Carbon Materials Research Articles

Recent Advances in Biomedical Nanotechnology Related to Natural Products.

Natural product processing via nanotechnology has opened the door to innovative and significant applications in medical fields. On one hand, plants-derived bioactive ingredients such as phenols, pentacyclic triterpenes and flavonoids exhibit significant pharmacological activities, on another hand, most of them are hydrophobic in nature, posing challenges to their use. To overcome this issue, nanoencapsulation technology is employed to encapsulate these lipophilic compounds and enhance their bioavailability. In this regard, various nano-sized vehicles, including degradable functional polymer organic compounds, mesoporous silicon or carbon materials, offer superior stability and retention for bioactive ingredients against decomposition and loss during delivery as well as sustained release. On the other hand, some naturally occurring polymers, lipids and even microorganisms, which constitute a significant portion of Earth's biomass, show promising potential for biomedical applications as well. Through nano-processing, these natural products can be developed into nano-delivery systems with desirable characteristics for encapsulation a wide range of bioactive components and therapeutic agents, facilitating in vivo drug transport. Beyond the presentation of the most recent nanoencapsulation and nano-processing advancements with formulations mainly based on natural products, this review emphasizes the importance of their physicochemical properties at the nanoscale and their potential in disease therapy.

Spent coffee grounds-derived carbon material as an effective adsorbent for removing multiple contaminants from wastewater: A comprehensive kinetic, isotherm, and thermodynamic study

Environmental contamination from various industrial sources poses a significant global concern, demanding effective remediation strategies. This study investigates the efficacy of spent coffee grounds-derived carbon material in removing various contaminants, including organophosphate pesticides, pharmaceutical residues, and cationic dyes from aqueous solutions. Adsorption experiments were conducted at different temperatures (25 °C, 30 °C, and 35 °C), and the adsorption behavior was analyzed using various kinetic (pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion) and isotherm models (Freundlich, Langmuir, Temkin, Dubinin-Radushkevich). Our findings reveal a complex adsorption process involving both monolayer and multilayer adsorption on the heterogeneous surface of the material. Temperature significantly influenced adsorption behavior, affecting maximum capacities and interactions. Using a material concentration of 0.5 mg mL−1 increases adsorption capacities for both pesticides, reaching 92.0 mg g−1 for malathion and 259 mg g−1 for chlorpyrifos adsorption. At a material concentration of 0.1 mg mL−1, the carbon material exhibited high adsorption capacities for methylene blue, rhodamine B, amoxicillin, and ceftriaxone, reaching values of 2085 mg g−1, 8250 mg g−1, 82 mg g−1, and 181 mg g−1, respectively. The adsorbent was successfully regenerated using 25 % ethanol solution and reused for at least 10 cycles without significantly impacting the adsorption capacity. These results underscore the potential of spent coffee grounds-derived carbon material as an efficient adsorbent for diverse contaminants, highlighting its promising role in environmental remediation efforts.

Waste hazelnut shell based effective hydrothermal carbon/SnO2 nanoparticles: Towards electrochemical sensing of catechol in green tea, fruit juice, and urine samples

This study focused on the electrochemical detection of catechol (CC), a carcinogenic for humans and a periodic environmental pollutant found in consumed food and beverages and has low degradability and high toxicity in the ecological environment. Also, in this study, for the first time, a new and green electrochemical detection platform was developed for the detection of CC through green carbon material (HZ) recycled from waste hazelnut shells with the hydrothermal carbonization technique (HTC) and SnO2 nanoparticles (NPs). The morphology, surface chemistry, chemical structure, and physicochemical properties of the synthesized green-based functional carbon material and SnO2 NPs were thoroughly investigated and elucidated using different characterization techniques. Thus, a green perspective was contributed to the studies of researchers working on CC detection in designing new types of nanosensors and developing electrode modifications. On GCE with an HZ-SnO2 modification, the effects of pH, the supporting electrolyte, and the scan rate on the electrochemical behavior of CC were investigated. The limit of detection (LOD) of the proposed nanosensor for CC was determined as 8.51 nM and the linearity range was determined as 0.80–80 µM under optimal conditions using adsorptive stripping differential pulse voltammetry (AdsDPV).The developed new type, the green method, has been performed to detect the CC in green tea, fruit juice, and urine samples with sufficient accuracy and precision.

Manipulating Cellulose-Based Dual-Network Coordination for Enhanced Electromagnetic Wave Absorption in Magnetic Porous Carbon Nanocomposites

A novel dual-network coordination strategy was utilized to prepare carbon based magnetic porous EMW absorption nanocomposites with controllable magnetic particles deposition on carbon matrices. Due to the conversion of carboxymethyl cellulose (CMC) into Prussian blue (PB) through coordination with Fe3+, the deposition of Fe3+ gradually tends to aggregate. Consequently, significant changes occur in the polycrystalline structure of magnetic Fe3O4 particles in the pyrolysis products, including alterations in grain size, orientation, and the overall size of polycrystalline particle. Finally, the obtained Fe3O4 decorated porous carbon nanocomposites showed ultrawide effective absorption band of 6.7 GHz owing to the advantageous impedance matching and the synergistic dielectric and magnetic loss effects. Overall, this study offers valuable insights into the design and comprehension of magnetic porous nanocomposites for efficient EMW absorption through the regulation of polycrystalline structure by controllable coordination deposition.

Electromagnetic wave absorbing biomass kelp derived porous carbon anchored by Fe3O4 nanocomposites

Increasingly serious electromagnetic pollution problems bring the threaten for national defense security and personal health, biomass carbon materials derived absorbers have arouse widespread interest due to their green, easy accessibility, structural diversity, rich functional groups. Herein, biomass kelp derived three-dimension (3D) porous carbon/Fe3O4 (KPC/Fe3O4) nanocomposites were successfully synthesized vis KOH activation as well as in-situ growth of Fe3O4 and following pyrolysis. Attributed to multiple transmission paths for electromagnetic wave from 3D porous structure, dielectric-magnetic synergistic effect, and numerous defects in the kelp-derived carbon with polarization loss caused by heteroatom doping and interfacial polarization, KPC/Fe3O4 nanocomposites possess outstanding impedance matching and extraordinary attenuation ability. In particular, the minimum reflection loss (RLmin) value of KPC/Fe3O4-0.1 nanocomposite reaches −75.02 dB at 10.5 GHz as well as the effective absorption bandwidth (EAB, RL < -10 dB) value achieves 4.83 GHz with a thickness of 2.85 mm. Unique structures and excellent EWA performance demonstrate that KPC/Fe3O4 nanocomposites can serve as potential absorbers for military and civilian fields.

Determining Eastern Red Cedar Biochar Soilless Media Supplementation Rates for Potted Ornamental Kale and Chrysanthemum Production

The increasing demand for soilless media, sustainability issues with peatmoss, and increasing cost of peatmoss have prompted studies of more environmentally friendly and less expensive substitutes. Biochar, a lightweight black carbon material produced by the pyrolysis of biomass, has gained popularity as a soilless media supplement. The objective of this study was to evaluate Eastern red cedar (ERC) biochar as a supplement to soilless media for the production of chrysanthemum and ornamental kale. Treatments included ERC biochar produced at three different temperature ranges of 300 to 350 °C, 400 to 450 °C, and 500 to 550 °C that were applied at 25%, 50%, and 75% v/v plus a control (100% v/v of standard commercial mix). Additionally, ERC bark was applied at the same rate as biochar. The 300 to 350 °C and 400 to 450 °C temperature ranges increased the bulk density of the media, whereas total porosity was greatest with just bark. Regarding the physical properties of the media, in general, the 75% v/v supplementation rate of ERC bark or biochar at any temperature increased air porosity but decreased the water holding capacity, except for the water holding capacity at 500 to 550 °C. As the biochar production temperature increased, so did the pH and electrical conductivity (EC), whereas volatile matter decreased. Plant height, width, shoot dry weight, root dry weight, number of flowers (chrysanthemum only), flower diameter, and water use efficiency were greatest with the 100% v/v soilless media for both species. In general, chrysanthemum plants grown with 25% v/v biochar supplementation or bark had similar height, width, and shoot dry weight at any temperature compared with those grown with the 100% v/v soilless media. For ornamental kale, the 25% v/v 400 to 450 °C biochar supplementation showed plant height and water use efficiency similar to those of the 100% v/v soilless media. In general, 25% ERC bark performed similar to 25% v/v and 50% v/v biochar at any temperature for plant width, shoot dry weight, root dry weight, water use efficiency, and root-to-shoot ratio. The media nutrient content and EC were greater with 100% v/v soilless media and a lower rate (25% v/v) of ERC bark and biochar than with higher rates. The higher levels of biochar were harmful and reduced the ornamental kale growth and quality. These results suggest that supplemented soilless media with lower rates (25% v/v) of ERC biochar could be recommended for chrysanthemum, but that less than 25% v/v may be necessary for ornamental kale.

Cocoa husk as precursor of carbonaceous materials for supercapacitors electrodes

Activated carbon materials are widely used as high-performance electrodes for supercapacitors because they allow improving the electrochemical performance of these devices. The development of high surface areas and high porosity contributes to the energy storage by double electric layer, whereas the content of different functional groups on their surface to the pseudocapacitive storage. In addition, they can be obtained from lignocellulosic wastes providing a novel and economic perspective for the development of carbon-based electrodes. In this work, activated carbons were synthesized from cocoa husks using KOH as activating agent. The materials were obtained at three impregnation ratios (1:1, 3:1, 5:1) and three carbonization temperatures (500, 650, and 800 °C), optimizing the best conditions to obtain materials with high surface areas and porosity together with surface functional groups to improve energy storage. The results show that the 800 °C synthesized material with 3:1 impregnation ratio presents a capacitance of 120 F/g at 1 A/g, with a retention capacity of 93 % after 12,000 cycles, being the best electrochemical behavior among the carbons prepared. This is attributed to the adequate micro-mesoporosity, content of surface oxygenated functional groups and high surface area (1444 m2/g).

Review on Biomass Derived Activated Carbons as Electrochemical Electrode Material for Supercapacitor Device

Abstract: To face the challenge of the finite nature of fossil fuels and large energy crises across the globe, there is an urgent requirement for sustainable and renewable energy sources. Moreover, it is essential to focus on energy storage in order to meet the demand of future generations. Among various energy storage devices such as fuel cells, batteries, capacitors, supercapacitors, flywheels, etc., it is the supercapacitor device that has elicited extensive research interest recently because of prominent features like high power density, fast recharge capability, and long cycle life. The main objective of this article is to review the enhancement of the electrochemical performance of supercapacitor devices. The electrochemical properties of the supercapacitor device majorly depend on the electrode materials used, which include carbonaceous materials, metal oxides, and conducting polymers. In order to reduce energy shortages and environmental pressure, carbon materials derived from biomass/waste materials have been considered remarkable candidates for electrode materials with the advantages of high abundance, low cost, and environmental friendliness. This review shows the complied study of various methodologies for the preparation of activated carbons derived from different biomass residues such as plants, animals, and microorganisms, which have been investigated in the past few years as electrochemical electrode materials for supercapacitors. Further, ongoing challenges and potential improvements in this area for creating efficient energy storage devices are also discussed. The goal of this review article is to aid in the creation of new insights for energy storage applications of biomass-generated carbons that will lead to sustainable energy development.

Electronic, thermoelectric and electrical transport properties of single layer γ-graphyne

Recently, graphyne has emerged as the sole two-dimensional carbon material exhibiting both sp and sp2 hybridization. It’s remarkable attributes have ignited considerable interest, particularly in the realm of optoelectronics, driven by its narrow band gap, signifying its vast potential in this field. In this paper we investigated electronic, thermoelectric and electrical transport properties of single layer γ-graphyne systematically and comparatively by using density functional theory (DFT). Our findings reveal that γ-graphyne displays pronounced absorption peaks within both the infrared (IR) and visible regions (VR), indicating its robust optical characteristics. Additionally, γ-graphyne showcases exceptional thermoelectric performance. The insights gained from this study elucidate the properties of γ-graphyne and suggest its applicability across various domains, including optical sensing and thermoelectric energy conversion devices.

Emerging trends in CDs@hydrogels composites: from materials to applications.

Carbon dots (CDs) are nanoscale carbon materials with unique optical properties and biocompatibility. Their applications are limited by their tendency to aggregate or oxidize in aqueous environments. Turning weakness to strengths, CDs can be incorporated with hydrogels, which are three-dimensional networks of crosslinked polymers that can retain large amounts of water. Hydrogels can provide a stable and tunable matrix for CDs, enhancing their fluorescence, stability, and functionality. CDs@hydrogels, known for their ease of synthesis, strong binding capabilities, and rich surface functional groups, have emerged as promising composite materials. In this review, recent advances in the synthesis and characterization of CDs@hydrogels, composite materials composed of CDs and various types of natural or synthetic hydrogels, are summarized. The potential applications of CDs@hydrogels in fluorescence sensing, adsorption, drug delivery, antibacterial activity, flexible electronics, and energy storage are also highlighted. The current challenges and future prospects of CDs@hydrogels systems for the novel functional materials are discussed.

A networked iron and nitrogen-doped ZIF-8/MWCNTs heterostructure for oxygen reduction reaction.

Zeolitic Imidazolate Frameworks-8 (ZIF-8) is commonly used as an ideal precursor for non-noble metal catalysts because of its high specific surface area, ultra-high porosity, and N-rich content. Upon pyrolyzing ZIF-8 at 900 °C in Ar, the resulting material, referred to as Z8, displayed good activity toward the oxygen reduction reaction (ORR). Then the ZIF-8 was mixed with various conductive carbon materials, such as multiwall carbon nanotubes (MWCNTs), Acetylene black (ACET), Vulcan XC-72R (XC-72R), and Ketjenblack EC-600JD (EC-600JD), to form Z8 composites. The Z8/MWCNTs composite exhibited enhanced ORR activity owing to its network structure, meso-/microporous hierarchical porous structure, improved electrical conductivity, and graphitization. Subsequently, iron and nitrogen co-doping is achieved through the pyrolysis of a mixture comprising Fe, N precursor, and ZIF-8/MWCNTs, which is denoted as FeN-Z8/MWCNTs. The intrinsically high electrical conductivity of MWCNTs facilitated efficient electron transfer during the ORR, while the meso-/microporous hierarchical porous structure and network structure of Fe, N co-doped ZIF-8/MWCNTs promoted oxygen transport. The presence of Fe-containing species in the catalyst acted as activity centers for ORR. This strategy of preparing Z8 composites and modifying them with Fe, N co-doping offers an insightful approach to designing cost-effective electrocatalysts.

In Situ Self-Assembly of Nitrogen-Doped 3D Flower-like Hierarchical Porous Carbon and Its Application for Supercapacitors

The hierarchical porous carbon-based materials derived from biomass are beneficial for the enhancement of electrochemical performances in supercapacitors. Herein, we report the fabrication of nitrogen-doped 3D flower-like hierarchical porous carbon (NPC) assembled by nanosheets using a mixture of urea, ZnCl2, and starch via a low-temperature hydrothermal reaction and high-temperature carbonization process. As a consequence, the optimized mass ratio for the mixture is 2:2:2 and the temperature is 700 °C. The NPC structures are capable of electron transport and ion diffusion owing to their high specific surface area (1498.4 m2 g−1) and rich heteroatoms. Thereby, the resultant NPC electrodes display excellent capacitive performance, with a high specific capacitance of 249.7 F g−1 at 1.0 A g−1 and good cycling stability. Remarkably, this implies a superior energy density of 42.98 Wh kg−1 with a power density of 7500 W kg−1 in organic electrolyte for the symmetrical supercapacitor. This result verifies the good performance of as-synthesized carbon materials in capacitive energy storage applications, which is inseparable from the hierarchical porous features of the materials.

Precise Control of Ultramicropores of Novel Carbons Molecule Sieves Derived from Coffee Bean for Efficient Sieving Propylene from Propane.

The development of granular carbon materials with outstanding selectivity for the separation of alkenes and alkanes is highly desirable in the petrochemical industry but remains a significant challenge due to closely similar molecular sizes and physical properties of adsorbates. Herein, we report a facile approach of using natural biomass to prepare novel granular carbon molecule sieves with a molecular recognition accuracy of 0.44 Å and propose a new three-region model for the pore size distribution of amorphous porous carbons. Coffee bean-based granule carbon molecular sieves (CFGCs) were prepared with precise micropore regulation with subangstrom accuracy and characterized using molecular probes to reveal the evolution of carbon structure during preparation. The CFGC-0.09-750 demonstrates exceptional selectivity adsorption toward C3H6 while excluding C3H8, with an uptake ratio of 106.75 and a C3H6 uptake of 1.88 mmol/g at 298 K and 100 kPa, showcasing its immense potential in industrial applications for separating C3H6 and C3H8. The novel three-region model established in this work can clearly and reasonably elucidate why the samples CFGCs can screen propylene from propane at the subangstrom level. This study provides important guidance for the development of new carbon molecular sieves with subangstrom accuracy in molecular recognition and separation capacity.

SYNTHESIS AND CHARACTERIZATION OF ACTIVATED CARBON PREPARED FROM RICE HUSK BY PHYSICS-CHEMICAL ACTIVATION

Activated carbon is an amorphous carbon material predominantly composed of free carbon atoms with high adsorption capacity. The amorphous structure in activated carbon affects its adsorption capacity; the higher the percentage of amorphous carbon, the greater the adsorption capacity of the activated carbon. Activated carbon can be obtained from rice husk waste containing 30-40% C in cellulose, hemicellulose, and lignin. Therefore, this study was conducted to observe activated carbon's phases, morphology, elemental composition, and particle size. Activated carbon was synthesized using a physics-chemical activation method, which began with washing the rice husk samples, followed by air drying, carbonizing into charcoal, and grinding it finely. The rice husk charcoal powder was then physically activated at a temperature of 500℃. The physically activated product was then chemically activated using 6M HCl with a charcoal-to-activator ratio of 1:10 (m/V), stirred at 250 rpm for 1 hour, and then allowed to settle for 24 hours. It was then washed and dried to produce activated carbon powder. XRD test results showed diffraction peaks at 2θ = 22.23° without sharp or pointed peaks, indicating that the activated carbon has an amorphous structure. SEM test results showed the morphology of rice husk-activated carbon with spherical particle shapes and a particle size distribution of 20-70 nm. EDX test results showed that the rice husk activated carbon is predominantly composed of C, O, and Si with respective percentages of 54.31%, 40.04%, and 2.49%.

Stability of Graphene/Nafion Composite in PEM FC Electrodes

Ensuring the stable operation of proton exchange membrane fuel cells is conducive to their real-world application. A promising direction for stabilizing electrodes is the stabilization of the ionomer via the formation of surface compounds with graphene. A comprehensive study of the (electrochemical, chemical, and thermal) stability of composites for fuel cell electrodes containing a modifying additive of few-layer graphene was carried out. Electrochemical stability was studied by cycling the potential on a disk electrode for 5000 cycles. Chemical stability was assessed via the resistance of the composites to H2O2 treatment using ion-selective potentiometry. Thermal stability was studied using differential thermal analysis. Composites were characterized by UV-Vis spectroscopy, Raman spectroscopy, EDX, and SEM. It was shown that graphene inhibits Nafion degradation when exposed to heat. Contrariwise, Nafion is corrosive to graphene. During electrochemical and chemical exposure, the determining change for carbon-rich composites is the carbon loss (oxidation) of the carbon material. In the case of carbon-poor composites, the removal of fluorine and sulfur from the Nafion polymer with their partial replacement by oxygen prevails. In all cases, the F/S ratio is stable. The dispersity of Nafion in a sample affects its chemical stability more than the G/Nafion ratio does.

Hydrogen peroxide electrosynthesis using commercial carbon blacks as catalysts: the influence of surface properties and adsorption performance

AbstractBACKGROUNDSurface properties and adsorption performance of carbon materials play a crucial role in the electrochemical two‐electron oxygen reduction to produce H2O2. However, there is still a lack of in‐depth research on commercial carbon blacks in this area. Herein, four typical commercial carbon blacks (Acetylene black (AB), Ketjen black EC 600JD, Vulcan XC 72 and Black Pearls 2000) were used as cathode catalysts to generate H2O2. Surface chemistry and pore structure of electrodes of the four carbon blacks were systematically characterized, and their effects on H2O2 adsorption, electrochemical generation and degradation were investigated.RESULTSAmong the four carbon blacks, AB has the highest content of C–O–C/COOH and CO, which are active groups catalyzing the two‐electron oxygen reduction reaction to generate H2O2. AB has the lowest level of defects and highest degree of graphitization, and AB‐modified graphite felt electrode (AB‐Ele) has the largest average pore diameter, smallest specific surface area and smaller charge transfer resistance. H2O2 production using AB‐Ele is the largest and reaches 567.7 mg L−1 at 180 min under a current density of 5 mA cm−2, and only decreases by 17.6% after 10 repeated uses.CONCLUSIONOverall, rich oxygen‐containing functional groups such as C–O–C, COOH and CO, high degree of graphitization, suitable surface area and porosity as well as weak H2O2 adsorption performance are beneficial for the two‐electron oxygen reduction reaction to generate H2O2. AB‐modified graphite felt electrode exhibits good catalytic activity and reusability in H2O2 electrosynthesis, demonstrating promising application prospects. © 2024 Society of Chemical Industry (SCI).

Preparation and Characterization of Lignin‐Based Activated Carbon by Rubidium Chloride Chemical Method

AbstractIn order to prepare carbon adsorbent materials, lignin was used as raw material and rubidium chloride as activator, activated carbon materials were prepared by chemical activation method, and its structure was characterized and its adsorption performance on methylene blue solution was investigated; the adsorption of crystalline violet dye was carried out at different temperatures, and the adsorption thermodynamics was studied. The results showed that: the specific surface area of the activated carbon was 433.32 m2/g, the pore volume was 0.2191 cm3/g, and the average pore size was 2.0222 nm; the adsorption value of methylene blue could reach 172.0 mg/g, and it could quickly and efficiently adsorb methylene blue solution; the adsorption effect on crystal violet solution was good, and the saturated adsorption amount at 40 °C was up to 279 mg/g, and the removal rate reached 93 %, belonging to the spontaneous adsorption thermodynamic reaction. The experiment proved that rubidium chloride can be used as an activator to activate lignin raw materials to prepare activated carbon samples, and can effectively adsorb dyes.

Investigating the expansion behavior of silicon nanoparticles and the effects of electrolyte composition using a graphene liquid cell

Understanding the volume expansion behavior of Si anodes and their interaction with electrolyte environments is crucial for developing high-performance lithium-ion batteries (LIBs). This study utilizes a graphene liquid cell for in situ imaging to systematically investigate the volume expansion and etching behavior of Si anode nanoparticles in different electrolyte environments. Comparative experiments on Si@C core-shell nanoparticles assess their volume expansion dynamics. The findings reveal significant variation in the expansion rate of nano Si depending on the electrolyte environment, with chemical etching observed under specific conditions. Conversely, Si@C core-shell structures show mitigated expansion due to the confinement effect of the carbon matrix. Battery performance experiments validate these results, demonstrating the excellent cycling stability of Si@C anodes. Various coating agents are explored to optimize Si@C structures, with dopamine thin layer coating exhibiting the best cycling stability. This study offers fundamental insights into Si anode expansion, electrolyte effects, and carbon coating impacts, advancing LIB technology.

Effect of Thermal Activation on the Structure and Electrochemical Properties of Carbon Material Obtained from Walnut Shells

A simple activation method has been used to obtain porous carbon material from walnut shells. The effect of the activation duration at 400 °C in an atmosphere with limited air access on the structural, morphological, and electrochemical properties of the porous carbon material obtained from walnut shells has been studied. Moreover, the structure and morphology of the original and activated carbon samples have been characterized by SAXS, low-temperature adsorption porosimetry, SEM, and Raman spectroscopy. Therefore, the results indicate that increasing the duration of activation at a constant temperature results in a reduction in the thickness values of interplanar spacing (d002) in a range of 0.38–0.36 nm and lateral dimensions of the graphite crystallite from 3.79 to 2.52 nm. It has been demonstrated that thermal activation allows for an approximate doubling of the specific SBET surface area of the original carbon material and contributes to the development of its mesoporous structure, with a relative mesopore content of approximately 75–78% and an average pore diameter of about 5 nm. The fractal dimension of the obtained carbon materials was calculated using the Frenkel–Halsey–Hill method; it shows that its values for thermally activated samples (2.52, 2.69) are significantly higher than for the original sample (2.17). Thus, the porous carbon materials obtained were used to fabricate electrodes for electrochemical capacitors. Electrochemical investigations of these cells in a 6 M KOH aqueous electrolyte were conducted by cyclic voltammetry, galvanostatic charge/discharge, and impedance spectroscopy. Consequently, it was established that the carbon material activated at 400 °C for 2 h exhibits a specific capacity of approximately 110–130 F/g at a discharge current density ranging from 4 to 100 mA/g.

Pseudocapacitive contribution in sulfur-doped porous carbon nanosheets enables high-performance sodium-ion storage

Sulfur-doped carbon materials have sparked considerable attention as the anodes for sodium-ion batteries (SIBs) due to their relatively high reversible specific capacity and excellent pseudocapacitive effect. However, the content of sulfur dopants in carbon materials is usually limited and an efficient doping strategy is urgently imperative to date. Herein, a space-confined doping strategy is proposed to fabricate porous carbon nanosheets with high sulfur dopant content by using low-cost pitch as a precursor with the help of sodium thiosulfate (Na2S2O3). The thermostable nano-MgO used in this system can occupy the specific space during pitch decomposition to induce the formation of hierarchical carbon nanosheets. Interestingly, such a space-confinement effect of nano-MgO is able to enlarge the accessible contact area of reactants and inhibit the loss of sulfur from Na2S2O3, thus significantly increasing sulfur dopant content within carbon frameworks. The optimized sulfur-doped carbon nanosheets (S-PCNs-2) with a high sulfur content of about 20.56 wt% as anode for SIBs delivers an ultrahigh pseudocapacitive contribution of 92.55 % at 5 mV s−1 and thus enable a desirable specific capacity of 428.6 mAh g−1 at 0.1 A g−1 with a high initial Coulombic efficiency of 84.9 % and superior rate performance of 380.6 mAh g−1 at 5 A g−1. Furthermore, a long cycling lifespan with a capacity retention of 88 % after 1000 charge/discharge cycles can be achieved for the S-PCNs-2 anode. This work provides a simple yet efficient doping approach to fabricate carbon anodes with high heteroatom contents for SIBs.