Structure Of Cellulose Research Articles

Achieving 3-D Structural Uniformity in Cellulose Gel Beads via Salt Screening

Cellulose microgel beads fabricated using the dropping technique suffer from structural irregularity and mechanical variability. This limits their translation to biomedical applications that are sensitive to variations in material properties. Ionic salts are often uncontrolled by-products of this technique, despite the known effects of ionic salts on cellulose assembly. In this study, the coagulation behavior of cellulose/salt solutions was explored as a way to combat these challenges. An ionic salt (NaCl) was added to a cellulose solution (cellulose/NaOH/urea) prior to coagulation in a hydrochloric acid bath. Quantification of the bead geometry and characterization of the pore architecture revealed that balancing the introduction of salt with the resultant solution viscosity is more effective at reducing structural variability and diffusion limitations than other pre-gelling techniques like thermal gelation. Three-dimensional visualization of the internal pore structure of neat cellulose, thermo-gel, and salt-gel beads revealed that adding salt to the solution is the most effective way to achieve 3-D structural uniformity throughout the bead. Coupled with nanoindentation, we confirmed that the salt produced during coagulation plays a critical role in mechanical variability, and that adding salt to the solution before dropping into the coagulation bath completely screens this effect, producing uniform microgel beads with reproducible mechanical properties.

A comprehensive review of the application of cold plasma technology in lignocellulosic biomass pretreatment

AbstractLignocellulosic biomass (LCB) is a promising feedstock for the sustainable production of biofuels and other biobased products, owing to its abundance, low cost, and minimal competition with food crops for resources. It is mainly composed of cellulose, hemicellulose, and lignin, forming a complex biomass matrix. Its utilization is hindered by its complex structure and pretreatment is required to break down the chemical resistance caused by the strong association between the cellulose, hemicellulose, and lignin structures. Conventional methods such as acid and alkali pretreatment are used frequently but they require the use of high temperatures, high pressure, and corrosive chemicals. This has encouraged research into environmentally friendly pretreatments to overcome these challenges. Recently, cold plasma (CP) technology has emerged as a promising alternative to the aggressive conventional methods for producing value‐added products, such as biofuels, and renewable chemicals from lignocellulosic biomass. Cold plasma technology uses electricity to generate a highly reactive, ionized gas in a variety of applications without producing any dangerous or polluting compounds. This review discusses the application of cold atmospheric pressure plasma in the biochemical conversion of biomass, with a focus on delignification, detoxification of biomass hydrolysate, surface modifications, and process intensification of cellulosic ethanol production.

Characterization and Sustainable Applications of Galinsoga parviflora Natural Fibers: A Pathway to Eco-Friendly Material Development

This study investigates the potential of natural fibers extracted from Galinsoga parviflora as sustainable alternatives to synthetic materials, addressing the increasing demand for eco-friendly and biodegradable options in material science. The main objectives were to evaluate the structural, mechanical, and biological properties of these fibers, focusing on their applicability in structural composites. Driven by environmental sustainability, we performed a range of analyses including X-ray Diffraction (XRD) to determine crystallinity and cellulose structure, Fourier-Transform Infrared Spectroscopy (FTIR) to identify functional groups related to biodegradability, and Scanning Electron Microscopy (SEM) to examine surface morphology and fiber dimensions. Key findings include a crystallinity index of 36.3% with cellulose I dominance, a tensile strength of 17.92 MPa, and a modulus of 11.3 GPa, indicating the fibers’ potential for structural applications. Elemental analysis using Energy-Dispersive X-ray Spectroscopy (EDX) revealed a high carbon content (53.0%) and oxygen content (41.3%), along with trace elements that may enhance interaction in polymer matrices. Antibacterial testing demonstrated effective inhibition of Staphylococcus aureus biofilms, with inhibition zones reaching up to 19 mm, comparable to streptomycin. Confocal Laser Scanning Microscopy (CLSM) further confirmed the fibers' biofilm disruption capabilities.Overall, the results highlight that G. parviflora fibers show significant promise as bio-based alternatives for sustainable material development, offering both mechanical strength and biological functionality for future eco-friendly technologies.

A structural investigation on the interactions of cotton fabric cellulose with olive oil and water

The cotton fabric consists of cellulose arranged in a complex structure with multiple levels of organization at different length scales. Understanding this structure and its interactions with water and oil is essential for developing efficient and environmentally friendly methods of cotton washing. In this study, the structure of raw cotton fabric cellulose and the effects of water and oil were examined across a broad range of length scales using spatially resolved synchrotron small-angle X-ray scattering (SAXS) and auxiliary techniques.Water was observed to penetrate the cotton fabric and interact across nearly all length scales. Although a certain amount of the material was not affected by water as seen by intact distance between microfibrils, fractal analysis of the scattering data indicated a loosening of the microfibril arrangement after contact with water. This process was hindered if the material had been pre-treated with oil and was not seen after subsequent washing with water or surfactant solution. Analyzing spatially resolved SAXS data using a bi-sinusoidal model and 2D maps of the oil-to-cotton ratio facilitates understanding the structure of the material and its interactions with oil on the molecular, nano and macrolevels.

Preparation of energy-efficient, environmentally friendly and high-strength biocomposites from wood fibre ultramicro self-composite cellulose matrices

Considering the diminishing forest as a natural resource, the efficient use of small-diameter shrubs is crucial for global sustainable development. This approach has significant potential to prevent wasting forest resources and reduce carbon emissions. However, small-diameter timber has inherent drawbacks, such as the looseness of this material, susceptibility to cracking and deformation, and low strength, all of which significantly impact its range of applications. In this study, an efficient, green method was developed to prepare adhesive-free biocomposites from discarded small-diameter shrubs via ultrasonic pretreatment and thermoforming. After the ultrasonic pretreatment, the flexural and tensile strengths of the biocomposites increased by 145% and 132%, respectively. Ultrasonic pretreatment separated and destroyed chemical bonds among the lignocellulosic biomass macromolecules through high-speed shear and microjets. This process significantly increased the amount of binding sites on the cellulose fibres, and further densified the cell walls through hot pressing. Moreover, the ultrasonic pretreatment may remove components of the wood flour that act as fillers or density enhancers, resulting in a reduction in the density of the biocomposite. Simultaneously, lignin acted as a binder and improved fibre bonding through both physical and chemical cross-linking, resulting in a dense cellulose structure with a three-dimensional lattice structure and a less hydrophilic surface, as evidenced by a water contact angle of 81.72°. In addition, the high-quality, binder-free biocomposites did not emit harmful gases such as formaldehyde. Hence, they are expected to become sustainable materials for building decoration and furniture applications in the future.

Applications of NMR based methodologies investigating the behavior of lignin and cellulose towards bio-based carbon fibers production

Cellulose–lignin blends are proposed as alternative precursors for carbon fiber (CF) production, offering a potential sustainable and cost-effective alternative to the expensive fossil-based polymers currently used. The characteristics of the precursor fibers including their crystallinity, the incorporated chemical structures and the distribution of the biopolymers have a significant influence on their carbonization behavior and the properties of the CFs. They are partly determined by the composition of the bio-based resources and the conditions used during the fiber fixation, i.e. the coagulation, an important processing step. In this work, 13C solid and 2D solution NMR methodologies were applied to investigate the impact of coagulation and thermostabilization conditions on cellulose and cellulose-lignin blends using a thin film model. Solid state NMR spectroscopy showed that the choice of the anti-solvent influenced the proportion of cellulose II versus amorphous regions in the coagulated films. Independent of the presence of lignin, the choice of anti-solvent seems to impact the rate of thermal reactions. After thermostabilization at 245 °C, the samples were investigated using a solution NMR protocol devised for cellulosic materials. At 275 °C, most of the samples became insoluble for solution NMR. However, solid state NMR revealed further changes in the chemical composition, which were dependent on both the presence of lignin and the choice of anti-solvent. This multi-faceted approach combining solid state and 2D solution NMR techniques provides a comprehensive understanding of the cellulose structure and the products formed for cellulose-lignin-based CFs, which is crucial for optimizing their properties and potential applications.

Cellulose intercalation activation of natural ramie fiber derived carbon electrode for flexible supercapacitors

The complex structure of cellulose leads to its low accessibility to reagents, which hinders the further development of cellulose-based natural fibers in supercapacitors. The key issue is how to achieve deep internal activation while maintaining the flexible self-supporting skeleton structure of cellulose. In this work, an intercalation activation method was proposed. The activator infiltrated into the cellulose microcrystalline structure under rapid swelling to construct a new hydrogen bond network. RC/N2 has a large specific surface area (1897 m2 g−1) and exhibits excellent electrochemical performance due to the uniform activation of NaOH pre-inserted between cellulose layers while ensuring the flexibility of cellulose. At a current density of 0.1 A g−1, it reaches 352 F g−1, and the assembled symmetric supercapacitor has a capacitance retention rate of 98 % after 70,000 cycles. In addition, the symmetric flexible supercapacitor assembled based on RC/N2 has good stability after multi-angle bending, which opens up further possibilities for the development of flexible energy storage devices.

Molecular modeling analyses of functionalized cellulose

Functionalization of cellulose with nanomaterials and functional groups is essential for enhancing its properties for specific applications, such as flexible sensors and printed electronics. This study employs Hartree Fock (HF) and Density Functional Theory (DFT) calculations to investigate the vibrational spectra of cellulose, identifying DFT: B3LYP/3–21 g** as the optimal model aligning with experimental spectra. Using this model, we examined the impact of functionalizing cellulose with various groups (OH, NH2, COOH, CH3, CHO, CN, SH) and graphene oxide (GO) on its electronic properties. The results indicate that cellulose functionalized with GO (Cellulose-GO) has the lowest bandgap energy (0.1687 eV), and improvements in reactivity, stability, and electronic properties were confirmed through Molecular Electrostatic Potential (MESP) and Total Dipole Moment (TDM) analyses. The spectrum of Density of States (DOS) for the cellulose functionalized with different groups shows several peaks, indicating various energy levels where electronic states are concentrated. The Projected Density of States (PDOS) analysis reveals how different functional groups affect the electronic structure of cellulose. Moreover, the (Cellulose-GO) composite was characterized using an Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectrometer, revealing interaction through the OH group of CH2OH, as indicated by a new band at 1710 cm−1, consistent with theoretical predictions. Overall, this study demonstrates that functionalization with GO enhances cellulose’s responsiveness, degradation, and electrical properties, making it suitable for applications in flexible electronic devices and protective barriers against corrosion.

High detail resolution cellulose structures through electroprinting

Electrospinning is a technique used to fabricate polymer fibers in micro- and nanoscales. Due to the large distance between the nozzle and collector, there is a limited positioning accuracy of electrospun fibers. To enhance the possibility of fabricating structures with micrometer placement, an electroprinting technique has been developed. By reducing the distance between the nozzle and the collector it is demonstrated that it is possible to get an improved control over fiber positioning which gives a possibility to fabricate designed 3D structures at the micron scale. In this study, cellulose acetate (CA) has been selected as a biomaterial to advance the 3D printing of membranes with possible use in separation applications. Various parameters, such as CA concentration and molecular weight, printing speed, printing pattern, applied voltage, etc. are evaluated with respect to printing control. Results indicate that by optimizing the printing parameters it is possible to print structures with inter- fiber distances down to 3 µm and fiber diameters at a sub-µm scale. This electroprinting development is promising for the fabrication of customized separation membranes. However, printing speed still remains a challenge.

Interfacial Pickering Emulsion Polycondensation for Degradable Nanocomposites.

Pickering emulsion polymerization is a practical method to fabricate functional composite materials. However, most reported systems proceed homogeneously within the stabilized monomer phase and create nondegradable chemical bonds. Here, interfacial Pickering emulsion polycondensation between aromatic aldehydes and polymercaptans is developed using sustainable cellulose nanoparticles as the stabilizer. When sulfonated cellulose nanocrystals (S-CNCs) were utilized, they also catalyzed the polycondensation to produce the oxidatively degradable S,S-acetal groups on the polymer chains. The influence of monomer and cellulose structures on the polymerization behavior and composite properties were compared.

Customising Sustainable Bio-Based Polyelectrolytes: Introduction of Charged and Hydrophobic Groups in Cellulose.

Cellulose has been widely explored as a sustainable alternative to synthetic polymers in industrial applications, thanks to its advantageous properties. The introduction of chemical modifications on cellulose structure, focusing on cationic and hydrophobic modifications, can enhance its functionality and expand the range of applications. In the present work, cationization was carried out through a two-step process involving sodium periodate oxidation followed by a reaction with the Girard T reagent, yielding a degree of substitution for cationic groups (DScationic) between 0.3 and 1.8. Hydrophobic modification was achieved via esterification with fatty acids derived from commercial plant oils, using an enzyme-assisted, environmentally friendly method. Lipase-catalysed hydrolysis, optimised at 0.25% enzyme concentration and with a 1 h reaction time, produced an 84% yield of fatty acids, confirmed by FTIR and NMR analyses. The degree of substitution for hydrophobic groups (DShydrophobic) ranged from 0.09 to 0.66. The molecular weight (MW) of the modified cellulose derivatives varied from 1.8 to 141 kDa. This dual modification strategy enables the creation of cellulose-based polymers with controlled electrostatic and hydrophobic characteristics, customisable for specific industrial applications. Our approach presents a sustainable and flexible solution for developing cellulose derivatives tailored to diverse industrial needs.

A novel bio-aerogel based on agroforestry waste chestnut shell for enhanced oil-water separation performance

Bio-based aerogels have attracted much attention due to their biodegradability and excellent oil-water separation properties. However, the preparation of inexpensive green aerogels with high separation efficiency is still a great challenge. In this paper, low-density, high-adsorption capacity and superhydrophobic chestnut shell-based bio-aerogels were prepared by chemical cross-linking and chemical vapor deposition using agricultural and forestry waste chestnut shells as the precursor of aerogels to achieve high efficiency of oil-water separation and to achieve the goal of “treating waste with waste”. The covalent cross-linking of chestnut shell cellulose and cross-linking agent to form silicone-containing functional groups improved the pore structure, hydrophobicity and mechanical properties of chestnut shell cellulose, and under the action of capillary force, the oil was retained in the pores of the bio-aerogels, which achieved the selective adsorption of oil and organic solvents in the oil-water mixture, with a separation efficiency of more than 98 %. After 10 cycles, the bio-aerogel still has good reusability. This eco-friendly and low-cost aerogel provides a practical method for resource conversion and recycling, as well as a green and innovative way for the treatment of oily wastewater.

Recyclable covalent organic frameworks/cellulose aerogels for efficient uranium adsorption

The advancement of efficient, recyclable adsorbents for the economical capture of uranium from seawater is critical for the sustainable progression of nuclear energy. In this work, a unique aerogel composed of covalent organic frameworks (COF-TpTHA)/cellulose nanofibrils (CNF) was synthesized under mild conditions for uranium adsorption. TpTHA/CNF aerogel resolves challenges related to the formability of COF. CNF utilized as the matrix to encapsulate COF-TpTHA in order to improve the dispersion and reinforce the composite materials. The introduction of COF-TpTHA endows CNF aerogel with sufficient active groups for uranium adsorption. X-ray diffraction (XRD) characterization confirmed the successful incorporation of COF while maintaining the type I structure of cellulose. Fourier-transform infrared (FT-IR) spectroscopy further validated the presence of hydrogen bonding interactions between COF and cellulose. The results demonstrated the excellent adsorption efficiency of TpTHA/CNF aerogel towards U(VI), with a maximum adsorption capacity of 177.90 mg g‐1 (experiment) for U(VI). Meanwhile, TpTHA/CNF aerogel exhibited favorable adsorption selectivity and reusability. This cellulose-encapsulated COF approach offers a simple and promising method for uranium extraction from seawater, demonstrating its significant application potential.

Enhancing Enzymatic Hydrolysis of Rice Straw by Acid-Assisted Mechanocatalytic Depolymerization Pretreatment

The inherent complexity of cellulose, hemicellulose, and lignin contributes to the recalcitrance of lignocellulosic biomass, resulting in a low conversion efficiency and high cost of bioethanol conversion. Pretreatment methods that disrupt the plant cell structure of lignocellulose, such as straw, can significantly enhance the conversion efficiency. In this study, we utilized an acid-assisted mechanocatalytic depolymerization technique to pretreat rice straw, and the results demonstrated a significant disruption of the cellulose structure of the straw. Compared to the untreated straw, the particle size of pretreated straw reduced from 279 μm to 11.8 μm, the crystallinity of cellulose decreased from 43.05% to 22.71%, the specific surface area increased by 177%, and the surface oxygen-to-carbon ratio (O/C) ratio was enhanced by 75%. The changes in microstructure enabled the pretreated straw to achieve a total sugar yield of over 95% within 12 h of enzymatic hydrolysis, significantly superior to the 36.24% yield from untreated straw, the 45.20% yield from acid impregnated straw, and the 73.25% yield from ball milled straw. Consequently, acid-assisted mechanocatalytic depolymerization emerges as a highly effective pretreatment strategy to enhance both the enzymatic hydrolysis and the overall conversion efficiency of rice straw.

Loblolly pine needles processing with deep eutectic solvents to develop porous structure

This work focused on the removal of lignin from pine needles, leaving oriented porous cellulose. Deep eutectic solvent pretreatment of loblolly pine needles allowed for the removal of lignin from the biomass, leading to the exposure of the desired cellulose structure. Heating under reflux and microwave heating methods were used to pretreat loblolly pine needles with 12:1 lactic acid: choline chloride deep eutectic solvent, 2:1 formic acid: choline chloride deep eutectic solvent, and 1:2 oxalic acid: choline chloride deep eutectic solvent. Characterization of the untreated and pretreated pine needles was done by Brunauer-Emmett-Teller analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. Fiber analysis was also performed on the untreated and pretreated pine needles. The DES pretreated pine needles showed significant enhancements in both specific surface area and pore volume, with microwave pretreatment giving the best results. The oxalic acid: choline chloride DES was the most efficient at eliminating acid-soluble lignin. The optimal duration for conductive heat pretreatment to enhance specific surface area and pore volume was found to be 80 minutes. For microwave treatment, the formic acid: choline chloride DES was found to be most effective to increase the overall cellulose to lignin ratio.

Production and characterization of bacterial cellulose synthesized by Enterobacter chuandaensis strain AEC using Phoenix dactylifera and Musa acuminata.

Bacterial cellulose (BC) is a biopolymer synthesized extracellularly by certain bacteria through the polymerization of glucose monomers. This study aimed to produce BC using Enterobacter chuandaensis with fruit extracts from Phoenix dactylifera (D) and Musa acuminata (M) as carbon sources. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) showed characteristic cellulose vibrations, while X-ray diffraction (XRD) identified distinct peaks at 15.34°, 19.98°, 22.58°, and 34.6°, confirming the cellulose structure. Whole-genome sequencing of E. chuandaensis identified key genes involved in BC production. The BC produced then exhibited a molecular weight of 1,857,804g/mol, with yields of 2.8g/L and 2.5g/L for treatments D and M, respectively. The crystallinity index of the purified BC was 74.1, and 13C NMR analysis confirmed the dominant cellulose Iα crystalline form. The BC showed high biocompatibility in cytotoxicity assays, with cell viability between 92% and 100%, indicating its potential for use in biomedical applications. This investigation represents the first report of BC production by E. chuandaensis, which promises a new avenue for sustainable and efficient BC synthesis using fruit extracts as carbon sources.

Study on the remediation of groundwater nitrate pollution by pretreated wheat straw and woodchips

Groundwater nitrate contamination poses a threat to both the ecological environment and human health. This study investigated the potential of using saturated Ca(OH)2 to pretreat wheat straw and woodchips, aiming to enhance their efficacy as carbon sources for denitrification. The optimization of pretreatment conditions, and the elucidation of underlying mechanisms were explored. The pretreatment process involved the dissolution of lignin and hemicellulose, exposure of the cellulose structure, reduction of hydrogen bonds within cellulose, hydrolysis of polymerized cellulose, and the formation of cracks and hierarchical structures on the surface of the carbon source. These alterations improved the attachment and utilization of microorganisms. The maximum enzymatic reducing sugar yields for wheat straw and woodchips were achieved at solid-liquid ratios of 1:40 and soaking times of 5 and 2 days, respectively. The response surface predicted the optimal pretreatment conditions for wheat straw to be a solid-liquid ratio of 1:88.1 and a soaking time of 8.2 h. Alkaline treatment increased the denitrification rate of woodchips by fivefold and prevented the initial organic matter leaching rate of wheat straw, thereby reducing the risk of secondary pollution. The predominant microbial communities in all samples exhibited functions related to lignocellulose degradation and denitrification. The community composition of solid-phase carbon sources was found to be richer than that of liquid-phase carbon sources, and the pretreatment increased the abundance of lignocellulose degradation and denitrification functional microorganisms. The pretreatment liquid of wheat straw achieved the highest denitrification rate constant (0.43 h−1). Our result validated the feasibility of using the pretreatment liquid as a denitrification carbon source and presenting a novel approach for waste resource utilization.

Construction of cellulose 3D network composite membrane supported by hydroxylated boron nitride with high surface charge density to achieve high-efficiency osmotic energy harvesting

Ion selectivity and mechanical persistence are critical properties of membranes to harvest osmotic energy. Two-dimensional nanofluidic membranes have been studied to enhance those properties, whereas they are usually constrained due to unsatisfactory mass transfer performances. Herein, a ternary three-dimensional membrane (T-CNF/PVDF/BN-OH composite membrane, abbreviated as CPBN) with distinct mechanical strength and high surface charge density (−2.65 mC·m−2) for sustainable osmotic energy harvesting is designed. In CPBN, negatively charged TEMPO-oxidized cellulose acts as a scaffold and constructs a 3D network structure together with the hydroxylated boron nitride (BN-OH) via a self-assembly process. The affluent nano-constrained ion channels effectively enhance the controllability and effectiveness of ion transport. The abundant ionized carboxyl groups extremely facilitate the selective transportation of the cations, while the BN-OH also assist this process, promoting the one-way transmission of cations in the channel. Additionally, the participation of PVDF polymer forms a network interlock structure, which significantly improves mechanical performances and stability in water. The membrane demonstrates a high power density (10.6 W/m2), measured in minimal testing areas, and an average power density around 1 W/m2 in larger areas, with an energy conversion efficiency of up to 30.7 %. This study provides a promising exploration of replacing traditional two-dimensional layered structure with three-dimensional network structure of cellulose for osmotic energy harvesting.

Study on Fenton-based discoloration of reactive-dyed waste cotton prior to textile recycling

The aim of this study is to investigate the feasibility of an alternative Fenton-based advanced oxidation process for the discoloration of reactive-dyed waste cotton as a pre-treatment for textile recycling. For that, pre-wetted dark-colored (black and blue) knitted samples of 300 cm2 are treated in 1200mL Fenton-solution containing 14 mM Fe2+ and 280mM H2O2 at 40 °C. Characterization of the textiles before and after the treatments are performed by UV VIS-spectrophotometry measuring color strength, microscopy, FTIR spectroscopy, thermal analysis and tensile testing measuring tenacity and elongation. Afterwards, the cotton is mechanically shredded for qualitative analysis of the recyclability. The color-strength measurements of the black and blue cotton led to discoloration-efficiencies of respectively 61.5 and 72.9%. Microscopic analysis of discolored textile fabric also showed significant fading of the colored textiles. Mechanical analysis resulted in reduced tensile strength after treatment, indicating oxidation of the cellulosic structure besides the degradation of the dye-molecules, also confirmed by reductions in thermal stability found after thermal analysis. Shredding of the fabric resulted in enhanced opening, but shorter remaining fibers after treatment. The findings of this study provide a proof-of-concept for an alternative color-stripping treatment concerning a Fenton-based advanced oxidation process as a pre-treatment for textile recycling.

Elimination of hydrogen bonds in cellulose enables high-performance disordered carbon anode in sodium-ion batteries

Pre-oxidation remains an advantageous method to regulate the cross-linking structure of cellulose to prepare an increasingly disordered hard carbon applied in sodium-ion batteries. However, it is ambiguous how the introduction of oxygen affects the changes in the molecular structure of cellulose as well as the micro-structure of hard carbon. We herein systematically investigate the effect of air pre-oxidation on the crystallinity and cross-linking structure of cellulose macro-molecules by controlling the degree of oxidation. The findings indicate that the introduction of air can break the hydrogen bonding network of cellulose in advance and release a large number of reactive hydroxyl groups on the surface to be oxidized to form ether and ester cross-linking bonds. Ether bonds can transversely cross-link and extend the carbon layer and the bent carbon layers enclose a well-developed connective pore structure. Additionally, the breakage of oxygen-containing functional groups leads to the escape of large amounts of oxygen-containing gases to etch out more open pore structures with large pore sizes. Benefiting from these advantages, the prepared hard carbon possesses a specific capacity of 335 mAh g−1 and 89 % of initial coulombic efficiency at 30 mA g−1 by pre-oxidating at 300 °C for 12 h.