Carbon Trends最新文献

To meet the growing energy demand for large-scale applications, potassium-sulfur batteries (KSBs) have gained enormous attention owing to their high energy density, natural abundance, and specific capacity. Nevertheless, the shuttle effect, the insulating nature of sulfur, and the large volume change hinder the development of KSBs. To address the different challenges of KSBs, we report eco-friendly and biodegradable in-situ banana fiber-modified carbonized bacterial cellulose as a free-standing and binder-free cathode (sulfur) host. The catholyte K₂S₆ is used as active sulfur for cell fabrication owing to a high sulfur loading and even distribution of active material. However, introducing the catholyte induces the potassium side reaction by reacting to it. Therefore, carbonized bacterial cellulose is used as an interlayer to reduce the notorious polysulfide shuttle effect. As a result, the fabricated cell delivers a specific capacity of 437, 354, and 193 mAh g^-1 at the current density of 0.2, 0.7, and 1.2 C, respectively. During the long cycling, the cell shows excellent electrochemical performance for 200 cycles with a capacity retention of 78 % at 0.7 C. This work paves the way to utilize an eco-friendly and cost-effective approach to fabricate a high-performance KSB.

The controlled release of antibiotics is crucial to improving antimicrobial efficacy, reducing the risk of bacterial resistance, and ensuring a localized therapeutic effect. In this work, In-vitro Gentamicin release was studied using fluorescence chitosan collagen-cerium hydroxyapatite nanocomposites. Cerium-hydroxyapatite nanoparticles were synthesized using the hydrothermal method, and the nanocomposites were prepared by mixing chitosan-collagen-cerium hydroxyapatite at different weight ratios. Structural characterization was conducted using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and fluorescence microscopy. Ultraviolet–visible spectroscopy (UV–Vis) was used to quantify the release of gentamicin in simulated body fluid. Results showed that hydroxyapatite releases 90 % of gentamicin in the first 10 min, and the Chitosan-collagen-cerium hydroxyapatite nanocomposites release 80 % of gentamicin after 2 h. The antibacterial activity was studied against Escherichia coli (E. coli) at different time intervals. These nanocomposites can potentially improve the performance of biomedical applications.

Nanofibers are extremely thin fibers produced from materials such as carbon, polymers, ceramics, and metals with diameters in the nanometer range that gained significant interest due to their unique properties. Carbon nanotubes, which could be considered the most popular fibers in the nanoscale, have gained widespread recognition primarily due to their remarkable strength derived from their cylindrical hexagonal lattice formed by carbon covalent bonds. Here, a new family of carbon nanofibers is proposed, arising from the combination of the tubular hexagonal configuration of carbon nanotubes and the spherical nanostructure of carbon fullerenes. These novel nanofibers, hereafter named carbon nanotuballs, are expected to demonstrate new advantaged characteristics such as better cross-section properties, enhanced interfacial interactions, and other unique physical attributes when used as fillers within other phases. Some preliminary theoretical investigations based on molecular dynamics are provided here to test the structural stability and mechanical behaviour of some single-walled carbon nanotuballs.

Diamond growth from Chemical Vapor Deposition (CVD) on foreign substrates can require different pretreatment not only to improve the film nucleation but also to assure its adhesion by decreasing the expected film/substrate interface stress. To improve boron-doped film nucleation, growth, and adherence, different substrate pretreatments have been used mainly from the seeding process with diamond powder at various particle sizes. Despite this, the development of diamond growth on a Ti mesh remains difficult because of the requirement of a cohesive film to cover a 3D macroporous sample with varying growth rates based on its distinct network geometry. Then, this work describes a novel approach to growing boron-doped diamond (BDD) and boron-doped ultrananocrystalline diamond (B-UNCD) on titanium dioxide nanotubes (TDNT) produced simultaneously on both sides of Ti mesh by an anodization process. The films were obtained from two-step growth processes by assuring the entire diamond overlay on both TDNT/Ti mesh sides, including their outer/inner surfaces, as a 3D sample. TiO₂ - TiC conversion has dominated the renucleation process, facilitating the nanometric scale control. The film morphologies were systematically analyzed by FEG-SEM images at different sample planes and depths for both sample sides at different stages of film growth. The unique morphology of titania nanotubes associated with columnar and/or renucleation development of BDD, considering the film defects and valley, can systematically increase the electrode specific area. Raman spectra showed the film quality and its micro and/or ultrananodiamond structure and the boron doping features. Also, this growth process allowed a dopant-controlled adjustable conductivity. Then, the boron doping levels for both films were evaluated from Mott-Schottky plots at around 10¹⁹ Bcm⁻³, characterizing them with good conductivity. In addition, electrochemical measurements from Cyclic Voltammetry (CV) confirmed the expected diamond response on redox pair following the quasi-reversible criteria as high-performance diamond electrodes and in situ Raman spectroelectrochemical measurements assessed the stability of samples during electrochemical measurements, ensuring structural integrity. Finally, the samples were applied to the degradation of methylene blue, proving to be superior materials for electrochemical applications due to their advantages compared to those of similar 2D electrodes.

Increasing graphite demand for energy storage applications creates the need to make graphite using precursors and processes that are affordable and friendly to the environment. Non-graphitizing precursors such as biomass or polymers are known for their low cost and sustainability; therefore, graphitizing them will be an accomplishment. In this work, a process of converting a non-graphitizing precursor, phenolic resin novolac (N), into a graphitic carbon is presented. This was achieved by the addition of five additives categorized as graphene oxide (GO) and its derivatives with varied oxygen concentrations. The hypothesis is that the additives act as templates that promote matrix aromatic alignment to their basal planes during carbonization (physical templating) in addition to forming radical sites that bond to the decomposing matrix (chemical templating). Results showed that the addition of reduced graphene oxide (RGO) additives of approximately 15.4 at.(%) oxygen content to the novolac matrix (RGO-N) show the best graphitic quality. In contrast, the addition of GO additive of twice or more oxygen content ≥ 30.8 at.(%) to the novolac matrix (GO-N) led to poor graphitic quality. This suggests that there is an optimum amount of oxygen content in GO additives needed to induce graphitization of the novolac matrix.

Although heteroatom doping is an effective method to improve the capacity of hard carbon (HC) anodes in Na-ion batteries (NIBs), the complicated structure of HC leads to uncertainty when understanding the effects of heteroatom doping on sodium storage. This study shows the effects of phosphorus and sulfur doping to HC on sodium storage using solid-state NMR to improve the capacity of HC prepared by the carbonization of resorcinol formaldehyde (RF) resin at 1100 °C. Heteroatom doping increased the battery capacity of the HC, especially the plateau capacity, but the interlayer distance of the carbon layers in the HC did not expand considerably. ²³Na solid-state NMR revealed that heteroatom doping facilitates the formation of quasi-metallic sodium clusters, thereby contributing to the plateau capacity increase. The metallicity of the sodium clusters in heteroatom-doped HC samples was controlled by the amount of doped-phosphorous. XPS and ³¹P NMR detected various phosphorus sites such as phosphine and phosphine oxide in the carbon structure.

Increasing energy storage demands, and the reducing device size have led to the development of high surface area nanoporous materials. However, the energy storage in such materials do not typically scale as expected according to the increase in the surface area. This is because of another capacitance that appears in series with the electric double-layer capacitors used for energy storage. This capacitance is termed quantum capacitance, which is although present in all materials but becomes considerable in value for materials with low density of electronic states. The quantum capacitance and its effects can greatly enhance our understanding of the double-layer capacitance. In this review, we present the understanding built behind quantum capacitance based on some of the some recent work elucidating the vastness of the area that can be explored.

To accelerate the implementation of zero-emission power installations based on proton-exchange membrane fuel cells, it is necessary to maximize the power characteristics of these devices. For this purpose, we have obtained and tested a new N-doped carbon support and a synthesized Pt/C catalyst based on it with a platinum loading of about 37.3 %. A comparison of the degradation resistance of the initial support and the N-doped one has shown greater stability of the latter. At the same time, Raman spectroscopy has confirmed the presence of the C–N bond, which indicates the successful doping of carbon with nitrogen. The resulting Pt/C catalyst based on an N-doped support is characterized by a substantially narrow size dispersion and an ultra-small nanoparticle size of about 2.6 nm. The high-angle annular dark-field scanning transmission electron microscopy images of the synthesized catalyst have confirmed the presence of individual platinum atoms/clusters uniformly distributed over the surface of the support, and their presence is due to nitrogen embedded into the carbon structure. This material is characterized by a 50 m² g_Pt^-1 larger electrochemically active surface area and a 227 A g_Pt^-1 greater mass activity compared to the commercial JM40 analog (40 % platinum loading). Meanwhile, the electrochemical parameters remaining after the accelerated stress testing are almost 2 times higher than those of JM40. And the power characteristics in the membrane electrode assembly for the catalyst synthesized by the facile one-pot synthesis method are 13 % (575 mW cm^-2) higher than those of the commercial analog (500 mW cm^-2). The Pt/C catalyst obtained during the research is deemed promising for commercial use in proton-exchange membrane fuel cells.

Pressurized carbonization is known to improve carbon content and create textural changes in resultant carbon compared to conventional (atmospheric) carbonization. However, further studies investigating the impact of these carbonization methods on the graphitic quality of the carbon precursors have not been explored extensively. This study investigates the influence of carbonization methods on the graphitization behavior of soft and hard carbons using a three-model system: phenolic resole (hard carbon), polyvinyl chloride (PVC) (soft carbon), and a 50:50 blend of resole and PVC. Carbonization was conducted under autogenic pressure (AGP) and atmospheric pressure (APP) at 500 °C for 5 h, followed by high-temperature treatment at varying temperatures. Various techniques, including X-ray diffraction and Raman spectroscopy showed hard carbon precursors exhibited improved properties under AGP carbonization such as larger crystallite size, sharp crystalline peaks, lower I_D/I_G ratio, and narrow G-full width half-maximum, an indication of improved crystallinity by lowering amorphous phase at high temperature. For soft carbon precursors, the method of carbonization did not impact the graphitization level. The most significant finding was the enhanced crystalline nature observed in hard carbon under AGP conditions, without the need for any catalyst. It shows the influence of pressure on improving the crystallinity of hard carbon precursors.

Electrocatalytic carbon dioxide (CO₂) reduction has emerged as a promising approach for converting CO₂ into value-added products and mitigating greenhouse gas emissions. Layered double hydroxides (LDHs) and metal-organic frameworks (MOFs) have attracted significant attention as potential electrocatalysts for CO₂ reduction due to their unique structural properties and tunable chemical compositions. In this review, we provide a comprehensive overview of recent advances in the utilization of LDHs and MOFs as electrocatalysts for CO₂ reduction. Scrutiny on various catalysts, along with their general design ways for CO₂ reduction is presented. This review will provide insight into the up-to-date research progress in MOF-based materials for CO₂ conversion. Furthermore, we highlight opportunities in this field and propose future research directions aimed at optimizing the performance of LDHs and MOFs for CO₂ reduction applications.