Higher Power Density Values Research Articles

Emerging Two–Dimensional Intercalation Pseudocapacitive Electrodes for Supercapacitors

AbstractThe growing need for efficient energy storage has spurred advancements in supercapacitors (SCs), aiming to offer high power and energy density simultaneously. While SCs offer longer cycles and higher power density values, their low energy densities limit practical applications. In response, pseudocapacitive materials have emerged, leveraging reversible Faradaic reactions at or near the surface for enhanced energy storage. This approach surpasses the constraints of the electrical double layer in SCs and the mass transfer constraints of batteries. Progress in asymmetric supercapacitors and high mass loading has improved energy density values, yet maintaining high mass loading without compromising power density remains a hurdle. Advancements in pseudocapacitance through intercalation during charging/discharging processes, especially in layered structures like graphite, graphene, transition metal oxides (TMOs) transition metal dichalcogenides (TMDCs), MXenes, and metal–organic frameworks (MOFs) have proven significant. The intercalated species induce reversible or irreversible structural changes, contributing to the physicochemical characteristics of the electrode materials. Exploring the intercalation mechanism in bulk two‐dimensional (2D) materials reveals distinct differences that enhance our understanding and improve electrochemical properties for superior energy storage. Finally, an in‐depth exploration of the intercalation pseudocapacitance in 2D materials such as TMDCs and MXenes underscores their significance, setting a benchmark for future electrochemical studies in the subsequent advancement of SCs research.

Activation of vibrational-induced CO2 dissociation in cold non-equilibrium plasma

The activation of vibrational-induced dissociation of CO2 in cold non-equilibrium plasma discharges is investigated by means of a 0D self-consistent kinetic model, which, with a state-to-state approach, is able to calculate the CO2 vibrational distribution function (vdf) of the asymmetric mode levels, the electron energy distribution function and the corresponding vibrational-induced and electron impact CO2 dissociation rates. The conditions for the onset of such activation are linked to the achievement of a sufficiently high CO2 vibrational excitation characterized by the presence of a non-equilibrium plateau in the CO2 vdf, resulting from the combined effect of electron–vibrational and vibrational–vibrational collisions, which, by overpopulating the higher vibrational levels, enhances dissociation. Such non-equilibrium conditions are maximized at lower gas temperature, lower pressure and higher power density values. In particular, for the power density, an activation threshold value can be obtained from simulations and its dependence on the gas temperature and pressure can be investigated. The dependence of the maximum vibrational temperature reached at the end of the discharge as a function of the gas temperature and pressure is also analyzed. A satisfactory agreement from our simulation results with the Kotov’s criterion for vibrational activation has been found.

Challenges Facing Pressure Retarded Osmosis Commercialization: A Short Review

Pressure-retarded osmosis (PRO) is a promising technology that harvests salinity gradient energy. Even though PRO has great power-generating potential, its commercialization is currently facing many challenges. In this regard, this review highlights the discrepancies between the reported power density obtained by lab-scale PRO systems, as well as numerical investigations, and the significantly low power density values obtained by PRO pilot plants. This difference in performance is mainly due to the effect of a pressure drop and the draw pressure effect on the feed channel hydrodynamics, which have significant impacts on large-scale modules; however, it has a minor or no effect on small-scale ones. Therefore, this review outlines the underlying causes of the high power density values obtained by lab-scale PRO systems and numerical studies. Moreover, other challenges impeding PRO commercialization are discussed, including the effect of concentration polarization, the solution temperature, the pressure drop, and the draw pressure effect on the feed channel hydrodynamics. In conclusion, this review sheds valuable insights on the issues facing PRO commercialization and suggests recommendations that can facilitate the successful development of PRO power plants.

CURRENT CONCERNS REGARDING THE CONSTRUCTION OF HIGH POWER DENSITY ELECTRICAL MACHINES FOR ELECTRICITY TRANSPORT SYSTEMS

"Applications such as electrification of transmission systems require electric machines with high power density values. Such electric cars offer beneficial volumes and weights that are desired in transportation systems that include electric cars, electrified planes, and other types of electric vehicles. In October 2017, the US DRIVE groupThe U.S. Department of Energy (DOE), a large automobile and power company, has published a paper entitled “Roadmap for Research and Innovation in Electrical and Electronic Technologies for Efficiency vehicles and energy sustainability ”. This paper outlines the performance values ​​that electric traction motors must have in 2025 to accelerate the development of innovative and pre-competitive technologies to achieve a wide range of clean and efficient vehicles as well as related energy infrastructure. Thus, for electric traction motors with powers of 100 kW, used in the drive systems of single-electric vehicles, which is used in both engine and generator mode, for their power density is expected to increase from the value of 5.7 kW / L achieved in 2020 to the value of 50 kW / L to be achieved in 2025, which means a volume reduction of 89%. This reduction in volume must be accompanied by a reduction in the cost of these engines, from $ 4.7 / kW in 2020 to $ 3.3 / kW in 2025, ie a cost reduction of 30%. One of the factors that limits the power density of electric cars is the cooling system. In the absence of adequate cooling systems, the energy losses that occur in electric cars can cause damage to the insulation system, short circuits between the windings of the windings, demagnetization of the permanent magnets and, finally, damage to the drive system. As a result, the analysis of ways to reduce energy losses in electric cars and the identification of efficient cooling systems are essential concerns for the realization of electric cars with high values ​​of power density. In this paper, a presentation is made of the results of recently published research on finding constructive solutions for the realization of electric machines with very low energy losses as well as solutions for the realization of high-efficiency cooling systems, solutions that allows the performance of performance indicators for electric cars, on power density and cost, expected by the US Drive group for 2025."

Activated carbon derived from ground nutshell as a metal-free oxygen reduction catalyst for air cathode in single chamber microbial fuel cell

A single-chamber microbial fuel cell (SCMFC) was constructed using activated carbon derived from ground nutshells (GAC) as a metal-free cathode catalyst. The prepared cathode catalyst was characterized by X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and Field emission scanning electron microscopy (FE-SEM), which demonstrates the chemical composition and the surface morphology of the synthesized material. The electrochemical characteristics of the cathode were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) analysis, which confirmed the high charge transfer capacity and catalytic activity property of GAC catalyst material. The MFC with GAC catalyst produces a maximum output voltage of 0.619 V and which is 1.61 times greater than that of bare carbon cloth (CC). For Pt/C and GAC-modified CC, high power density values of 0.763 W m−2 and 0.521 W m−2 were obtained at current densities 1.65 A m−2 and 1.0 A m−2, respectively at 100 Ω. These results demonstrate that the GAC/CC is a promising cost-effective cathode catalyst for SCMFC.

Performance Improvement of a Single PEM Fuel Cell Using an Innovative Flow Field Design Methodology

Flow fields of polymer electrolyte membrane fuel cells (PEMFCs) are used to feed reactant gases over the surface of catalyst layer homogeneously and remove byproduct, water. Optimization of the flow field design would improve homogeneity of the gas distribution and pressure drop values resulting in higher power density values. Flow field designs inspired from veins of tree leaves have been analyzed and tested. A mathematical model has been conducted for verifying the experimental results. A decrease in pressure drop and homogeneous distribution of gasses without flooding was observed with our novel designs. The dimensions of the flow channels were selected based upon tree leaves that obey Murray’s law. Semi cylindrical obstacles were fabricated on the ground to direct the gas flow to the gas diffusion layer. The effect of these obstacles was observed at high current values. The cell performance and current density–temperature distribution analysis showed performance improvement up to 42.1% in comparison with the standard serpentine design. Homogeneity of current and temperature distributions was also improved with the proposed design. Additionally, water removal was improved with the current design.

On the use of 3-cyanopropionic acid methyl ester as alternative solvent for high voltage dual carbon lithium ion capacitors

In this work we report for the first time the use of 3-cyanopropionic acid methyl ester (CPAME), with vinylene carbonate (VC) as additive, as an alternative solvent when targeting high voltage lithium ion capacitors (LICs). In view of the promising viscosity, conductivity, and electrochemical stability window, its use in LICs is explored. To this end, a hard carbon (HC) is selected as the negative electrode, while an activated carbon (AC) is the preferred choice as the positive electrode, both being biomass (olive-pits) waste derived. The electrochemical characterization of the HC shows good specific capacities at both low and high current densities (e.g. 322 mAh g−1 at C/10 and 80 mAh g−1 at 10C). In addition, the cyclic voltammogram of the AC reveals a stable electrochemical potential window rising to 4.6 V vs. Li+/Li. This fact allows to develop a LIC operating at 1.5–4.5 V able to deliver high energy and high power density values (i.e. 121 Wh kg−1AM at 299 W kg−1AM and 69 Wh kg−1AM at 2217 W kg−1AM).

Chemometrical assessment of the electrical parameters obtained by long-term operating freshwater sediment microbial fuel cells

The electrical parameters of nine freshwater sediment microbial fuel cells (SMFCs) were monitored for a period of over 20months. The developed SMFCs, divided into three groups, were started up and continuously operated under different constant loads (100, 510 and 1100Ω) for 2.5months. At this stage of the experiment, the highest power density values, reaching 1.2±0.2mW/m2, were achieved by the SMFCs loaded with 510Ω. The maximum power obtained at periodical polarization during the rest period, however, ranged between 26.2±2.8 and 35.3±2.8mW/m2, strongly depending on the internal cell resistance. The statistical evaluation of data derived from the polarization curves shows that after 300days of operation all examined SMFCs reached a steady-state and the system might be assumed as homoscedastic. The estimated values of standard and expanded uncertainties of the electric parameters indicate a high repeatability and reproducibility of the SMFCs' performance. Results obtained in subsequent discharge–recovery cycles reveal the opportunity for practical application of studied SMFCs as autonomous power sources.