Carbon Letters最新文献

The high theoretical capacity of transition metal-based compounds makes them promising candidates for lithium-ion battery (LIB) anodes. Among them, iron selenide (FeSe₂) has attracted considerable interest because of its excellent electrical conductivity and superior lithium storage capacity. However, pristine FeSe₂ suffers from rapid capacity fading and structural instability during repeated cycling. Thus, this study used a facile solvothermal method to synthesize a FeSe₂@rGO composite with enhanced structural integrity and electrical conductivity. By incorporating reduced graphene oxide (rGO), the composite demonstrated improved charge transfer kinetics and mechanical robustness. Morphological and structural characterizations were performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy analyses (XPS), which confirmed the successful formation of the composite and its uniform distribution. Electrochemical properties were evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge, long-term cycling, and electrochemical impedance spectroscopy. The optimized FeSe₂@rGO electrode delivered a high reversible capacity of 971.95 mAhg^-1 at 500 mAg^-1 after 350 cycles. The underlying charge storage mechanism was investigated using scan rate-dependent CV, which revealed a dominant capacitive-controlled contribution at higher scan rates. The study findings indicate that the FeSe₂@rGO composite can serve as a high-performance anode material with excellent cycling stability and rate capability, providing a viable strategy for the development of advanced LIBs.

Incorporating nanotechnology into cement composites significantly improves mechanical properties such as strength, toughness, and durability. Graphene, with high tensile strength and large surface area, shows great promise as a nanofiller, but its hydrophobicity complicates its dispersion in cement matrices. This study used a graphene-cellulose nanofiber (G@CNF) hybrid filler to ensure a highly uniform dispersion within the cement microstructure. The hybrid filler acts as a bridge and efficiently fills voids within the matrix. The planar structure of graphene also provides nucleation sites for hydrated products, leading to a denser microstructure. The cement composite containing 0.01 wt.% graphene exhibited a compressive strength of 72.7 MPa, representing a 47.5% improvement over the plain cement. Furthermore, the resulting cement demonstrated enhanced water resistance compared to graphene oxide-reinforced-cement. This approach offers a cost-effective and sustainable way of producing high-strength, durable cement composite.

The effect of metal codoping on hydrogen storage has been meticulously studied in small cubic C₈ nanocluster within the framework of density functional theory (DFT). Initially, a C₈ nanocluster was doped with two Li atoms [C₈(Li)₂], achieving a hydrogen uptake of 15.5 wt% with an adsorption energy of 0.16 eV. Although this configuration demonstrates a high hydrogen storage capacity, its thermodynamic stability under ambient conditions is limited due to weak binding interactions between Li and H₂ molecules. By introducing metal atoms that have stronger binding with the C₈ framework, it is expected to enhance the overall structural stability. For that, we have chosen Na, K, Be, Mg, Ca, Sc, Ti, V, and Cr metal atoms along with Li to investigate the influence of codoping on hydrogen storage characteristics. The Ti- and V-codoped structures exhibited significant distortion of the C₈ nanocluster during optimization primarily due to strong charge transfer, steric repulsion arising from the larger atomic radii of Ti and V, and partial bond breaking within the nanocluster framework and were, therefore, excluded from further calculations. The resulting codoped structures—C₈LiNa, C₈LiK, C₈LiBe, C₈LiMg, C₈LiCa, C₈LiSc, and C₈LiCr—yielded hydrogen uptake of 16.1 wt%, 14.6 wt%, 11.2 wt%, 13.7 wt%, 12.4 wt%, 9.8 wt%, and 11.5 wt%, respectively, all surpassing the U.S. Department of Energy 2025 target of 5.5 wt%. Among these, the LiCr codoped C₈ nanocluster exhibited significantly improved adsorption energies of 0.31 eV, which is within the ideal range of 0.2–0.6 eV for faster adsorption–desorption kinetics. Furthermore, Gibbs free energy corrections to H₂ adsorption energy at various temperatures and pressures revealed superior thermodynamic stability of the C₈LiCr structure, suggesting its promising potential for practical hydrogen storage applications. These results highlight the significant impact of metal codoping as a powerful strategy for enhancing hydrogen uptake, stability, and overall H₂ storage performance in nanostructured materials.

Graphical abstract

Medium- and low-temperature coal tar pitch can be prepared as coal-based mesophase pitch for its high value-added utilization. However, its lower aromaticity and higher content of heteroatoms (especially O atoms) led to a higher content of the resulting mesophase pitch mosaic structure. In this study, mesophase pitch was prepared by co-carbonization of high aromaticity, low oxygen content high-temperature refined pitch (RHCTP) with medium- and low-temperature coal tar refined pitch (RCTP). The impact of various blending ratios on the optical and microcrystalline structures of mesophase pitch was analyzed using polarized light microscopy, X-ray diffraction, and Raman spectroscopy. The addition of RHCTP to modify RCTP significantly enhanced the optical and microcrystalline structures of the co-carbonized products. The optimal blending ratio (R-25%) was obtained. Needle coke prepared from mesophase pitch obtained from R-25% had superior fine fiber structure, lowest average resistivity (157.37 μΩ·m) and high true density (2.125 g/cm³). The thermal conversion behavior of the blended refined pitch during co-carbonation was analyzed using thermogravimetric data of the R-25% sample through four isoconversion methods. The thermal conversion of the R-25% sample occurs in three stages: the first stage follows the Parabola law model, while the second and third stages adhere to the random nucleation and nuclei growth model. This analysis of thermal conversion kinetics offers theoretical insights for optimizing mesophase pitch preparation process conditions and reactor design.

This paper reviews MAX phases (bulk) and their 2D derivative, MXenes, focusing on synthesis methods, properties, and applications. Traditional and advanced synthesis techniques, including solid-state synthesis and spark plasma sintering, are examined, emphasizing structural diversity. Key characteristics, such as thermal stability, electrical conductivity, and mechanical resilience, are explored alongside their mechanisms. The review also highlights advancements in energy harvesting applications, such as H(_2) production, solar cells, energy storage, catalysis, spintronics, electronic devices, and environmental remediation. Additionally, future research directions are outlined to address existing gaps and enhance their role in next-generation technologies and environmental remediation.

To enhance the fixed carbon content and recovery rate of flotation concentrates from low-grade natural flake graphite (NFG), this study employed synchronous ultrasonic flotation in combination with inorganic salt ion (NaCl) enhancement. Flotation experiments were conducted to investigate the synergistic effects of these two methods. X-ray photoelectron spectroscopy, contact angle analysis, laser particle-size analysis, Raman spectroscopy, infrared spectroscopy, zeta potential measurements, electron microscopy, and Debye length calculations confirmed that ultrasonic cavitation disrupted particle agglomeration and cleaned the graphite surface. This process generated fine micro-/nanobubbles with enhanced hydrophobicity, significantly improving concentrate recovery rates. NaCl addition compressed the double electric layer on particle surfaces and suppressed bubble coalescence, stabilizing the froth and promoting graphite–bubble adhesion, which markedly increased the fixed carbon content of the concentrate. The results demonstrated that through the integrated approach, low-grade NFG with an initial fixed carbon content of 7.98% was upgraded after rough processing to a concentrate containing 79.24% fixed carbon, with a recovery rate of 65.76%. These findings demonstrate that combining ultrasonic flotation with NaCl addition substantially improved both fixed carbon content and recovery rate in the concentrate. Overall, this study provides a novel technical pathway for the efficient utilization of low-grade graphite ore resources.

Graphical abstract

Activated carbons with high micro-/meso-porosity derived from biomass are increasingly popular as sustainable materials. However, these carbons often struggle with low carbon content and limited structural stability. Here, we present Mongolian anthracite-based carbons synthesized via carbonization and chemical activation. Structural analysis shows that Act-MRA samples develop plate-like morphologies with reduced particle size and greater porosity as KOH content increases. The Act-MRA samples have a disordered carbon structure with small graphitic domains, even at higher KOH ratios without significant crystal defects. Notably, Act -MRA3 displays a large specific surface area and high pore volume, with well-developed micropores (7–20 Å) and mesopores (20–50 Å) that expand as KOH ratios rise. Electrochemical tests indicate that Act -MRA3 achieves high specific capacitance (220.6 F/g at 5 mV/s) and rate retention (~ 80% at 300 mV/s), owing to its optimized pore structure and enhanced ion transport. These findings underscore the importance of tailored pore structures and defect engineering in boosting activated carbon performance for energy storage.

This work introduces a high-performance absorber based on a lightweight composite material of corn straw biochar and magnetic cobalt nickel zinc ferrite. A composite absorber of corn straw biochar with hierarchical pore structure and magnetic zinc cobalt nickel ferrite particles (Ni–Co–Zn ferrite/C) was prepared by a simple two-step approach of carbonization followed by in-situ growth method. The morphology, structure, function, and absorbing properties of the prepared samples were characterized, and RCS simulation was performed. The results show that the optimal reflection loss value of Ni–Co–Zn ferrite/C-2 reaches −38.04 dB when the layer thickness is 3.5 mm, and the effective absorption bandwidth is 4.32 GHz. The potential of Ni–Co–Zn ferrite/C-2 composite material in stealth applications is verified. It is mainly attributed to the excellent impedance matching performance caused by the multi-level pore structure and the strong polarization loss caused by the rich heterogeneous interface and active sites, which plays a key role in the attenuation of electromagnetic waves. This study provides a useful reference for the design of magnetic ferrite particles/metal oxides/biomass-derived carbon microwave absorbing materials with hierarchical porous structure characteristics.

Fluorinated carbons (CF_X) are promising cathode materials for lithium primary batteries due to their high energy density, yet suffer from poor electronic conductivity. Manganese dioxide (MnO₂), on the other hand, offers superior rate capability, but limited capacity. Here, we design MnO₂/CF_x hybrid cathodes by combining MnO₂ with CF_X materials synthesized at controlled fluorination levels (x = 0.4–1.0) to synergistically optimize both energy and power performance. Structural and spectroscopic analyses reveal that moderate fluorination (x = 0.6) induces a favorable balance of semi-ionic C–F and interfacial O–F bonds, enhancing electron delocalization and charge transfer at the MnO₂/CF_X interface. In contrast, excessive fluorination (x ≥ 0.8) leads to the formation of electrochemically inert C–F₂ and C–F₃ species, suppressing redox kinetics. As a result, MnO₂/CF_X-0.6 delivers a discharge capacity of 390 mAh g–1⁻¹ at 0.05 C and retains 182 mAh g–1⁻¹ at 4 C, outperforming both pristine MnO₂ and other CF_X variants. This work establishes interfacial fluorine bonding configuration, not just bulk F/C ratio, as a critical design parameter for high-performance hybrid cathodes.

This study investigates the repeated impact behavior and compression-after-impact (CAI) performance of triaxially braided carbon/glass fiber-reinforced polymer (C/GFRP) composite tubes. A two-stage experimental strategy was proposed to evaluate the synergistic effect of interlayer hybridization and axial yarn reinforcement on damage evolution and mechanical performance. In Stage I, six hybrid braided tubes with different carbon/glass stacking configurations—including pure carbon, pure glass, layered, and reversed-layered structures—were subjected to repeated low-velocity impacts at 31 J. Micro-CT was employed to reconstruct the internal damage morphology and assess damage accumulation. The optimal interlayer configuration was selected based on impact force, displacement, energy absorption, and internal failure characteristics. In Stage II, the selected structure was further reinforced with four types of axial yarns (none, carbon, glass, and carbon/glass alternating), and their axial compressive and CAI performance after 10 J impact was tested. Results revealed that reversed interlayer design effectively suppressed crack propagation and improved damage tolerance under cyclic impacts. Moreover, the inclusion of hybrid axial yarns significantly enhanced residual compressive strength without compromising energy absorption. This study establishes a lightweight, high-performance braided tube design strategy suitable for aerospace and transportation applications.