High Power Density Research Articles

Co/CoTe heterostructure internal hairy fibers as high-efficiency oxygen electrocatalyst for Zn-air batteries

The design of highly efficient catalysts to enhance the kinetics of oxygen reduction (OER) and oxygen evolution (ORR) reactions is the key issue for the development of high-performance Zn-air battery. In this work, we report the design of Co-CoTe heterostructured fibers as the bifunctional oxygen catalyst for Zn-air battery. Firstly, the theoretical analysis was carried out on Co-CoTe heterostructure. The large work function difference is favorable to construct strong interfacial built-in electric field (BIEF), and the low energy barrier endows high catalytic activities. Moreover, the in-situ grown carbon shell was designed to build “core–shell” Co-CoTe/C unit to realize its high performance. They assemble the Co-CoTe@HFS fiber with good self-supporting and flexible features. Taken the advantages of the strong BIEF, the “core–shell” basic unit, and the freestanding substrate, the Co-CoTe@HFS fiber achieves the good electrocatalytic properties and high reliability. The full Zn-air battery (ZAB) with the Co/CoTe@HFS air cathode achieves the high peak power density and cycling stability over long-term cycling. Therefore, this work provides a clue to design bifunctional oxygen catalysts for high-performance ZABs.

High-performance rechargeable zinc-air batteries enabled by cobalt iron anchored on nitrogen-doped carbon matrix as bifunctional electrocatalyst

Developing efficient bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) electrocatalysts is potential ways for achieving high rechargeable zinc-air (Zn-air) battery performance. Herein, we report an iron (II) acetate-assisted strategy to synthesize Co3Fe7-NC-OAc catalyst with cobalt iron (Co3Fe7) alloy anchored on nitrogen-doped carbon (NC) matrix, which can serve as efficient ORR/OER bifunctional electrocatalysts for rechargeable Zn-air batteries. Apart from alloying with Co to form ORR/OER active Co3Fe7 nanoparticles, the incorporation of iron (II) acetate has expanded the pore size inside the Co3Fe7-NC-OAc catalyst to serve as gas transfer channels, and has induced synergetic electronic coupling between Co3Fe7 nanoparticles and NC matrix for boosting catalytic activity. Therefore, Co3Fe7-NC-OAc exhibits favorable ORR activity with a most positive half-wave potential of 0.90 V vs. RHE, fast ORR kinetics with a highest kinetic current density of 57.4 mA cm−2 at 0.85 V vs. RHE, and fast O2 diffusion and transport that enables smaller mass transport overpotential at high current density up to 800 mA cm−2. Additionally, Co3Fe7-NC-OAc can catalyze OER with low overpotential of 310 mV at 10 mA cm−2. When employed as air electrode for Zn-air batteries, Co3Fe7-NC-OAc achieve high peak power densities of 193 mW cm−2 and 587 mW cm−2 in liquid and solid-state Zn-air batteries. The liquid battery also exhibits high specific capacity and remarkable cycling performance. This work opens up a new opportunity for developing highly efficient bifunctional electrocatalysts for Zn-air battery applications.

High-performance triboelectric nanogenerator with aminated barium titanate composite nanoparticles for early Parkinson’s disease diagnosis

High dielectric constant nanoparticles into polymer matrices have attracted much attention because this process can improve the nanofriction generator performance. However, the dispersion of the developed materials remains a challenge. In this paper, we present a novel high-performance nanofriction generator (FBT-TENG) based on composite nanoparticles of Amino-functionalized barium titanate and functionalized graphite oxide (FGO/ABTO) with Polyimide (PI) as substrate, which can be used as a sensor for intelligent monitoring systems. Specifically, we introduced amino groups on the surface of barium titanate to improve its dispersion in the PI solution, and the dual effect composite with functionalized graphite oxide improved the TENG performance of the PI film. Due to the FGO/ABTO synergy, the FBT-TENG can generate high output voltages, currents and power densities of 75 V, 13 µA and 4.6 W/m2, respectively, which is a 9 times increase in power density compared to the original PI film. FBT-TENG is capable of powering capacitors. In addition, the FBT-TENG can be used as a sensor to build an early Parkinson’s disease detection system, which provides a more convenient option for the early diagnosis of Parkinson’s patients and has the potential for a wide range of medical applications.

Development and Characterization of an Advanced Voltage-Controllable Capacitor Based on AlInGaN/GaN-Si (111) Epitaxy

The AlInGaN/GaN heterojunction epitaxy material with high cutoff frequency and saturated power density has become a very popular candidate for millimeter wave applications in next-generation mobile communication. In this study, an advanced voltage-controllable capacitor based on the AlInGaN/GaN-Si (111) epitaxy was proposed by employing a bi-directional series MIS capacitor structure. The capacitor was fabricated by using a pad area of 40 μm × 40 μm, with a 1 μm distance between the positive and negative electrodes. The test results show that the capacitance is turned on with a saturation capacitance density and a maximum leakage current density of 0.30 fF/μm2 of 0.37 pA/μm2, respectively, for the control voltage from −6.5 V to 6 V. In particular, in the proposed design method, the saturation capacitance required for the practical application can be obtained by simply adjusting the capacitance area. The capacitor showcases characteristics of rapid turn-on and turn-off responses coupled with low loss, underscoring its promising prospects for deployment in RF switching applications.

A novel phosphate detection sensor: From FTIR to EC-QCL

Excessive discharges of industrial and domestic sewage containing high concentrations of phosphorus are causing damage to the environment, so the detection of these pollutants in bodies of water is extremely critical. External cavity quantum cascade laser (EC-QCL) spectroscopy is a novel measurement technology that surpasses conventional infrared spectroscopy techniques. In this research, we propose a transmission detection system with a long optical path based on an EC-QCL for the detection of phosphate concentration in water bodies. Linear regression models were established based on this detection system, with all determination coefficients higher than 0.98 and a minimum detection limit smaller than 5.1 ppm. Additionally, the high-power spectral density of the EC-QCL permits the construction of a model using the raw radiation intensity data, as opposed to the conventional technique which depends on a reference background. The results show that the overall performance of the model based on the raw radiation intensity is similar to that of the model based on absorbance data. The EC-QCL detection system proposed in this study can ensure accuracy in the detection of pollutants, and the advantage of miniaturization provides a novel idea for the following development of portable phosphate in-situ sewage detection sensors.

Kinetic investigation of the energy storage process in graphene fiber supercapacitors: Unraveling mechanisms, fabrications, property manipulation, and wearable applications

AbstractGraphene fiber supercapacitors (GFSCs) have garnered significant attention due to their exceptional features, including high power density, rapid charge/discharge rates, prolonged cycling durability, and versatile weaving capabilities. Nevertheless, inherent challenges in graphene fibers (GFs), particularly the restricted ion‐accessible specific surface area (SSA) and sluggish ion transport kinetics, hinder the achievement of optimal capacitance and rate performance. Despite existing reviews on GFSCs, a notable gap exists in thoroughly exploring the kinetics governing the energy storage process in GFSCs. This review aims to address this gap by thoroughly analyzing the energy storage mechanism, fabrication methodologies, property manipulation, and wearable applications of GFSCs. Through theoretical analysis of the energy storage process, specific parameters in advanced GF fabrication methodologies are carefully summarized, which can be used to modulate nano/micro‐structures, thereby enhancing energy storage kinetics. In particular, enhanced ion storage is realized by creating more ion‐accessible SSA and introducing extra‐capacitive components, while accelerated ion transport is achieved by shortening the transport channel length and improving the accessibility of electrolyte ions. Building on the established structure–property relationship, several critical strategies for constructing optimal surface and structure profiles of GF electrodes are summarized. Capitalizing on the exceptional flexibility and wearability of GFSCs, the review further underscores their potential as foundational elements for constructing multifunctional e‐textiles using conventional textile technologies. In conclusion, this review provides insights into current challenges and suggests potential research directions for GFSCs.

Development of an efficient bifunctional electrocatalyst based on Co/CoSe2 nanoparticles embedded in N, Se co-doped carbon for AEMFC and rechargeable Zn-air battery

We suggest a hollow-structured N, Se dual-doped carbon framework embedded with Co/CoSe2 nanoparticles (Co/CoSe2@NSeC) as highly efficient bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The prepared electrocatalyst exhibits high electrochemical active surface area attributed to its unique hollow/porous structure and defective heteroatom doping sites. Furthermore, the strongly coupled heterojunction between Co and CoSe2 species not only provides abundant and highly active sites but also generates built-in electric field, thereby promoting electron transfer during the electrocatalytic reaction. Based on the above considerations, the prepared catalyst shows excellent bifunctional electrocatalytic performance. Leveraging the excellent ORR activity of Co/CoSe2@NSeC, alkaline exchange membrane fuel cells (AEMFC) with the Co/CoSe2@NSeC as air cathode exhibits high power density of 171.23 mW cm2. Furthermore, the rechargeable Zn-air battery employing the Co/CoSe2@NSeC shows high specific capacity (729.4 mAh gZn−1), peak power density (192.88 mW cm2), and sustained stability over 300 cycles.

MnO2‐Infused PAN Carbon Nanofibers Synthesized via Electrospinning for Enhanced Supercapacitor Performance

AbstractSupercapacitors (SCs) are crucial for high‐performance energy storage, offering high power density, swift charge–discharge rates, and durability. The enhancement of their performance hinges on the development of advanced electrode materials. This study presents an innovative method involving polyacrylonitrile (PAN) nanofibers adorned with manganese dioxide (MnO₂) nanoparticles (NPs), created through electrospinning and subsequent thermal treatment. This synergy exploits the extensive surface area and electrical conductivity of PAN nanofibers along with the substantial capacitance of MnO₂. The MnO₂‐coated PAN nanofibers reached an impressive specific capacitance of 247 F g−1 at a scan rate of 10 mVs−1, markedly boosting the efficacy of all‐solid‐state asymmetric SCs. The SCs, incorporating a polyvinyl alcohol (PVA)/potassium hydroxide (KOH) gel electrolyte, exhibited an energy density of 8.2 Wh kg−1 at a power density of 700 W kg−1, preserving 80.4% of their original capacitance after 5000 cycles. This research is pioneering in combining MnO₂ with PAN nanofibers, marking a significant leap forward in supercapacitor technology with enhanced energy storage capacity and prolonged stability. These findings underscore the promise of these composite materials in future energy storage solutions.

Sulfur doping and oxygen vacancy in In2O3 nanotube co-regulate intermediates of CO2 electroreduction for efficient HCOOH production and rechargeable Zn-CO2 battery

By manipulating the distribution of surface electrons, defect engineering enables effective control over the adsorption energy between adsorbates and active sites in the CO2 reduction reaction (CO2RR). Herein, we report a hollow indium oxide nanotube containing both oxygen vacancy and sulfur doping (Vo-Sx-In2O3) for improved CO2-to-HCOOH electroreduction and Zn-CO2 battery. The componential synergy significantly reduces the *OCHO formation barrier to expedite protonation process and creates a favorable electronic micro-environment for *HCOOH desorption. As a result, the CO2RR performance of Vo-Sx-In2O3 outperforms Pure-In2O3 and Vo-In2O3, where Vo-S53-In2O3 exhibits a maximal HCOOH Faradaic efficiency of 92.4% at −1.2 V vs. reversible hydrogen electrode (RHE) in H-cell and above 92% over a wide window potential with high current density (119.1 mA cm−2 at −1.1 V vs. RHE) in flow cell. Furthermore, the rechargeable Zn-CO2 battery utilizing Vo-S53-In2O3 as cathode shows a high power density of 2.29 mW cm−2 and a long-term stability during charge-discharge cycles. This work provides a valuable perspective to elucidate co-defective catalysts in regulating the intermediates for efficient CO2RR.

Electro-functionalized 2D nitrogen-carbon nanosheets decorated with symbiotic cobalt single-atoms/clusters

Two-dimensional (2D) materials loaded with single atoms and clusters are being set at the forefront of catalysis due to their distinctive geometric and electronic features. However, the usually-complicated synthesis procedures impede in-depth clarification of their catalytic mechanisms. To this end, herein we developed an efficient one-step dimension-reduction carbonization strategy, with which we successfully architected a highly-efficient catalyst for oxygen reduction reaction (ORR), featured with symbiotic cobalt single atoms and clusters decorated in two-dimensional (2D) ultra-thin (3.5 nm thickness) nitrogen-carbon nanosheets. The synergistic effects of the two components afford excellent oxygen reduction activity in alkaline media (E1/2=0.823 V vs. RHE) and thereof a high power density (146.61 mW cm−2) in an assembled Zn-air battery. As revealed by theoretical calculations, the cobalt clusters can regulate electrons surrounding those individual atoms and affect the adsorption of intermediate species. As a consequence, the derived active sites of single cobalt atoms lead to a significant improvement of the ORR performance. Thus, our work may fuel interests to delicate architecture of single atoms and clusters coexisting 2D support toward optimal electrocatalytic performance.

High Power Density Self-Resonant Coupler for Flexible Surface Wireless Power Transfer System With Nanocrystalline Ribbon

High Power Density Self-Resonant Coupler for Flexible Surface Wireless Power Transfer System With Nanocrystalline Ribbon

Development of High Power-Density Motors for Electric Axles using Nd-Based Bonded Magnets

Development of High Power-Density Motors for Electric Axles using Nd-Based Bonded Magnets

Rational synthesis of vertical graphene supported TiN@N-Li4Ti5O12 as advanced high-rate electrodes for lithium-ion batteries

The Li4Ti5O12 (LTO) is demonstrated to be one of the most promising anode materials for lithium-ion batteries (LIBs) to provide safe and high-power density cells but suffer from poor electrical conductivity. In this study, we present a TiN-decorated N-LTO on a vertical graphene (VG) array (TiN@N-LTO) as a potential anode material for lithium-ion batteries (LIBs). The use of atomic layer deposition (ALD) enables the formation of a thin layer of LTO on VG, with precise control over the thickness. The VG serves as highly conductive channels, facilitating the transfer of electrons. Moreover, the introduction of nitrogen heteroatoms into the LTO under an active N2 plasma atmosphere has been shown to enhance its intrinsic conductivity, which is achieved by reducing the bandgap and expanding the diffusion pathways of ions. Concurrently, a small number of metallic TiN are formed and deposited on the surface of N-LTO, thereby further improving its conductivity. COMSOL simulations and DFT calculations demonstrate that the introduced TiN acts as a "conductive bridge", improving the charge distribution of LTO electrodes and enhancing the Li+ transport rate. The TiN@N-LTO exhibits a high rate performance (169.51, 131.61 and 101.08 mAh/g at 0.2, 2 and 20 C, respectively) and remarkable cycling stability (a capacity retention of 99.6% after 5000 cycles at 10 C).

High-performance supercapacitor materials based on NiMn-LDH layered structures with MXene layers

In recent years, the environmental degradation exacerbated by extensive fossil fuel use has underscored the urgent need for cleaner and more efficient energy storage systems. This study addresses the challenges faced by hybrid supercapacitors (HSCs), which, despite their high power density and long lifespan, still suffer from low energy density and high self-discharge rates. We employ a co-precipitation method to integrate MXene with NiMn-layered double hydroxides (LDHs), optimizing the performance of HSCs. The incorporation of MXene enhances the conductivity and structural stability of NiMn-LDH, addressing issues of poor conductivity and instability during cycling. The developed NiMn-LDH@MXene electrodes demonstrate remarkable electrochemical performance, including a specific capacitance of 1530 F g⁻¹ at 2 A g⁻¹, a capacity retention rate of 90.52 % after 20,000 cycles at 10 A g⁻¹, a high energy density of 60.56 Wh kg⁻¹, and an excellent power density of 924.95 W kg⁻¹. This research not only marks a significant advancement in electrode material performance but also provides valuable insights into the development of next-generation energy storage devices with enhanced stability and efficiency.

Cooling System of A High-Pressure Centrifugal Compressor: Development and Impact on Wheel Temperatures (GT2024-121464)

Abstract High power density, low fuel consumption, and a compact design with competitive total costs of ownership are key requirements for internal combustion engines for conventional fuels and carbon-free or carbon-neutral future fuels. These requirements influence the development targets of charging systems and call for single-stage charging systems with increased charge air pressures. However, high compressor pressure ratios of the turbocharger lead to challenging material temperatures in aluminum alloy wheels. Consequently, creep becomes the fundamental lifetime-limiting damage mechanism for these wheels. In order to meet customer requirements regarding total costs of ownership, the lifetime is of major importance for the development of aluminum compressor wheels for turbochargers with pressure ratios beyond 6. This paper focuses on a high-pressure compressor design with a water-cooling system for a new turbocharger generation. The development of its components and their validation based on numerically predicted and measured wheel temperatures are discussed. After introducing the need for high-pressure ratios and the accompanying lifetime challenges, the paper presents the design strategy and methods of the development process. Finally, the paper summarizes the achievements obtained by this procedure. Detailed and rarely before documented temperature measurements from the rotating compressor wheel are published. As will be shown, the temperature measurements confirm the predictions from the pre-development phase. A comparison of the temperature measurements from the recently developed wheel with measurements carried out for a state-of-the-art wheel reveals the improvements achieved by this new generation of high-pressure compressors.

Amino Acid Functionalized SrTiO3 Nanoarrays with Enhanced Osseointegration Through Programmed Rapid Biofilm Elimination and Angiogenesis Controlled by NIR-Driven Gas Therapy.

Bacterial biofilm formation is closely associated with persistent infections of medical implants, which can lead to implantation failure. Additionally, the reconstruction of the vascular network is crucial for achieving efficient osseointegration. Herein, an anti-biofilm nanoplatform based on L-arginine (LA)/new indocyanine green (NICG) that is anchored to strontim titanium oxide (SrTiO3) nano-arrays on a titanium (Ti) substrate by introducing polydopamine (PDA) serving as the interlayer is designed and successfully fabricated. Near-infrared light (NIR) is used to excite NICG, generating reactive oxygen species (ROS) that react with LA to release nitric oxide (NO) molecules. Utilizing the concentration-dependent effect of NO, high power density NIR irradiation applied during the early stage after implantation to release a high concentration of NO, which synergized with the photothermal effect of PDA to eliminate bacterial biofilm. Subsequently, the irradiation power density can be finely down-regulated to reduce the NO concentration in subsequent treatment for accelerating the reconstruction of blood vessels. Meanwhile, SrTiO3 nano-arrays improve the hydrophilicity of the implant surface and slowly release strontium (Sr) ions for continuously optimizing the osteogenic microenvironment. Effective biofilm elimination and revascularization alongside the continuous optimization of the osteogenic microenvironment can significantly enhance the osseointegration of the functionalized Ti implant in in vivo animal experiments.

Fully Conjugated Covalent Triazine Framework Integrating Hexaazatrinaphthylene Unit as Anode Material for High-Performance Hybrid Lithium-Ion Capacitors.

As a high-performance energy storage device consisting of a battery-type anode and a capacitor-type cathode, hybrid lithium-ion capacitors (HLICs) combine the advantages of high energy density of batteries and high power density of capacitors. However, the imbalance in electrochemical kinetics between the battery-type anode and the capacitor-type cathode hinders the further development of HLICs. Fully conjugated covalent organic frameworks have great potential as electrode materials for HLICs due to the designability of their structure. Herein, a fully conjugated covalent triazine framework (PT-CTF) integrating the hexaazatrinaphthylene unit was constructed, which provides abundant active sites (C═N and C═C groups) as the pseudocapacitive anode material for HLICs. And the connection of the triazine unit of PT-CTF improves the molecular conjugate degree, facilitating the transport of electrons. The fabricated PT-CTF||AC HLICs exhibit a high energy density (164.9 Wh kg-1 at 100 mA g-1), large power density (13.1 kW kg-1 at 4 A g-1), and excellent cycling capability (72% after 10 000 cycles at 2 A g-1).

Simple Voltage Balancing Control of Four-Level Inverter

Multilevel inverters with improved voltage quality are widely used in applications such as motor control and electric vehicles. The four-level active neutral point clamped (4L-ANPC) inverter effectively meets the demands for high power density and low device voltage stress. However, balancing the capacitor voltage and reducing its low-frequency voltage fluctuation are critical challenges that need to be addressed. To address these challenges, this paper proposes a “variable reference + zero-sequence injection” method that requires only three reference voltage signals to determine the injected zero-sequence components. Particularly, the expression of the midpoint current, regarding the modulation index and phase current amplitude, is theoretically derived. This reveals the fundamental connection between the zero-sequence voltage signal and the midpoint current, providing a theoretical foundation for the zero-sequence injection method in four-level inverters. Subsequently, a simulation model and an experimental platform of the 4L-ANPC inverter were developed to compare and analyze the waveforms of the upper and lower capacitor voltages, phase currents, and line voltages under different modulation methods. Additionally, the upper and lower capacitor voltage waveforms were examined for various modulation indices. The results indicate that as the modulation index increases, the low-frequency voltage fluctuation in the upper and lower capacitor voltages also rises. At a modulation index of 0.95, the “variable reference + zero-sequence injection” method effectively suppresses the fluctuation in the upper and lower capacitor voltages to be no more than 1 V. These experimental findings validate the effectiveness of the proposed method.

Advancements in Legged Walking Robots: Review

The purpose of this review paper is to contribute to the body of knowledge surrounding legged walking robots, specifically those utilizing four legs. It aims to inform researchers, engineers, and enthusiasts about the advancements, potential applications, and future prospects of these robots, ultimately driving further research and development in this exciting field. The review covered the most recent research articles in the field of designing and manufacturing robots, as well as how to choose the mechanism of actuator between hydraulic or electric systems and their impact on the weight increase and energy consumption, or potential noise generation during the operation like Bigdog robot. The payload was also assessed, with a comparison of the speed chart for each quadruped robot. It has been found that several critical technologies driving quadruped robots' advancement include new biomimetic structures, high power density actuators, techniques for controlling in real time and integrated environmental perception, depending on the application fields, such as industrial automation, healthcare, and exploration. Each of these elements is essential for achieving high-performance quadruped robots. Notably, the paper also delves understanding the fundamental methods used by mobile robots to perceive their surroundings, pay load (N), normalized speed (m/s), and engine mechanism. This work is valuable for all researchers in the field of a five-bar mechanism legged robot to keep up with the most recent advancements in this field. Furthermore, this review paper can be considered as a guideline for researchers who are intended to perform further research on mobile robot. Index Terms: Quadruped mobile robot, Payload, Mechanism, DOF, robotic leg.

Rice husk-derived nitrogen-doped graphitic carbon/graphene nanosheets self-assembly for high-performance supercapacitors with chemical blowing method

Carbon materials derived from waste biomass are increasingly popular in energy devices due to their renewability, environmental benefits, and rich heteroatom functionalization. Herein, a simple and low-cost method for synthesising rice husk-derived nitrogen-doped graphitic carbon/graphene nanosheets (RNGNs) by chemical blowing was developed. Carbon was derived from rice husk (RH), while nitrogen was sourced from ethylenediaminetetraacetic acid and iron sodium salt hydrate (EDTA-FE), serving multiple roles as a blowing agent, an activating agent and a graphitization catalyst in a closed system. This approach facilitates the formation of a unique 3D structure of 2D graphene self-assembly on the wrinkled surface of graphitic carbon. As an electrode material for supercapacitors, the obtained RNGN800–1:1 with high nitrogen content (5.02 %) shows good electrical conductivity and a large specific surface area (1130 m2 g−1). These characteristics bring about an impressive electrochemical performance (334.5 F g−1 at 0.5 A g−1, 75.6 % retention at 20 A g−1). Moreover, when assembled into symmetrical device, the RNGN800–1:1 demonstrates a high power density of 9.4 kW kg−1and an excellent energy density of 15.2 Wh kg−1 with outstanding long-term cyclability (remains 94.77 % after 25000 cycles). This study introduces a straightforward and environmentally friendly approach for synthesizing nitrogen-doped graphitic carbon/graphene nanosheets from sustainable biomass resources. The resulting material is expected to have broad applications across various areas, including adsorption, catalysis, and energy storage.