Search Results (154)

Zinc (Zn)-based batteries have attracted significant interest for applications ranging from electric bikes to grid storage because of its advantageous properties like high abundance, non-toxicity and low-cost. Zn offers a high theoretical capacity of two electrons per atom, resulting in 820 mAh/g, making it a promising anode material for the development of highly energy dense batteries. However, the advancement of Zn-based battery systems is hindered by the limited availability of cathode materials that simultaneously offer high theoretical capacity, long-term cycling stability, and affordability. In this work, we present a new mixed material cathode system, comprising of a mixture of manganese dioxide (MnO₂) and copper oxide (Cu₂O) as active materials, that delivers a high theoretical capacity of ~280 mAh/g (MnO₂ + Cu₂O active material) (based on the combined mass of MnO₂ and Cu₂O) and supports stable cycling for >200 cycles at 1C. We further demonstrate the scalability of this novel cathode system by increasing the electrode size and capacity, highlighting its potential for practical and commercial applications. Full article

Adipic acid (AA), a pivotal precursor for nylon-6,6 and polyurethane, was synthesized via an innovative catalytic electrocatalytic oxidation strategy in this study. Four distinct MnO_x/CNT nanocatalysts were prepared by hydrothermal and co-precipitation methods and fabricated into electrodes for the oxidation of cyclohexanol (Cy-OH) in a K₂SO₄ neutral solution. Comprehensive characterization revealed that the catalytic performance depended on both crystalline phase configuration and manganese valence states. MnO(OH) and MnO_x were identified as the main active species, with the synergy between MnO species and carbon nanotubes significantly enhancing catalytic activity. Mechanistic investigations demonstrated that under Mn⁴⁺-dominant conditions, low-valence manganese species facilitated Cy-OH-to-cyclohexanone (Cy=O) conversion, while an optimal O_ads/O_lat ratio (≈1) effectively promoted subsequent Cy=O oxidation to AA. Under optimized conditions (1.25 V vs. Ag/AgCl, 80 °C, 15 h), complete Cy-OH conversion was achieved with 56.4% AA yield and exceptional Faradaic efficiency exceeding 94%. This work elucidates manganese-based electrocatalytic oxidation mechanisms, proposes a sequential reaction pathway, and establishes an environmentally benign synthesis protocol for AA, advancing sustainable industrial chemistry. Full article

Thin films of manganese–nickel–cobalt oxide with graphene (G@MNCO) were deposited on copper foam using electrochemical deposition. NiCo₂O₄ is the main phase in these films. As the proportion of graphene in the precursor solution increases, the oxygen vacancies in the samples also increase. The microstructure of these samples evolves into hierarchical vertical flake structures. Cyclic voltammetry measurements conducted within the potential range of 0–1.2 V reveal that the electrode with the highest graphene content achieves the highest specific capacitance, approximately 475 F/g. Furthermore, it exhibits excellent cycling durability, maintaining 95.0% of its initial capacitance after 10,000 cycles. The superior electrochemical performance of the graphene-enhanced, manganese-doped nickel–cobalt oxide electrode is attributed to the synergistic contributions of the hierarchical G@MNCO structure, the three-dimensional Cu foam current collector, and the binder-free fabrication process. These features promote quicker electrolyte ion diffusion into the electrode material and ensure robust adhesion of the active materials to the current collector. Full article

Nitrite (NO₂⁻) has long been recognized as a contaminant of concern due to its detrimental effects on both human health and the environment. As a result, there is a continuing need to develop sensitive, real-time, low-cost, and portable systems for the accurate detection of trace levels of NO₂⁻ in drinking water. We present a novel, low-cost, and easy-to-fabricate amperometric sensor designed for detecting low concentrations of NO₂⁻ in drinking water. The fabrication technique involves the electrodeposition of manganese and copper oxides onto a carbon working electrode. CuO and MnO₂ act synergistically as efficient catalysts for the electrooxidation of nitrite to nitrate (NO₃⁻) thanks to their complementary redox properties. The resulting sensor exhibits high catalytic activity toward the electrooxidation of NO₂⁻, with a sensitivity of 10.83 μA/µM, a limit of detection (LOD) of 0.071 µM, and a good linear dynamic concentration range (0.2–60 µM). The sensor’s performance was evaluated against potential interfering analytes (NO₃⁻, Cl⁻, NH₄⁺, and NH₂Cl), all of which showed negligible interference. Reproducibility (maximum standard deviation 2.91%) and repeatability (usable up to three times) were also evaluated. Full article

Lithium-ion batteries (LIBs) are widely used in diverse applications, ranging from portable ones to stationary ones. The appropriate handling of the immense amount of spent batteries has, therefore, become significant. Whether recycled or repurposed for second-life applications, knowing their chemistry type can lead to higher efficiency. In this paper, we propose a novel machine learning-based approach for accurate chemistry identification of the electrode materials in LIBs based on their temperature dynamics under constant current cycling using gated recurrent unit (GRU) networks. Three different chemistry types, namely lithium nickel cobalt aluminium oxide cathode with silicon-doped graphite anode (NCA-GS), nickel cobalt aluminium oxide cathode with graphite anode (NCA-G), and lithium nickel manganese cobalt oxide cathode with graphite anode (NMC-G), were examined under four conditions, 0.2 C charge, 0.2 C discharge, 1 C charge, and 1 C discharge. Experimental results showed that the unique characteristics in the surface temperature measurement during the full charge or discharge of the different chemistry types can accurately carry out the classification task in both experimental setups, where the model is trained on data under different cycling conditions separately and jointly. Furthermore, experimental results show that the proposed approach for chemistry type identification based on temperature dynamics appears to be more universal than voltage characteristics. As the proposed approach has proven to be efficient in the chemistry identification of the electrode materials LIBs in most cases, we believe it can greatly benefit the recycling and second-life application of spent LIBs in real-life applications. Full article

Combining carbon materials with oxides in a hybrid electrode is an effective way to control supercapacitor performance in terms of balancing energy and power density with cycling stability. However, it is still unclear how the mixing method of each component affects the supercapacitor performance. In this study, the influence of mixing reduced graphene oxide (rGO) with ilmenite-type nickel-manganese oxide (NiMnO₃) on the capacitive behaviour of the resulting composites is investigated. Two preparation methods are compared: mechanical mixing and ultrasonication. The capacitive characteristics were evaluated in hybrid supercapacitors using 6M KOH electrolyte. The bulk, surface, and morphological changes of the composites after long-term cycling were probed by EIS and ex situ XRD, XPS, and SEM analyses. It is established that the composites obtained by mechanical mixing exhibit better performance due to the stable contact between rGO and NiMnO₃ particles, favourable surface reactions with KOH and preserved morphology of rGO. These findings indicate that efficient hybrid electrodes can be achieved without relying on costly synthesis techniques such as hydrothermal or ultrasonic treatments. Full article

Electrolytic metallic manganese (EMM) is used as an alloying metal to provide resistance to abrasion and corrosion. Highly pure EMM is obtained through electrorecovery or electrowinning. Efforts are ongoing to improve the efficiency and profitability of this process, as 85 to 90% of manganese is produced by the mining industry. This study applied computer-aided engineering (CAE) to provide information on the behavior of the potential distribution at the electrodes in cells separated by membranes, which allows for the optimization of the EMM production process. The experimental results obtained galvanostatically for EMM allowed for validation of the simulation parameters. It was determined that the cell with 11 compartments is more suitable compared to cells with fewer compartments, since it has lower oxidation-normalized current density and oxidation potential, which affect the distribution of cathodic potential in the process of obtaining EMM. The simulation highlighted a better distribution of the cathodic and anodic potentials due to the increase in the number of electrodes. This saves time and resources in the design of electrochemical cells with a greater number of compartments. Full article

With increasing energy demands, fuel cells are a popular avenue for portability and low waste emissions. Hydrogen fuel cells are popular due to their potential output power and clean waste. However, due to storage and transport concerns, hydrogen peroxide fuel cells are a promising alternative. Although they have a lower output potential compared to hydrogen fuel cells, peroxide can act as both the oxidizing and reducing agent, simplifying the structure of the cell. In addition to reducing the complexity, hydrogen peroxide is stable in liquid form and can be stored in less demanding methods. This paper investigates chelated metals as electrode material for hydrogen peroxide fuel cells. Chelated metal complexes are ring-like structures that form from binding organic or inorganic compounds with metal ions. They are used in medical imaging, water treatment, and as catalysts for reactions. Copper(II) phthalocyanine, phthalocyanine green, poly(copper phthalocyanine), bis(ethylenediamine)copper(II) hydroxide, iron(III) ferrocyanine, graphene oxide decorated with Fe₃O₄, zinc phthalocyanine, magnesium phthalocyanine, manganese(II) phthalocyanine, cobalt(II) phthalocyanine are investigated as electrode materials for peroxide fuel cells. In this study, the performance of these materials is evaluated using cyclic voltammetry. The voltammograms are compared, as well as observations are made during the materials’ use to measure their effectiveness as electrode material. There has been limited research comparing the use of these chelated metals in the context of hydrogen peroxide fuel cells. Through this research, the goal is to further the viability of hydrogen peroxide fuel cells. Poly(copper phthalocyanine) and graphene oxide doped with iron oxides had strong redox catalytic activity for use in acidic peroxide single-compartment fuel cells, where the poly(copper phthalocyanine) electrode compound generated the highest peak power density of 7.92 mW/cm² and cell output potential of 0.634 V. Full article

Manganese-based oxides, particularly β-MnO₂, have emerged as promising cathode materials for aqueous zinc-ion batteries (ZIBs) due to their high theoretical capacity, low cost, and intrinsic safety. However, their sluggish reaction kinetics, limited active sites, and poor conductivity often lead to suboptimal electrochemical performance. To address these limitations, we propose a facile ethanol-mediated hydrothermal strategy to engineer rod-like β-MnO₂ nanostructures with tailored oxygen vacancies. By precisely adjusting ethanol addition (3–5 mL) during synthesis, oxygen vacancy concentrations were optimized to enhance electronic conductivity and active site exposure. The experimental results demonstrate that β-MnOx-2-5 synthesized with 5 mL of ethanol delivers an exceptional areal capacity of 4.87 mAh cm⁻² (348 mAh g⁻¹, 469.8 Wh kg⁻¹) at 200 mA cm⁻² under a high mass loading of 14 mg cm⁻². Further, a hybrid electrode combining oxygen-deficient β-MnO₂-x-3 (air-calcined) and structurally stable β-Mn₅O₈-y-3 (Ar-calcined) achieves a retained capacity of 3.9 mAh cm⁻² with stable cycling performance, achieving an optimal equilibrium between high capacity and long-term operational durability. Systematic characterizations (XPS, ESR, XANES, FT-EXAFS) confirm vacancy-induced electronic structure modulation, accelerating ion diffusion and redox kinetics. This scalable vacancy engineering approach, requiring only ethanol dosage control, presents a viable pathway toward industrial-scale ZIB applications. Full article

Dinuclear di-µ-oxo complexes of Mn³⁺ and Mn⁴⁺ ions, and mononuclear complexes of Mn³⁺ ions with tetraazamacrocycles ([12]aneN₄, [14]aneN₄, [15]aneN₄) and C-substituted derivative (Me₆[14]aneN₄) as well as mononuclear complexes of Mn²⁺ ions with N-substituted derivatives ((N-Me)₂[14]aneN₄, (N-Me)₄[14]aneN₄, (N-Me)Me₂py [14]aneN₄) and with oxo₂[14]aneN₄ were studied. Based on spectroscopic (UV VIS and IR) and conductometric studies, the types of synthesised complexes (cis or trans isomers of mononuclear Mn³⁺ complexes, oxygen bridges and class II according to Robin and Day classification for dinuclear complexes) were determined. On the basis of voltammetric and spectroelectrochemical studies, trans-cis isomerisation at the level of Mn²⁺ ion complexes and cis-trans isomerisation at the level of Mn³⁺ ion complexes were demonstrated for complexes of ligands with free C positions. The N-substituted derivatives oxidise according to the EC mechanism, in which the follow-up reaction is a disproportionation reaction. The thermodynamic stabilisation of Mn³⁺ ions was determined by comparing the formal potentials (E_f⁰), the disproportionation constants (k₁) and the formation constants (β^III). The study showed the possibility of oxidation of mononuclear, pseudo-octahedral Mn³⁺ ion complexes to dinuclear complexes and the greatest stabilisation of Mn³⁺ ions, both in monomers and dimers of ligands with free N positions. Full article

This paper presents entropy measurements for a large set of commercial Li-ion cells. We present entropy data on full cells with a variety of common Li-ion cell electrode chemistries; graphite, hard carbon, lithium-titanium-oxide (LTO), lithium cobalt-oxide (LCO), nickel manganese cobalt oxides (NMC), nickel cobalt aluminium oxide (NCA), lithium iron-phosphate (LFP), as well as electrodes with mixes of these. All data were collected using an accelerated potentiometric method in steps of approximately 5% State-of-Charge (SoC) across the full SoC window. We observe that the entropy profiles depend on the chemistry of the Li-ion cells, but that they also vary between different commercial cells with the same chemistry. Entropy contributions are quantified with respect to both, their means, positive and negative contributions as well as their SoC variation. In addition, we present how different cyclic ageing temperatures change the entropy profiles for a selected commercial Li-ion cell through ageing. A clear difference in entropy profiles is observed after a capacity loss of 20%. This difference can be attributed to different ageing mechanisms within the Li-ion cells, leading to changes in the balancing of electrodes, as well as changes in the electrode materials. Full article

Ammonia zinc refining has the benefits of low energy consumption, high zinc recovery, and good environmental protection compared with traditional acid and alkaline zinc refining. However, in the production process of refining zinc with ammonia, the anode undergoes chlorine precipitation, and then the oxidation of the ammonia precipitation of some nitrogen occurs. Ammonia replenishment is a cumbersome process that results in large amounts of ammonia volatilization and environmental pollution. In ammonia zinc refining, it is important to ensure the concentration of ammonia and chlorine, as the graphite anodes used in conventional ammonia zinc refining do not retain chlorine and ammonia and dissolve slowly due to oxidation. Therefore, this paper proposes a new measure to conserve chlorine and ammonia to reduce anode chlorine generation by adding an anionic barrier layer and selecting manganese anode materials with selective oxygen precipitation. Under the conditions of 50 × 100 mm sized electrodes, a current density of 350 A/m², and a temperature of 60 °C, a graphite anode and manganese anode were used for electrowinning and for the collection of anode gas under different additive conditions. For the first time, we present a comparative analysis of gas composition, using gas chromatography to demonstrate the feasibility of the different measures used to preserve chlorine, ammonia, and oxygen for industrial applications, as well as the advantages of using these methods in reducing costs. And the experiments show that, by adding the anionic barrier layer, adding urea, and using manganese anode materials with selective oxygen precipitation, the nitrogen precipitation in the anode gas can be reduced to 40–50%, and oxygen precipitation reaches 48.76%. Full article

Lithium nickel manganese cobalt oxides (NMCs) are widely used as cathode materials in commercial batteries. Efforts have been made to enhance battery energy density and stability by adjusting the element ratio. Nickel-rich NMC shows promise due to its high capacity; however, its commercial viability is hindered by severe capacity fade, primarily caused by poor mechanical stability. To address this, understanding the chemo-mechanical behavior of Ni-rich NMC is crucial. The mechanical failure of Ni-rich NMC materials during battery operation has been widely studied through theoretical approaches to identify possible solutions. The elastic properties are key parameters for structural analysis. However, experimental data on NMC materials are scarce due to the inherent difficulty of measuring the properties of electrode active particles at such a small scale. In this study, we employ molecular dynamics (MDs) simulations to investigate the elastic properties of NMC materials with varying compositions (NMC111, NMC532, NMC622, NMC721, and NMC811). Our results reveal that elasticity increases with nickel content, ranging from 200 GPa for NMC111 to 290 GPa for NMC811. We further analyze the contributing factors to this trend by examining the individual components of the elastic properties. The simulation results provide valuable input parameters for theoretical models and continuum simulations, offering insights into strategies for reducing the mechanical instability of Ni-rich NMC materials. Full article

The growing demand for efficient energy storage solutions has highlighted the potential of aqueous sodium-ion (Na⁺) batteries, known for their cost-effectiveness and environmental benefits. Despite their promise, challenges such as low specific capacities resulting from proton (H⁺) intercalation issues have limited their effectiveness. This study introduces a novel alkaline electrolyte environment using tetrabutylammonium hydroxide (TBAH) combined with chloride ions (Cl⁻) to improve the Na⁺ storage performance of manganese oxide (MnO₂) cathodes. The optimized electrolyte achieved a remarkable reversible capacity of 101 mAh g⁻¹ for γ-MnO₂ at a current density of 0.1 A g⁻¹, surpassing conventional aqueous solutions. The synergistic effect of TBAH and Cl⁻ not only suppresses H⁺ intercalation, but also prevents the formation of manganese hydroxide passivation layers during cycling. These advancements contribute to a better understanding of electrolyte design for high-performance Na⁺ storage electrodes, marking a significant step forward in aqueous sodium-ion battery technology. Full article

High-performance electrode materials are fundamental to improving supercapacitor performance, serving as key factors in developing devices with high energy density, high power density, and excellent cyclic stability. Non-stoichiometric spinels with phase deficiencies can achieve electrochemical performance that surpasses that of stoichiometric materials, owing to their unique structural characteristics. In this study, we used a microwave-assisted method to synthesize a high-performance non-stoichiometric spinel material with phase deficiencies, Mn_0.5Co_2.5O₄, which displayed a wide potential window (1.13 V in a traditional aqueous three-electrode system) and high specific capacitance (716.9 F g⁻¹ at 1 A g⁻¹). More critically, through microwave-assisted doping engineering, nickel was successfully doped into the phase-deficient Mn_0.5Co_2.5O₄, resulting in a spinel material, Ni−Mn_0.5Co_2.5O₄, with significant lattice defects and a mixed 1D/2D morphology. The doping of nickel effectively promoted the high-state conversion of manganese valence states within the manganese cobaltite material, substantially increasing the quantity of highly active Co³⁺ ions. These changes led to an increase in the density of reactive sites, effectively promoting synergistic interactions, thereby significantly enhancing the material’s conductivity and energy storage performance. The specific capacitance of Ni−Mn_0.5Co_2.5O₄ reached 1180.6 F g⁻¹ at 1 A g⁻¹, a 64.7% improvement over the original Mn_0.5Co_2.5O₄; at a high current density of 10 A g⁻¹, the capacitance increased by 14.3%. Notably, the charge transfer resistance was reduced by a factor of 41.6. After 5000 cycles of testing, the capacity retention stood at 79.2%. This work reveals the effectiveness of microwave-assisted doping engineering in constructing high-performance non-stoichiometric spinel-type bimetallic oxide materials, offering advanced strategies for the development of high-performance electrode materials. Full article