Carbon Letters最新文献

Mn-based catalysts like hopcalite (Cu–Mn oxide) are widely studied for low-temperature CO oxidation, with efforts focused on enhancing their redox properties. Incorporating defect-free graphene as a support has shown promise in improving both structural and catalytic performance, making the development of scalable graphene-supported Cu–MnO_x (Gr/Cu–MnO_x) composites highly desirable. In this study, fluid flow control systems were effectively employed to produce exfoliated graphene sheets, which were subsequently utilized for synthesizing Gr/Cu–MnO_x composite catalysts. The enhanced shear stress and mass transfer within the fluid flow system improved the textural properties of the composite catalysts, resulting in higher surface areas and pore volumes compared to those of the unmodified Cu–MnOx composite. The Gr/Cu–MnO_x composite catalysts exhibited superior toluene removal performance, achieving a T₉₀ value of 200 °C, surpassing the T₉₀ value of 250 °C of the unmodified Cu–MnO_x composite. Furthermore, the water resistance was assessed by evaluating the catalytic performance after exposure to 5 vol% water vapor. The presence of hydrophobic graphene in Gr/Cu–MnOx enhanced water resistance compared to that of unmodified Gr/Cu–MnO_x.

Here we report self-propagated growth of lanthanum hexaboride (LaB₆) decorated Carbon Nano Tubes (CNTs) from the pyrolytic graphite rods treated with nitrogen arc plasma. The system so formed is named as LaB₆-CNTs. Two pyrolytic graphite rods were used as electrodes in the arc plasma reactor whereas, the LaB₆ sample kept onto anode acts as catalyst. The anode left out with residue of LaB₆ was exposed to normal atmospheric conditions which show ignition of self-propagated growth of CNTs decorated with LaB6 . Such growth was observed within a couple of days after exposure to the environment without any external supply of energy. The growth is found to be slow and continues till complete erosion of the pyrolytic graphite block. The self-propagated powder obtained was characterized thoroughly using XRD, Raman spectroscopy, FESEM and TEM techniques. These nanostructures were found to exhibit efficient field-emitting properties with a low turn-on electric field of ~ 2 V/µm, and a current density of ~ 1.5 A/cm² at an applied electric field of 1.8 V/m. Therefore, the nanostructures obtained can be explored for electron emission applications.

The efficient utilization of biomass resources has garnered substantial research interest as a strategic approach to mitigate reliance on fossil fuels and achieve waste valorization. Furfural (FFA), a renewable biomass-derived platform compound, offers an environmentally benign pathway for producing oxygenated value-added chemicals such as cyclopentanone (CPO) and cyclopentanol (CPL) through hydrogenative rearrangement, thereby offering an alternative to conventional petroleum-based decarboxylative cyclization methods. Over the past decade, significant research efforts have been dedicated to optimizing the catalytic hydrogenation and rearrangement of FFA into CPO/CPL, with a focus on enhancing catalytic efficiency, product selectivity, cost competitiveness, and environmental sustainability. This review systematically discusses the structural characteristics, catalytic performances, and reaction mechanisms of diverse metal-based catalysts, with particular emphasis on how active sites modulate reaction pathways and reaction mechanism. Furthermore, the key innovations in catalyst engineering are analyzed and the promising pathways to design catalytic systems combining high activity, selectivity, and stability for sustainable FFA upgrading into CPO/CPL are proposed.

Constructing high-density single-walled carbon nanotubes (SWCNTs) network assemblies is essential for improving their electrical conductivity. However, controlling the nanoporosity, including specific surface area (SSA) and pore structure, is critical for maintaining reversible capacity in CNT-based energy storage systems. In this study, we investigated a solution-based strategy using acid and surfactant treatments to enhance the electrical conductivity of SWCNT networks while minimizing changes in nanoporosity. HNO₃/H₂SO₄ acid treatment and sodium dodecyl benzene sulfonate (SDBS)-assisted dispersion were applied to form uniform, densely packed SWCNT assemblies. Acid treatment increased the SSA from 246 to 732 m² g⁻¹ and the micropore volume from 0.06 to 0.28 mL g⁻¹. In contrast, SDBS treatment moderately increased the SSA (246 to 350 m²·g⁻¹) with minor changes in meso/microporosity and preserved the overall pore structure well. In addition the electrical conductivity increased by a factor of 3.5 after acid treatment and by a factor of 6 after SDBS treatment, reaching 1.39 × 10⁵ and 2.36 × 10⁵ S m⁻¹, respectively. These results demonstrate that SDBS treatment, via surfactant-driven reassembly, offers a simple, scalable, and structure-preserving strategy to tailor nanoporosity and enhance the performance of SWCNT-based electrochemical devices.

Insulated gate bipolar transistor (IGBT) is a kind of power switching device owns the advantage of gate voltage control and high power capacity, while remaining the problem of potential catastrophic failures in high voltage. A novel structure of IGBT combined with a vacuum field emission transistor (VFET) and a bipolar junction transistor (BJT) was introduced which exhibits high blocking voltage, high frequency characteristics and excellent robustness toward catastrophic failure such as latch-up and gate oxide breakdown. A pulsing current overshooting effect due to the gate-cathode capacitance of VFET was observed to expedite the switching process, offering a novel approach to shorten the switching time of IGBT. Benefit from this, the field emission IGBT (FE-IGBT) was capable of operating over a broad frequency range from DC to 100 kHz. The static and dynamic characteristics of the device were reported, including a blocking voltage of 800 V, a maximum output current of 0.5 A. This work presented a new route to bloom the performance of IGBT and also created a feasibility to connect vacuum electronics device with solid-state semiconductor devices.

Ethylene tar pitch (ETP), primarily derived from the residues of carbon black production and naphthalene purification in ethylene tar processing, is a polycyclic aromatic hydrocarbon with high carbon content and low ash content. It is considered a promising precursor for high-quality synthetic carbon materials. Thermal conversion is a critical step in the preparation of pitch-based carbon materials, as it largely determines the final structural quality of the carbon product. In this study, ETP was selected as the research subject, and a combination of analytical techniques, including group composition analysis, elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR), polarized optical microscopy (POM), Raman spectroscopy, and X-ray diffraction (XRD) were employed to investigate the evolution of the average molecular structure and carbon microstructure during the thermal conversion process. The results indicate that with increasing thermal conversion temperature and duration, the degree of aromatic condensation in the ETP-derived products gradually increases. Simultaneously, the internal carbon microcrystals become more ordered and larger in size. Notably, when the thermal conversion temperature reaches 480 °C, the aromaticity index (I_ar) sharply increases to 0.42, and anisotropic structures begin to appear under POM. This suggests that 480 °C is a critical temperature point at which ETP undergoes intensified thermal polycondensation and exhibits enhanced molecular reactivity. This study provides both theoretical and experimental support for the efficient utilization of ETP in the production of advanced carbon materials.

Graphical abstract

Using ethylene tar pitch as the raw material, the entire experimental process is carried out in a well-type furnace. Under 400 ^oC, the structure is isotropic under the optical microscope; at a temperature of 480 ^oC, significant volumetric expansion occurs, along with the appearance of a large number of mesocarbon microbead structures; the final condition involves maintaining a constant temperature of 500 ^oC for 4 hours, resulting in an optical microstructure primarily composed of fibrous and Leaflet.

Catalytic decomposition of methane (CDM) enables CO_x-free H₂ while co-producing solid carbon. Its viability hinges on catalysts that couple high activity with stable carbon co‑product formation. We evaluate Ni catalysts on FeAl₂O₄ (hercynite) and identify ~ 40 wt% NiO as the optimum loading that balances activity with carbon yield. Promoter screening (La, Mg, Co; 5 wt%) reveals distinct control of reducibility and metal–support interaction (MSI). La lowers the reduction temperature, refines Ni/NiO crystallites, and increases Ni dispersion, delivering the highest initial CH₄ conversion (52.3%) and H₂ production rate (90.6 mmol g_cat⁻¹ min⁻¹), albeit with deactivation at ~ 150 min due to rapid carbon encapsulation. Mg strengthens the MSI and stabilizes residual NiO through MgO/MgAl₂O₄, lowering the initial activity. In contrast, Co promotes spinel formation and Ni aggregation, yielding the weakest activity. CDM is highly selective to H₂ with carbon as the sole co-product; the carbon forms multi-walled carbon nanotubes (MWCNTs) with ~ 16–24 nm diameters. Operating parameters further tune performance, with 650 °C being most effective. Lowering the space velocity extends the time-on-stream to ~ 450 min, increases the initial conversion to 59.4%, and raises the carbon yield from ~ 970% to ~ 1470%. Comprehensive characterization links promoter-dependent reducibility and metal–support interaction to activity, stability, and MWCNT yield. These results provide practical guidance for co-optimizing composition and operating conditions in CDM. NiO/FeAl₂O₄ with ~ 40 wt% NiO can serve as a baseline; La addition elevates initial rates, and operating at lower space velocity mitigates carbon-induced deactivation, thereby increasing H₂ productivity and improving CNT quality.

Nickel-cobalt layered double hydroxide (NiCo-LDH) is a promising supercapacitor material, but its performance is limited by nanosheet stacking and poor conductivity. Incorporating a porous carbon support is an effective strategy to overcome these issues. Herein, porous carbon derived from both puffed and unpuffed sorghum seeds was synthesized at various pre-carbonization temperatures. The optimized carbon from puffed seeds (PH-R4A7), abundant in pyridinic-N and oxygen groups, facilitates the uniform growth of NiCo-LDH. The resulting NiCo-LDH/PH-R4A7 composite delivers a high specific capacitance of 807.2 C g^− 1 at 1 A g^− 1 and excellent capacitance retention (69.9% at 20 A g^− 1), surpassing both pristine NiCo-LDH and its unpuffed counterpart (NiCo-LDH/PC-R4A7). Furthermore, an asymmetric supercapacitor (NiCo-LDH/PH-R4A7//PH-R6A7) achieves a high energy density of 85.1 Wh kg^− 1 at a power density of 799.9 W kg^− 1, along with outstanding cycling stability (88.4% capacitance retention after 10,000 cycles). This work demonstrates that puffing pretreatment is an important strategy for enhancing the structural and electrochemical properties of NiCo-LDH/porous carbon composites.

The demand for energy storage devices with both high power and energy density has risen significantly because of growing global environmental concerns. Lithium metal capacitors (LMCs) have emerged as promising candidates for next-generation energy storage systems by addressing the low energy density limitations of conventional electric double-layer capacitors (EDLCs). However, lithium dendrite formation and volume expansion in lithium metal anodes pose major challenges, leading to performance degradation and safety risks. In this study, a three-dimensional nano-perforated graphene (3-D NPG) with SnO₂ composite as an advanced anode material for LMCs. The 3-D NPG improved electrochemical performance by offering a high surface area, reducing local current density, and mitigating volume expansion. Furthermore, the lithiophilicity of SnO₂ facilitated lithium deposition by effectively reducing the lithium nucleation overpotential. The composite exhibited the lowest lithium nucleation overpotential (39.44 mV), along with a superior rate capability and remarkable cycle stability, retaining 88.5% of its capacity after 10,000 cycles at 2 A/g. The improved lithium-ion transport and lithiophilicity of the composite significantly suppressed dendritic lithium growth, thereby enhancing the electrochemical performance of LMCs. These results demonstrate the potential of 3-D SnO₂/NPG as a next-generation anode material for high-performance energy storage applications.

To study the influence of mass and heat transfer on the microcrystalline structure and properties of mesophase pitch and resulting carbon fiber properties, mesophase pitches were synthesized via pressurized/N₂-blowing thermal condensation with different stirring rates, with experimental conditions optimized using response surface methodology (RSM). RSM analysis confirmed that mesophase content was highly dependent on stirring rate (p < 0.05), and the influencing factors on the formation of mesophase pitch is ranked as reaction temperature > duration time > stirring rate > reaction pressure. The results demonstrated that a moderate increase in stirring rate enhanced molecular diffusion and heat transfer, improving reaction kinetics and aromatic molecule interactions. This accelerated mesophase sphere growth and coalescence while inducing molecular orientation via shear, ultimately yielding a wide-domain optical texture with 100 vol% mesophase content and an optimal softening point (294 °C). The mesophase pitch produced at 300 rpm (MP-300) exhibited a high aromatic structure content (H_ar = 73.24 wt%), methylene bridges (H_F = 3.21 wt%), and fusible/soluble TI-PS sub-fraction (35.7 wt%). MP-300 also displayed exceptional aromaticity (f_a = 0.91) and molecular stacking ((L_c = 5.4674 nm, N = 14.7536). Consequently, the resulting carbon fiber (MPCF-300) achieved optimal mechanical properties, with a tensile modulus of 168 GPa and a tensile strength of 1428 MPa. However, excessive stirring rates were found to disrupt molecular cross-linking and stacking, reducing condensation degree, disordering the orderly arrangement of the mesophase molecules, and ultimately impairing the fiber performance. These findings advance the understanding of mesophase pitch formation and provide critical insights for optimizing liquid-phase carbonization theory.