Carbon Trends最新文献

As an important intermediate for dual carbon targets, catalytic CO oxidation under mild conditions has received sufficient attention, as the reaction mechanism is directly related to the type of employed catalyst. High performance computing is performed with density functional theory to elucidate the mechanism of CO oxidation catalyzed by sulfur doped fullerene (C_60-xS_x (x = 1 ∼ 3)). The total activation energy for the first CO oxidation on C₅₉S, C₅₈S₂, and C₅₇S₃ increases gradually, as implies that the CO oxidation on C₅₉S should be easier than those on the other two dopants. Distinct electrons (0.852 e and 1.479 e) are transferred to oxygen atoms (O₂) from C₅₉S with the adsorption of O₂ and CO. There is no synergistic effect for the doping S atoms. All elementary reactions on C₅₉S are exothermic processes. This means that C₅₉S is a potential material for addressing environmental protection issues and H₂ purification for fuel cell applications.

In response to the escalating demand for cleaner energy sources, this study investigates the potential of carefully selected functionalized graphene-based materials for enhancing hydrogen sulphide (H₂S) removal in fuel streams, utilizing semi-empirical and density functional theory (DFT) calculations for molecular-level insights. A particular focus is placed on aliphatic methyl (-CH), alcohol (-COH), carboxylate (-COO), carbonyl (-CO), and acid (-COOH) -functionalized graphene, aiming to bridge gaps between desulphurization methods and graphene applications, specifically targeting H₂S removal. Through extensive computational analyses, the research unravels the intricate interactions between chosen functionalized graphene materials and sulfur compounds like H₂S, emphasizing mechanisms contributing to improved desulphurization efficiency. Our study's analysis highlights the superior performance of carboxylate (-COO)-functionalized graphene, mainly through dissociative adsorption mechanisms. The study systematically evaluates the influence of selected functional groups on adsorption activity, emphasizing the significance of dissociation. Overall, this research advances desulphurization strategies and underscores the potential of functionalized graphene in sustainable energy solutions.

Due to the excessive consumption of fossil fuels, which leads to significant greenhouse gas emissions and rapid climate change, it is crucial to develop various carbon capture and sequestration strategies. CO₂ sequestration in solid, porous adsorbents like low-cost biochar has emerged as a promising approach to achieve this goal. However, slow adsorption kinetics are one of the issues that limit the widespread use of this approach. While the characteristics of the biochar are important and impact CO₂ adsorption, the conditions under which adsorption occurs are equally critical. In this work, a novel strategy is proposed to accelerate the CO₂ uptake rate on carbon adsorbents by utilizing Low-Frequency High Amplitude resonant vibratory mixing during the adsorption process. With this approach, the rate of adsorption (characterized by the adsorption rate constant) exhibits an increase of 46.6% and 91.3%, as calculated by two different kinetic models: the Weber and Morris model, and the Pseudo-First-Order model. Experimental observations indicate that adsorption kinetics have a mixed control between external/internal diffusion and the physisorption process. Resonant vibrations enhance system energy, promoting collisions between CO₂ molecules and carbon surfaces, subsequently improving CO₂ transport and surface/gas interactions, facilitating the adsorption process and thus leading to enhanced kinetic rates. Furthermore, an analysis of variance determined the sensitivity of CO₂ uptake to several operating parameters associated with the resonant vibrations. This analysis indicated that the adsorption of CO₂ is most sensitive to the level of fill of the adsorption vessel and the time exposed to resonant vibrations.

Octadecylphosphonic acid self-assembled monolayers were used as a combined carbon and hydrogen source to grow graphene films on sapphire substrates via hot filament chemical vapor deposition. The functionalized substrates were sealed with a thin Cu film and heated to 950°C under Ar flow. After synthesis, the Cu was etched away. The graphene samples then underwent a hydrogenation treatment in the same reactor setup, exposed to a CH₄/H₂ gas mixture at 820°C for 2 hours. The structure and properties of the graphene films before and after hydrogenation were characterized. Raman spectroscopy was employed to probe the defect-related bands and C-H bonding. X-ray diffraction provided insights into the crystalline structure and interlayer spacing. The ferromagnetic response was measured using a PPMS system across a range of temperatures and magnetic fields. XPS was used to assess the chemical composition and bonding. This multi-step process enabled a detailed evaluation of the novel synthesis protocol and its effects on the resulting hydrogenated graphene material.

In this study, the electrochemical properties of bioderived activated carbon-based electrodes for supercapacitors formed using a sintered ceramic binder were investigated. Activated carbon derived from Jack wood tree (Artocarpus heterophyllus) with variable amounts of TiO₂ nanoparticles as a binder, were used as electrodes in order to get good, activated carbon films on FTO substrates. No other binders were used in this study since most conventional binders devastate the electrical conductivity in the films. Furthermore, TiO₂ has higher temperature tolerance compared to polymeric binders thus the electrode prepared can be used in wider applications. A series of electrochemical double-layer capacitors were fabricated and characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The supercapacitors prepared showed double-layer capacitive behavior. The electrodes that contain 90 % activated carbon and 10 % TiO₂ show optimum performance along with an impressive specific capacitance of 147 F g⁻¹ at 2 mV s⁻¹ scan rate. This supercapacitor exhibits a power density of 68.5 W kg⁻¹ while the energy density is 8.02 Wh kg⁻¹. When the power density is as high as 1186.51 W kg⁻¹ the energy density drops to 5.71 Wh kg⁻¹. According to cyclic voltammetry measurements taken for 1000 cycles, the supercapacitor shows excellent cycle stability without any traces of capacitance drop.

The present work focuses on the synthesis of hybrid La₂CoCrO₆/Co₃O₄/rGO composite via solvothermal technique for supercapacitor application. X-ray diffraction, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET), and Barrett-Joyner-Halenda analyses are employed to assess phase structure, morphology, chemical state, surface area, and porosity of synthesized materials, respectively. The formation of mesoporous spheres is confirmed through FESEM and BET analysis. The inclusion of redox additive KMnO₄ in KOH electrolyte enhances the accessibility of electrochemical sites in the mesoporous spheres of the La₂CoCrO₆/Co₃O₄/rGO electrode, resulting in excellent charge storage. Electrochemical analysis of the La₂CoCrO₆/Co₃O₄ exhibits specific capacitance of 633.2 F/g at 2 A/g in a redox electrolyte (6 M KOH + 0.05 M KMnO₄) with capacitive retention of approximately 81 % over 5000 cycles. Furthermore, the addition of rGO improves the overall performance of La₂CoCrO₆/Co₃O₄/rGO composite (763.9 F/g at 2 A/g with capacitive retention of approximately 86 %). The electrochemical analysis of hybrid La₂CoCrO₆/Co₃O₄/rGO composite showed improved performance, owing to the synergy of double perovskite (La₂CoCrO₆), cobalt oxide (Co₃O₄), and reduced graphene oxide (rGO). These findings suggest promising applications for the material in advanced energy storage devices.

Large surface area, excellent electrical conductivity, homogeneous structure, and extended cycling stability are desirable characteristics for energy materials. Carbon-derived structures exhibit porous structure, work well in a wide potential window, and are highly conductive. Hence, they can show enhanced rate capability and cycle life. Despite ongoing efforts, the synthesis of carbons at lower temperatures remains a challenge. In comparison, the high-temperature synthesis protocols lead to a high CO₂ footprint. Here, we report the synthesis of unique carbon morphologies, namely capped carbon nanostructures (CCS) and bowl-like carbon structures (BCS). Their performances are either comparable or higher than those conventionally used morphologies of carbon, such as nanospheres, microspheres, nanotubes, graphene oxide, and layered structures. The four-sided opening in BCS particles ensures higher adsorption of electrolyte ions, which is even higher than hierarchical or spherical structures. The cap formation on the CCS acts like an additional layer on top of the sphere. Further, the CCS is arranged in a sequential honeycomb array, which leads to the formation of definitive channels for electrolyte diffusion. The unique carbon morphologies showed nearly ∼ 40 % increment in the specific capacitance values compared to other commonly used carbon structures. The novel morphologies also have a much lower carbon footprint, as shown by the life cycle assessment (LCA) studies.

Green energy systems must be able to provide a significant proportion of the energy needed to meet the ever-increasing demand for energy. Fuel cells are a promising solution to bridge the gap in the green energy transition. This study aims to enhance the energy efficiency of fuel cells by utilizing 2D supported nanocatalysts in the anode compartment. Borophene was synthesized using the liquid phase exfoliation method to be used as a support structure due to its superior properties. To use borophene as a supporting material in methanol fuel cells, a borophene-palladium hybrid structure (Pd@Borophene) was prepared using the chemical reduction method. The scanning electron microscopy (SEM) images showed that the obtained particle had a partially formed layered structure. The electrocatalytic activity of the Pd@Borophene was investigated through anodic reactions in Direct Methanol Alcohol Fuel Cells (DMFC). Electrochemical analyses were conducted to compare the effect of borophene on Pd and Pd@borophene nanocatalysts on the anodic reaction. The anodic peak current value of methanol oxidation for Pd@borophene was found to be 24.3 mA/cm², which is approximately four times higher than that of unsupported Pd nanoparticles. Additionally, the ratio of forward current (If) to reverse current (Ib), which serves as an indicator of catalyst poisoning, was determined to be 2.27. This study contributes significant findings to the literature by demonstrating that borophene, an advanced 2D material, can be synthesized using a low-cost liquid phase exfoliation method and can be utilized in fuel cell applications for energy generation.

For large-scale device fabrication, information about film inhomogeneities is crucial for high fabrication yield. In this work, inhomogeneities in two-inch diameter heavily boron-doped nanocrystalline diamond (BNCD) films have been studied. Two BNCD films were grown using chemical vapour deposition (CVD) with different boron-to-carbon (B/C) ratios. Their superconducting properties were measured as a function of distance from the centre of the film. The critical temperature ($T_c$) and critical magnetic field ($H_{c2}$) decreased radially outwards from the centre for both films. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were done on the samples to pinpoint the underlying explanation for the observed behaviour. Raman spectroscopy suggested a reduction in boron concentration and diamond purity over both films while moving radially outwards from the centre. XPS data from both films, however, did not show similar behaviours to that observed from the Raman data for the B/C ratios or diamond content. The AFM scans and SEM analysis showed a decreasing grain size further away from the film centre irrespective of the B/C ratio. This is due to the film being thinner at the edges when compared with the centre of the film. Raman analysis showed that the film with the higher B/C ratio had a higher diamond purity across the film. As expected, the film with a higher B/C ratio showed a more robust superconducting behaviour. The observed reductions in boron concentration, diamond purity, film thickness and decreased grain sizes are responsible for the diminishing superconductivity at the edge of the films.