Peak Specific Power Research Articles

Ru‐MnO Heterostructure Clusters Toward Efficient and CO‐Tolerant Alkaline Hydrogen Oxidation Reaction

AbstractDesigning efficient and CO‐tolerant catalysts for hydrogen oxidation reaction (HOR) in anode is one of the challenges for alkaline exchange membrane fuel cells in practical application. Herein, Ru‐MnO heterostructure with two adjacent clusters supported on commercial carbon (BP 2000) (denoted as Ru‐MnO/C) is designed to accelerate the sluggish kinetics of alkaline HOR. The cluster–cluster heterostructure interface modifies the electronic structure of Ru sites with electron transfer from Ru to MnO, then optimizes the adsorption of intermediates on Ru sites. Consequently, this catalyst exhibits high catalytic HOR activities in alkaline media with high exchange current density (3.71 mA cm−2) and mass activity (0.78 A mgRu−1). Meanwhile, the alkaline exchange membrane fuel cell delivers a specific peak power density (PPD) of 7.0 W mg−1Ru under H2/O2 condition, which is higher than that of most reported catalysts. More importantly, the catalyst also demonstrates the remarkable stability and CO‐tolerance. This work presents the superiority of cluster–cluster heterostructure interface toward efficient HOR, which is expected to further enlighten the design of advanced catalysts for electrocatalysis.

One-dimensional lepidocrocite titania mesoparticles integrated with activated carbon for high-performance supercapacitor applications

Herein, we mix titania-based, TiO2, porous mesostructured, comprised of one-dimensional lepidocrocite nanofilaments, 1DLs, ≈ 5 × 7 Å2 in cross-section, with activated carbon, AC, to create unique composite structures with exceptional electrochemical properties. The synthesis method is facile, cost-effective, and scalable. While the porous mesoparticles, PMs, possess excellent protonic conductivity and exhibit enhanced faradic behavior in acidic aqueous media, their low electronic conductivity restricts their power output. The problem is solved by mixing the PMs with AC powders with various loadings. Electrolytes used were sulfuric acid, H2SO4, potassium hydroxide, KOH, lithium and Na-sulphates. The best PM loading was found to be 25 wt%. The resulting composite exhibits a specific capacitance (capacity) of 1024 Fg−1 (554 mAhg−1) at a 2 mVs−1 scan rate, with 97 % cyclic stability over 10,000 cycles when the electrolyte was 1 M H2SO4. Upon integration into a symmetrical device, the composite exhibited a specific energy of 135 Whkg−1 at 0.5 Ag−1. Further, it demonstrated a peak specific power of 18 kWkg−1, while retaining a specific energy of 54 Whkg−1 at 5 Ag−1. Notably, following 100,000 cycles at 1 Ag−1, the symmetrical cell sustained approximately 50 % of its initial specific capacitance. Subsequently, a 24 h self-discharge test revealed a decrease in cell voltage from 1.95 V to 0.48 V, thereby highlighting the potential suitability of these supercapacitors for short-term energy storage applications.

Hexagonal electrohydraulic modules for rapidly reconfigurable high-speed robots.

Robots made from reconfigurable modular units feature versatility, cost efficiency, and improved sustainability compared with fixed designs. Reconfigurable modules driven by soft actuators provide adaptable actuation, safe interaction, and wide design freedom, but existing soft modules would benefit from high-speed and high-strain actuation, as well as driving methods well-suited to untethered operation. Here, we introduce a class of electrically actuated robotic modules that provide high-speed (a peak contractile strain rate of 4618% per second, 15.8-hertz bandwidth, and a peak specific power of 122 watts per kilogram), high-strain (49% contraction) actuation and that use magnets for reversible mechanical and electrical connections between neighboring modules, thereby serving as building blocks for rapidly reconfigurable and highly agile robotic systems. The actuation performance of each hexagonal electrohydraulic (HEXEL) module is enabled by a synergistic combination of soft and rigid components; a hexagonal exoskeleton of rigid plates amplifies the motion produced by soft electrohydraulic actuators and provides a mechanical structure and connection platform for reconfigurable robots composed of many modules. We characterize the actuation performance of individual HEXEL modules, present a model that captures their quasi-static force-stroke behavior, and demonstrate both a high-jumping and a fast pipe-crawling robot. Using embedded magnetic connections, we arranged multiple modules into reconfigurable robots with diverse functionality, including a high-stroke muscle, a multimodal active array, a table-top active platform, and a fast-rolling robot. We further leveraged the magnetic connections for hosting untethered, snap-on driving electronics, together highlighting the promise of HEXEL modules for creating rapidly reconfigurable high-speed robots.

Synthesis and Electrochemical Characterization of ZnMoS4 Nanorods on Nickel Foam Substrate for Advanced Hybrid Supercapacitor Applications.

A single-step hydrothermal method was utilized to grow ZnMoS4 (ZMS) nanorods uniformly. Initially, [MoS4]2- and Zn2+ ions interacted to create active nucleation centers, which then led to the formation of primary particles. These particles then underwent spontaneous aggregation and self-assembly on the nickel foam (NF) substrate, which served as a superior 3D interconnecting network template. This aggregation occurred nearly perpendicular to the NF and promoted the uniform growth of ZMS nanorods. The nanorods structure ensures efficient and rapid electrolyte accessibility and ion diffusion, resulting in an increased specific capacitance (Cs) of 2,116 Fg1- (846.4 C g-1) at 1 A g-1 and maintaining about 90% of their capacitance after 10,000 cycles of galvanic charge-discharge (GCD). In a hybrid supercapacitor configuration, ZMS@NF//AC@NF achieved a peak specific power of 7.2 kW.kg-1 and a specific energy of 40.3 Wh.kg-1. Remarkably, it preserved 93% of its initial capacitance after more than 20,000 cycles. These findings affirm the potential of binder-free ZMS nanorods as effective positive electrodes in advanced hybrid supercapacitors.

Controllable multi-soliton spectral tunneling by airy pulses in photonic crystal fiber

A straightforward method to induce tunable multi-soliton spectral tunneling (SST) using a finite energy Airy pulse in a photonic crystal fiber (PCF) featuring three zero-dispersion wavelengths is proposed numerically in the paper. The study reveals that the distinctive multi-envelope structure of the Airy pulse enables the control of tunneling distances, properties, and soliton numbers through modulation of its attenuation factor and peak intensity. Notably, the SST process involving the Airy pulse generates multiple blue-shifted and red-shifted dispersion waves, along with associated trapping waves, contributing to the formation of an ultra-flat and ultra-wide supercontinuum. Furthermore, the velocity and efficiency of multi-SST can be manipulated to enhance the overall tunability of the phenomenon. The findings underscore the potential application of Airy pulse-driven SST in secure multi-frequency signal transmission and controlled supercontinuum generation, with the tunability of these processes being governed by the specific attenuation factor and peak power settings of the input Airy pulse. This work advances the understanding of multi-SST dynamics in PCFs and provides a theoretical framework for exploiting these dynamics in practical information security and optical spectrum management contexts.

Strategic Model for Yellow Hydrogen Production Using the Metalog Family of Probability Distributions

Storing energy in hydrogen has been recognized by scientists as one of the most effective ways of storing energy for many reasons. The first of these reasons is the availability of technology for producing hydrogen from water using electrolytic methods. Another aspect is the availability of relatively cheap energy from renewable energy sources. Moreover, you can count on the availability of large amounts of this energy. The aim of this article is to support the decision-making processes related to the production of yellow hydrogen using a strategic model which exploits the metalog family of probability distributions. This model allows us to calculate, with accuracy regarding the probability distribution, the amount of energy produced by photovoltaic systems with a specific peak power. Using the model in question, it is possible to calculate the expected amount of electricity produced daily from the photovoltaic system and the corresponding amount of yellow hydrogen produced. Such a strategic model may be appropriate for renewable energy developers who build photovoltaic systems intended specifically for the production of yellow and green hydrogen. Based on our model, they can estimate the size of the photovoltaic system needed to produce the assumed hydrogen volume. The strategic model can also be adopted by producers of green and yellow hydrogen. Due to precise calculations, up to the probability distribution, the model allows us to calculate the probability of providing the required energy from a specific part of the energy mix.

Impact of Reduced Activity on Endurance of Rat Diaphragm Muscle

The diaphragm muscle (DIAm) as the major inspiratory pump is highly active. During breathing, fatigue resistant DIAm motor units are recruited that comprise type I and IIa fibers. Accordingly, these fibers have substantially higher mitochondrial volume density (MVD) and mitochondrial respiratory capacity (SDHmax) compared to more fatigable type IIx/IIb fibers. Cervical spinal cord injury disrupts descending inspiratory drive and markedly reduces eupneic activity of the DIAm. With C2 spinal cord hemisection (C2SH) DIAm activity on the ipsilateral side is reduced. Following a two-week period of C2SH, we found reduced MVD and SDHmax in type I and IIa DIAm fibers. As a result, we hypothesize that endurance of the DIAm is reduced. Female and male Sprague Dawley rats were used. EMG electrodes were placed in the left and right DIAm 3 days prior to C2SH surgery, and baseline recordings of eupneic DIAm activity were obtained in awake animals. The right C2 spinal cord was hemisected, and the extent of injury was confirmed by the absence of eupneic DIAm activity on the ipsilateral side while animals were anesthetized. Subsequently, DIAm EMG activity was recorded at 3, 7 and 14 days post C2SH. After two weeks, rats were anesthetized and the DIAm was excised. DIAm strips were cut and suspended in a tissue chamber containing Rees-Simpson solution maintained at 26oC, with thecostal margin clamped and the central tendon attached to a Cambridge Dual-Mode force/length transducer. DIAm strips were stimulated using platinum plate electrodes with supramaximal current (~250 mA) pulses (1 ms), and maximum specific force was determined at 75 Hz. The force-velocity relationship was then determined by systematically changing load, and maximum velocity (Vmax) was estimated based on curve fitting with the Hill-equation. Based on the force-velocity measurements peak power of the DIAm was calculated. Subsequently, the DIAm was repetitively stimulated and allowed to shorten at 30% maximum velocity (isovelocity approximating peak power output). Endurance of the DIAm was then determined as the duration that peak power output was sustained. Finally, the DIAm was rapidly frozen, and cross-sections were cut for fiber type and cross-sectional area (CSA) measurements. C2SH resulted in a marked decrease in eupneic DIAm EMG activity across the two-week period, which disproportionately affected type I and IIa DIAm fibers. However, there was no impact of C2SH on DIAm fiber type proportions or CSA. Following two-weeks C2SH, maximum specific force, Vmax, and peak power output of the DIAm were comparable between intact and injured sides. However, endurance of the DIAm was reduced on the injured side compared to the intact side. These results support our hypothesis that reduced activity of DIAm, reduces oxidative capacity of type I and IIa fibers and thereby reduces endurance. In clinical conditions such as mechanical ventilation DIAm activity is reduced and if maintained for longer periods of time this may affect DIAm endurance post weaning. Research supported by NIH grant: HL146114 (GCS). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Multi-Objective Optimization Method for Single Intersection Signals Considering Low Emissions

The exponential growth of urban centers has exacerbated the prevalence of traffic-related issues. This surge has amplified the conflict between the escalating need for travel among individuals and the constricted availability of road infrastructure. Consequently, the escalation of traffic accidents and the exacerbation of environmental pollution have emerged as increasingly pressing concerns. Urban road intersections, serving as pivotal junctures for vehicle convergence and dispersal, have remained a focal point for scholarly inquiry regarding enhanced operational efficacy and safety. Concurrently, vehicles navigating intersections are subject to external influences, such as pedestrian crossings and signal controls, causing frequent fluctuations in their operational dynamics. These fluctuations contribute to heightened exhaust emissions, exacerbating air pollution and posing health risks to pedestrians frequenting these intersections. A reasonable signal timing scheme can enable more vehicles to pass through the intersection safely and smoothly and reduce the pollutants generated by transportation. Therefore, optimizing signal timing schemes at intersections to alleviate traffic problems is a topic that needs to be studied urgently. In this paper, the emission model based on specific power is analyzed. Through an analysis of the correlation between specific power distribution intervals and the emission rates of individual pollutants, it has been observed that vehicle emission rates are at their lowest during idle speed, progressively increasing with rising vehicle speeds. Investigation into specific power distribution based on variables, such as vehicle type, frequency of stops, and varying delays, has led to the deduction that the peak specific power of vehicles at intersections consistently occurs within the (0, 1) interval. Furthermore, it has been established that high-saturation intersections exhibit higher peak specific power compared to low-saturation intersections.

A facile synthesis of iron single-atom electrocatalyst for high-performing oxygen reduction reaction and remarkable rechargeable zinc-air battery

Iron-based single-atom catalysts (SACs) are considered to the most promising catalysts to replace Pt for efficient oxygen reduction reaction (ORR). However, the precise synthesis of high-performance SACs and the understanding of their ORR origin remain challenging. In this work, microporous nitrogen-doped carbon with abundant and accessible atomically dispersed N-coordinated Fe sites (Fe-N-C) is prepared by molecular-confined coupling pyrolysis strategy. The Fe-N-C exhibits excellent ORR activities in acid (E1/2 of 0.78 V vs. RHE) and alkaline (E1/2 of 0.91 V vs. RHE) electrolytes. When integrated into a rechargeable aqueous Zinc-air battery (ZAB), both large specific capacity (770 mAh g−1) and high peak power density (240 mW cm−2) are achieved. Remarkably, the as-prepared ZAB presents amazing charge-discharge cycle performance of 1600 h at the large current density, which is 52.5 times of that using Pt/C+RuO2. Furthermore, all-solid-state ZAB delivers ultra-robust cycling stability even under bending. This work may advance a critical step towards the design of rational and controlled preparation of remarkable and ultra-stable catalysts.

Low Pt loading for high-performance fuel cell electrodes enabled by hydrogen-bonding microporous polymer binders.

A key challenge for fuel cells based on phosphoric acid doped polybenzimidazole membranes is the high Pt loading, which is required due to the low electrode performance owing to the poor mass transport and severe Pt poisoning via acid absorption on the Pt surface. Herein, these issues are well addressed by design and synthesis of effective catalyst binders based on polymers of intrinsic microporosity (PIMs) with strong hydrogen-bonding functionalities which improve phosphoric acid binding energy, and thus preferably uphold phosphoric acid in the vicinity of Pt catalyst particles to mitigate the adsorption of phosphoric acid on the Pt surface. With combination of the highly mass transport microporosity, strong hydrogen-bonds and high phosphoric acid binding energy, the tetrazole functionalized PIM binder enables an H2-O2 cell to reach a high Pt-mass specific peak power density of 3.8 W mgPt-1 at 160 °C with a low Pt loading of only 0.15 mgPt cm-2.

Post-synthetic electrostatic adsorption-assisted fabrication of efficient single-atom Fe-N-C oxygen reduction catalysts for Zn-air batteries

Highly efficient platinum-group metal (PGM)-free electrocatalysts are essential for the large-scale utilization of Zn-air batteries (ZABs). Herein, we report the simple fabrication of a single atomic PGM-free electrocatalyst, Fe-SA/N-C, via a post-synthetic electrostatic absorption (PSEA) strategy. The single Fe atoms are anchored on the three-dimensiaonal (3D) porous carbon with adjacent N atoms, forming atomic Fe-N4 active sites. Fe-SA/N-C exhibits excellent ORR activity in 0.1 mol L−1 KOH aqueous solution (E1/2 = 0.92 V) and 0.5 mol L−1 H2SO4 aqueous solution (E1/2 = 0.77 V), superior to those of commercial Pt/C (0.85 and 0.79 V, respectively). As a proof of concept, homemade liquid ZAB with Fe-SA/N-C catalyst displays outstanding discharging specific capacity and peak power density, outperforming the commercial Pt/C. According to the density functional theory calculation, the Fe-N4 sites with graphitic N dopant can improve the activation of intermediates and decrease the energy barrier of the rate-determining step. This work highlights new insights for the experimental and theoretical guidance of PGM-free electrocatalysts and prescribes a general strategy for the rational design of PGM-free electrocatalysts used in ZABs.

3D-Structured Au(NiMo)/Ti Catalysts for the Electrooxidation of Glucose

In this study, 3D-structured NiMo coatings have been constructed via the widely used electrodeposition method on a Ti surface and decorated with very small Au crystallites by galvanic displacement (Au(NiMo)/Ti). The catalysts have been characterized using scanning electron microscopy, energy dispersive X-ray analysis, and inductively coupled plasma optical emission spectroscopy. Different Au(NiMo)/Ti catalysts, which had Au loadings of 1.8, 2.3, and 3.9 µgAu cm−2, were prepared. The electrocatalytic activity of the Au(NiMo)/Ti catalysts was examined with respect to the oxidation of glucose in alkaline media by cyclic voltammetry. It was found that the Au(NiMo)/Ti catalysts with Au loadings in the range of 1.8 up to 3.9 µgAu cm−2 had a higher activity compared to that of NiMo/Ti. A direct glucose-hydrogen peroxide (C6H12O6-H2O2) single fuel cell was constructed with the different Au-loading-containing Au(NiMo)/Ti catalysts as the anode and Pt as the cathode. The fuel cells exhibited an open circuit voltage of ca. 1.0 V and peak power densities up to 8.75 mW cm−2 at 25 °C. The highest specific peak power densities of 2.24 mW µgAu−1 at 25 °C were attained using the Au(NiMo)/Ti catalyst with the Au loading of 3.9 µg cm−2 as the anode.

(Digital Presentation) Thermal Runaway Initiation, Propagation and the Potential for Propagation Inhibition in Commercial Automotive Lithium-Ion Cells and Modules

Lithium-ion batteries, containing flammable electrolytes, have become safer in many ways since their invention. As the technology matures, energy and power densities increase: the European Council for Automotive R&D set 2030 (cell level) targets for battery electric vehicle energy density of 1000 Wh L-1, with 450 Wh kg-1 specific energy and 1800 W kg-1 peak specific power. This rise in energy and power densities increases the risk of accidental release of energy from the batteries and thermal runaway (TR). Safety is thus a key concern when designing a lithium-ion battery system for electric vehicles (EV).TR relates to fast heating of a battery cell caused by exothermic chemical decomposition reactions of the materials inside the cells. It develops in a cell when heat is generated and cannot be dissipated quickly enough to the surroundings, giving rise to an abrupt (exponential) temperature increase and subsequent reaction rate increase. During TR, various exothermic side reactions can occur, leading to temperature increase, accompanied by pressure increase as electrolyte evaporates and venting. This can result in the emission of highly flammable gas and the formation of toxic atmosphere, as well as, in fire and, in very rare circumstances, in explosion. The corresponding temperature increase in adjacent cells (or modules) might then be sufficient to cause them to also go into TR – leading to a process known as thermal runaway propagation (TRP).Fit-for purpose testing procedures to assess the risks associated with TRP are therefore of utmost importance and the focus should always be the safety of the EV occupants, bystanders, first responders and property. Some tests in current standards and regulations try to simulate internally driven failures (e.g. internal short circuit), but whether these tests are suitable to represent field failures remains an open question.This work will give an insight into two selected TR initiation methods assessed within JRC’s TR initiation and propagation test campaigns, namely (a) localised rapid external heating, as developed and patented internationally by NRC (National Research Council Canada) and (b) ceramic nail penetration, as described in the IEC TR 62660-4 standard. It examines the response of short-stacks of pouch cells extracted from automotive batteries after TR is triggered in a single cell. Experimental data and analysis to better understand how TR propagates and the potential for TRP inhibition will be reported. The potential of inhibiting TRP is explored on 2- and 5-cell assemblies with a multi-layer, porous, composite insulation material between cells. Separating the cells can delay significantly TRP in adjacent cells in modules constructed with pouch cells, whereas TRP may be slowed and even inhibited as the thickness of the multilayer material varies.

Amplification of laser radiation at the edge of the KrF (B–X) spectral line

We report the results of experimental and numerical studies of the KrF electric discharge amplifier operating on a mixture of He – Kr – F2 gases. The possibility of expanding the short-wavelength spectral region of the induced radiation tuning at the B – X transition of the KrF molecule by removing the inverse population from the upper vibrational states of the electronic B level is shown. It is demonstrated that at the boundary of the active medium gain contour, the measured gain at a wavelength of 246.8 nm is 0.053 cm−1. Using the developed 1D model of the KrF electric discharge amplifier, it is shown that when the active medium is excited by a pump pulse with a specific peak power of ∼10 MW cm−3, the gain in this spectral region is due to a longer relaxation time of the population of excimer molecules from the upper vibrational levels compared with the characteristic time of their production.

Regeneration of spent cathodes of Li-ion batteries into multifunctional electrodes for overall water splitting and rechargeable Zn-air batteries by ultrafast carbothermal shock

Lithium-ion batteries (LIBs) are widely used in electric vehicles and consumer electronics and require reliable recycling strategies. In this paper, we investigated how an ultrafast carbothermal shock treatment can be used to convert spent cathodes of LIBs (LiNi0.8Mn0.1Co0.1O2) into Ni/Ni-Mn-Co-O (N/NMCO) composites with a remarkable electrocatalytic performance toward oxygen evolution, oxygen reduction, and hydrogen evolution reactions. The converted spent cathodes can be employed as cathodes and anodes in an overall water-splitting system, and they displayed a low overpotential of 1.61 V and remarkable stability at different current densities. Moreover, N/NMCO electrodes can be used as cathodes in rechargeable Zn-air batteries, which displayed long-term stability (>30 h), high specific capacity (781 mA h g−1) and peak power density (137 mW cm−2), as well as a small charge/discharge voltage gap of 0.71 V. Thus, our study offers a “waste-to-treasure” strategy for the regeneration of spent cathodes of LIBs and their applications in other advanced energy storage and conversion technologies.

Comparisons of Spray Characteristics between Non-circular and Circular Nozzles with Rotating Sprinklers

HighlightsExperiments were conducted to investigate the hydraulic performance of the solid-set rotating sprinkler.The effects of nozzle shape and working pressure on the droplet characteristics and kinetic energy of the rotating sprinkler were analyzed.The circular nozzle has a large wetting radius and large droplet size.Use of a non-circular nozzle could result in higher irrigation uniformity and lower kinetic energy imparted to the soil surface by water droplets under low working pressures.Abstract. Reducing the working pressure of sprinklers can effectively reduce sprinkler irrigation energy requirements. However, the reduction in working pressure and variation of nozzle shape inevitably lead to changes in the hydraulic performance of the sprinkler. To evaluate the spray characteristics of selected non-circular (the shape of the nozzle opening was asymmetric) and circular nozzles at low pressure, experiments were conducted to investigate the effects of working pressure, nozzle shape, and nozzle diameter on flow rate, radius of throw, water application rate, droplet size, droplet velocity of the rotating sprinkler, and kinetic energy of the water droplets impacting on the soil surface. The coefficients of irrigation uniformity were calculated for the non-circular and circular nozzles under different rectangular sprinkler spacing and working pressures. The results show that the flow rates of the non-circular and circular nozzles were equal under the same working pressure and with the same nozzle size, while the throw radius of the circular nozzle was longer than that of the non-circular nozzle. The circular nozzle produced a larger droplet size than the non-circular nozzle did. Since the droplet size and kinetic energy per unit droplet volume increased along the radius of throw, and the peak water application rate of the circular nozzle was located near the perimeter of the radius of throw, the peak specific power impact on the soil surface by the water droplets of the circular nozzle was greaterspecifically, 1.26 to 1.97 times that of the non-circular nozzle. With the increase in working pressure, the peak values of specific power and water application rate decreased. The irrigation uniformity coefficients of the non-circular and circular nozzles were more than 85% within the recommended pressure range of the manufacturer when the sprinkler spacing was less than 11 m. It was easier to obtain higher irrigation uniformity and lower impact kinetic energy under low working pressure when using a non-circular nozzle. Keywords: Application rate, Irrigation uniformity, Kinetic energy, Sprinkler irrigation, Working condition.

MnOx anchored on N and O co-doped carbon nanotubes encapsulated with FeCo alloy as highly efficient bifunctional electrocatalyst for rechargeable Zinc–Air batteries

Currently, development of OER/ORR bifunctional electric catalysts with low cost, high catalytic activity and stability is the key step to promote the practical application of zinc-air batteries. Herein, composite catalyst with manganese oxide on N and O co-doped carbon nanotubes encapsulated with FeCo alloy ([email protected]/MnO) was prepared in situ on CFP by hydrothermal and CVD pyrolysis methods. Owing to rich CO functional group on in situ growing carbon nanotubes with 3D open structure, alloying effect of CoFe core metal embedded in carbon nanotube and the contribution of MnO supported on carbon nanotubes to ORR performance and stability, the [email protected]/MnO catalyst exhibits low overpotential of 193 mV at the current density of 10 mA/cm2 for OER, larger diffusion-limited current density of 5.75 mA/cm2 and half-wave potential (E1/2 = 0.85 V) for ORR, high specific capacity (810 mAh/gZn) and peak power density (164 mW/cm2) with the Zn-air battery and superior stability. Moreover, the peak power density of the single [email protected]/MnO-based quasi-solid state ZAB could reach 142 mW/cm2, and two quasi-solid state ZABs connected in series can power a mini fan.

Raw and pyrolyzed (with and without melamine) graphene nanoplatelets with different surface areas as PEM fuel cell catalyst supports

Platinum (Pt) catalysts dispersed on carbon-based support materials are generally used in the polymer electrolyte membrane (PEM) fuel cells. In this study, commercial graphene nanoplatelets (GNPs), with different surface areas (320, 530, 800 m2 g−1), were used as catalyst supports in PEM fuel cells. These GNPs were also pyrolyzed under the inert atmosphere, with and without melamine, as the nitrogen (N) source. Various characterizations (Elemental analysis, FTIR, Raman spectroscopy, BET, TEM, HRTEM, SAED, XRD, TGA, ICP-MS, contact angle measurement, CV, ORR, chronoamperometry, EIS, PEM fuel cell performance test) were performed for the detailed analysis of Pt/GNPs. Based on the three-electrode cell system, the lowest electrochemical surface area (ECSA) loss (29.9%), Pt mass activity loss (20.3%) and overall (charge and mass) resistance (42.2 Ω) were obtained with the Pt/M-530 catalyst. According to the in-situ PEM fuel cell performance results, the specific peak power density was recorded as (450 mW mg Pt−1) for the Pt/R-530 catalyst, which has also the second most hydrophobic catalyst layer surface with the 146.5° ± 1.28° contact angle value. On the heels of Pt/R-530, the two best performances also belong to the Pt/M-530 (391 mW mg Pt−1) and Pt/P-530 (378 mW mg Pt−1) catalysts of the same group.

Rechargeable Zn-Air Batteries with Outstanding Cycling Stability Enabled by Ultrafine FeNi Nanoparticles-Encapsulated N-Doped Carbon Nanosheets as a Bifunctional Electrocatalyst.

Despite grand advances in Zn-air batteries in recently years, their commercialization remains challenging due largely to the lack of efficient bifunctional oxygen catalysts. Herein, we report the crafting of a bifunctional electrocatalyst comprising ultrafine alloyed FeNi nanoparticles encapsulated within N-doped layered carbon nanosheets (denoted FeNi/N-LCN) for high-efficiency Zn-air batteries. The FeNi/N-LCN electrocatalyst is yielded via the coordination of triphenylimidazole-containing polyaniline (TPANI) oligomer with Fe- and Ni-containing precursors, followed by hydrogen binding with melamine and subsequent pyrolysis. The as-constructed FeNi/N-LCN manifests outstanding activity and stability toward both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The primary Zn-air battery assembled with FeNi/N-LCN delivers both high specific capacity and peak power density. Remarkably, the rechargeable Zn-air battery can be repeatedly charged and discharged for 1100 h at 5 mA cm-2 and for 600 h at 10 mA cm-2, representing the highest cycling stability among various reported Zn-air batteries.

Reliability of bilateral and shear components in a two-legged counter-movement jump

Strength asymmetry can be detrimental to athlete performance and may lead to injury. The countermovement jump (CMJ) can be used to measure strength asymmetry via shear force production. The reliability of parameters and effects of asymmetry and shear force production on vertical CMJ performance were evaluated in a study with 15 university-level sprint and high jump athletes ( m = 11, f = 4). The athletes performed three CMJs on two occasions, separated by 1 week. Tri-axial ground reaction force (GRF) was recorded using two force platforms embedded within a bespoke weight training area. Key performance metrics were calculated in real-time describing total CMJ performance, asymmetry and shear force production. Changes in the means and coefficients of variation (CV) were used to express reliability. Twenty-six parameters from the Total analysis and 21 Asymmetry analysis parameters showed a CV lower than 10%. Temporal and kinetic variables describing Asymmetry analysis highlight a lower CV compared with equivalent parameters derived from Total analysis. Shear parameters show high levels of CV compared with Total analysis and Asymmetry analysis. The measures of asymmetry calculated using methods described in this work were shown to be reliable for monitoring CMJ performance. No significant negative relationships were found between measures of asymmetry or shear force and traditional performance metrics in the CMJ (e.g. jump height, specific peak power and peak force). Further work is required to identify the potential of reducing asymmetry on CMJ performance.