Search Results (966)

Seawater electrolysis is emerging as a key alternative strategy for sustainable hydrogen production in water-scarce regions such as the Atacama Desert; however, the high concentration of chloride ions poses significant challenges related to material stability, selectivity, and corrosion resistance. In this context, Prussian Blue Analogues (PBAs) have recently gained attention as multifunctional materials capable of operating in highly saline environments such as seawater. This review provides a critical analysis of PBAs as electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in seawater and brine systems, with a particular emphasis on nickel hexacyanoferrate (NiHCF), cobalt hexacyanoferrate (CoHCF), and copper hexacyanoferrate (CuHCF). In addition, a comparative analysis across different electrochemical applications is presented, highlighting the limited number of studies conducted under real seawater conditions. Furthermore, the limitations of current electrochemical evaluation protocols are discussed, and a framework for realistic benchmarking under saline conditions is proposed. Finally, emerging opportunities in hybrid materials and high-entropy PBAs are addressed, positioning PBAs as a promising platform for next-generation electrochemical technologies for sustainable solar hydrogen production from seawater or highly chloride-concentrated brines. Full article

Co-based oxides are commonly introduced into porous ceramic membranes to add catalytic activity, but their attachment at the atomic scale remains unclear. We examined a buried Co₃O₄/Al₂O₃ interface formed by sol–gel deposition and thermal conversion. Site-specific focused-ion-beam (FIB) lift-out, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDS), and high-resolution transmission electron microscopy (HRTEM) were used to access and characterize the interface. A Co-rich spinel-type domain with a (111) lattice spacing was observed next to Al₂O₃(012). The observations guided density functional theory (DFT) initial models. After structural relaxation, substrate-O-mediated Co-O contacts emerged from both starting geometries: the O-bridged-start model exhibited eight contacts across four Co sites, whereas the non-bridged-start model developed three contacts around one Co site. Around the Co-O-Al linkages, there is a clear manifertation of the interface polarization and charge redistribution, indicated by charge-density-difference and Bader analyses. In both models, projected density of states (PDOS) showed coupling between Co 3d and O 2p states, while integrated crystal orbital Hamilton population (ICOHP) analysis further indicated that O atoms retained Al-O bonds while forming occupied-state Co-O bonds. These results support a representative, laterally distributed Co-O-Al motif as an atomic-scale pathway for chemically attaching the functional oxide to porous alumina. Full article

The growing demand for sustainable, flexible, and high-performance electrode materials for energy storage has motivated the development of polymer-based composite electrodes with enhanced electrochemical properties. In this study, flexible cobalt oxide (Co₃O₄)-iron oxide (Fe₂O₃) nanoparticle-impregnated sodium alginate (NaAlg) as the polymer matrix composite membranes were developed via a simple solution-casting method to exploit the synergistic pseudocapacitive behaviour of mixed metal oxides together with the excellent film-forming ability, flexibility, and eco-friendly nature of NaAlg. The prepared membranes’ structural features, morphology, and electrochemical properties were examined through a set of techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Universal Testing Machine (UTM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation (PDP), and galvanostatic charge–discharge (GCD). Characterisation techniques validated the effective loading of Co₃O₄ and Fe₂O₃ nanoparticles within the NaAlg matrix, and revealed the efficient interfacial interactions, structural integrity, and electrochemical properties of the composites. GCD tests showed a very high specific capacitance of 571.43 F g⁻¹ at 1.2 A g⁻¹. The best-performing electrode produced a top energy density of 155.56 Wh kg⁻¹ at a power density of 2800 W kg⁻¹ and still showed around 91% capacitance retention after 2500 charging–discharging cycles with coulombic efficiency close to 100%. Boosted electrochemical performance is due to the synergistic effect of Co₃O₄-Fe₂O₃ nanoparticles that not only offer plenty of electroactive sites but also help in effective electron and ion transport within the polymer matrix. The results obtained here confirmed the capabilities of Co₃O₄-Fe₂O₃@NaAlg composite membranes as green and potent electrode materials for future supercapacitor devices. Full article

Vanadium-doped cobalt ferrite nanoparticles, Co_1−xV_xFe₂O₄ (x = 0.0–0.04), were synthesized via a guar gum-assisted alkaline co-precipitation. Guar gum biopolymer proved to be a stabilizing and templating agent that improves vanadium incorporation and porous structure development. Both the as-synthesized and annealed Co-V catalysts are monophasic spinel ferrites, as determined by XRD. XRF and EDS confirmed the presence of Co, Fe, V, and O and allowed assessment of the elemental composition of the synthesized samples. The BET isotherms are of type IV, indicating that a mesoporous surface was formed. Vanadium doping increased the specific surface area approximately threefold, from 29.6 m²/g for CoFe₂O₄ to 86.24 m²/g for Co_0.97V_0.03Fe₂O₄. The vanadium-substituted cobalt ferrites were found to be effective catalysts in the decomposition of hydrogen peroxide and degradation of 4-nitrophenol. After annealing at 500 °C, the catalytic efficiency decreased by about half, indicating that the pristine surface of the as-synthesized ferrites has specific sites for H₂O₂ activation. The incorporation of vanadium atoms had a non-linear effect on catalytic performance. The optimal vanadium ion content for catalytic activity is x(V) = 0.03, as determined from the rate constants of H₂O₂ decomposition and 4-nitrophenol oxidation. The maximum degradation of 4-nitrophenol was recorded at 93% after 120 min. Measurements of ortho-phenylenediamine oxidation showed that CoV-0.03 is the most active radical-generating catalyst, confirming the close relationship between H₂O₂ decomposition and radical formation. XPS results confirm the catalytic redox cycling of Fe and Co ions, while subsurface V ions likely act as structural and electronic promoters. The obtained results identify Co_0.97V_0.03Fe₂O₄ as an effective magnetic catalyst for Fenton-like water treatment applications. Full article

Lithium-ion battery-powered (LIB-powered) electric bicycles (E-bicycles) are widely used in China, with many accidental fires occurring in parking facilities in high-rise buildings. E-bicycle parking areas in high-rise buildings have become fire-prone zones. There is an urgent need to establish fire codes for the parking facilities in high-rise buildings. However, only limited research has been conducted on protecting against such fires. Uncertainties also remain about appropriate methods for fire barriers and fire suppression in parking facilities. To better understand parking facility fires in high-rise buildings, four fire scenarios and a total of six experiments on LIB-powered E-bicycle fires were studied in this paper, aiming to seek principles on how to prevent serious fire accidents by isolating E-bicycles parked in parking facilities. Fire spread between the LIB-powered E-bicycles and the propagation patterns of smoke generated by E-bicycle fires within parking facilities were studied. The effectiveness of different fire extinguishing methods in suppressing LIB-powered E-bicycles fires was discussed. The reasonable fire separation distance for E-bicycles was determined. It was found that LIBs with ternary lithium-ion batteries (such as nickel-cobalt-manganese) are more prone to initiate thermal runaway. Setting appropriate separation distances could effectively minimize the spreading of E-bicycle fires in high-rise buildings. A sprinkler system with a lower hazard class is proposed to operate under lower water pressure and flow rates. Fire control methods were proposed, including fire-resistive eave and fire barrier. The results can be used in setting up fire code. Full article

Two diastereoisomers of bis(mepirizole)bis(isothiocyanato-κ,N)cobalt(II) (1 and 2) are isolated from the reaction of cobalt(II) thiocyanate and mepirizole, depending on the crystallization solvent (ethanol, 1; acetonitrile, 2). In both crystal structures, the Co(II) ions exhibit distorted octahedral [CoN₄N′₂] environment. The analysis of the packing frameworks shows a cooperative relationship between non-classical H-bonds C(sp³)-H···X (X = N, O, S, π) and π-hole bonds, which control the arrangement of the supramolecular 3D networks. The values of the shortest intermolecular metal–metal separation are 8.584(2) Å in 1 and 8.249(1) Å in 2. Both diastereoisomers exhibit magnetic behavior typical of mononuclear Co(II) systems with significant zero-field splitting (ZFS) values, with D being 75.8(1) and 52.9(2) cm⁻¹ for 1 and 2, respectively. Q-band EPR studies confirm the positive value for the D parameters for both compounds. Alternating current dynamic susceptibility measurements show that 1 and 2 exhibit field-induced slow relaxation of the magnetization, which is reminiscent of single-ion magnet (SIM) behavior. Full article

The development of high-performance anode materials remains a key challenge for advancing lithium-ion battery (LIB) technology. In this work, an oxy-bridged polymer cobalt phthalocyanine (Poly-CoPc) and its single-walled carbon nanotube-modified composite (Poly-CoPc/SWCNT) were successfully synthesized and systematically investigated as potential anode materials. The structural, chemical, and morphological properties of the materials were thoroughly characterized using Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (SEM-EDX), and transmission electron microscopy (TEM) techniques. Morphological studies demonstrated a uniform dispersion of Poly-CoPc over the SWCNT network, leading to an interconnected conductive structure with enhanced surface area. Electrochemical performance was evaluated and compared with pristine Poly-CoPc. Compared to pristine Poly-CoPc, the Poly-CoPc/SWCNT composite exhibited significantly improved electrochemical behavior, including higher specific capacity, enhanced rate performance, and superior cycling stability. The composite delivered a high initial discharge capacity of 2016 mA g⁻¹ and maintained an excellent reversible capacity of 1047 mA g⁻¹ after 100 cycles at 0.1 A g⁻¹. Furthermore, it demonstrated outstanding rate capability, retaining a capacity of 855 mA g⁻¹ at 0.5 A g⁻¹. This enhanced performance is attributed to the synergistic effect between the redox-active Poly-CoPc and the highly conductive SWCNT network, which facilitates efficient electron transport, improves ion diffusion, and stabilizes the electrode structure during cycling. These results highlight that SWCNT-modified Poly-CoPc is a promising candidate for next-generation high-performance LIB anodes. Full article

This study investigated how acid concentration affects leaching from pyrolyzed LIBs’ (lithium-ion batteries’) black mass (BM) by stepwise acidification with eight acids at 70 °C under identical starting conditions. A citric-acid control without BM matched the calculated pH, whereas BM buffered solutions to ∼pH 9.5 and increased the measured pH. Stabilized pH provided a consistent reference within each experiment, but similar pH values across acids produced very different leaching efficiencies. At pH ≈ 3, lithium leaching was ∼pH 85% for formic acid and ∼pH 60% for citric acid. The maximum lithium leaching ranged from 49% (ascorbic acid) to 92% (sulfuric acid), while organic acids often showed limited cobalt and nickel dissolution. For formic acid, speciation and metal-formate solubility calculations showed that higher acid concentration does not necessarily increase transition-metal leaching and may suppress cobalt and nickel. Thus, pH is stable within each acid system but not transferable across acids, and high solid loading (250 g L⁻¹) further requires acid-specific evaluation. The results indicate that acid-dependent speciation and complexation, rather than proton concentration alone, control extraction and can decouple acid dosage from leaching performance. Full article

Recycling of lithium-ion batteries (LIBs) remains challenging due to high energy requirements, losses of key elements like lithium, and the heterogeneity of waste streams arising from different cathode chemistries. This study evaluates multiple recycling methods for LIBs black mass (BM), to recover critical raw materials and other valuable components. Three types of BM including nickel–manganese–cobalt (NMC), lithium iron phosphate (LFP) and a heterogeneous mixture of cell phones and laptops (HL; German: Handy/Laptops), were treated using froth flotation, pyrometallurgy, and biohydrometallurgy and their respective recovery efficiencies were assessed. The flotation results revealed that the HL sample had the lowest mis-recovery of non-ferrous metals into the froth product (around 10%), leading to further flotation only for HL. During screening, 94–99% of iron, phosphorus, and carbon in LFP-type BM were recovered in the fine fraction (<45 µm), while 92–99% of lithium, cobalt, manganese, nickel, and carbon in NMC-type BM were recovered in the same fraction. During precipitation, 99% of iron and 100% of phosphorus were recovered from LFP bioleachates at pH 3, while ~97–100% of dissolved cobalt, manganese, and nickel were recovered from NMC bioleachates. These findings confirm that no single recycling method is optimal for all battery chemistries. Full article

Objective: Our objective was to determine the salivary levels of cobalt, nickel, chromium, and titanium ions at the end of fixed orthodontic treatment and during the post-removal period (1 and 3 months after removal of the fixed appliance). Methods: This pilot longitudinal study included fifteen individuals (10 females and 5 males). Five milliliters of saliva was collected at three time points: T1 (before withdrawal of orthodontic appliances), T2 (one month post-withdrawal), and T3 (three months post-withdrawal). The concentrations of nickel (Ni), titanium (Ti), chromium (Cr), and cobalt (Co) in the samples were analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). All samples were analyzed in triplicate. The data were analyzed by repeated-measures ANOVA, and differences were considered significant if the p-value was ≤0.05. Results: The concentrations of Co, Cr, and Ti at the three time points were low and decreased after the removal of the orthodontic appliance, while Ni showed an increase at T3. Co and Ni showed significant differences between T3 and T1 (p = 0.016 and p = 0.029, respectively). There was also significantly increased Ni ion release at T3 compared to T2 (p = 0.010). The Cr and Ti levels at all three time points were significantly different (Cr: p = 0.001; Ti: p = 0.001 and p = 0.005). Conclusions: The levels of cobalt, chromium, and titanium in saliva decreased after removal of the orthodontic appliance, whereas nickel increased at T3. However, the levels were below the mean dietary intake levels; therefore, these concentrations can be considered non-toxic. This study has limitations that should be considered when interpreting the results. Full article

Battery Energy Storage Systems (BESS), utilising chemistries based on Nickel Manganese Cobalt (NMC) containing lithium-ion devices, often present fire safety hazards that existing qualitative risk frameworks, including NFPA 855’s 5 × 5 consequence-likelihood matrix, are insufficiently granular to quantify. This paper presents an original probabilistic risk assessment (PRA) of fire hazards associated with BESS for a 485.52 kWh NMC installation at the Equinix SG4-4A data centre in Singapore, using Monte Carlo simulation (N = 10,000 iterations) to characterise uncertainty in hydrogen fluoride (HF) gas dose, time to Immediately Dangerous to Life or Health (IDLH) concentration, cabinet-to-cabinet propagation probability, and suppression effectiveness. The HF yield is modelled as a triangular distribution (0.3–0.8 g/kWh, mode 0.5 g/kWh), ventilation activation delay as log-normal (median 90 s), and suppression effectiveness as a piecewise function of water application delay. The results demonstrated that HF dose exceeded the National Institute for Occupational Safety and Health (NIOSH) IDLH of 25 mg/m³ in 100% of simulated scenarios for both single- and two-compartment designs, thus confirming that threshold HF toxicity was essentially unavoidable for any occupant present during a full thermal runaway event, and that ventilation alone cannot achieve adequate risk reduction. The single-stage suppression effectiveness was found to be only 37.9% (mean), providing quantitative confirmation that two-stage (clean agent + water) suppression is warranted for NMC chemistry. The two-compartment design was found to reduce the peak HF dose by 50%, and also reduced the mean IDLH clearance time from 599 to 301 min, thus shifting residual risk from As Low As Reasonably Practicable (ALARP)-tolerable to broadly acceptable under UK Health and Safety Executive (HSE) criteria. The paper proposes a quantitative PRA framework as a complement to NFPA 855 Chapter 5’s qualitative Hazard Mitigation Analysis, enabling more informed engineering decisions for BESS fire safety. To the best of our knowledge, this is the first study to apply Monte Carlo simulation to HF dose modelling in a tropical data-centre BESS context and thereby address a documented gap in the literature. Full article

In the context of an increasing demand for electricity, batteries increasingly appear as one of the main sources of power supply. In particular, research on batteries is mainly focused on new and high-performance materials, and innovative and more sustainable production processes. This work addresses both aspects by developing a gravure-printed cathode based on lithium nickel manganese cobalt oxide (NMC 111, LiNi_0.33Mn_0.33Co_0.33O₂). To this end, the formulation of a gravure-printable ink was investigated in order to meet both the printing and functional requirements. The formulation of a multicomponent dispersion able to produce a cathodic layer was particularly challenging, since such a system was found to be highly sensitive to the composition and specific interactions among the active material and the other components involved in ink preparation. Although a methodology based on Ca, aimed at obtaining layers with high macroscopic printing quality, was adopted, only a few printable inks having similar characteristics were obtained. From a microscopic point of view, printing allowed the identification of the best ink formulation able to produce the greatest layer homogeneity, thus yielding the best possible performance (150 mAh g⁻¹ at C/20). Full article

The rapid increase in electric vehicles has increased the generation of spent lithium-ion batteries (LIBs) and the need for efficient lithium recovery technologies. This study compared two distinct sulfation roasting routes, using sodium sulfate (Na₂SO₄) at 750 °C and sulfuric acid (H₂SO₄) at 550 °C, applied to black mass derived from lithium iron phosphate (LFP) and lithium nickel manganese cobalt oxide (NCM) batteries. Metal extraction efficiencies were determined by inductively coupled plasma optical emission spectrometry, while reaction products were identified by X-ray diffraction analysis. Sulfation roasting using Na₂SO₄ resulted in low lithium recovery for both materials, with maximum extractions of 5.7% for LFP and 24.5% for NCM. In contrast, H₂SO₄-assisted roasting achieved high lithium recovery from NCM black mass, reaching 90.8%, 91.5%, and 88.5% at 45, 90, and 180 min at 550 °C, respectively, with lithium predominantly converted into water-soluble lithium sulfate. Lithium extraction from LFP black mass remained below 13% under all conditions. Statistical analysis confirmed that lithium recovery at 45 min was equivalent to longer residence times, while prolonged roasting increased manganese coextraction and altered cobalt and nickel behavior. Overall, sulfuric acid-assisted sulfation roasting is an efficient and energy-favorable route for lithium recovery from NCM black mass, whereas sulfation roasting is unsuitable for LFP materials, under the tested conditions. The results highlight the importance of cathode chemistry segregation and demonstrate the feasibility of reducing processing time without compromising lithium recovery. Full article

Cobalt–nickel–copper alloys were electrodeposited over a range of current density and with three different aqueous electrolytes having variable metal ion ratios, in order to examine changes in the deposit composition and to use them as cathodes for nitrate electrolysis. The alloys were electrodeposited galvanostatically from a citrate electrolyte onto rotating cylindrical steel substrates. The electrodeposition process exhibited anomalous codeposition behavior, favoring Co reduction over Ni and Cu. These electrodeposits were then used to examine their ability to reduce nitrate in simulated wastewater with 50 mg-N/L of NO₃⁻, sodium chloride, and sodium sulfate. Nitrate conversion and selectivity were characterized after electrolysis in a single-compartment cell with the alloys serving as the working electrode. Despite co-evolving hydrogen, the electrodeposited alloys were effective at generating both N₂ at high electrolysis current densities and ammonia species at lower values, with the deposit composition also affecting the conversion and products. It is the first demonstration of using Co-Ni-Cu ternary alloys for nitrate reduction. Full article

Capacitive deionization (CDI) is an environmentally advantageous desalination technology that is particularly suitable for the treatment of low- to medium-concentration saline water. Among different electrode materials, carbon materials are widely used due to their good electrical conductivity and high specific surface area, while they suffer from limited ion adsorption capacity. In this study, a cobalt/nitrogen-doped porous carbon fiber composite with Zn-induced porosity (CoNG@V@CNF), where “V” stands for “volatile pore-forming agent”, has been successfully prepared via electrospinning combined with a high-temperature carbonization process. The introduction of trace Co nanoparticles enhances the stability of porous graphene. In addition, N doping contributes to improved wettability and electronic conductivity, and the carbon fiber structure constructs a three-dimensional conductive network, providing fast channels for ion transport. Electrochemical tests show that the specific capacitance of CoNG@V@CNF reaches 252.76 F g⁻¹, demonstrating its superior charge storage capability. Furthermore, this study achieved a high salt adsorption capacity of 58.28 mg g⁻¹ and a competitive desalination rate performance of 1.94 mg g⁻¹ min⁻¹. After 40 cycles of testing, the salt adsorption capacity (SAC) remains at 56.72 mg g⁻¹, demonstrating its high stability during multiple charging and discharging processes. This work provides a new design strategy for developing high-performance CDI electrode materials. Full article