Search Results (450)

Transition-metal sulfides are promising electrode materials for high-performance supercapacitors but are often limited by poor conductivity, particle agglomeration, and insufficient active sites. Herein, Co-doped NiS₂ with tunable sulfur vacancies was directly grown on flexible carbon cloth via a facile one-step solvothermal method by systematically controlling sulfur source ratio, Ni:Co ratio, temperature, and reaction time. Structural analyses reveal that the optimized conditions of S:(Ni + Co) = 3:1, Ni:Co = 2:1, 160 °C, and 15 h promote the formation of phase-pure Co-doped NiS₂ hierarchical microspheres with enhanced crystallinity and abundant active sites from the synergistic interaction between Ni and Co. Consequently, the optimized electrode delivers an impressive capacitance of 1296 F g⁻¹ at a current density of 1 A g⁻¹, along with excellent rate performance, retaining more than 88% of its capacitance after 1500 charge/discharge cycles at current densities ranging from 2 to 20 A g⁻¹. This work highlights the critical role of synthesis parameter engineering in regulating defect chemistry, structure, and electrochemical performance in advanced energy storage applications. Full article

The development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) material was obtained using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim of creating efficient materials for hydrazine oxidation (HzOR) and direct hydrazine–hydrogen peroxide fuel cells (DHHPFC, N₂H₄–H₂O₂). The composition, structure, and surface morphology of the created materials were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N₂H₄–H₂O₂ fuel-cell tests were performed by applying the catalysts as both the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness. Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order of AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm⁻²), outperforming AWC–Cu–N (17.7 mW cm⁻²). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs. Full article

The adoption of lithium-ion batteries (LIBs) as secondary rechargeable batteries across many industries, including consumer electronics, electromobility, industrial tools, and electrical energy storage, is on the rise. As lithium-ion batteries approach the end of their life, there is a need to assess them for the possibility of a secondary application or reuse for a less demanding application. The extra connections of individual cells, BMS, temperature sensors, and other components to form a compact battery pack pose a challenge for second-life assessment, which usually prefers to separate individual cells for testing before discarding very bad cells for recycling and grading cells with substantive capacity based on their remaining capacity. This is a high cost for the second-life assessment. This work seeks to investigate an approach that avoids dismantling the battery pack into individual modules, cells, and BMS by including a BMS feature that allows the capacity and power ratings to be rescaled onboard after its first use. A set of cells with different chemistries was used in this work: a nickel–cobalt–aluminium oxide cathode with a silicon-doped graphite anode (NCA-GS), a nickel–cobalt–aluminium oxide cathode and graphite, and a lithium–nickel–manganese–cobalt oxide (NMC) cathode with a graphite anode (NMC-G) with various ageing states and behaviours. Their internal resistance and capacity at the beginning and end of life were compared. The scaling factor was obtained by finding the square root of the ratio of the internal resistance at EOL to that at BOL. With the current obtained by multiplying the cycling current rate by the rescaling factor, the surface temperature profile of the aged cells during cycling became the same as the temperature at the beginning of life. The relaxation voltage after discharge to 0% SOC and charge to 100% SOC was used to set the low and high cut-off voltages, respectively. This contributed significantly to reduced ageing and to a lower temperature rise in the spent cells. This set the stage for rescaling or derating battery systems without separating the individual cells, which is a huge cost for second-life use of lithium-ion batteries. BMS can be designed with configurable voltage and current limits, so that when repurposed for a second life, only a simple configuration or firmware update may be necessary. Full article

The selective conversion of syngas (CO + H₂) to higher alcohols (C₂₊OH) via Fischer–Tropsch synthesis (FTS) is a strategically important but challenging process, requiring catalysts that can simultaneously sustain C–C chain growth and preserve C–O bonds in reactive intermediates. Over the past decade (2015–2025), perovskite-type complex oxides with the formula ABO₃ have emerged as powerful precatalysts for this application, with LaCoO₃ attracting particular attention due to its structural flexibility, controllable reducibility, and the unique catalytic role of the La₂O₃ phase formed upon reduction. This review systematically covers recent advances in synthesis strategies for LaCoO₃ and substituted perovskites, including sol–gel, co-precipitation, mechanochemical, and template-assisted (KIT-6, SBA-15) methods; effects of A-site (Sr) and B-site (Cu, Ga, Ni, Mn) substitution on reducibility, active phase dispersion, and product selectivity; alkali promotion and its interaction with the perovskite-derived active phase; mechanistic understanding of the alcohol-forming pathway, including the Co⁰/Co³⁺ bifunctional site concept, CO insertion mechanism, and the role of La₂O₃ in suppressing the Boudouard reaction; and catalyst stability and deactivation pathways under FTS conditions. Original data from LaCoO₃ catalysts prepared by co-precipitation with ethylene glycol (LCO-1: S_KOH = 90%, Y_KOH = 57 mg·g⁻¹·h⁻¹) and via citrate/KIT-6 template synthesis (LCO/KIT-6: Y_KOH = 80 mg·g⁻¹·h⁻¹, S_BET = 220 m²/g) at 240 °C and 2 MPa serve as the primary experimental reference throughout. Key challenges, including the surface area–selectivity trade-off, long-term stability under industrial conditions, and opportunities in CO₂ hydrogenation, are critically discussed. Full article

Faced with a global energy crisis and ecological degradation, overall water splitting (OWS) is a pivotal approach for renewable energy conversion and storage. However, its industrial application is hindered by the high energy barriers/sluggish kinetics of the anodic oxygen evolution reaction (OER), as well as the scarcity of precious metal catalysts limiting large-scale deployment. Herein, a cobalt-based layered double hydroxide (Co-LDH) was used as the precursor, and a multi-strategy synergistic modification (hydrothermal synthesis, Fe doping, sulfurization, and external magnetic field magnetization) was applied to fabricate the Fe-Co₃S₄-MS-20 min electrocatalyst. This strategy establishes Fe-Co bimetallic synergistic active centers, and magnetic treatment modulates the electron configuration of Fe 3d orbitals without changing the material’s lattice spacing or morphology. Structural characterizations and electrochemical measurements were used to investigate the effects of combined modifications on the catalyst’s phase structure, morphology, electronic structure, and trifunctional catalytic performance toward the hydrogen evolution reaction (HER), OER, and urea oxidation reaction (UOR). The Fe-Co₃S₄-MS-20 min catalyst exhibits a larger electrochemical active surface area, lower charge transfer resistance, and smaller Tafel slope in 1 M KOH, it achieves overpotentials of 165 mV for HER (10 mA·cm⁻²) and 310 mV for OER (100 mA·cm⁻²), along with superior UOR performance and long-term stability. In situ impedance and Raman spectroscopy confirm that magnetization accelerates charge transfer and promotes in situ reconstruction. Synergistic multi-strategy regulation optimizes the electronic structure of active centers, reducing electrocatalytic energy barriers. This work provides new insights into designing high-performance non-precious metal electrocatalysts and offers experimental support for external magnetic field regulation in electrocatalyst modification. Full article

In this study, metal (copper, nickel, cobalt, chromium)-decorated ZnO nanorods are successfully grown on glass substrates via a hydrothermal synthesis method to test their electrical and gas-sensing properties. SEM images revealed the formation of metal nanoparticles surrounding the ZnO nanorods. To confirm that these structures originated from the metal nanoparticles, EDX analysis was performed, and the presence of metal nanoparticles was validated. XRD analysis indicated that the crystal structure of the ZnO nanorods was hexagonal, and shifts in the (002) plane were observed due to metal nanoparticle doping. ZnO nanorods functionalized with metal nanoparticles were tested at 200 °C against various gases (hydrogen, ethanol, chloroform) and at different gas concentrations. The time-dependent variation in current was observed when ZnO nanorods functionalized with metal elements were exposed to hydrogen gas at test concentrations ranging from 1000 ppm to 5000 ppm at 200 °C. The results demonstrated a clear correlation between the rate of current change and hydrogen concentration, with higher concentrations resulting in faster responses. Additionally, the sensitivity of ZnO nanorods with decorated metal nanoparticles to ethanol and chloroform gases at concentrations ranging from 1000 ppm to 5000 ppm, as well as their sensor responses to different gases at 200 °C, were also measured. Full article

Cobalt-free Li-rich Mn-based layered oxides are promising cathode materials for next-generation lithium-ion batteries because of their high capacity and reduced reliance on cobalt resources. However, their practical application is still limited by low initial Coulombic efficiency, sluggish reaction kinetics, severe voltage decay, and progressive structural degradation during cycling. In this work, a Na-assisted sol–gel strategy was developed to construct a cobalt-free Li-rich Mn-based cathode with multiple twin boundaries, and the optimized sample with the composition of Li_1.13Na_0.06Mn_0.594Ni_0.219O₂ was denoted as SG-TB. Unlike conventional surface coating or elemental doping, this strategy focuses on regulating the bulk crystal framework through crystallographic defect engineering. Structural characterizations indicate that SG-TB contains repeatedly distributed twin-boundary-related interfaces, supporting the presence of multiple twin boundaries within the layered cathode. Benefiting from this structural feature, SG-TB delivers an initial Coulombic efficiency of 96%, an initial discharge capacity of 256 mAh/g, a discharge capacity of 167 mAh/g at 5 C, and a capacity retention of 77% after 200 cycles at 1 C. Further analyses suggest that the multiple twin boundaries help reduce electrochemical polarization, enhance Li⁺ diffusion kinetics, and improve structural retention during cycling. This work demonstrates that Na-assisted multiple twin-boundary engineering is an effective strategy for improving the reaction reversibility and structural stability of cobalt-free Li-rich Mn-based cathodes. Full article

Cobalt oxide (Co₃O₄), a transition metal oxide with a cubic spinel structure, shows high potential in peroxymonosulfate (PMS) activation, while its catalytic efficiency is often limited by sluggish interfacial charge transfer. In this study, a chlorine-doped Co₃O₄ (Cl-Co₃O₄) was synthesized via a hydrothermal method for the degradation of bisphenol A (BPA) through PMS activation. Systematic characterizations and electrochemical tests demonstrated that chlorine doping could effectively modulate the surface electronic structure of the catalyst, significantly reducing the interfacial charge transfer resistance. Degradation performance evaluations revealed that, compared to pristine Co₃O₄, Cl-Co₃O₄ exhibited a significantly enhanced BPA degradation, achieving near-complete removal of BPA within 15 min under neutral to weakly alkaline conditions. The optimal operational parameters were determined as catalyst dosage of 0.20 g/L, PMS concentration of 0.10 mM and initial pH of 7.0–9.0, with the pseudo-first-order rate constant reaching 0.37 min⁻¹. High-concentration NO₃⁻ showed weak inhibition, while Cl⁻ showed moderate inhibition; 50 mM HCO₃⁻ drastically reduced the rate constant to 0.05 min⁻¹ and almost completely suppressed the reaction. Sulfate (SO₄•⁻) and superoxide (O₂•⁻) radicals were the primary reactive species in this system, explicitly excluding the role of the non-radical electron transfer pathway. Furthermore, three plausible BPA degradation pathways involving C-C bond cleavage, hydroxylation and C-O bond breakage were proposed with 19 intermediates identified. Ecotoxicological assessments based on ECOSAR verified that both acute and chronic toxicity of the intermediates to fish, daphnid and green algae decreased gradually, and the final small-molecule products exhibited significantly lower toxicity than the parent BPA. This study provides a novel strategy for enhancing the PMS activation performance of cobalt-based catalysts by modulating their electronic structures via halogen doping. Full article

A Co interface-doped hierarchical magnesium hydroxide (Co-PMH) heterojunction is fabricated by incorporating Co²⁺ into the L-threonate-directed crystallization of Mg(OH)₂ and its subsequent phosphorization. The interface-doped Co narrows the bandgap of magnesium hydroxide, resulting in enhanced visible light conversion and improved broad-spectrum antimicrobial activity. Under visible light irradiation for 30 min, the Co_0.1-PMH demonstrates an antibacterial efficiency exceeding 97% against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and methicillin-resistant S. aureus (MRSA). Mechanism analysis indicates that the stable doped Co-Mg heterojunction interface brings strong redox capabilities via a Z-scheme charge transfer pathway, driving the generation of ROS (primarily ·OH and ·O₂⁻) to eliminate bacteria adsorbed in situ. Even after three cycles, Co_0.1-PMH maintains high bactericidal activity (>95%) and biocompatibility (>93% cell survival). This makes Co-PMH a promising candidate for antimicrobial infection control. Full article

Nitrogen-doped carbon dots (CDs) were fabricated via a one-pot hydrothermal route using hydroquinone and o-phenylenediamine as dual precursors. The as-prepared CDs were then anchored onto iron-cobalt oxide nanosheets (FeCo-ONSs) to construct a composite nanozyme, denoted as CDs/FeCo-ONSs. Although FeCo-ONSs possess intrinsic peroxidase-like (POD-like) activity, the integration of CDs with FeCo-ONSs resulted in a remarkable enhancement of catalytic performance. Specifically, in the presence of hydrogen peroxide (H₂O₂), the CDs/FeCo-ONS composite promoted the efficient oxidative transformation of 3,3′,5,5′-tetramethylbenzidine (TMB), leading to the formation of a blue-colored oxidized product. Based upon the enhanced POD-like activity of CDs/FeCo-ONSs, a highly sensitive colorimetric sensor was developed for the detection of ascorbic acid (AA). This method exhibited a wide linear detection range of 0.1 to 50 µM with a low limit of detection (LOD) of 0.018 µM. Furthermore, the developed method was successfully applied to the determination of AA in commercial beverages and fresh fruits, verifying its potential feasibility for practical applications in food quality control. Full article

The electrochemical nitrate reduction reaction (NO₃RR) represents a promising strategy for wastewater remediation and sustainable ammonia (NH₃) production. However, its practical application is hindered by low selectivity and competition from the hydrogen evolution reaction (HER). Herein, a series of PtBi-Co_X (X = 4.9, 5.3, and 6.1) ternary alloy nanoplates was synthesized via a one-pot method with tunable Co content. Structural characterization indicates that Co incorporation does not significantly alter the hexagonal crystal structure of the PtBi phase. Electrochemical measurements reveal that the NO₃RR performance varies with PtBi-Co_X (X = 4.9, 5.3, 6.1), with PtBi-Co_5.3 exhibiting the optimal balance of activity and selectivity among the studied samples. At −0.5 V vs. RHE, it achieves a Faradaic efficiency (FE) of 97.75 ± 0.75% and an NH₃ yield rate of 9.33 ± 0.50 mg h⁻¹ mg_cat⁻¹ under the tested conditions. In addition, the catalyst exhibits relatively suppressed HER activity compared to samples with higher Co content, along with good stability. These findings provide useful insights into the design of PtBi-based ternary alloy catalysts for efficient nitrate reduction. Full article

Co²⁺-doped CsPbI₃ nanocrystals (NCs) (CsPbI₃:xCo, x = 0, 5, and 10 mol%) were synthesized in situ within a borosilicate glass matrix by the fusion method followed by controlled thermal treatment at 500 °C for 6–24 h. Transmission electron microscopy images showed quasi-spherical NCs with mean diameters of 4.9–7.1 nm. Energy-dispersive X-ray spectroscopy suggested cobalt incorporation within the nanocrystalline regions. X-ray diffraction patterns confirmed the exclusive stabilization of the cubic α-phase across all compositions, with systematic lattice contraction from a = 6.321 Å to a = 6.301 Å with increasing Co content, consistent with preferential B-site substitution of Pb²⁺ by Co²⁺. Transmittance measurements confirmed macroscopic optical transparency of all glass-NC composites after thermal treatment. The crystal field theory and Tanabe–Sugano analysis for d⁷ ions in tetrahedral (Td) symmetry yielded Δ = 5032 cm⁻¹ and B = 725 cm⁻¹ in the as-prepared state, evolving to Δ = 4428 cm⁻¹ and B = 805 cm⁻¹ after thermal treatment, confirming Td Co²⁺ coordination and significant metal–iodide covalency. CIE 1931 chromaticity analysis revealed tunable emission from deep-red coordinates to near-white-light regions, demonstrating potential for LED and single-material WLED phosphor applications. Long-term photoluminescence measurements demonstrated full preservation of α-phase excitonic emission after approximately 365 days under ambient conditions, establishing the robust phase stability of CsPbI₃:xCo NCs embedded in borosilicate glass. Full article

The flotation performance of a low-grade, polymetallic copper ore, dominated by chalcocite and transitional copper phases, was investigated to assess the interplay between collector chemistry, gangue mineralogy, and entrainment. QEMSCAN analysis identified chalcocite as the main copper host (62%), with minor covellite and bornite, and gangue, predominantly quartz (94%), with variable muscovite (up to 50%). Chalcocite was moderately liberated (100–200 µm), while secondary copper phases showed low exposure and strong gangue association, challenging selective recovery. Baseline flotation with potassium amyl xanthate (PAX) and sodium isobutyl xanthate (SIBX) across pH and dosage ranges showed that PAX yielded higher copper recovery but lower grade, indicating unselective gangue entrainment; SIBX offered lower recovery but higher grade, reflecting superior selectivity. Controlled muscovite doping experiments (10–50 wt.%) were employed to decouple gangue-driven selectivity loss from collector-specific interactions. Results indicate a collector-dependent sensitivity to gangue loading: PAX exhibited a pronounced decline in both copper recovery (82%–67%) and grade under increasing muscovite content, with water recovery rising by approximately 32%, whereas SIBX showed more gradual performance degradation and lower entrainment (15% increase in water recovery), highlighting its resilience in gangue-rich systems. UV-Vis and zeta potential (electrokinetic) measurements confirmed stronger PAX adsorption, consistent with its longer hydrocarbon chain, while flotation trends demonstrated a shift from true flotation-dominated recovery to entrainment-dominated regimes at high muscovite levels, particularly for PAX. This framework links mineralogy, collector chemistry, and gangue entrainment, guiding optimization of circuits for ores like Mt. Gunson while enhancing critical metal recovery, including cobalt. Full article

With changes in the global energy structure, ammonia has emerged as a favorable hydrogen storage medium due to its excellent properties. This work details the synthesis of a barium-doped cobalt–iron alloy catalyst via subsequent heat treatment. This alloy efficiently catalyzes the decomposition of ammonia into hydrogen. The results showed that using characterization methods such as TEM and XRD indicated that adding Ba to this system could regulate the microstructure of the Co-Fe alloy. After calcination, the barium promoted a reduction in the particle size of Co-Fe nanoparticles, enabling their uniform dispersion on the surface and a more uniform dispersion and improving the accessibility of the exposed surface. The optimized catalyst (0.05Ba-0.25CoFe/CeO₂) achieved an ammonia conversion of 93.2% at 550 °C under a gas hourly space velocity of 30,000 mL·g_cat⁻¹·h⁻¹. Mechanistic analysis based on XPS and CO₂-TPD results indicated that the barium optimized the electronic structure and alkaline sites of Co-Fe, promoted the desorption of nitrogen, and thereby accelerated the reaction kinetics of ammonia decomposition. This research provides a strategic method and theoretical basis for designing high-performance non-precious metal catalysts for ammonia decomposition. Full article

To optimize the oxygen reduction reaction activity and long-term stability of the PrBaFe₂O_6-δ (PBF) cathode for protonic ceramic fuel cell (PCFC), this study employed the sol–gel method to dope Sc at the Fe-site of PBF, preparing a novel PrBaFe_1.8Sc_0.2O_6-δ (PBFS) cathode. The effects of different sintering temperatures on the phase composition, microstructure, and electrochemical performance of the PBFS cathode were systematically studied. Results showed that the PBFS cathode sintered at 1000 °C formed a single cubic perovskite structure, exhibiting excellent chemical compatibility with the electrolyte. Sc doping induced Fe in the cathode to exhibit a mixed valence state of Fe²⁺/Fe³⁺/Fe⁴⁺, thus significantly increasing the oxygen vacancy concentration. The single cell assembled achieved a peak power density of 1.303 W·cm⁻² and a polarization resistance as low as 0.035 Ω·cm² with H₂ as the fuel at 700 °C. Moreover, after 100 h of long-term operation at 650 °C, the power density decayed by only 5.23%, thus demonstrating excellent long-term stability. This study offers an efficient cobalt-free cathode candidate for PCFC. Full article