an energy density of >92 Wh kg−1 at a high power of >5100 W kg−1. The ability to provide such high‐rate performance and long‐life opens the way to the development of practical cathodes for multivalent metal batteries., Self‐conditioning: The metalloporphyrin based electrodes exhibit reversible insertion/deinsertion of Mg2+ and bulky anions as well as excellent capacity retention over several hundred cycles at very fast charge‐discharge rates. This opens the pathway for development of new organic electrode materials for stable high‐energy and high‐power multivalent metal‐based energy storage systems.

With suitable water dissociation (WD) catalysts, bipolar membranes (BPMs) can efficiently dissociate water into H+ and OH– at the junction between anion- and cation-exchange layers (AEL and CEL, re...

Sn-based perovskite solar cells have attracted much attention as the lead-free next generation of perovskite solar cells. However, their efficiency is still low (∼12%). One reason is that the carri...

It is shown that it is possible to obtain nanostructured layers with an increased thickness (up to 2 mm), suitable for the repair of worn surfaces of component parts made of aluminum alloys during electrospark alloying of the surface of the aluminum alloy (D1) by the processing electrode of an Al–Sn alloy (20% Sn) with the use of the high current density and two-phase technology for producing a multilayer coating (applying–melting).

In the present study, we report a simple method to prepare indium(III) selenide (In2Se3) nanocubes synthesized by laser ablation in aqueous medium. The morphological characterization carried out us...

Transition-metal (oxy)hydroxides with an abundance of redox metal sites are important for the development of electrochromic devices, rechargeable metal–air batteries, pseudo-capacitors, and industr...

Organic light-emitting diodes (OLEDs) are promising candidates for solid-state lighting but suffer from decreased efficiency at the high current density required for lighting applications. This dec...

Three-dimensional (3D) current collectors have shown great potential in realizing dendrite-free lithium (Li) metal anodes. However, the rigid 3D current collectors could not simultaneously suppress Li dendrite growth and allow Li plating/stripping under high capacities and large current densities. Here, we report a dynamic intelligent Cu (DICu) current collector that dynamically accommodates the volume change by changing the packing density of the assembled particles. The Li/DICu electrode achieves a high Coulombic efficiency of 99.6% after 800 cycles. The symmetrical cell shows exceptional cycling stability under the high current density of 10 mA cm-2. Notably, when assembled in full-cell batteries, the Li/DICu|LiFePO4 battery maintains a specific capacity of 139.5 mAh g-1 at 1 C for 500 cycles, and the Li/DICu|S battery delivers a specific capacity of 804 mAh g-1 after 500 cycles at 0.5 C, corresponding to the best performance among Li metal batteries with Cu-based current collectors to date.

SmTiO3/SrTiO3 interfaces are of potential interest for electronic devices as they exhibit novel electronic phenomena such as metal–insulator transitions. However, good transistor performance from t...

Ni(HCO3)2 working for the first time as an adsorption site for hydroxyl species for a MoS2-based catalyst has efficiently facilitated the alkaline HER kinetics, as demonstrated by experimental and DFT calculation results. The ultra-small Ni(HCO3)2 is vital to achieving excellent HER activity of Ni(HCO3)2/MoS2/CC in alkaline media, which transcended the performance of Pt/C at high current density.

Although recent studies on the oxygen evolution reaction (OER) have achieved great progress, it remains a great challenge to achieve a smaller overpotential at high current density. In order to further improve the performance of the OER, we adopted a novel method to load Fe nanoparticles on a Ni3S2 nanoplate array grown on nickel foam (Fe NPs-Ni3S2 NA/NF) which formed an amorphous structure. In particular, this catalyst exhibited an overpotential of 206 mV at 150 mA cm−2, outmatching most non-noble OER catalysts reported so far; it also operates smoothly in various stability tests.

Hydrogen is expected to have an important role in future energy systems; however, further research is required to ensure the commercial viability of hydrogen generation. Proton exchange membrane steam electrolysis above 100 °C has attracted significant research interest owing to its high electrolytic efficiency and the potential to reduce the use of electrical energy through waste heat utilization. This study developed a novel composite membrane fabricated from graphitic carbon nitride (g-C3N4) and Nafion and applied it to steam electrolysis with excellent results. g-C3N4 is uniformly dispersed among the non−homogeneous functionalized particles of the polymer, and it improves the thermostability of the membranes. The amino and imino active sites on the nanosheet surface enhance the proton conductivity. In ultrapure water at 90 °C, the proton conductivity of the Nafion/0.4 wt.% g-C3N4 membrane is 287.71 mS cm−1. Above 100 °C, the modified membranes still exhibit high conductivity, and no sudden decreases in conductivity were observed. The Nafion/g-C3N4 membranes exhibit excellent performance when utilized as a steam electrolyzer. Compared with that of previous studies, this approach achieves better electrolytic behavior with a relatively low catalyst loading. Steam electrolysis using a Nafion/0.4 wt.% g-C3N4 membranes achieves a current density of 2260 mA cm−2 at 2 V, which is approximately 69% higher than the current density achieved using pure Nafion membranes under the same conditions.

Electrochemical water splitting technology for producing "green hydrogen" is important for the global mission of carbon neutrality. Electrocatalysts with decent performance at high current densities play a central role in the industrial implementation of this technology. This field has advanced immensely in recent years, as witnessed by many types of catalysts designed and synthesized toward industrially-relevant current densities (> 200 mA cm-2 ). By discussing recent advances in this field, we summarize several key aspects that affect the catalytic performance for high-current-density electrocatalysis, including dimensionality of catalysts, surface chemistry, electron transport path, morphology, and catalyst-electrolyte interplay. We highlight the multiscale design strategy that considers these aspects comprehensively for developing high-current-density electrocatalysts. We also put forward our perspectives on the future directions in this emerging field. This article is protected by copyright. All rights reserved.

Highly selective electrochemical reduction of CO2 (CO2RR) to multi-carbon (C2+) products at high current density remains a big challenge. Herein we report copper oxide nanosheets (CuO-st) for selective electrochemical conversion of CO2 to C2+ products at high current density. Benefiting from the defect-rich structure verified by HR-TEM and XPS characterization and the designed gas diffusion electrode, such a CuO-st material exhibits CO2RR FE (C2+) of 86 and 80 % at 1.0 and 1.8 A cm−2, respectively, with excellent durability of 50 h @ 500mAcm−2 and storable lifetime for >10 months. Importantly, using quasi-situ XPS and in-situ Roman spectra, we have shown the first evidence for the presence of Cu (ǀ) during the eCO2RR on initial Cu (ǁ) material, and the proportion of Cu (ǀ) varies with the reaction current density. The rough and defective surface of CuO-st serves as a favorable reservoir to produce enough Cu (ǀ) to assist the C-C coupling, thus achieving selective CO2RR to C2+ products at high current density. Our study not only provides a new insight into CO2RR, but also suggests that in-situ forming active species from stable Cu (ǁ) materials during the reaction may be a good choice for the practical application, which will be very helpful to the development of cost-effective CO2RR electrocatalysts.

CuO nanorods were synthesized on copper foil substrate through wet chemical approach. The effect of growth time on the field electron emission properties of CuO nanorods was studied. The field electron emission tests were performed under AC bias on the CuO nanorod (CuO NR) samples. The growth reaction time was varied between 1, 3, 7 and 11 h. It was observed that CuO NR sample which was processed for 11 h demonstrates the optimum properties such as lowest turn on field (0.56 V/µm), high current density (1.52 mA/cm2) at low electrical field (9 V/µm), good field enhancement factor and excellent stability of emitters for extended working hours which makes it suitable for applications field emission devices.

Traditional silicon-based power electronics have approached their performance limits for high-power electronic applications. The U.S. Navy is actively pursuing the implementation of wide bandgap (WBG) semiconductor materials to realize reliable devices for use in high-power, high-current, and high-voltage applications. Gallium nitride (GaN) is a promising candidate for these applications due to its inherent material properties, and recent efforts to produce high quality bulk GaN have begun to enable the production of commercial-grade devices. However, much is still unknown regarding the reliability of GaN devices, especially Schottky diodes, which are often affected by issues involving barrier height inhomogeneity (BHI). First, a stress testing system capable of taking in-situ current-voltage-temperature (I-V-T) measurements while applying electrical stress was constructed. Next, a sample of commercial-grade vertical n-type palladium/gallium nitride (Pd/GaN) Schottky diodes were subjected to a series of step current and constant current stress tests. Current densities above 1.3 kA/cm^2 were achieved. Finally, the effects of electrical stress on material properties were observed through comparison of pre-, post-, and in-situ I-V-T data. The in-situ I-V-T measurements enabled degradation to be observed as a function of stress time. Results show that significant degradation to the material properties of the Schottky diodes occurs within the first few hours of stress testing. Lieutenant, United States Navy Approved for public release. Distribution is unlimited.

Chromium plating has excellent corrosion resistance and is widely used in industry. However, it also has a high environmental load. As an alternative, electric Ni-W plating is attracting attention. However, it is not widely used because the stress is high and the film is prone to cracks. Furthermore, although it is necessary to thicken the film to improve the corrosion resistance, there are also problems that the current efficiency is low and the plating time is long. Therefore, we investigate a film with high corrosion resistance by using the jet-flow plating method that enables plating at a high current density. Our results show that the jet-flow plating enables plating of 50 µm, and high corrosion resistance is obtained by randomly generating fine cracks in the film at 20 A·dm−2. We also found that the stress changed depending on the current density and shape of the crack also changed.

В работе методами растровой электронной микроскопии и ультрамягкойрентгеновской эмиссионной спектроскопии были проведены исследования особенностейформирования многослойных структур пористого кремния и установлено влияние изменения плотности тока при электрохимическом травлении монокристаллических пластин кремния на фазовый состав поверхностных слоев сформированной пористой структуры. ЛИТЕРАТУРА1. Moshnikov V., Gracheva I., Lenshin A., Spivak Yu. Porous silicon with embedded metal oxides for gassensing applications // Journal of Non-Crystalline Solids, 2012 v. 358(3), pp. 590–595. DOI: https://doi.org/10.1016/j.jnoncrysol.2011.10.0172. Pacholski C. Photonic crystal sensors based on porous silicon // Sensors, 2013, v. 13(4), pp. 4694–4713.DOI: https://doi.org/10.3390/s1304046943. Harraz F. Porous silicon chemical sensors and biosensors: A review // Sensors and Actuators B, 2014,v. 202, pp. 897–912. DOI: https://doi.org/10.1016/j.snb.2014.06.0484. 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The electrochemical CO2 reduction reaction (CO2RR) towards CO allows to turn CO2 and renewable energy into feedstock for the chemical industry. Previously shown electrolyzers are capable of continuous operation for more than 1000 h at high faradaic efficiencies and industrially relevant current densities. However, the crossover of educt CO2 into the anode gas has not been investigated in current cell designs: Carbonates (HCO3 − and CO3 2−) are formed at the cathode during CO2RR and are subsequently neutralized at the anode. Thus, CO2 mixes into the anodically evolved O2, which is undesired from commercial perspectives. In this work this chemical transport was suppressed by using a carbonate-free electrolyte. However, a second transport mechanism via physically dissolved gases became apparent. A transport model based on chemical and physical absorption of CO2 and O2 will be proposed and two solutions were experimentally investigated: the use of an anode GDL (A-GDL) and degassing the anolyte with a membrane contactor (MC). Both solutions further reduce the CO2 crossover to the anode below 0.1 CO2 for each cathodically formed CO while still operating at industrially relevant current densities of 200 mA/cm2.

A promising electrode material for energy storage, the SnS2/g-C3N4 composite is reported, which is prepared by a simple hydrothermal route. The SnS2/g-C3N4 composite shows a good specific capacitance of 552 F g−1 at the current density of 0.5 A g−1 in 3 M KOH, and also exhibits excellent cycling stability of 95.8% capacitance retention after 15000 cycles even at a relatively high current density of 10 A g−1. The SnS2/g-C3N4 composite is proved to be a promising candidate for the electrode materials in supercapacitor applications.

In this article, the design approach for a miniaturized high-current-density sheet electron beam (SEB) source has been reported. A study through simulation using COMSOL Multiphysics has been carried out to analyze the role of geometrical parameters of the hollow cathode in miniaturized SEB generation. These geometrical parameters play a very important role in defining the discharge inside the hollow cathode geometry and subsequent beam generation through a rectangular aperture. The hollow cathode diameter “D”, the length of the hollow cathode “L”, and the aspect ratio of the sheet beam defined by the aperture size in front of the hollow cathode region have been optimized for the generation of a SEB. The ratio of the length to the width of the rectangular aperture defines the aspect ratio of the SEB. It has been found that the beam aspect ratio plays an important role in the penetration of the accelerating field inside the hollow cathode geometry, which affects the transient behavior of the discharge. The hollow cathode dimensions have been optimized for the applied gap voltage varying between 15 and 25 kV, while the beam aspect ratio has been analyzed for the range between 5:1 and 12:1 keeping the fill factor constant.

Purpose Crack sensor based on RFID tag has become a research hotspot in the field of metal structural health monitoring for its significant benefit of passive wireless transmission. While in practice, crack location will impact the performance of crack depth-sensing tag. The purpose of this paper is to provide a method for reducing disturbance of crack location on crack depth-sensing tag. Design/methodology/approach The effect analysis of crack location on crack depth-sensing tag is presented first to find disturbance reason and disturbance law. On the basis of that, a miniaturized tag is proposed to improve the current distribution and reduce the disturbance introduced by crack location. Findings The degree of crack location disturbance is closely related to the current distribution in the coverage area of tag. Because sensing tag performs better when crack locates in the high current density area, miniaturization of sensing tag is exploited to expand the high current density area and make the area more symmetrical. The simulated and experimental results demonstrate that tag miniaturization can enhance the performance of crack depth-sensing tag. Originality/value This paper provides a method to enhance the performance of crack depth-sensing tag.

Mechanisms and characteristics of optimized main junction for 4H-SiC trench junction barrier Schottky (TMJBS) diodes were investigated by theories and experiments. From these simulation and experimental values, we can conclude that TMJBS device has better reverse performance, such as the best reverse blocking capability and lowest reverse surface leakage current than the conventional JBS and TJBS device while maintaining good forward characteristics. Furthermore, The large area TMJBS Diodes with high current density show the better reverse characteristics than the small area one at an acceptable forward characteristics. The TMJBS structure can significantly reduce the influence of the Schottky interface and is more suitable for manufacturing high current density and large area devices.

We developed a silicon carbide (SiC) power module that can switch large currents at high speed. The withstand voltage of this power module is 1200 V, and two SiC MOSFETs are built-in and constitute a circuit for one inverter phase. This power module incorporates a snubber circuit for reducing the surge voltage generated by the SiC MOSFET for high-speed switching. In this study, switching at 270 A (a current density of 1000 A/cm 2 or more for the SiC MOSFET) was performed to evaluate this module. The turn-off switching time tf was ~10 ns, and the maximum dv/dt was 80 kV/us. Furthermore, this research examines the design and performance of the proposed power module.

There are increasing interests in fabricating Fe2O3 anode materials in recent years owing to their high theoretical capacity and natural abundance. However, Fe2O3 anode materials encounter great challenges in association with their intrinsic poor electronic conductivity and drastic volume variation during cycling. Herein, rod-like Fe2O3 is prepared through a simple thermal decomposition method. When evaluated as anode material for LIBs, the rod-like Fe2O3 exhibits excellent rate capability (∼400 mAh g−1 capacity even at high current density of 7 A g−1). Furthermore, high reversible capacity of ∼500 mAh g−1 can be retained at 3 A g−1 after 1000 cycles. This work demonstrates that the thermal decomposition method is facile and efficient for the preparation of high-performance Fe2O3 anode materials for LIBs.

High-power proton exchange membrane (PEM) fuel cell vehicles are important for the realization of carbon neutrality in transportation. However, it is difficult to maintain enough fuel supply and quick water removal capacity at a high current density where reactant gas transportation and water concentration are directly affected by flow channel configurations. This study aims to investigate the tapered slope effects of a flow channel on fuel cell performance using a 3-D CFD model. The positive, negative, zero and hybrid tapered slopes are proposed to illustrate the fuel cell voltage, reactant gas and water vapor concentration in the flow channels. Among them, the flow channel with a positive tapered slope performs better, especially at a high current density. Then, the positive tapered slope effects are discussed, including different tapered slopes, inlet depths and widths of flow channels. The results show that the larger the tapered slope, the smaller the depth and width, and the better the fuel cell performs; the corresponding current densities are increased by a maximum of 6.53%, 12.72% and 61.13%. The outcomes stated above provide a key direction for flow channel design that can particularly achieve higher fuel cell power density at high current densities.

Carbon corrosion in catalysts is one of the main limitations of proton exchange membrane fuel cell (PEMFC) lifetime. Water flooding can accelerate the carbon corrosion rate in PEMFCs, especially at high current densities. Increasing the operation temperature can effectively mitigate water flooding and improve the water management performance of PEMFCs. However, elevated temperatures also increase the carbon corrosion reaction kinetics, accelerating the degradation of PEMFCs lifetime. To study the effects of temperature on carbon corrosion at high current densities, PEMFCs operating for 100 h at 65 °C and 90 °C under 1600 mA·cm−2 were investigated. The results showed that the electrochemical active surface area (ECSA) of the cathode catalyst layer decreased by 9.16% and 13.92% at 65 °C and 90 °C, respectively. The reduction rate of the catalyst layer in the nonflooding area increased as the operating temperature increased. However, the reduction rate decreased by 69.82% and 54.04% at 65 °C and 90 °C, respectively, at the outlet of the PEMFC. Therefore, water flooding is the key issue causing lifetime degradation, and water management is essential for PEMFCs that operate at high current densities, especially at the outlet of PEMFCs.

Ferroelectric tunnel junction (FTJ) with ultrathin 3 nm-thick Hf 0.5 Zr 0.5 O 2 (HZO) is investigated. The high current density up to 100 A/cm2 is at least 10 times higher than that in previously reported HZO FTJs. It is suitable for future nanoscale FTJ with a GΩ cell resistance for the application of in-memory computing. The insertion of a thin Al 2 O 3 interfacial layer is found critical to alter the switching polarity and increase current density.

Highlights N-doped graphene-coated structure and mesoporous nano-sheet can efficiently boost active sites and stability for hydrogen and oxygen evolution reaction.NiCo@C-NiCoMoO/NF exhibits low overpotentials for HER (266 mV) and OER (390 mV) at ± 1000 mA cm−2.For water electrolysis, it can hold at 1000 mA cm−2 for 43 h in 6.0 M KOH + 60 °C condition. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00607-5., Developing highly effective and stable non-noble metal-based bifunctional catalyst working at high current density is an urgent issue for water electrolysis (WE). Herein, we prepare the N-doped graphene-decorated NiCo alloy coupled with mesoporous NiCoMoO nano-sheet grown on 3D nickel foam (NiCo@C-NiCoMoO/NF) for water splitting. NiCo@C-NiCoMoO/NF exhibits outstanding activity with low overpotentials for hydrogen and oxygen evolution reaction (HER: 39/266 mV; OER: 260/390 mV) at ± 10 and ± 1000 mA cm−2. More importantly, in 6.0 M KOH solution at 60 °C for WE, it only requires 1.90 V to reach 1000 mA cm−2 and shows excellent stability for 43 h, exhibiting the potential for actual application. The good performance can be assigned to N-doped graphene-decorated NiCo alloy and mesoporous NiCoMoO nano-sheet, which not only increase the intrinsic activity and expose abundant catalytic activity sites, but also enhance its chemical and mechanical stability. This work thus could provide a promising material for industrial hydrogen production. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00607-5.

Commercialization of lithium-oxygen batteries faces many challenges, such as electrolyte decomposition, short cycle life, low energy and power density, and high cell mass. However, the commercialization of LiO2 batteries for aeronautics is more challenging due to additional safety constraints on cyclability and performance (high specific-power and specific-energy). In this paper, we perform experiments and use the results to calibrate a 1-D finite element model to simulate discharge profiles up to 5 mA cm-2. The calibrated model is used to perform parametric studies of geometrical, microstructural, transport, and material properties for different discharge times, and discharge current densities. Next, a simulation-based optimization study shows optimal cell designs for various electrolytes for high specific-power. Results show that a high specific-power LiO2 cell needs to have a cathode with a thickness equal to oxygen diffusion length, thin separator, optimized anode, and other components with low mass. The specific-power is sensitive to discharge time, discharge current density, and microstructural and geometrical properties. Also, in some cases, electrolytes with high oxygen solubility or high external partial pressure can compensate for electrolytes with low oxygen diffusivity. However, reducing the cell mass is the most straight forward path to improving specific-power.

Commercialization of lithium-oxygen batteries faces many challenges, such as electrolyte decomposition, short cycle life, low energy and power density, and high cell mass. However, the commercialization of LiO2 batteries for aeronautics is more challenging due to additional safety constraints on cyclability and performance (high specific-power and specific-energy). In this paper, we perform experiments and use the results to calibrate a 1-D finite element model to simulate discharge profiles up to 5 mA cm-2. The calibrated model is used to perform parametric studies of geometrical, microstructural, transport, and material properties for different discharge times, and discharge current densities. Next, a simulation-based optimization study shows optimal cell designs for various electrolytes for high specific-power. Results show that a high specific-power LiO2 cell needs to have a cathode with a thickness equal to oxygen diffusion length, thin separator, optimized anode, and other components with low mass. The specific-power is sensitive to discharge time, discharge current density, and microstructural and geometrical properties. Also, in some cases, electrolytes with high oxygen solubility or high external partial pressure can compensate for electrolytes with low oxygen diffusivity. However, reducing the cell mass is the most straight forward path to improving specific-power.

Purpose: Neuromuscular electrical stimulation (NMES) recruits motor units (MUs) at unphysiologically high rates, leading to contraction fatigability. Rotating NMES pulses between multiple electrodes recruits different MUs from each site, reducing MU firing rates and fatigability. This study aimed to determine whether rotating pulses between an increasing number of stimulation channels (cathodes) reduces contraction fatigability and increases the ability to generate torque during NMES. A secondary outcome was perceived discomfort. Methods: Fifteen neurologically-intact volunteers completed 4 sessions. NMES was delivered over the quadriceps through 1 (NMES1), 2 (NMES2), 4 (NMES4) or 8 (NMES8) channels. Fatigability was assessed over 100 contractions (1s on/1s off) at an initial contraction amplitude that was 20% of a maximal voluntary contraction (MVC). Torque-frequency relationships were characterized over 6 frequencies from 20-120Hz. Results: NMES4 and NMES8 resulted in less decline in torque (42% and 41%) and generated more torque over the 100 contractions than NMES1 and NMES2 (53% and 50% decline in torque). Increasing frequency from 20-120Hz increased torque by 7, 13, 21 and 24% MVC, for NMES1, NMES2, NMES4 and NMES8, respectively. Perceived discomfort was highest during NMES8 . Conclusion: NMES4 and NMES8 reduced contraction fatigability and generated larger contractions across a range of frequencies than NMES1 and NMES2 . NMES8 produced the most discomfort, likely due to small electrodes and high current density. During NMES, more is not better and rotating pulses between 4-channels may be optimal to reduce contraction fatigability and produce larger contractions with minimal discomfort compared to conventional NMES configurations.