Power Density Research Articles (Page 1)

rGO/polypyrrole-modified bioelectrode reshapes microbial communities for enhanced energy-recovering denitrification in carbon-limited wastewater.

ABSTRACT This study investigates a 2-stroke hydrogen-oxygen-steam combustion process optimized for stationary hydrogen reconversion, i.e. converting stored hydrogen from electrolysis back into electricity. A quasi-dimensional combustion model incorporating gas dynamics, thermodynamics, wall heat transfer and a fractal-based combustion scheme was developed to simulate the full in-cylinder cycle. The model was validated against experimental data from a 4-stroke hydrogen engine to confirm its predictive capability. Parametric studies show that optimized valve timing, injection, and dilution yield 54 kW per 1.3 L cylinder and 54.6% indicated efficiency − 44% higher efficiency and 105% greater power density than a comparable 4-stroke engine.

Electroactive biofilms from activated sludge: Mechanistic insights into electron transport on nanostructured electrodes for the development of biosensors and microbial fuel cell devices.

Nowadays, new electrode materials for energy storage devices like mixed ligands and bi-metal MOFs have attracted a lot of attention owing to their high porosity and high capacity for charge storage. In this study, a Co-based metal-organic framework (4,4'-bpy = 4,4'-Bipyridine and H3BTC = 1,3,5-Benzenetricarboxylic acid) was successfully fabricated by a hydrothermal method. To obtain good electrochemical behavior, Co-MOFs were modified using a porous spherical scaffold of NiS/Ni3S4 nanoparticles. The electrochemical efficiency was analyzed by electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge methods. Detailed electrochemical scrutiny performed by Co-MOF/NiS-Ni3S4 in a 6M KOH electrolyte reveals a high specific capacity of 136.67 mAh/g at 1A/g, with a superb cycle life of 91%. Co-MOF/NiS-Ni3S4//AC asymmetric supercapacitor produces a large amount of energy density (33.32 Wh/kg) and power density (600W/kg). The produced composite is an appropriate candidate for electrodes in both batteries and hybrid supercapacitors, owing to its favorable electrochemical characteristics.

Constructing core-shell structures is an encouraging method to increase the energy storage ability of supercapacitors. In this study, a tree-like NiCoP@NiCoS/CC (CC: carbon cloth) composite was synthesized, with NiCoP nanowires serving as a conductive skeleton for stable electron transport and structural support. NiCoS nanosheets coated the nanowires, forming a conductive network that increased the atom utilization and area for electrochemical reactions. The number of NiCoS electrodeposition cycles was varied to optimize the electrochemical performance. Electrochemical test results revealed optimal performance with 10 deposition cycles (2372.6 F g-1 at 1 A g-1). An asymmetric supercapacitor (ASC) was assembled using NiCoP@NiCoS/CC as the positive electrode and activated carbon as the negative electrode. The device delivered a power density of 800 W kg-1 at 1.6 V and an energy density of 55.42 Wh kg-1, with only 23.7% capacity loss after 10,000 cycles. These results underscore the potential of NiCoP@NiCoS/CC electrodes for advancing core-shell heterostructures in next-generation wearable energy storage devices.

Abstract The application of Machine Learning (ML) models coupled with metaheuristic optimization algorithms represents a potentially powerful development in the field of predictive modeling, as it relates to sustainable energy materials. In this study, the electrochemical performance of biomass material from bamboo for energy storage applications is explored, focusing on the prediction of power density. The central objective is to enhance model accuracy with a novel hybrid model of Kernel Extreme Learning Machine (KELM) and Slime Mould Algorithm (SMA), Sunflower Optimization (SFO), and Social Ski Driver (SSD). The optimal predictive performance was achieved with KELM-SFO with a test Root Mean Square Error (RMSE) of 10,421.05, Mean Absolute Error (MAE) of 4,654.07, and R-squared (R 2 ) of 96.2 %. Early and fast plateauing of the SFO algorithm’s convergence curve indicated stable, early-stage optimization. In addition to filling a significant knowledge gap in ML-incorporated materials modeling, this work opens the door for future research on deep learning techniques, adaptive hybrid optimization algorithms, and real-time experimental validations to improve the electrochemical prediction efficiency in energy storage systems inspired by biomass.

Carbon-based supercapacitor electrodes derived from biomass have recently garnered significant attention due to their low cost, natural abundance, and environmental sustainability. In this study, charcoal was pretreated using a simple ultrasonic method and was employed as the active electrode material in both three-electrode and symmetric supercapacitor configurations. To further enhance electrochemical performance, a sustainable and dual-functional strategy was implemented by introducing methylene blue, a redox-active additive, into an aqueous sodium chloride electrolyte. Structural and morphological characterizations revealed that charcoal possessed a highly porous architecture with preserved plant-based vascular channels, facilitating efficient electrolyte penetration and ion transport. Electrochemical analyses demonstrated that the incorporation of methylene blue significantly enhanced charge storage through a synergistic combination of electric double-layer capacitance and pseudocapacitive behavior. The optimal device, utilizing the MB35 electrolyte composition, delivered a high specific capacitance of 212.23F g-1 at 0.5A g-1, an energy density of 15.34 Wh kg-1 at a power density of 350W kg-1, and excellent cycling stability, retaining 91.3% of its initial capacitance after 2000 cycles and 84.3% after 5000 cycles at the high loading mass of 2mg cm- 2. This work presents a cost-effective route for fabricating high-performance biomass-derived supercapacitors while offering a novel approach for the reutilization of dye pollutants in sustainable energy storage applications.

This study investigates the synergistic interaction of CuO and SnO 2 in a heterostructure catalyst (CuO@SnO 2 ) for the conversion of C1 carbon dioxide (CO 2 ) reduction products to C2 products and its application in high‐performance aqueous Zn‐CO 2 batteries. This synergistic combination enhances the Faradaic efficiency (FE) for ethanol production from 12.5% to 41.8%, shifting the selectivity from C1 to C2 products. The flow‐type aqueous Zn‐CO 2 battery exhibits an ultrahigh power density of 6.5 mW cm −2 , demonstrates a high discharge voltage of 0.9 V, and maintains stable operation over 140 cycles, underscoring the catalyst's exceptional reversibility and durability. During battery discharge, the system achieves a FE of 36.86% for ethanol production. These results highlight the pivotal role of the CuO@SnO 2 synergy in optimizing CO 2 conversion efficiency while generating electrical energy. The findings advance the development of dual‐function energy storage systems that integrate renewable electricity generation with sustainable CO 2 utilization, paving the way for industrial‐scale applications.

Laser shock peening (LSP) is a robust surface treatment technique widely exploited by industries of the modern era. In this study, aluminium 6061 alloy was treated with LSP at different power densities, and properties like hardness, surface roughness, microstructural evolution, and tribological behaviour were investigated. LSP applied at 3 GW/sq. cm raised the hardness and surface roughness to 97.1 HV and 0.499 μm, respectively, due to a fine-grained microstructure averaging 4.12 μm. Formation of a strain-hardened layer with dense dislocations improved the tribological performance of the LSPed specimens with minimal wear at 5 N load.

Abstract Multi-photon (MP) imaging is a well-established optical microscopy technique capable of high-resolution imaging with reduced photodamage and deep tissue penetration. On a single cell level MP imaging enables non-invasive monitoring of cellular states, such as the metabolic activity, which is strongly linked to early detection of abnormal cellular behaviour. In this proof-of-principle study, we present the implementation of sub-10-fs few-cycle laser pulses for label-free MP imaging, representing a potential advancement in the evolution of MP-imaging techniques. Our primary focus is on label free metabolic imaging (MI) of live cells. To assess photoinduced damage from ultrashort laser pulses, we examine their effects on live HeLa cells in vitro. At a power density in the terawatt per square centimetre (TW/cm2) range, the few-cycle laser pulse result in a measurable decrease in NAD(P)H fluorescence in HeLa cells- an early indicator of photoinduced cellular damage. 
We further demonstrate the application of few-cycle MI in live HeLa cells treated with the therapeutic agent Doxorubicin (DOX). Remarkably, a metabolic shift towards oxidative phosphorylation is observed within just 15 min of DOX incubation. In these therapeutic experiments prolonged exposure to the few-cycle laser also leads to a significant increase in NAD(P)H autofluorescence, particular in nuclear and mitochondrial regions-sites rich in DNA-suggesting a photoactivation effect of DOX that enhances NAD(P)H fluorescence emission. Overall, this study demonstrates the feasibility of using a few-cycle broadband laser excitation source for label-free bioimaging. The results reveal complex interaction dynamics between the laser´s spectral components and cellular targets. These findings highlight the need for careful optimization to minimize phototoxic while also suggesting new opportunities therapy-triggering and real-time metabolic monitoring through spectral engineering. 

Passive ammonia fuel cells (PAFCs) offer modular adaptability but face dual challenges: limited power density and dependency on noble metals. Here, a comprehensive strategy is presented to address these issues through coordinated materials and system design. Pre-oxidized nickel substrates direct the formation of β-phase NiOOH/Ni3P (β-NiOOH/Ni3P) heterointerfaces in anode, significantly enhancing ammonia oxidation reaction (AOR) kinetics with a high current density of 171mAcm-2 at 0.7V. A spinel-structured MnCo2O4/C cathode catalyst demonstrates remarkable ammonia tolerance and outperforms Pt/C in stability. A polytetrafluoroethylene/layered double hydroxide (PTFE/LDH) composite membrane is also introduced, which effectively reduces ammonia crossover. Their integration with an optimized graphite prototype further enhances PAFCs' efficiency and stability. This synergistic multi-phase optimization enables record-breaking performance for non-noble metal-based PAFCs, achieving a peak power density (PPD) of 61mWcm-2 and an open circuit voltage (OCV) of 0.87V (outperforming Pt-based PAFCs). Stable discharge can be sustained by the present PAFC for 9 h by replenishing the ammonia supply. This work establishes a prototype-to-performance strategy for cost-effective PAFC, highlighting the potential of non-noble metal catalysts in ammonia electrochemical energy conversion.

With the global low-voltage power market expanding rapidly, lead-free dielectric ceramics exhibit excellent stability and environmental friendliness, but their strong field-dependence limits low-field applications. There is an urgent need to develop lead-free ceramic systems with outstanding energy-storage performance under modest electric fields to meet the rapidly expanding global low-voltage power market for bulk ceramics. In this study, high-entropy ceramics (1 − x%)(NaBiBa)0.205(SrCa)0.1925TiO3-x%La(Zr0.5Mg0.5)O3 (x = 0–8) were successfully prepared. The introduced La(Zr0.5Mg0.5)O3 not only dissolves well in the high-entropy elementary lattice but also effectively improves its relaxation characteristics. High-entropy ceramics show optimal energy-storage characteristics, as indicated by an excellent energy-storage density of 4.46 J/cm3 and an energy-storage efficiency of 94.55% at 318 kV/cm. Moreover, its power density is as high as 92.20 MV/cm3, and the discharge time t0.9 is only 145 ns.

In the first paper of this series, we presented radio observations of three giant double-double radio galaxies: J1021+1216, J1528+0544, and J2345--0449. We reported the asymmetries and minor misalignments identified in the outer and inner doubles of all three sources, in addition to an uncommon trace of emission with a relatively flat spectrum in the spectral index map of J1528+0544. Furthermore, we discovered core extensions in the J1021+1216 and J1528+0544 high-resolution maps, suggesting that the two sources are triple-double radio galaxies. In this paper, we continue our investigation of the three sources in search of the causes behind these observed peculiarities. Our goal is to carry out a detailed study of a selection sample of giant double-double radio galaxies. By determining the properties of these sources and their environments, we obtained a comprehensive image of the processes influencing their evolution, which we could then use to make comparisons with the model results on radio-galaxy evolution from the literature. In this work, we used the radio maps prepared and presented in the first paper of this study to perform a spectral aging analysis with the Broadband Radio Astronomy ToolS software and dynamical modeling with the dynage software. From this modeling, we recovered a range of parameters describing the conditions in and around the observed sources, including the duration of the active and quiescent phases, jet power, and external medium density. Based on our radiative and dynamical models, we report long durations for the active phases in the outer doubles of J1021+1216 and J2345--0449. We report ages of t_ rad,J10 =43±4 Myr and t_ dyn,J10 =250 Myr for J1021+1216, and t_ rad,J23 =42±4 Myr and t_ dyn,J23 =176 Myr for J2345--0449. The inner double of J1021+1216 was found to be expanding at a speed ∼!!0.5c inside a relic cocoon with a density of łog(̊ho_0 : kg: m^ )=-25.7. In J1528+0544, all the parameters that could influence the evolution of the outer lobes are not out of the ordinary. However, we found a radiatively young structure in the outer lobes, which we interpreted as a trace of a restarted jet belonging to an ``intermediate'' phase of activity. We conclude that there is no single universal factor stimulating the growth of the GRGs. In J1021+1216 and J2345--0449 outer doubles, with projected sizes ∼1.85 Mpc and ∼1.7 Mpc, respectively, the main factor stimulating their growth is the exceptionally long duration of their active phases. In J1021+1216 inner double, with a projected size of ∼1 Mpc, the main factor is its fast expansion inside a low-density medium. The outer double J1528+0544, with a projected size ∼715 kpc, represents the case of a giant radio galaxy, where growth was stimulated by the recurrent activity of the galactic nucleus. Furthermore, we report the discovery of two radio galaxies with three separate phases of activity visible at once: J1021+1216 and J1528+0544.

On‐water surface synthesis has emerged as a powerful approach for constructing thin‐layer, crystalline 2D polyimines and their layer‐stacked covalent organic frameworks. This is achieved by directing monomer preorganization and subsequent 2D polymerization on the water surface. However, the poor compatibility of water with many organic monomers has limited the range of accessible 2D polyimine structures. Herein, the on‐liquid surface synthesis of crystalline 2D polyimine films from a water‐insoluble, C 3 ‐symmetric monomer previously deemed incompatible with aqueous systems is reported. In situ grazing incidence X‐ray scattering reveals a stepwise evolution of monomer adsorption, preorganization, and 2D polymerization assisted by the fluorinated surfactant monolayer, leading to the formation of large‐area, face‐on‐oriented 2D polyimine films. Notably, a pronounced lattice expansion from 3.4 nm in the monomer assembly to 5.3 nm in the 2D polyimine framework is observed, highlighting the templating effect of the preorganized monomers in defining the final crystallinity. The representative 2DPI‐TCQ‐DHB is obtained as free‐standing thin film with well‐defined hexagonal pores, mechanical robustness, and a negatively charged surface (zeta potential: −58.8 mV). Leveraging these structural characteristics, it is integrated 2DPI‐TCQ‐DHB films into osmotic power generators, achieving a power density of 16.0 W m −2 by mixing artificial seawater and river water, surpassing most nanoporous 2D membranes.

To address the intermittent nature of renewable energy, highly efficient high-performance energy storage devices are essential. Among various options, supercapacitors have attracted significant attention because they provide high power density, rapid charge–discharge capability, and long cycle life. In this study, a composite of amorphous Cu(OH)<sub>2</sub> grown on a metal–organic framework ZIF-67 (Cu(OH)<sub>2</sub>@ZIF-67) was successfully synthesized via a facile solvothermal method. Detailed structural and surface analyses, including scanning and transmission electron microscopy as well as X-ray diffraction measurements, revealed that ultrathin Cu(OH)<sub>2</sub> nanosheets were uniformly grown on the ZIF-67 surface. The combination of the amorphous phase with the MOF provided abundant electrochemically active sites and facilitated rapid ion transport, significantly contributing to greatly improved charge storage behavior. Electrochemical characterization demonstrated that Cu(OH)<sub>2</sub>@ZIF-67 exhibited a specific capacitance of 168 F/g at 3 A/g, approximately four times higher than that of pristine ZIF-67, while maintaining superior energy density across a wide power range. These findings demonstrate that introducing an amorphous structure onto MOF-derived metal supports not only effectively enhances the overall performance of supercapacitors but also provides valuable insights for the rational design, optimization, and potential practical and technological applications of hybrid electrode materials in next-generation high-performance energy storage systems.

Moisture-voltaic power generation using hygroscopic materials harnesses atmospheric water to produce clean, sustainable energy. Yet environmental complexity means single mode moisture to electricity conversion suffers from efficiency limits and poor adaptability, making the development of flexible, multimodal clean‑energy harvesters essential. Here, a strategy is presents that combines hygroscopic polyelectrolyte material with light-responsive BiOBr nanosheets to create a moisture-light harvesting electric generator (MLEG). We utilized the PSS/AMPS-Na/PVA/BiOBr (PAPBO) composite as the flexible active layer, achieving highly efficient hydrovoltaic power output. Additionally due to the incorporation of BiOBr, long-lived holes are generated through light harvesting, which further enhances the output performance through water oxidation. When exposed to an environment with 75% relative humidity, a single MLEG delivers a substantial open-circuit voltage of 0.77 V and a short-circuit current of 18.73 µA. After the MLEG harvests light energy, the consumption of holes by water molecules generates additional hydrogen ions, resulting in a 60.98% increase in output power density (from 72.75 to 117.11 µW cm-2). The device can also function as a humidity sensor, responding to humidity levels from 10% to 100%. This work provides a novel approach to harvesting and converting multiple natural energy sources, boosting the hydrovoltaic effect and opening a new path for sustainable power generation.

The increasing trend towards electrification in transportation highlights the potential for electric ships and the demand for safe, rapid charging systems. Underwater capacitive power transfer (UCPT) is considered a suitable solution due to its high power density potential. This article presents research on and optimization of UCPT for shore-to-ship charging in freshwater environments. It proposes a design for an insulation coupler and explores the influence of parasitic capacitance in the environment. This study demonstrates how the ship and shore impact the coupler’s coupling coefficient and mutual capacitance, thereby affecting the power and efficiency. Through theoretical calculations and finite element analysis, a kW-level UCPT coupler is designed. Experimental verification under different cases confirms the efficiency and constant current output characteristics, with superior performance observed when the coupler is positioned further away from the ship or shore. This study showcases the potential of UCPT to provide reliable and efficient power supply for electric ships, while emphasizing the importance of considering environmental factors and parasitic effects in system design and operation. These findings contribute to advancing UCPT technology and offer insights for further optimization to enhance practical applicability.

To simultaneously improve mass transfer and minimize pressure drop in proton exchange membrane fuel cells (PEMFCs), this study proposes a novel bionic flow field inspired by the streamlined abdominal structure of the peregrine falcon. A three-dimensional channel geometry is developed from this biological prototype and integrated into a single-channel PEMFC model for numerical simulation. A series of computational fluid dynamics (CFD) analyses compare the new design against conventional straight, trapezoidal, and sinusoidal flow fields. The results demonstrate that the falcon-inspired configuration enhances oxygen delivery, optimizes water management, and achieves a more uniform current density distribution. Remarkably, the design delivers a 9.45% increase in peak power density while significantly reducing pressure drop compared to the straight channel. These findings confirm that biologically optimized aerodynamic structures can provide tangible benefits in PEMFC flow field design by boosting electrochemical performance and lowering parasitic losses. Beyond fuel cells, this bio-inspired approach offers a transferable methodology for advanced energy conversion systems where efficient fluid transport is essential.

A hybrid plasma resulting from a combination of a stationary microwave electron cyclotron resonance (with magnetic field) discharge, and a pulsed laser ablation plasma was used to deposit aluminum nitride (AlN) thin films. The hybrid plasma was created at a working pressure of 8 × 10−2 Pa in nitrogen atmosphere. The use of the hybrid plasma allowed efficient laser ablation at low working pressures. Different samples were grown varying the laser power density deposited on the aluminum target. The variation of this power produced ions with different mean kinetic energy (Ek) in the laser ablation plasma. The values of the mean kinetic ion energy were determined using a Langmuir planar probe and were used as the working parameter. The composition of the AlN thin films was measured using the XPS technique. These measurements showed that most of the bonds between Al and N corresponded to that of the AlN compound and their amount increases with Ek. The bandgap of the samples was determined as a function of Ek and was observed to vary between 5.4 and 6 eV. Nano indentation measurements showed a variation of the hardness between 23 and 30 GPa as a function of Ek. The wear rate and friction coefficient were evaluated on samples deposited under different values of Ek, using a reciprocating tribometer.

Aiming at the limitations of direct drive wave energy conversion (DD-WEC), especially the poor power density, low energy conversion efficiency, and a large volume of linear generators (LGs), a novel magnetic helix hybrid excitation rotary generator (MH-HERG) with the higher power density and higher energy conversion efficiency is proposed. The proposed MH-HERG can convert linear motion into rotary motion without contact with a hybrid excitation magnetic screw (HEMS) unit, so it has high energy conversion efficiency. Furthermore, a new quasi-Halbach magnetization array is used in the proposed MH-HERG to increase its power density and allows a hybrid excitation method to be used to make the thrust adjustable to further improve power density. The analytical solution model is established to derive the calculation equations of air gap flux density, which are validated through the finite element simulation. Arc-shaped permanent magnets (PMs), instead of tile-type PMs, are designed to weaken cogging torque and harmonic content in proposed MH-HERG’s no-load back electromotive force (back-EMF), thereby improving output power quality. Finally, the prototype is built and an experiment is conducted to ascertain the effectiveness and superiority of the proposed MH-HERG which has increased power density by 4.4 times and energy conversion efficiency by 3 times compared to existing LGs.