One-step Carbonization Process Research Articles

Bimolecular Salt Strategy Enhances Heteroatom Doping and Porosity Optimization of Porous Carbon for Supercapacitors.

The incompatibility between electrolyte ions and electrode pore sizes, coupled with the extensive use of activators and dopants, significantly restricts the fabrication of porous carbon materials. Consequently, developing environmentally sustainable and efficient methodologies that exploit the intrinsic properties and pretreatment of materials to facilitate self-activation and self-doping becomes crucial. In this study, potassium histidine and magnesium histidine molecular salts were synthesized as precursors, enabling specific ion activation and bimetallic template-directed tunable porosity through a one-step carbonization process. Notably, the ratio of bimolecular salts significantly influenced the porous structure of carbon, the properties of heteroatoms, and the electrochemical performance. By optimizing the ratio, the porous carbon materials exhibited high accessibility to electrolyte ions and effective ion/electron transport channels. Consequently, the optimal sample (NOSPC-2) achieved a high specific capacitance of 318 F g-1 at 0.1 A g-1 and a good capacitance retention rate of 98.8% after 50,000 cycles at 5 A g-1. In addition, NOSPC-2 also boasted high energy density and power density, reaching 22 Wh kg-1 and 25 kW kg-1, respectively. This research represents a significant stride in advancing preparation technologies for small molecule derived porous carbon materials, providing valuable insights for the rational design of carbon electrode materials for capacitive energy storage.

Highly porous carbon with rich inherent groups for ultrahigh adsorption of organic dyes from wastewater

Activated carbon from renewable biomass or its waste to purify various dyeing wastewater from textile industry is highly desired. In this work, porous activated carbon was prepared by using silk waste as precursor via a simple one-step carbonization process. The obtained SWC-1-800 had ultrahigh adsorption for anionic dye AR73 and cationic dye MB owing to its ultrahigh specific surface area (2774 m2 g−1) and rich functional groups. SWC-1-800 had an increased adsorption capacity reaching 1310 and 928 mg g−1 for AR73 and MB respectively as the initial concentration up to 1000 mg L−1. Moreover, the adsorption capacity was stable under a wide range of Na+ and SDS concentration. By adjusting the temperature and pH value, the maximum adsorption capacity reached 1337 and 1000 mg g−1 for AR73 and MB respectively, keeping the removal rate of AR73 and MB more than 80 % after 5 adsorption cycles. Besides, SWC-1-800 demonstrated quite good adsorption ability for many other kinds of dyes, which adsorption capacity as high as 1998 mg g−1 (Rh B). The adsorption mechanism was further proposed according to the structural characteristics, inherent functional groups and adsorption properties. Using silk waste-derived carbon to effectively absorb the harmful dyes in the wastewater shows dual value for cleaner production via a “waste-waste to clean products” model, which has great application potential in dyeing wastewater purification.

High Capacitance Performance N, O Codoped Carbon Foams Synthesized via an All-In-One Step Carbonization of Molecular Salt Strategy.

The preparation of porous carbon is constrained by the extensive use and detrimental impact of activators and dopants. Therefore, developing green and efficient strategies that leverage the intrinsic properties and pretreatment of the materials to achieve self-activation and self-doping is particularly crucial for porous carbon materials. Herein, potassium histidine was utilized as the molecular salt precursor, attaining the efficient and streamlined preparation of porous carbon through a one-step carbonization process that enables self-activation, self-doping, and self-templating. More interestingly, the carbonization temperature significantly impacts the porous structure of the molecular salt precursors, the properties of the heteroatoms, and electrochemical performance. The designed electrodes exhibit high accessibility to electrolyte ions and effective ion-electron transport channels. Therefore, the optimal carbon material (KHis800) has an excellent mass-specific capacitance of 305.2 F g-1 at 0.2 A g-1, and a high capacitance retention rate of 115.6% (50,000 cycles at 5 A g-1). Notably, KHis800 also shows a maximum energy density of 19.6 Wh kg-1. This research is dedicated to exploring a more efficient preparation method for porous carbon material via molecular salts, offering insights for the sustainable development of carbon materials.

Self-templating synthesis strategy of oxygen-doped carbon from unique wasted pulping liquid directly as a cathode material for high-performance zinc ion hybrid capacitors

Affinity and storage capacity for zinc ions of the electrode materials are crucial factors on the properties of zinc ion hybrid capacitors (ZHICs). Wasted pulping liquor with abundant carbohydrates, lignin and inorganic matter served as a unique precursor to produce embedded oxygen-doped hierarchical porous carbon directly through a one-step carbonization process in this investigation. In carbonization process, lignin can serve effectively as the carbon framework, carbohydrates not only act as sacrificial templates but also offer a plentiful oxygen source which can increase the affinity for Zn2+, and sodium-containing inorganic substances plays a role as hard templates to optimize the pore structure. The resulting porous carbon under carbonization temperature of 800 °C shows a high specifical area of 2186 m2g−1 with oxygen content of 4.8 %, which can reduce the adsorption energy of Zn2+ from −0.16 eV to −0.32 eV through electrochemical techniques and density functional theory (DFT) calculations, the incorporation of oxygen was demonstrated to enhance the adsorption and desorption kinetics of Zn2+, suggesting a bright future for application in the domain of energy storage. The resulting ZIHC assembly showcases a notable energy density of 84.6 Wh kg−1 at a power density of 359 W kg−1. Remarkably, even after 10,000 charge and discharge cycles, it exhibits exceptional cycle stability with retaining 86.56 % of its capacity. Consequently, this approach provides fresh insights for exploring the facile and commercial fabrication of biomass-derived cathodes for ZIHCs, thereby propelling the progress of eco-friendly energy storage devices.

ZIF-derived "cocoon"-like in-situ Zn/N-doped carbon as high-capacity anodes for Li/Na-ion batteries

Owing to the unique structure and physicochemical properties, including high specific surface area, self-doped N atoms, open pore structure and good chemical stability, zeolitic imidazolate frameworks (ZIFs) and their derivatives have been widely used in the field of energy storage. Here, a new type of "cocoon"-like Zn/N doped ZIF-derived porous carbon (Zn@N-C-800) is synthesized as an anode for lithium-ion batteries (LIBs) and sodium ion batteries (SIBs) through a one-step carbonization process using a novel Zn-ZIF as the precursor. In Zn@N-C-800, the "cocoon"-like disordered carbon skeleton is conducive to electrolyte infiltration, while the Zn/N doping can provide additional active sites for ion storage. Benefiting from these unique structural characteristics, Zn@N-C-800 achieves excellent electrochemical performances as anode for both LIBs and SIBs: an ultrahigh rate capability of 352 mAh g−1 can be delivered at 12.8 A g−1 for LIBs; an outstanding long-term cycling stability (312 mAh g−1 at 1 A g−1 after 2000 cycles) can be achieved for SIBs. This paper provides new ideas for the design and preparation of high-performance anodes for LIBs and SIBs.

Carbon/C3N4 heterostructures constructed from lignin toward enhanced lithium-ion storage

Lithium-ion batteries (LIBs) are widely used in portable energy storage. The capacity of commercial graphite is difficult to improve due to the stoichiometry limit of LiC6 of graphite, thus new anodes need to be developed to meet the demand of high-energy–density LIB. The growing interest in graphitized carbon nitride (g-C3N4) stems from its structural resemblance to graphite and its capacity to offer abundant adsorption and intercalation sites. However, g-C3N4, as a semiconductor, has a low lithium transfer rate due to its poor conductivity and high diffusion resistance. Improving the electron transport rate of g-C3N4 and reducing the adsorption energy barrier of Li+ in g-C3N4 are the keys to improving the electrochemical performances of g-C3N4. In this study, lignin and melamine were homogeneously mixed using the spray drying method, followed by the preparation of covalently bonded C3N4/LC material through a one-step carbonization process. The uniform dispersion of g-C3N4 in amorphous carbon can improve the conductivity and reduce the diffusion energy barrier of Li+. As a result, the C3N4/LC-x anode has better electrochemical behavior, including higher reversible capacity, better rate performance, and cycle stability.

Simultaneous synthesis of carbon quantum dots and porous carbon using one step hydrothermal method for supercapacitor applications

The present work reports a one-step hydrothermal carbonization process used to simultaneously produce carbon quantum dots and porous carbon. The synthesized materials were characterized by using a Fourier transform infrared spectrometer (FT-IR) to study the chemical interactions, the optical properties were studied with the help of UV-visible absorption spectroscopy, and the morphology analysis of CQDs and porous carbon was examined using FESEM, in which spherical morphology confirms the formation of CQDs, while XRD confirms the amorphous nature of the porous carbon. The application of CQDs and porous materials is evaluated as a supercapacitor material by using the cyclic voltammetry technique. The specific capacitance of porous carbon was 161.33 Fg−1 at 0.01mVs−1 scan rate. This makes CQDs and porous carbon a promising candidate for applications in energy storage devices such as supercapacitors.

Green one-pot synthesis of spongy hierarchical porous carbon with interconnected channels towards high-performance supercapacitors

Green and convenient construction of three-dimensional (3D) hierarchical porous carbon for supercapacitors (SCs) has drawn widespread attention due to their effective ion adsorption and transport capabilities. In this study, sucrose-derived spongy hierarchical porous carbon materials were successfully prepared using a one-step carbonization process with sodium chloride and sodium bicarbonate acting as collaborative pore-forming agents. The optimal carbon material exhibits a distinct 3D spongy structure with interconnected channels, high specific surface area, and proper pore size distribution. Consequently, it displays a specific capacitance of 263.5 F g−1 at 0.5 A g−1 and could retain 221.9 F g−1 (84.21%) at 20 A g−1. Additionally, the as-fabricated device delivers a supreme energy density of 17.0 Wh kg−1 at 80 W kg−1 and possesses exceptional cycling stability of 94.36% after 20000 cycles. Through the combination of raw material carbonization properties and synergistic pore-making mechanisms, the present work provides an effective and eco-friendly approach for fabricating 3D spongy hierarchical porous carbon materials with interconnected channels for high-performance SCs.

Biobased chitosan-derived self-nitrogen-doped porous carbon nanofibers containing nitrogen-doped zeolites for efficient removal of uremic toxins during hemodialysis

Highly efficient adsorbents are needed to remove uremic toxins and reduce the economic and societal burden of the current dialysis treatments in resource-limited environments. In this study, nanostructured porous carbon nanofibers with nitrogen-doped zeolites (NZ-PCNF) were prepared, by electrospinning zeolites with chitosan-poly(ethylene oxide) blends, followed by a one-step carbonization process, without further activation steps or aggressive chemical additives for N-doping. The results showed that N-zeolites were successfully integrated into an ultrafine carbon nanofiber network, with a uniform nanofiber diameter of approximately 25 nm, hierarchical porous structure (micro- and mesopores), and high specific surface area (639.29 m2/g), facilitating uremic toxin diffusion and adsorption. The self-N-doped structure in the NZ-PCNF removed more creatinine (∼1.8 times) than the porous carbon nanofibers when using the same weight of precursor materials. Cytotoxicity and hemolysis tests were performed to verify the safety of NZ-PCNF. This study provides a novel strategy for transforming chitosan-based materials into state-of-the-art porous carbon nanofiber/zeolite self-N-doped composites, affording an efficient bioderived adsorbent for the removal of uremic toxins in patients with chronic kidney disease.

Hydrothermal carbonization of size-controlled carbon microspheres from waste disposable towel with correlation analyze

The utilization of one-step hydrothermal carbonization (HTC) process on disposable waste towels resulted in the production of carbon microspheres characterized by uniform particle sizes. By adjusting the concentration of reactants, temperature, and residence time during hydrothermal carbonization, precise control over the size and surface morphology of carbon microspheres can be achieved. Additionally, an in-depth analysis of the chemical structure of carbon spheres was conducted, which enabled the formulation of a comprehensive mechanism for their formation and growth. The calculation of various morphological parameters was carried out based on the examination of carbon microspheres using a Scanning Electron Microscope (SEM) of the carbon microspheres under different hydrothermal carbonization conditions. The correlation of two experimental parameters, four size descriptors, four morphology descriptors, and the adsorption properties were also investigated for carbon microspheres, which simplified various characterization parameters of the carbon microspheres. The analysis of the correlation between various parameters holds significant guidance in simplifying the parameters and optimizing the process.

Fe3N Nanoparticle-Encapsulated N-Doped Carbon Nanotubes on Biomass-Derived Carbon Cloth as Self-Standing Electrocatalyst for Oxygen Reduction Reaction.

The design and fabrication of low-cost catalysts for highly efficient oxygen reduction are of paramount importance for various renewable energy-related technologies, such as fuel cells and metal-air batteries. Herein, we report the synthesis of Fe3N nanoparticle-encapsulated N-doped carbon nanotubes on the surface of a flexible biomass-derived carbon cloth (Fe3N@CNTs/CC) via a simple one-step carbonization process. Taking advantage of its unique structure, Fe3N@CNTs/CC was employed as a self-standing electrocatalyst for oxygen reduction reaction (ORR) and possessed high activity as well as excellent long-term stability and methanol resistance in alkaline media. Remarkably, Fe3N@CNT/CC can directly play the role of both a gas diffusion layer and an electrocatalytic cathode in a zinc-air battery without additional means of catalyst loading, and it displays higher open-circuit voltage, power density, and specific capacity in comparison with a commercial Pt/C catalyst. This work is anticipated to inspire the design of cost-effective, easily prepared, and high-performance air electrodes for advanced electrochemical applications.

Hierarchical porous structure for superior microwave absorption in biomass-derived carbon microcoils

Carbon micro/nanocoils with excellent electromagnetic cross-polarization capability have promising applications in the microwave absorption field. However, carbon micro/nanocoils with hierarchical porous structures remain challenging. Herein, a novel catalyst-free strategy and a one-step carbonization process were provided to fabricate biomass-driven carbon microcoils with hierarchical porous structures from waste biomass. Due to the synergistic effects of interfacial polarization, multiscale relaxation, and negative imaginary permeability formed by the helical/chiral open-loop pore structure, the porous carbon microcoils (PCMC) exhibits optimized impedance matching, improved dielectric loss, and enhanced electromagnetic wave attenuation and absorption efficiency. The minimum reflection loss (RLmin) of PCMC reaches −63.65 dB at 4.68 GHz, and the RLmin of PCMC reaches −27.6 dB even at 1.59 mm thickness. The maximum effective absorption bandwidth (EAB) can reach 5.78 GHz at 1.86 mm matching thickness. These results can serve as a basis for reusing other green wastes and for manufacturing advanced PCMC-based microwave absorbers at low cost.

Porous Carbon Materials Based on Blue Shark Waste for Application in High-Performance Energy Storage Devices

The scientific community’s interest in developing sustainable carbon materials from biomass waste is increasing steadily, responding to the need to reduce dependence on fossil fuels. Every day, different biomass sources are suggested for obtaining porous carbon materials with characteristics for application in different areas. Porous carbon materials with a high specific surface area are a subject of interest for application in energy storage devices. This work reports the use of blue shark chondroitin sulfate and gelatine as precursors for developing porous carbon materials for energy storage devices. Commercial chondroitin sulfate was used for comparison. The porous carbons obtained in this study underwent various characterization techniques to assess their properties. A BET surface area analyzer measured the specific surface area and pore size. Additionally, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), a high resolution-scanning transmission electron microscope (HR-STEM), Raman spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed to examine the morphology, composition, and structure of the carbons. A modified glassy carbon (GC) electrode was used as the working electrode for the electrochemical characterization. Cyclic voltammetry and galvanostatic charge/discharge techniques were employed with ethaline, an environmentally friendly and sustainable electrolyte based on choline chloride, to assess the electrochemical performance. Furthermore, the most promising samples were subjected to ball-milling to investigate the impact of this process on surface area and capacitance. Blue shark chondroitin sulfate-based carbon presented a specific surface area of 135.2 m2 g−1, compared to 76.11 m2 g−1 of commercial chondroitin sulfate, both carbonized for 1 h at 1000 °C. Blue shark gelatine presented a specific surface area of 30.32 m2 g−1. The associated specific capacitance of these three samples is 40 F g−1, 25 F g−1, and 7 F g−1. Ball-milling on these samples increased the specific surface area and capacitance of the three studied samples with different optimal milling times. This study presents the novel utilization of carbon materials derived from blue shark (with and without ball-milling) through a one-step carbonization process. These carbon materials were combined with an environmentally friendly DES electrolyte. The aim was to explore their potential application in energy storage devices, representing the first instance of employing blue shark-based carbon materials in this manner.

Defined organic-octamolybdate crystalline superstructures derived Mo2C@C as efficient hydrogen evolution electrocatalysts

Hydrogen evolution electrocatalysts derived from metal-organic crystalline frameworks can inherit the merits of ordered and adjustable structures with high surface area. In this paper, organic-octamolybdate crystalline superstructures (OOCS) with a fixed stoichiometric ratio of Mo8(L)2 and high Mo content (>40 wt%) were synthesized using flexible ligands with controllable lengths (named as OOCS-1–3). Then, molybdenum carbides coated with carbon layers as electrocatalysts (Mo2C@C-1–3) can be obtained directly from a one-step high-temperature carbonization process using OOCS-1–3 as precursors. As a typical example, Mo2C@C-3 exhibits satisfactory hydrogen evolution activity with a low overpotential of 151 mV (1.0 mol/L KOH) at 10 mA/cm2 and stability for 24 h. The electrocatalytic activity is mainly from the synergistic interactions between the carbon layers and molybdenum carbide species. Furthermore, compared with the initial content of C, N, Mo in OOCS and Mo2C@C, the catalytic activity increases with the N amount. This work makes organic-octamolybdate crystalline superstructures used as general precursors to product high Mo content electrocatalysts applied in energy storage and conversion fields.

Cellulose as a novel precursor to construct high-performance hard carbon anode toward enhanced sodium-ion batteries

Cellulose, as it has high content and low cost along with the absence of heteroatoms, can well balance the cost and structural consistency issues raised by mass production. Herein, the cellulose-derived hard carbon as an anode material for sodium-ion batteries with high performance has been prepared by a one-step direct carbonization process using pure cellulose as a precursor in the temperature range of 900–1400 °C. Moreover, the effect of carbonization temperature on the microstructure and the sodium battery storage properties of cellulose-derived hard carbon was investigated by structural and morphological characterization, as well as electrochemical performance testing. The results show that the CHC-1300 electrode material displays a high reversible capacity of 373.2 mAh g−1 at 30 mA g−1, and exhibits a desirable cycling stability with 89.7 % capacity retention even after 200 cycles. Furthermore, cyclic voltammetry technique (CV) at different scan rates and galvanostatic intermittent titration technique (GITT) have been employed to explore the sodium storage mechanism and sodium storage kinetics of cellulose-derived hard carbon. The results exhibit that the rate performance of the electrode material would be affected by the low apparent diffusion coefficient of sodium ions in the plateau region. Besides, a full-cell has been assembled with CHC-1300 as the anode and Na0.83Mg0.11Ni0.22Mn0.63O2 (NMNM) as the cathode. The CHC-1300//NMNM full-cell shows high energy density and good cycling stability, which could verify the practical application of the cellulose-derived hard carbon.

3D lamellar skeletal network of porous carbon derived from hull of water chestnut with excellent microwave absorption properties

Biomass derived carbon has attracted extensive attention in the field of microwave absorption because of its sustainability and porous structure beneficial to microwave attenuation. In this study, 3D lamellar skeletal network porous carbon was successfully obtained from hull of water chestnut using biomass waste as raw material by controlling the ratio of KOH and precursors in a one-step carbonization process. The optimization of biomass carbon morphology was achieved and its microwave absorption properties were investigated. At the temperature of 600 °C, when the ratio of hull of water chestnut to KOH is 1:1, the porous carbon material with filling ratio of 35% can reach the effective absorption bandwidth (RL < −10 dB) of 6.0 GHz (12–18 GHz) at the matching thickness of 1.90 mm, covering the whole Ku band. When the thickness is 2.97 mm, the optimal reflection loss reaches −60.76 dB. The surface defects, interface polarization and dipole polarization of 3D porous skeleton network structure derived from hull of water chestnut contribute to the excellent reflection loss and bandwidth of porous carbon materials. The porous carbon with low density, low cost and simple preparation method has broad application prospects in the preparation of biomass-derived microwave absorbers.

Chitins from Seafood Waste as Sustainable Porous Carbon Precursors for the Development of Eco-Friendly Supercapacitors

Carbon materials derived from marine waste have been drawing attention for supercapacitor applications. In this work, chitins from squid and prawn marine wastes were used as carbon precursors for further application as electrodes for energy storage devices. Chitins were obtained through a deproteinization method based on enzymatic hydrolysis as an alternative to chemical hydrolysis as commonly presented in the literature. The obtained porous carbons were characterized using a BET surface area analyzer to determine the specific surface area and pore size, as well as scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), Raman spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), to characterize their morphology, composition, and structure. The electrochemical characterization was performed using a glassy carbon (GC) electrode modified with marine waste-based porous carbons as the working electrode through cyclic voltammetry and galvanostatic charge/discharge using ethaline, a choline chloride-based deep eutectic solvent (DES), as an eco-friendly and sustainable electrolyte. Squid and prawn chitin-based carbons presented a surface area of 149.3 m2 g-1 and 85.0 m2 g-1, pore volume of 0.053 cm3 g-1 and 0.029 cm3 g-1, and an associated specific capacitance of 20 and 15 F g-1 at 1 A g-1, respectively. Preliminary studies were performed to understand the effect of -OH groups on the chitin-based carbon surface with DES as an electrolyte, as well as the effect of aqueous electrolytes (1 mol L-1 sulphuric acid (H2SO4) and 1 mol L-1 potassium hydroxide (KOH)) on the capacitance and retention of the half-cell set up. It is provided, for the first time, the use of chitin-based carbon materials obtained through a one-step carbonization process combined with an eco-friendly DES electrolyte for potential application in energy storage devices.

Water Soluble PMPC-Derived Bright Fluorescent Nitrogen/Phosphorous-Doped Carbon Dots for Fluorescent Ink (Anti-Counterfeiting) and Cellular Multicolor Imaging.

Here, a simple one-step hydrothermal-assisted carbonization process was adopted for the preparation of nitrogen/phosphorous-doped carbon dots from a water-soluble polymer, poly 2-(methacryloyloxy)ethyl phosphorylcholine (PMPC). By the free-radical polymerization method, PMPC was synthesized using 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and 4,4'-azobis (4-cyanovaleric acid). The water-soluble polymers, PMPC, that have nitrogen/phosphorus moieties are used to prepare carbon dots (P-CDs). The resulting P-CDs were thoroughly characterized by various analytical techniques such as field emission-scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy (EDS), high-resolution transmittance electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible (UV-vis) spectroscopy and fluorescence spectroscopy to determine their structural and optical properties. The synthesized P-CDs displayed bright/durable fluorescence, were stable for long periods, and confirmed the enrichment of functionalities including oxygen, phosphorus, and nitrogen heteroatoms in the carbon matrix. Since the synthesized P-CDs showed bright fluorescence with excellent photostability, excitation-dependent fluorescence emission, and excellent quantum yield (23%), it has been explored as a fluorescent (security) ink for drawing and writing (anti-counterfeiting). Further, cytotoxicity study results advised for biocompatibility and thus were used for cellular multicolor imaging in nematodes. This work not only demonstrated the preparation of CDs from polymers that can be used as advanced fluorescence ink, a bioimaging agent for anti-counterfeiting, and cellular multicolor imaging candidate, but additionally prominently opened a new perspective on the bulk preparation of CDs simply and efficiently for various applications.

Bifunctional carbon nanofibrous interlayer embedded with cobalt single atoms for polysulfides trapping and catalysis in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are in the spotlight as one of the most promising energy storage systems, specifically suitable for electric vehicles and intelligent electronic devices. However, Li-S batteries still suffer from the shuttle effect of intermediate polysulfides, inducing the loss of active materials and slow redox reaction kinetics. Herein, a freestanding functional nanofibrous membrane with cobalt single atoms supported by porous carbon nanofiber skeletons is fabricated using a one-step carbonization process. The flexible nanofiber structure can provide the characteristics of good conductivity and lightweight, helping the polysulfides trapped in the porous structure of the fibrous skeleton. Moreover, the results of electrocatalytic characterization and theoretical calculation demonstrate the existence of the metal coordinate center Co-Nx sites, and their functions of reducing polarization voltage and accelerating polysulfide conversion. Using this functional nanofiber membrane as an interlayer with the Co-Nx coordination structure (Co@N-PCNFs), the assembled Li-S batteries exhibit a high initial specific capacity (1522 mAh·g−1 at 0.1C) and outstanding rate performance (905 mAh·g−1 at 2C). Especially, the specific capacity of the Li-S batteries can achieve 786 mAh·g−1 at 0.5C with a sulfur loading of 4 mg·cm−2 after 100 cycles. This effective method of fabricating nanofibrous interlayers can effectively promote the development of advanced Li-S batteries and the application of electrospun materials in energy storage fields.

A highly efficient and sustainable photoabsorber in solar-driven seawater desalination and wastewater purification.

Producing freshwater from seawater and wastewater is of great importance through interfacial solar steam generation (ISSG). Herein, the three-dimensional (3D) carbonized pine cone, CPC1, was fabricated via a one-step carbonization process as a low-cost, robust, efficient, and scalable photoabsorber for the ISSG of seawater as well as a sorbent/photocatalyst for use in wastewater purification. Taking advantage of the large solar-light-harvesting ability of CPC1 due to the presence of carbon black layers on the 3D structure, its inherent porosity, rapid water transportation, large water/air interface, and low thermal conductivity, a conversion efficiency of 99.8% and evaporation flux of 1.65 kg m-2 h-1 under 1 sun (kW m-2) illumination were achieved. After carbonization of the pine cone, its surface becomes black and rough, which leads to an increase in its light absorption in the UV-Vis-NIR region. The photothermal conversion efficiency and evaporation flux of CPC1 did not change significantly during 10 evaporation-condensation cycles. CPC1 exhibited good stability under corrosive conditions without significant change in its evaporation flux. More importantly, CPC1 can be used to purify seawater or wastewater by the removal of organic dyes as well as by the reduction of polluting ions, like nitrate ions in sewage.