As-prepared Carbon Research Articles

Bamboo waste derived hard carbon as high performance anode for sodium-ion batteries

Biomass-derived hard carbon stands out as one of the most promising anode materials for advancing the commercial viability of sodium-ion batteries (SIBs). In this study, we harnessed a straightforward and eco-friendly two-step carbonization approach to fabricate high-performance hard carbon materials, ingeniously repurposing industrial bamboo waste. Concurrently, we delved into the impact of carbonization temperature on the microstructure and properties of the hard carbon derived from bamboo waste. The findings revealed that the as-prepared hard carbon at 1400 °C (HCB-1400) showcased the most desirable sodium-ion storage capabilities. The HCB-1400 material not only can deliver a substantial reversible capacity of 328.4 mAh g−1 at 30 mA g−1 in its maiden charge-discharge cycle but also display remarkable cycling stability. Moreover, the HCB-1400//Na3V2(PO4)3 full cell, when assembled, exhibited an impressive energy density of 249.25 Wh kg−1, with a capacity retention rate of 93 % after enduring 200 cycles at a current density of 1.0 C. This research underscores the potential of transforming biomass waste into high-performance hard carbon, heralding a sustainable path for SIB applications.

Nitrogen and sulfur co-doped porous carbon obtained from direct carbonization of a renewable biomass for counter electrode of efficient dye-sensitized solar cells

It is highly necessary to fabricate cost-effective counter electrode for promoting the development and practical deployment of dye-sensitized solar cells (DSSCs). Herein, nitrogen and sulfur co-doped porous carbon (NSPC) is prepared through directly carbonizing a renewable biomass, Eupatorium fortunei Turcz., and used as an alternative to expensive Pt to fabricate low-cost counter electrode for high-performance DSSCs. Scanning electron microscopy and N2 adsorption analyses demonstrate that the obtained carbon sample displays a hierarchical pore structure containing macropore channels and well-developed mesopores formed on the wall of macropore channels. X-ray photoelectron spectroscopy measurements suggest that nitrogen and sulfur atoms are doped in the framework of as-prepared carbon sample. These favorable characteristics endow the obtained NSPC counter electrode with a superior electrocatalytic performance. Consequently, the assembled DSSC with NSPC counter electrode shows an efficiency of 8.25%, nearly matching the efficiency of the cell with conventional Pt counter electrode.

Microstructure reconstruction via confined carbonization achieves highly available sodium ion diffusion channels in hard carbon

Hard carbon is considered as the main candidate negative electrode material for sodium-ion batteries (SIBs) due to its high stability and electrochemical performance. However, the complex carbon structure and composition of hard carbon are difficult to achieve precise control during the preparation process, which leads to difficulties in accurately determining the attribution of electrochemical behavior. Here, we propose a confined carbonization strategy to achieve microstructure reconstruction of hard carbon, characterized by the anchoring of polymers in the mesopores of porous carbon to generate ordered carbon structures at high temperatures. The stacking of ordered carbon on micropores in porous carbon achieves the transition from exposed pores to closed pores (nano cleithral pores). Through mechanism detection, it is found that the ordered carbon structure provides sub nanochannels for sodium ion migration, which contributes to high slope capacity. In addition, the nano cleithral pores are sites filled with sodium ions and provide high plateau capacity. Benefiting from theses available sodium ion transport channels, carbon materials have achieved a transition from surface-controlled process to diffusion-controlled process in the sodium storage process via confined carbonization. The as-prepared carbon delivers a superior capacity of 356.2 mAh g–1 (215.6 mAh g–1 for plateau capacity) at 20 mA g–1 with excellent rate and cycling performance. This work reveals the correlation between structure and electrochemical performance for carbon electrode, providing profound guidance for the precise preparation of high-performance carbon materials.

Rapid conversion of biomass to hierarchical porous carbons via one-step microwave carbonization/activation for long cycle-stable supercapacitor and zinc-ion capacitor

Biomass derived carbons as electrode materials for supercapacitors have drawn great attention owing to their low cost, high specific areas and abundant surface functional groups, but most of their preparation processes are time-consuming and power-wasting. In this work, we report a rapid and energy-saving strategy for preparing hierarchical porous carbons derived from loofah sponges for supercapacitors via one-step microwave carbonization/activation. Utilizing KOH as the microwave absorption medium and activator, the microwave carbonization/activation process can be completed within 6–10 min. The resulting loofah sponges derived porous carbons demonstrate a high specific capacitance of 294 F g−1 at 0.5 A g−1 and an outstanding retention rate of 74.8 % at 20 A g−1 in three-electrode setup for supercapacitor. The fabricated zinc-ion capacitor based on the as-prepared carbon materials displays a comparable energy density of 62.3 Wh∙kg−1 at the power density of 160 W kg−1. Notably, a remarkable long-term cyclic stability by retaining of 93.6 % of its initial capacitance is acquired after 30,000 cycles. Our research not only fabricates sustainable electrode materials for supercapacitors and zinc-ion capacitors but also provides a fast and energy efficient route for producing biomass derived carbon materials with high capacitive performances for commercial applications.

Deepening the Understanding of Carbon Active Sites for ORR Using Electrochemical and Spectrochemical Techniques.

Defect-containing carbon nanotube materials were prepared by subjecting two commercial multiwalled carbon nanotubes (MWCNTs) of different purities to purification (HCl) and oxidative conditions (HNO3) and further heat treatment to remove surface oxygen groups. The as-prepared carbon materials were physicochemically characterized to observe changes in their properties after the different treatments. TEM microscopy shows morphological modifications in the MWCNTs after the treatments such as broken walls and carbon defects including topological defects. This leads to both higher surface areas and active sites. The carbon defects were analysed by Raman spectroscopy, but the active surface area (ASA) and the electrochemical active surface area (EASA) values showed that not all the defects are equally active for oxygen reduction reactions (ORRs). This suggests the importance of calculating either ASA or EASA in carbon materials with different structures to determine the activity of these defects. The as-prepared defect-containing multiwalled carbon nanotubes exhibit good catalytic performance due to the formation of carbon defects active for ORR such as edge sites and topological defects. Moreover, they exhibit good stability and methanol tolerances. The as-prepared MWCNTs sample with the highest purity is a promising defective carbon material for ORR because its activity is only related to high concentrations of active carbon defects including edge sites and topological defects.

Effect of acid soak treatment of the precursor on the structure and properties of polypropylene-based carbon fibers

Polyolefin fibers have received wide attention as the precursor for low-cost carbon fiber, and cross-linking of linear polyolefin by strong acid has been proven to be an effective way to stabilize the precursor fiber prior to carbonization. However, the conventional temperature used in sulfonation process is too high and could result in severe decomposition of the linear chain of the polymer, which further deteriorated the mechanical properties of the as-prepared carbon fiber. Thus, reducing the duration of sulfonation process operated at high temperature may alleviate the degradation behavior, conferring the polyolefin-based carbon fibers with better performance. In this paper, polypropylene (PP) fibers were soaked in sulfuric acid at 50 °C–90 °C, before the conventional preparation protocol of PP-based carbon fiber. The structural evolution from PP to carbon fiber were characterized by Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The mechanical and conductive properties of carbonized fibers where further measured. The results showed that the soak in sulfuric acid resulted in swelling of PP fibers in diameter direction, as well as reducing the crystallinity of the fibers, both of which were physical transformation, and could be easily controlled by soak temperature. The subsequent sulfonation at conventional temperature was fastened for the soaked PP fibers, and the duration of sufficient sulfonation were almost reduced by half. The obtained carbon fibers exhibited better thermal conductivity and mechanical properties, which were enhanced by 25 % and 40 %, respectively, compared with that without soak pretreatment.

Laser-induced nitrogen and phosphorus-doped spongy carbon with graphene wings derived from lignin for significantly enhanced capacitance deionization performance

Efficient capacitive deionization (CDI) technology puts forward higher requirements for electrode materials. However, the traditional process of preparing porous carbon (PC) electrodes by alkaline chemical activation is polluting and energy-consuming. In this work, the N/P co-doped biocarbon material (H-AL/APP) was prepared by using alkali lignin (AL) and ammonium polyphosphate (APP) as carbon precursors based on laser-induced carbonization and hydrothermal activation technology. The as-prepared carbon material shows a three-dimensional (3D) structure with a hierarchical porous structure, large specific surface area of 405.98 m2/g (SSA), excellent pore volume, and outstanding mesoporosity. Compared with commercial YP80 activated carbon, The H-AL/APP electrode exhibits a higher specific capacitance of 210F/g with excellent rate performance and cycle stability. When assembled for desalination, H-AL/APP shows the highest removal rate of 23 mg/g/min with an outstanding desalination capacity of 34.6 mg/g than those of YP80 activated carbon. Furthermore, reasonable cycle stability and reproducibility highlight their promising application prospects. In summary, this work provides a green, efficient, and economical method for preparing high-performance heteroatom-doped PCs for efficient CDI desalination.

Dopamine inspired lignin-derived green emissive carbon dots for pH sensing and metal ions separation

Lignin is the most abundant, but underutilization polyphenolic material on the earth. In this paper, an integrated platform for pH sensing and ions separation was prepared from lignin to make use of this abundant bioresource. Demethylation of enzymatic hydrolysis lignin was first achieved to mimic the catechol structure of dopamine. The demethylated lignin was then converted into carbon dots by a facile hydrothermal treatment. The as-prepared carbon dots emit green fluorescence with enhanced quantum yield, and exhibited pH-responsive color changes from yellow-green to blue. When incorporated into a chitosan aerogel, the pH-responsive property of the carbon dots was intact, whereas the adsorption capacity of the aerogel for Cu2+ ions was noticeably improved, which was owed to the abundant oxygen containing functional groups and unique optical properties of the as-prepared carbon dots. This study provides a feasible approach to convert lignin into fluorescent nanomaterials for pH sensing and metal ions recovery from wastewater.

Sustainable chitosan derived 3D hierarchically porous carbon aerogel toward advanced infrared-radar compatibility

Simultaneously achieving infrared-radar compatibility in one material is an important challenge for multi-spectral compatible stealth technology. Chitosan-derived three-dimensional (3D) hierarchically porous carbon aerogel can effectively solve the problem. Inspired by floors-pillars concept, this work elaborately designed and successfully fabricated 3D skeletons consisted of two-dimensional (2D) sheets and one-dimensional (1D) struts. Benefiting from esterification and directional freeze drying method, the entire network could provide sufficient space for reducing thermal conductivity and motivating dipole polarization sites. Thanks to the facile calcination process, conductive components could be obtained, which guarantee low infrared (IR) emissivity and high conduction loss performance. In this work, the as-prepared carbon aerogel with ultra-low density of 0.005 g cm−3 exhibits superb infrared stealth property. It shows a low thermal conductivity coefficient of only 0.0933 W m−1 K−1. In addition, the heating rate of the upper surface is slow when placed on a heating platform of 60 °C. The relevant IR emissivity value is as low as 0.563 in 3–5 μm band and 0.432 in 8–14 μm band. Under relatively thin thicknesses, the prominent radar stealth performance including the optimum reflection loss value of −75.90 dB, the maximum effective bandwidth of 3.93 GHz, and the simulated radar cross section reduction value of 27.66 dB m2, can be obtained. This study not only introduces innovative design ideas but also offers technical approaches, facilitating further development in the realm of infrared-radar compatible stealth.

Kinetic Modulation of Carbon Nanotube Growth in Direct Spinning for High-Strength Carbon Nanotube Fibers.

With impressive individual properties, carbon nanotubes (CNTs) show great potential in constructing high-performance fibers. However, the tensile strength of as-prepared carbon nanotube fibers (CNTFs) by floating catalyst chemical vapor deposition (FCCVD) is plagued by the weak intertube interaction between the essential CNTs. Here, we developed a chlorine (Cl)/water (H2O)-assisted length furtherance FCCVD (CALF-FCCVD) method to modulate the intertube interaction of CNTs and enhance the mechanical strength of macroscopic fibers. The CNTs acquired by the CALF-FCCVD method show an improvement of 731% in length compared to that by the conventional iron-based FCCVD system. Moreover, CNTFs prepared by CALF-FCCVD spinning exhibit a high tensile strength of 5.27 ± 0.27 GPa (4.62 ± 0.24 N/tex) and reach up to 5.61 GPa (4.92 N/tex), which outperforms most previously reported results. Experimental measurements and density functional theory calculations show that Cl and H2O play a crucial role in the furtherance of CNT growth. Cl released from the decomposition of methylene dichloride greatly accelerates the growth of the CNTs; H2O can remove amorphous carbon on the floating catalysts to extend their lifetime, which further modulates the growth kinetics and improves the purity of the as-prepared fibers. Our design of the CALF-FCCVD platform offers a powerful way to tune CNT growth kinetics in direct spinning toward high-strength CNTFs.

Metal Valence State Modulation Strategy to Design Core@shell Hollow Carbon Microspheres@MoSe2/MoOx Multicomponent Composites for Anti-Corrosion and Microwave Absorption.

The exploitation of multicomponent composites (MCCs) has become the main pathway for obtaining advanced microwave absorption materials (MAMs). Herein, a metal valence state modulation strategy is proposed to tune the electromagnetic (EM) parameters and improve microwave absorption performances. Core@shell hollow carbon microspheres@MoSe2 and hollow carbon microspheres@MoSe2/MoOx MCCs with various mixed-valence states content are well-designed and produced by a simple hydrothermal reaction or/and heat treatment process. The results reveal that the thermal treatment of hollow carbon microspheres@MoSe2 in Ar and Ar/H2 leads to the in situ formation of MoOx and multivalence state, respectively, and the enhanced content of Mo4+ in the designed MCCs greatly boosts their impedance matching characteristics, polarization, and conduction loss capacities, which lead to their evidently improved EM wave absorption properties. Amongst, the as-prepared hollow carbon microspheres@MoSe2/MoOx MCCs achieve an effective absorption bandwidth of 5.80 GHz under a matching thickness of 1.97 mm and minimum reflection loss of -21.49 dB. Therefore, this work offers a simple and universal method to fabricate core@shell hollow carbon microspheres@MoSe2/MoOx MCCs, and a novel and feasible metal valence state modulation strategy is proposed to develop high-efficiency MAMs.

Detection of ferric ions by nitrogen and sulfur co-doped potato-derived carbon quantum dots as a fluorescent probe

This paper reports the detection of ferric ions (Fe3+) based on nitrogen and sulfur co-doped carbon quantum dots. These nitrogen and sulfur co-doped carbon quantum dots were synthesized via a hydrothermal route using northern Shaanxi potatoes as carbon sources and ammonium sulfate as nitrogen and sulfur sources. The quantum yields of the carbon quantum dots were found to be 16.96% and 4.23% with and without doping, respectively. The structural details, morphology, and optical properties of carbon quantum dots were analyzed using Fourier transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), ultraviolet-visible absorption spectroscopy (UV–vis), and fluorescence spectroscopy. The as-prepared co-doped carbon quantum dots were utilized as a fluorescent probe for detecting Fe3+ ions, where the fluorescence intensity of carbon quantum dots was remarkably quenched in the presence of Fe3+ ions. A good linear relationship for Fe3+ ion detection was obtained from 0 to 500 μmol/L with a detection limit as low as 0.26 μmol/L. Furthermore, the proposed method also provided satisfactory results in the tap water.

One-step generation of hollow graphitic carbon nanospheres with suitable oxygenated structures as conductive additives for water-soluble binder in highly stable supercapacitor electrodes

Although the weight ratio of electron conductive additives and the binder to porous carbons in the electrode component of electric double-layer capacitors (EDLC) is minimal, however, without them the electrochemical performances of EDLC would decay quickly. In this work, we present a one-step approach for manufacturing a unique conductive carbon material that shows highly connecting hollow structures as well as approximate oxygenated surface groups to create a synergy effect with aqueous binder and the main component, porous carbon. The as-prepared carbon nanospheres (HCNs) were generated from a typical carbon black-PC20 in air (denoted as PC20HT) at mild temperatures ranging from 400 to 700 °C for 2–4 h at a massive scale of approximate 1 kg h−1. The as-prepared PC20HT displays a high specific surface area of 657 m2 g−1 (the pristine PC20 has 112 m2 g−1) with a pore volume of 0.71 cm3 g−1, and an oxygen content of 14.10 wt%. Interestingly, a premixing of PC20HT and porous carbon is required before making the electrode pastes. The well-premixed carbon materials and a water-soluble binder-polyacrylic acid are composed into highly-stable components as EDLC electrodes in an organic electrolyte. As consequently, the PC20HT-assisted electrodes demonstrate highly stable life cycles (charge-discharge behaviors), with a retention rate 82.13 % over 50,000 cycles at a narrow voltage window of 2.5–2.7 V at 0.5 A g−1 when compared to two conventional conductive carbons, BP2000 (68.45 %) and Super P (67.46 %). Thermal annealing at 900 °C in Ar reduces the oxygen content of PC20HT to 4.25 wt% (referred to as TPC20HT), increasing the retention rate of life cycle to 88.89 % after the same cycles. TPC20HT-assisted EDLC electrodes exhibit a superior energy density of 34.76 Wh kg−1, which is higher than CB-BP2000 and Super P-assisted EDLC electrodes. The transforming of structural morphologies as well as the surface oxygenated and graphitic structures of the as-prepared HCS, PC20HT, and TPC20HT were also described before and after long-term cycling. This simple route for producing conductive carbons is applicable in an aqueous binder system for preparing EDLC electrodes with a cost-effective and environmentally friendly approach.

Superior initial Coulombic efficiency and areal capacity of hard carbon anode enabled by graphite-assisted carbonization for sodium-ion battery

Hard carbons are perceived as promising anode materials in sodium-ion batteries, while their practical implementation is largely impeded by the insufficient initial Coulombic efficiency (ICE). Hard carbons with self-supporting architecture are intriguing to enhance ICE owing to the omission of binder and conductive agent; whereas elaborate architecture and microstructure design are still required to further raise the ICE to the level of commercial graphite in lithium-ion batteries, especially under high areal capacity. Herein, we propose a graphite-assisted pressurization strategy during carbonization to achieve remarkable ICE and high areal capacity in resulting self-supporting cellulose tissue derived hard carbon anode. The intimate contact of graphite plate enables suitable local ordering of pseudo-graphitic nanodomains with low intrinsic defects, responsible for enhanced ICE. While the pressure-reinforced dense yet self-interwoven fibrous networks render high areal capacity. Consequently, the as-prepared self-supporting hard carbon anode displays remarkable ICE to 95% and areal capacity of 2.4 mAh cm−2, far exceeding the reported value of less than 0.8 mAh cm−2. Meanwhile, the rate and durability are not scarified under such superior ICE due to the well-manipulated pseudo-graphitic nanodomains and porous fibrous networks. The practicality is further demonstrated in coin-type and pouch-type full cells delivering high capacity and long-term stability. Our finding offers an impetus for the development of high ICE and areal capacity for sodium-ion battery anode.

Integration of jackfruit seed-derived carbon dots and electronic nose for a sensitive detection of formaldehyde vapor

The preparation of carbon dots from jackfruit seeds through a pyrolysis method at 280℃ and their use for the detection of formaldehyde were reported. The as-prepared carbon dots showed a high fluorescence efficiency with a quantum yield of 12.7% and excellent photostability and dispersibility in aqueous solution with a zeta potential of ‒62.5 mV. The integration of carbon dot thin film and a home-made optical electronic nose system possessed sensitivity towards formaldehyde vapor with a detection limit of 24.7%v/v across a linear range of 25%v/v to 100%v/v. Furthermore, the sensor showed the highest sensitivity towards formaldehyde against other volatile organic compounds through a strong interaction between the carbonyl groups and the carbon dots. Additionally, principal component analysis (PCA) was conducted to achieve quantitative measurements of formaldehyde content in different formaldehyde volume ratios with substantial variance. Due to the significance of methanol as a typical chemical precursor for the industrial manufacturing of formaldehyde, the quantitative analytical method is essential to determining formaldehyde or methanol concentration. The sensing ability of carbon dot film-integrated electronic nose towards formaldehyde in formaldehyde/methanol mixtures was measured to be 10.74%v/v in a linear range of 25%v/v to 100%v/v. The PCA showed orderly linear combinations of the data set, which can be potentially utilized to analyze formaldehyde and methanol content in industrial processes. The results indicate the significant potential of carbon dots and optical electronic nose system as an effective formaldehyde sensing platform. Potential applications include the quantification of formaldehyde from methanol conversion and determination of methanol contaminant in formaldehyde.

Hollow core mesoporous carbon spheres as catalyst support for improved platinum utilization in phosphoric acid fuel cells

Using a well-known sol-gel technique, monodispersed silica spheres measuring 380 nm in size are generated in situ. These silica spheres serve as a template for the synthesis of hollow core mesoporous shell (HCMS) carbon spheres. Inside the pores of the template, a polymer is synthesized using azoisobutyronitrile and divinylbenzene polymerization route. Polymer carbonization followed by template remotion yielded HCMS carbon spheres. This HCMS carbon is mesoporous and offers uniform Pt crystallite distribution for acid fuel cell applications. As-prepared HCMS carbon is examined by field emission gun SEM, TEM, nitrogen adsorption/desorption isotherm (BET surface area and BJH pore size distribution analysis), and apparent density using Helium pycnometry. The HCMS carbon obtained demonstrates a BET surface area of 623 m2g-1, showcasing a uniform pore size distribution centered at 3.8 nm. This specific characteristic renders it an ideal support material for fuel cell catalysts. The electrochemical studies reveal the key parameters like corrosion resistance, bulk electrical conductivity, the electrochemical surface area of Pt chemically deposited on HCMS carbon, and unit fuel cell performance under phosphoric acid environment. These parameters are compared with the standard carbon powder, Vulcan XC72R and a commercial catalyst to evaluate the HCMS carbons’ suitability for fuel cell applications.

Superstructured Carbon with Enhanced Kinetics for Zinc-Air Battery and Self-Powered Overall Water Splitting.

The present study proposes a novel engineering concept for the customization of functionality and construction of superstructure to fabricate 2D monolayered N-doped carbon superstructure electrocatalysts decorated with Co single atoms or Co2P nanoparticles derived from 2D bimetallic ZnCo-ZIF superstructure precursors. The hierarchically porous carbon superstructure maximizes the exposure of accessible active sites, enhances electron/mass transport efficiency, and accelerates reaction kinetics simultaneously. Consequently, the Co single atoms embedded N-doped carbon superstructure (Co-NCS) exhibits remarkable catalytic activity toward oxygen reduction reaction, achieving a half-wave potential of 0.886V versus RHE. Additionally, the Co2P nanoparticles embedded N-doped carbon superstructure (Co2P-NCS) demonstrates high activity for both oxygen evolution reaction and hydrogen evolution reaction, delivering low overpotentials of 292mV at 10mAcm-2 and 193mV at 10mAcm-2 respectively. Impressively, when employed in an assembled rechargeable Zn-air battery, the as-prepared 2D carbon superstructure electrocatalysts exhibit exceptional performance with a peak power density of 219mWcm-2 and a minimal charge/discharge voltage gap of only 1.16V at 100mAcm-2. Moreover, the cell voltage required to drive an overall water-splitting electrolyzer at a current density of 10mAcm-2 is merely 1.69V using these catalysts as electrodes.

Green synthesis of carbon dots from fish scales for selective turn off-on detection of glutathione.

Carbon dots as fluorescent probes were fabricated using readily available grass carp fish scales as the carbon source via one-step synthesis based on a pyrolytic reaction. The as-prepared grass carp fish scale carbon dots (GF-CDs) exhibited good biocompatibility and excellent optical properties with a high fluorescence quantum yield of 23.8%. Glutathione (GSH) is an essential small tri-peptide molecule present in every body cell and plays a crucial role in vivo and performs a wide range of biological functions. Ag+ can effectively quench the fluorescence of GF-CDs because of the electron transfer between GF-CDs and Ag+; however, the addition of GSH can significantly increase GF-CD-Ag+ fluorescence. Because of their combination with Ag+ and GSH, GF-CDs show selective fluorescence recovery. GF-CDs can serve as fluorescent probes for GSH detection. This detection method covered a wide linear range (1.6-36.0 μg mL-1) with the lowest detection limit of 0.77 μg mL-1 and manifested great advantages such as a short analysis time, good stability, repeatability, and ease of operation.

Breakage of the dense structure of coal precursors increases the plateau capacity of hard carbon for sodium storage.

Hard carbon is considered the most commercially viable anode material for sodium ion batteries due to its excellent sodium storage properties. However, the production cost of hard carbon is high, so optimizing the electrochemical performance of coal-derived hard carbon is adopted. However, due to the dense structure of coal, it is difficult to prepare closed pores inside the coal-derived hard carbon, which is not conducive to increasing capacity. Therefore, we propose Zn2(OH)2CO3 assisted ball milling pretreatment followed by carbonization to generate closed pores in coal-derived hard carbon. The reason for the formation of closed pores is that the uniform pores on the coal surface generated by the wear and etching of Zn2(OH)2CO3 are repaired at high temperatures. Via mechanism characterization, we verified that the plateau capacity is related to the filling of sodium ions in closed pores. Therefore, the as-prepared coal-derived hard carbon delivers a high capacity of 325.3 mA h g-1 (plateau capacity accounting for 45.1%) at a current density of 0.03 A g-1 with a capacity retention rate of 83.5% over 500 cycles. This work has demonstrated that reasonable pore design is an effective strategy to improve the electrochemical sodium storage performance of coal-derived hard carbon, providing an effective approach for the high value-added utilization of coal.

Upcycling of aureomycin hydrochloride residue into highly meso-microporous carbon with remarkable adsorption capacity for benzene capture

The exploration of high-value utilization of antibiotic bacteria residues is of great importance at the environmental and resource levels. In this study, we report an aureomycin hydrochloride residue-derived activated carbon and its application in the adsorption of hazardous benzene. Self-N-doped activated carbon with excellent benzene adsorption properties was prepared by K2CO3-assisted activation pyrolysis using aureomycin hydrochloride residue as carbon and nitrogen sources. It is found that the pore structure and the benzene adsorption behavior could be optimized through regulating the mass ratio of K2CO3 to carbon (mK2CO3/mC) and the activation temperature. Under the pyrolysis conditions of mK2CO3/mC = 3:1 and 800 ºC, the specific surface area and total pore volume of the as-prepared carbon reached 1564 m2 g−1 and 0.70 cm3 g−1, respectively, whereas those of the micropores were 1440 m2 g−1 and 0.48 cm3 g−1, respectively, implying that the proportion of micropores reached 68.6%. The adsorption capacity of benzene based on the optimal adsorbent (AHRC-3PC-800) was as high as 1303 mg g−1 at 25 ºC and relative pressure (P/P0) of 0.9–1. Therefore, the aureomycin hydrochloride residue-based activated carbon adsorbent has a broad application prospect in the removal of volatile organic compounds.