Carbon Letters最新文献

The insulating nature of elemental sulfur has been regarded as a major challenge limiting the electrochemical performance of Li–S batteries. Consequently, previous efforts have focused on developing conductive porous materials to enhance sulfur contact. In this study, we review this conventional assumption and demonstrate that the insulating property of sulfur is not the primary factor affecting Li–S battery performance. Instead, we introduce a novel sulfur host design using polar mesoporous carbon (p-MC), which possesses ultra-low electrical conductivity (6.45 × 10⁻⁷ S cm⁻¹) and functional groups. Our results demonstrate that all sulfur particles within the nearly insulating p-MC matrix actively participate in electrochemical reduction during the initial discharge. A comparative study with a nonpolar mesoporous carbon host, which features a similar porous structure but higher conductivity (1.07 × 10⁻¹ S cm⁻¹), showed that the p-MC host achieved superior cycling stability. This performance is attributed to the strong interaction between the polar functional groups of p-MC and lithium polysulfides, enabling effective and stable confinement of the active materials during cycling. Our findings highlight a paradigm shift in the design of sulfur host materials and the critical role of polar functionalities. This study offers a promising strategy for the development of durable and high-performance Li–S batteries.

Tannic acid (TA) is one of the active components in the Galla Chinensis and has various effects, including antioxidant and anti-inflammatory properties. However, research on its antiviral properties remains limited. Here, tannic acid carbon dots (TA-CDs) were prepared as potential antiviral drugs from polyphenol TA under different temperature conditions (180, 200, 220 and 240 °C). Compared to TA alone, TA-CDs exhibited lower cytotoxicity and a tenfold enhanced in antiviral activity. Additionally, the antiviral effects of TA-CDs varied with preparation temperatures, with the best effect observed at 200 °C (CDs-2), reaching a titer of 2.8 orders of magnitude in porcine reproductive and respiratory syndrome virus (PRRSV), mainly due to its relatively higher number of functional groups and smaller particle size. Mechanically, CDs-2 was shown to inhibit PRRSV by targeting the stages of inactivation, adsorption, invasion, replication, and down-regulating reactive oxygen species (ROS) levels. Moreover, CDs-2 exhibited a high inhibitory effect on porcine epidemic diarrhea virus (PEDV), reaching a titer of 7 orders of magnitude. This study reveals the importance of temperature in synthesis of traditional Chinese medicine-derived carbon dots (TCM-CDs) and confirms their potential as antiviral drugs, providing valuable information for development of TCM antiviral drugs.

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Biochar is considered as key anode material for alkali metal (lithium, sodium, and potassium) ion batteries (AIBs) owing to its rich microstructural features, high specific surface area, active sites, excellent conductivity, and mechanical strength. The multidimensional structures and diverse functional groups of biochar make it enable easy modification to improve ion transport, interface deposition behavior, and electrolyte stability. In addition, biochar-based derivatives, such as silicon/biochar composite anode materials, combine the advantages of high-energy density and low lithiation potential of silicon materials, as well as the superior conductive ability and outstanding mechanical qualities of biochar. In this review, the microstructure, properties, and synthesis methods of biochar materials are systematically clarified, and then, their applications in AIBs are presented followed by summarizing the energy storage mechanism and advanced physicochemical characterizations. Common structural configurations and preparative technique for biochar/silicon-based composites are summarized, such as core–shell, yolk–shell, and embedded coating structures with improved electrochemical and mechanical stability. Finally, toward practical application of biochar and biochar-based derivatives in future AIBs, the issues and challenges are outlined.

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Electrochemical exfoliation of graphite to produce graphene flakes is receiving increased attention worldwide due to the simplicity and efficiency of the method. This study examines the effects of different exfoliation mediums, such as nitric acid, sulfuric acid, hydrochloric acid, and potassium hydroxide, on the characteristics of electrochemically exfoliated graphene flakes (EEGFs) and their performance in supercapacitor applications. The study demonstrates that the choice of exfoliation medium significantly impacts the electrochemical characteristics and energy storage capabilities of the resultant graphene flakes. Graphene exfoliated in hydrochloric acid exhibits superior performance, which is attributed to an optimal balance of high conductivity, low defect density, and accessible surface area. Nitric acid-exfoliated graphene, despite being defect rich, offers competitive performance due to increased active sites and enhanced ion accessibility. In contrast, graphene flakes exfoliated in potassium hydroxide present the lowest electrochemical performance and the highest defect density. These findings provide valuable insights into tailoring the properties of electrochemically exfoliated graphene for high-performance energy storage devices.

The development of high specific surface area and mesoporous activated carbons is required to improve the electrochemical performance of EDLC. In this study, kenaf-derived activated carbons (PK-AC) were prepared for high-power-density EDLC via phosphoric acid stabilization and steam activation. The pyrolysis behavior of kenaf with respect to the phosphoric acid stabilization conditions were examined via TGA and DTG. The textural properties of PK-AC were studied with N₂/77 K adsorption–desorption isotherms. In addition, the crystalline structure of PK-AC was observed via X-ray diffraction. The specific surface area and mesopore volume ratio of PK-AC were determined to be 1570–2400 m²/g and 7.7–44.5%, respectively. In addition, PK-AC was observed to have a high specific surface area and mesopore volume ratio than commercial coconut-derived activated carbon (YP-50F). The specific capacitance of PK-AC was increased from 77.0–99.5 F/g (at 0.1 A/g) to 49.3–88.9 F/g (at 10.0 A/g) with activation time increased. In particular, K-P-15-H-9–10 observed an approximately 35% improvement in specific capacitance at a higher current density of 10.0 A/g compared to YP-50F. As a result, the phosphoric acid stabilization method was confirmed to be an efficient process for the preparation of high specific surface area and mesoporous biomass-derived activated carbons, and the kenaf-derived activated carbons prepared by this process have great potential for application as electrode active materials in high-power EDLC.

Akaganeite (β-FeOOH) and hybrid active materials (akaganeite/maghemite (γ-Fe₂O₃)) containing carbon nanoparticles have been successfully developed through hydrothermal process using oxidation debris of graphene oxide and iron (II) chloride tetrahydrate. The obtained akaganeite sample and the hybrid material containing 29% akaganeite and 71% maghemite were confirmed using Mӧssbauer analysis. Two types of cathode made of akaganeite (β-FeOOH) and hybrid active materials supported on reduced graphene oxide (RGO) for RGO/AKA-100 and RGO/AKA-29 were taken as the main air electrode. The full-cell zinc–air battery prototypes (with 6 M KOH electrolyte) were tested for 500 cycles at room temperature. The result showed that the discharge capacity was achieved as high as 131.05 mAh/cm² for RGO/AKA-100 and 137.26 mAh/cm² for RGO/AKA-29. These performances are better than that using zinc–air batteries with carbon black/MnO₂ (CB/MnO₂) as air cathode, that give a discharge capacity of 115.7 mAh/cm². The charge–discharge efficiency of RGO/AKA-100 and RGO/AKA-29 was examined in relation to their distinct catalytic activity for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) when incorporated into electrochemically rechargeable zinc–air batteries. In addition, the different morphology of zinc deposit and dendrite was characterized using SEM, TEM, and PXRD analysis. From this study, the high performance of active material was suggested to be due to the hybrid effect among akaganeite, maghemite, and reduced graphene oxide, which can produce a synergetic improvement.

Phase change materials (PCM) with enhanced thermal conductivity and electromagnetic interference (EMI) shielding properties are vital for applications in electronic devices, energy storage, and aerospace. However, achieving a synergistic improvement in both thermal and EMI shielding performance remains a significant challenge. This study presents the development of phase change composites reinforced with 3D Ag foam and short carbon fibers (SCF) to address this challenge. Ag@SCF/PCM composites were fabricated using a vacuum-assisted impregnation and curing process. Polyethylene glycol and epoxy resin formed the PCM matrix, while SCF and Ag foam created a dual-scale interpenetrating network to provide channels for phonon and electron transmission. The dual-scale network significantly improves thermal conductivity (2.24 W/m·K) and EMI shielding (69.7 dB), while maintaining latent heat storage (melting: 71.5 J/g, freezing: 68.7 J/g). These multifunctional properties make Ag@SCF/PCM composites promising candidates for applications requiring simultaneous thermal management and electromagnetic performance optimization.

In recent years, there has been growing interest in the potential applications of carbon-based non-metallic catalysts in various fields, such as electrochemical energy storage, electrocatalysis, thermal catalysis, and photocatalysis, owing to their unique physical and chemical properties. Modifying carbon catalyst surfaces or incorporating non-metallic heteroatoms, such as nitrogen (N), phosphorus (P), boron (B), and sulfur (S), into the carbon structure has emerged as a promising approach to improve the catalytic performance. This method enables the adjustment of the electronic structure of the carbon catalyst's surface, leading to the formation of new active sites or the reduction of side reactions, ultimately enhancing the catalyst's performance. Here, the preparation methods for doped non-metallic heteroatom carbon catalysts have been systematically explored, encompassing techniques, such as impregnation, pyrolysis, chemical vapor deposition (CVD), and templating. Finally, the existing challenges in the application of non-metallic atomic catalysts have been discussed, insights into potential future development opportunities and new preparation methods of carbon catalysts in the future have been offered.

In order to optimize the manufacturing of polypropylene-derived few-layer graphene, an innovative utilization of non-supported iron oxide nanoparticles generated under various fuel environment conditions was studied. Three distinct fuel combustion environment circumstances (fusion, fuel shortage, and fuel excess) produced a variety of Fe₂O₃ nanoparticles for cost-effective and green graphene deposition. XRD, H₂-TPR, Raman, and TGA measurements were used to characterize both new and spent catalysts. Remarkably, the microstructure of the generated Fe₂O₃ nanoparticles could be controlled by the citric acid/iron nitrate ratio, ranging from spheroids (Fe₂O₃(0)) to sheets (Fe₂O₃(0.5-0.75)) and a hybrid microstructure that consists of sheets, spheroids, and interconnected strips (Fe₂O₃(1-2)). According to fuel situation (citric acid/iron nitrate ratio, Fe₂O₃(0-2)), various graphitization level and yields of graphene derivatives including sheets, ribbons, and onions have been developed. With the ideal fuel/oxidant ratio (ɸ = 1), the Fe₂O₃(0.75) catalyst demonstrated the best catalytic activity to deposit the largest yield of highly graphitized few graphene layers (280%). Lean and rich fuel conditions (1 > ɸ > 1) have detrimental effects on the amount and quality of graphene deposition. It is interesting to note that in addition to graphene sheets, an excess of citric acid caused the production of metallic cores, hollow, and merged carbon nano-onions, and graphene nano-ribbons. It was suggested that carbon nano-onions be converted into graphene nano-ribbons and semi-onion shell-like graphene layers.

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In aluminum electrolysis, carbon anodes fulfill dual functions: providing electrical conductivity and participating in electrochemical reactions. However, these anodes face challenges such as cracking and degradation, which adversely affect their performance and longevity. Consequently, improving the quality of carbon anode is crucial to enhancing the production efficiency of electrolyzers. Key properties, including porosity and air permeability, significantly influence anode consumption and durability. This study presents the development of carbon anodes with reduced porosity and air permeability through optimized forming, sintering, and doping processes. Results revealed that using powdered pitch as a binder led to higher densification, improved flatness, and reduced porosity. Molding under a pressure of 20 MPa for 45 min further enhanced anode quality. Sintering reduced layer spacing and increased graphitization, with optimal conditions determined to be 1100 ℃ for 45 min. These conditions produced carbon anodes with maximum bulk density, minimum resistivity, and an air permeability of 2.54 nPm. The introduction of fusible B₂O₃ effectively sealed internal pores, coated the carbon substrate surfaces, and formed a protective film. This innovation reduced air permeability to 2.05 nPm and significantly enhanced the oxidation resistance of the anodes. These findings provide valuable insights into the production of high-performance carbon anodes, contributing to improved efficiency in aluminum electrolysis.