Carbon Trends最新文献

Carbon fiber paper is one of the most important substrates used in the gas diffusion layer of the polymer electrolyte membrane fuel cell. A novel approach to creating carbon fiber paper using polyacrylonitrile compounds was proposed in this study. The technique incorporated varying amounts of carbon materials, including carbon black (Vulcan), graphite powder, and carbon nanotubes. Polyacrylonitrile carbon materials were prepared through the spinning process, followed by oxidative stabilization under an oxygen atmosphere at a temperature range of 160–300 °C as the first step. The pliable material undergoes a conversion process to create a compound or ladder that is non-plastic, which is then stabilized in an N₂ atmosphere. The fibers are then pre-carbonized at temperatures ranging from 300 to 600 °C and further carbonized between 600 and 1100 °C. After that, Teflon is added and the resulting fibers are made into sheets during the production process. Finally, physical measurements and electrochemical methods such as: checking the amount of water absorption, scanning electron microscope (SEM), chronopotentiometry, electrochemical impedance spectroscopy, electron resistance of carbon sheet, double layer capacitance, and surface roughness parameter were evaluated. The results indicate that the best performance is related to CP7 carbon paper (with a 30–70 % combination of polyacrylonitrile and carbon black).

In this study, two heterocyclic compounds, 2,2-dimethyl-1,3-dioxane-4,6‑dione (DMDO) and 2,2,5-trimethyl-1,3-dioxane-4,6‑dione (5-DMDO), were thermally decomposed in an inert atmosphere of nitrogen to obtain oxygen functionalized carbon. The decomposition of these compounds was investigated by thermal gravimetric analysis (TGA) and gas chromatography-mass spectroscopy (GCMS) as well as hybrid-density functional theory (h-DFT). DMDO was found to have better thermal stability compared to 5-DMDO and thus gave a higher yield of carbon after decomposition at 1000 °C. This experimental observation was supported by the h-DFT analysis of the energy barriers of the two decomposition mechanisms proposed from the initial decomposition products detected above 100 °C with GCMS analysis and the thermodynamic spontaneity of the final product (solid carbon) at 800 to 1000 °C with TGA. X-ray photoelectron spectroscopy, scanning electron microscopy / energy dispersion spectroscopy and cyclic voltammetry were used to characterize the carbon and evidence was found to suggest that the electrochemical activity of the material towards the [Fe(CN)₆]⁴⁻/[Fe(CN)₆]^3- redox couple was dependent on the oxygen content of the carbon.

Axitinib, marketed as Inlyta, finds various medical applications in the treatment of conditions such as breast cancer, myeloid leukemia, and juvenile myelomonocytic leukemia. Initially, the synthesis of this cytidine analog, and its deoxy derivative decitabine, was carried out in Czechoslovakia to explore their potential as chemotherapeutic agents for cancer treatment. Recent research has been focused on understanding the reactivity and chemical structure of Axitinib, which are believed to contribute to its anticancer properties. As part of this investigation, the adsorption process of Axitinib onto a fullerene (C60) adsorbent in the gas and water phases was examined using the DFT/B3LYP/6-311+G(d, p) method. This analysis involved the assessment of the adsorption energy and a chemical perspective on the interaction between Axitinib and the adsorbent molecule. Furthermore, various thermodynamic characteristics, including Gibbs free energy (-4004.73 kJ), Enthalpy (-4004.52 kJ), and Entropy (709.79 J/mol-kelvin), as well as thermodynamic capacity (349.69 J/mol-kelvin), were calculated. Additionally, key electronic parameters, such as σ(0.20), µ(-2.97), ω(0.88), χ(2.97), and η(5.01) (all in eV), were estimated to elucidate the compound's chemical properties. The calculation of the HOMO (-7.99 eV) and LUMO (2.04 eV) energy levels revealed six regions of chemical activity for Axitinib, confirming its thermodynamic stability and indicating the significance of this adsorption process in delivering Axitinib to biological mechanisms.

In contrast to alternant, in non-alternant nanographenes (NGRs) and graphene nanoribbons (GNRs) no “sublattice structure” can be defined, associated with significant conceptual and computational simplifications. This leads to some fundamental differences between the two. We uncover here the broken electron-hole symmetry in non-alternant NGRs as one fundamental difference closely related to distorted Dirac points (cones) and their diradical open-shell character. We also show by higher level calculations beyond common DFT, based on many-body (MPn) and coupled clusters (CCSD(T)) theory, that the alternant series of peri‑acenes (bisanthene, peri‑tetracene, peri‑pentacene, … etc.), contrary to opposite reports in the literature, have clearly closed singlet ground states, in contrast to their non-alternant isomers based on Stone-Wales (SW) defects. We suggest that this can be experimentally verified by sub-molecularly resolved STM images. The misconceptions in the literature are due to insufficient correlation. For non-alternant SW-NGRs/GNRs with antiaromatic rings the driving force for open-shell states and distorted Dirac points (involving localized electrons and delocalized holes) is antiaromaticity, which is a sufficient but not always necessary condition. This is in juxtaposition to the aromaticity of the alternant isomers with closed shell states. Thus, in both cases sublattice problems, such as sublattice imbalance or complete lack of sublattice would lead to open shell magnetic states; ferromagnetic (e.g. triangulenes), or antiferromagnetic respectively (e.g. SW3 × 2, SW4 × 2), in contrast to non-magnetic (diamagnetic) states for balanced sublattices (e.g. armchair GNRs, AGNRs). Obviously, similar results, regarding the role of antiaromaticity and the broken electron-hole symmetry would be expected for larger NGRs/GNRs obtained by concatenation of such SW-motifs.

Insect biomass, rich in chitin and chitosan, is a sustainable and abundant resource with substantial promise for advancing green energy storage solutions. In this study, we explored cricket flour as a biomass candidate for carbon electrodes in electrochemical capacitors, aiming at creating a material with a high nitrogen content upon carbonization. The optimized material boasted a specific surface area exceeding 3300 m²/g, with most pores falling within the 0.5–2 nm diameter range. In a symmetrical Swagelok-type cell, this material delivered exceptional performance, yielding capacitances of 273.5 F/g, 200.2 F/g, and 161.6 F/g at 1 A/g in 6 M KOH, 1 M H₂SO₄, and 9.2 M NaClO₄ electrolytes, respectively. Furthermore, it showcased a capacity retention of 89.6 % and 87.9 % over 5000 cycles in 1 M H₂SO₄ and 6 M KOH, respectively. The cricket-based electrochemical capacitor exhibited robust cycling stability, suggesting its suitability for prolonged use. The resulting device demonstrated remarkably high specific capacitance, positioning it as a promising candidate for energy storage applications.

Hydrogenated nanodiamonds (NDs) get increasing attention as promising nanomaterial in biology as well as optoelectronics. This study shows how the ND synthesis process and ND size are reflected in their different colloidal/hydration and electronic properties. We employ three different ND types: detonation ND (DND), top-down high-pressure high-temperature ND (TD_HPHT ND) prepared by milling of HPHT monocrystals, and bottom-up high-pressure high-temperature ND (BU_HPHT ND) prepared by HPHT synthesis from chloroadamantane. Zeta potential measurements and Fourier transform infrared spectroscopy analysis (FTIR) reveal the best colloidal stability in neutral to basic pH and the strongest affinity to water for DND. Electrical and FTIR measurements connected with an annealing treatment show a steep increase of electrical conductivity in BU_HPHT ND above 2 nm and reveal different contribution of transfer doping in BU_HPHT ND and TD_HPHT ND despite similar conductivity values (≈ 10⁻⁵ S.cm⁻¹). We also confirm the correlation of the ND conductivity with IR transmission at the phonon frequency of the diamond (1330 cm⁻¹). Neutron irradiation of a TD_HPHT ND corroborates the crucial role of structural defects in the above colloidal and electronic properties of hydrogenated nanodiamonds.

The historicity and versatility of activated carbons (ACs) and other carbon derivatives (OCDs) date back to antiquity. This article reviews the recent advances in synthesis, characterization, and environmental applications of these demand-driven adsorbents from biomass and non-biomass sources. It first identifies relevant literature sources and knowledge gaps and then segmentalizes and scrutinizes the theme to elucidate contemporary carbon-based adsorbents. Conventional and advanced syntheses are highlighted. Current trends in adsorbents' characterization and remediation are also presented. The conventional AC synthesis includes one-step or two-step chemical or physical activation or a combinatorial synthesis of the two. Issues in the combinatorics are examined. Advanced techniques such as hydrothermal carbonization/activation and microwave-assisted irradiation are described, which may also involve one-step or two-step procedures. OCDs, including carbon nanotubes, carbon nanofibers, and carbon dots, mainly employ advanced syntheses, for example, nanotechnology. Currently, ACs and OCDs are mainly characterized using advanced techniques like scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), nitrogen (N₂) adsorption, and X-ray diffraction (XRD), which elucidate their structures, properties, and potential efficacies. Their applications for removing water, soil, and air pollutants are evaluated. The highest percent removal efficiency was activation type-specific, reflecting the precursor's nature, synthesis method, product properties, and quality. For instance, the chemical activation of neem leaves by H₃PO₄ activation and Fe nanoparticles from tea extracts were 100% successful for Pb²⁺and Cr⁶⁺, respectively, whereas physical activation of rice husk produced 91.8% success for Cr³⁺. However, their differential adsorptivities for other metals were moderate, with H₃PO₄ activation the lowest. Due to the high cost, tedious processes in producing and restoring ACs, and their non-selectiveness, researchers continually search for suitable alternatives, which this review considers. Also, applying artificial intelligence (AI) techniques in advancing novel ACs and OCDs for environmental remediation is discussed. Finally, future research dimensions are proposed.

Rising carbon dioxide emissions due to fossil fuel combustion has led to the urgent need to investigate and adopt different energy solutions that can mitigate this problem. Hydrogen has surfaced as a promising alternative in the pursuit for CO₂-neutral energy systems. Microwave pyrolysis of methane has recently emerged as an innovative method to accomplish this goal. To enhance our understanding of this technique and its scalability, it is essential to explore the microwave characteristics of the carbon used and generated during this process. This work investigates the microwave properties of two carbon samples (seed carbon; SC and product carbon; PC) from microwave-driven pyrolysis of methane. The cavity perturbation technique was employed from room temperature to 1250 °C for frequencies of 397, 912, 1429, 1948 and 2467 MHz. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis were also performed to elucidate the permittivity results. It was found that SC initially showed a decline in permittivity values up to 200 °C which is attributed to the release of moisture from the sample. These results were correlated to TGA/DSC which showed 5 % mass loss from 100 to 155 °C. The permittivity gradually reached a peak after which it started to fall due to high conductivity. In the case of the PC, the permittivities exhibited undulations but the values remained consistent. Since this form of carbon is formed at elevated temperature, no loss in moisture was seen in TGA/DSC. These findings indicate that the microwaves can penetrate and heat both the samples uniformly across their entire volume, resulting in efficient heating. SC demonstrated higher permittivity magnitudes compared to PC, suggesting its better responsiveness to microwave fields. Nonetheless, the possibility of thermal runaway in SC renders it less favorable for applications involving microwave-driven pyrolysis. XRD analysis showed that the samples SC and PC demonstrated amorphous carbon structures, with PC showing indications of graphitization to some extent. Both SC and PC have the potential to serve as microwave heat carriers in the methane pyrolysis process. This suggests that utilizing the carbon produced can enable a self-sufficient process, eliminating the necessity for costly catalysts.

Carbon materials are unique materials for their diversity, owing to three possible hybridisation states (sp, sp², sp³), their ability to switch from one phase to another upon various external stresses (thermal, mechanical, pressure…), and the tolerance of graphene (sp²C) to defects of many kinds. This makes their description difficult, due to the lack of standardised vocabulary and misuses or ignorance of the existing ones. A common language is needed so that every word has the same meaning to everyone and that carbon scientists understand each other as accurately as possible. This paper aims to clarify the basic terminology to be used on this matter, by reminding some important definitions or terms, e.g. allotrope, polymorphism, molecular form, crystallite, graphitic, graphene, graphene layer, graphenic, graphitisation, graphitisation treatment..., based on authoritative publications when available. In addition, as sp²C-based carbon materials exhibit the largest variability, a four-term description scheme (namely: morphology, texture, nanotexture, structure) is proposed and argued, which is believed to be sufficient (and necessary) to describe any kind of carbons, but molecular forms. Applying the recommendations proposed is expected to bring more consistency, clarity, and understandability to the forthcoming literature dealing with carbon materials.

The race and the discovery of novel two-dimensional (2D) carbon-based materials have been intensified because many are suitable for energy storage systems, thermoelectric devices, and catalysis applications. Therefore, this study introduces to the scientific community a novel 2D nanosheet named graphenyldiene (GPD), which is formed by arranging cyclobutadiene and bi-phenyl groups to create a monolayer with octadecagonal, hexagonal and tetragonal rings. The cohesive energy of GPD is only 1.37 and 0.65 eV/atom higher than graphene and biphenylene, respectively. Molecular dynamics simulations confirmed its structural and thermal stability. The GPD monolayer remains stable, with no significant deformations at around 1000 K, and the disintegration of the geometry occurs only at a temperature of 1500 K, which is characterized by the formation of an amorphous graphdiyne. The GPD electronic structure shows a direct band gap transition, 1.26 eV, at the Γ point. GPD is a promising alternative to electronic devices due to its carrier mobility of around 10³.cm²/V.s. Also, the GPD satisfies the Born-Huang criterion for mechanical stability with elastic constants C₁₁ = 157.62 N/m, C₁₂ = 53.66 N/m and C₆₆ = 51.98 N/m. The Bader's topological analysis indicated that all bonds have strong shared shell characteristics. Finally, the vibrational analysis identified 54 modes, where 21 are Raman active, with A_1g and E_2g modes dominating the spectrum at 1347, 1685 and 1697 cm⁻¹.