Hierarchical Porous Structure Research Articles

Novel design of hollow carbon nanocage modified with nanotubes as a bifunctional electrocatalyst for high performance Zn–air batteries

Microcavities play a crucial role as microreactors in the transport of molecular/ionic guests and the exposure of active sites, thus significantly influencing the electrocatalytic performance. This study prepares Co/N-codoped hollow carbon (HT-CoN/C) with surface-distributed carbon nanotubes by pyrolysis of PDA-coated Zn/Co bimetallic ZIF (BM-ZIF@PDA). Benefiting from the hierarchical porous structure, high specific surface area (307.17 m2 g−1) and abundant Co clusters, the HT-CoN/C exhibits remarkable bifunctional oxygen electrocatalytic activity with an overpotential of the ORR/OER processes (ΔE = 0.703 V). The density functional theory (DFT) calculations also verify that the configuration of C-coated N-coordinated Co clusters (Co4-Nx) affect the electrocatalytic activity of ORR and OER, illustrating the source of the excellent oxygen electrocatalytic activity of HT-CoN/C. The aqueous rechargeable zinc-air battery (RZAB) using HT-CoN/C as the air electrode is characterized by a superior peak power density (175 mW cm−2), a prolonged cycle life (1230 cycles/410 h at 5.0 mA cm−2) and a high open-circuit voltage (1.47 V). Meanwhile, the flexible solid-state RZAB assembled by the HT-CoN/C also exhibits a higher peak power density (117 mW cm−2) and an excellent bending performance. This work is extremely valuable for the design and synthesis of Co/N co-doped carbon electrocatalysts.

Microstructure, thermal, and mechanical properties of hierarchical porous silicon carbide made by direct ink writing

AbstractHierarchical porous silicon carbide (SiC) ceramics were fabricated by combining particle‐stabilized emulsions and three‐dimensional (3D) printing. Direct ink writing (DIW) was used as the 3D printing technique. The formulation for successful printing is discussed in relation to the rheology of the emulsions. The SiC emulsions were able to be printed with a lower storage modulus (G′) and apparent yield shear stress (τy) than previously reported SiC ink pastes. The printed and sintered porous SiC ceramics possess a total porosity of 73.7% with an average pore size within the filaments of 2.2 µm in diameter. A hierarchical pore structure that contains pore sizes of about 250 µm, around 1–10 µm and smaller than 0.5 µm can be observed in the microstructure and pore size distribution. The mechanical properties showed a good strength‐to‐density ratio, and the thermal conductivity was reduced to 4.9 W/m·K. This study provides a new reliable approach for fabricating hierarchical porous SiC ceramics with low thermal conductivity.

Performance and Mechanism of Porous Carbons Derived from Biomass as Adsorbent for Removal of Cr(VI)

To solve the problem of heavy metal hexavalent chromium (Cr(VI)) pollution in water bodies, this study was carried out to prepare nitrogen-doped porous carbon by using bamboo shoots as the raw material and KHCO3 as the activator, which has a good ability to remove Cr(VI) from water bodies. The prepared N-doped carbon materials were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and scanning electron microscopy (SEM). The results showed that the prepared carbon material had hierarchical pore structures and abundant functional groups, which is conducive to the adsorption of Cr(VI). The effects of various factors on the adsorption performance of Cr(VI), such as the carbon materials prepared under different conditions, the pH of the initial solution, the concentration of the initial solution, and the contact time between the carbon and Cr(VI), were explored. The results showed that the bamboo shoot-based nitrogen-doped carbon materials, especially BSNC-800 (prepared at 800 °C with a mass ratio of KHCO3 to bamboo shoot of 4:1), performed well in removing Cr(VI) from a water solution. The maximum adsorption of Cr(VI) by BSNC-800 under equilibrium conditions was 385.8 mg g−1 (conditions: at the pH of 2 with the initial concentration of 400 mg L−1). The adsorption kinetics and isotherms were analyzed, and the adsorption mechanism was discussed. It can be found that the adsorption of Cr(VI) by BSNC-800 fits better with the Langmuir isotherm model and the pseudo-second-order kinetic model. The adsorption mechanism between the Cr(VI)-containing solution and BSNC-800 was controlled by membrane diffusion and chemisorption. The results broaden the ways of utilizing biomass resources as precursors of carbon materials, which is significant and helpful for applying biomass carbon materials as adsorbents for wastewater treatment.

Nanofibrous Covalent Organic Frameworks as the Cathode, Separator, and Anode for Batteries with High Energy Density and Ultrafast-Charging Performance.

To meet the demand for longer driving ranges and shorter charging times of power equipment in electric vehicles, engineering fast-charging batteries with exceptional capacity and extended lifespan is highly desired. In this work, we have developed a stable ultrafast-charging and high-energy-density all-nanofibrous covalent organic framework (COF) battery (ANCB) by designing a series of imine-based nanofibrous COFs for the cathode, separator, and anode by Schiff-base reactions. Hierarchical porous structures enabled by nanofibrous COFs were constructed for enhanced kinetics. Rational chemical structures have been designed for the cathode, separator, and anode materials, respectively. A nanofibrous COF (AA-COF) with bipolarization active sites and a wider layer spacing has been designed using a triphenylamine group for the cathode to achieve high voltage limits with fast mass transport. For the anode, a nanofibrous COF (TT-COF) with abundant polar groups, active sites, and homogenized Li+ flux based on imine, triazine, and benzene has been synthesized to ensure stable fast-charging performance. As for the separator, a COF-based electrospun polyacrylonitrile (PAN) composite nanofibrous separator (BB-COF/PAN) with hierarchical pores and high-temperature stability has been prepared to take up more electrolyte, promote mass transport, and enable as high-temperature operation as possible. The as-assembled ANCB delivers a high energy density of 517 Wh kg-1, a high power density of 9771 W kg-1 with only 56 s of ultrafast-charging time, and high-temperature operational potential, accompanied by a 0.56% capacity fading rate per cycle at 5 A g-1 and 100 °C. This ANCB features an ultralong lifespan and distinguished ultrafast-charging performance, making it a promising candidate for powering equipment in electric vehicles.

In Situ Synthesis of Copper-Based Metal-Organic Frameworks with Ligand Defects for Electrochemical Reduction of CO2 into C2 Products.

Electrochemical reduction of CO2 into high-value-added products is a potential approach to solving environmental problems but is limited by poor product selectivity and low efficiency. Metal-organic framework (MOF) materials have been considered one of the most promising catalysts, but their application is limited by complicated preparation processes, especially during the synthesis of organic ligands. In this work, a new three-dimensional Cu-MOF (JXUST-301) with high porosity was constructed based on the naphthalene diimide (NDI) ligand. Furthermore, JXUST-301 with ligand defects (JXUST-301D) originating from the missing NDI unit was synthesized via an in situ reaction. The presence of ligand defects endows JXUST-301D with a better CO2RR performance with a FEC2 of 56.7% and a jC2 of -162.4 mA cm-2. Mechanistic studies revealed that the hierarchical pore structure and amino sites are created from the absence of the NDI unit, which promotes the exposure of catalytically active sites and CO2 enrichment. Furthermore, the electronic structure of the Cu sites is modulated to upshift the d-band center, facilitating chemical adsorption and activation of key reaction intermediates. This work provides new insight into the in situ preparation of efficient Cu-MOF catalysts by introducing defects for the CO2RR.

One-Step Construction of Hierarchical Porous and Defect-Rich Zn2+-Doped NH2-MIL-125(Ti) to Enhance Photocatalytic Degradation of Tetracycline Hydrochloride.

The development of efficient metal-organic framework (MOF) photocatalysts for the degradation of tetracycline hydrochloride (TC) is crucial for environmental and public health. Herein, NH2-MIL-125(Ti) flakes (namely, ZnxTi1-x-NML), featuring defect-rich and Zn2+-doping, were synthesized using a one-step solvothermal method. For the first time, the crystal structure of Zn-doped NML was determined by combining extended X-ray absorption with fine structure spectroscopy. The formation mechanisms of the flake morphology with hierarchical porous structures were thoroughly investigated. Compared to NH2-MIL-125(Ti), Zn0.15Ti0.85-NML achieved a 3.4-fold increase in removal of TC under simulated sunlight. The adjusted electronic structure enhances superoxide radical production, coupled with a flake-like and porous architecture that promotes reaction sites, improved mass transfer, and reduced charge distances. Combined with theoretical calculations of the density of states and electrostatic potential, the ligand-metal-metal charge transfer process was elucidated. The possible pathway for the photocatalytic degradation of TC by Zn0.15Ti0.85-NML was further speculated. Moreover, the safety of the photocatalytic pathway was assessed by predicting the toxicity of the degradation intermediates. Our findings link the structure of MOFs to their catalytic efficiency, guiding the creation of sustainable photocatalysts.

MnO2-decorated flexible carbon nanofibers with controllable hierarchical porous nanostructures for high energy density supercapacitors

Constructing hierarchical porous structures and reducing material size enhance the electrochemical efficiency of porous carbon-based electrodes. In this study, ultrafine hierarchical porous carbon-based nanofibers were synthesized via electrospinning a blend of polyacrylonitrile, polymethyl methacrylate (PMMA), and zinc acetate dihydrate (ZAH), followed by pre-oxidation, carbonization, and acid washing. Adjusting the ZAH content allowed precise control of fiber diameters (300-600nm) and promoted significant hierarchical porous structures, achieving an optimal mesopore to micropore ratio (1.65) and a high specific surface area (SSA) of 599 m²/g. MnO2 nanosheets were in-situ modified on the carbon nanofibers, forming a hybrid electrode (MnO2@HPCNFs) with excellent flexibility, high SSA value, and rich pore structure. This electrode demonstrated a specific capacitance value equal to 1035 F/g at 0.5 A/g and maintained 80.7% capacitance at 10 A/g. The assembled asymmetric supercapacitor achieved an energy density of 54.81 Wh/kg. This study presents new possibilities for binder-free, self-supporting electrodes in electrochemical energy storage devices.

Shape controlled synthesis and crystal facet dependent gas sensitivity of tungsten oxide

Gas sensors can achieve remarkable functionality through the optimization of particle size, shapes, crystal facets, and oxygen defects, resulting in unsaturated coordination atoms, high charge densities, and enhanced bond energies. In this study, WO2.72 nanourchins, WO3-x nanowires, and WO3 nanorods/nanocube with (010), (001), (200), and (002) dominant crystal facets were synthesized and used as gas sensing materials. It was found that WO2.72 nanourchins exhibit an excellent response of Ra/Rg=21 to 100 ppm acetone with good selectivity among other sensors as-fabricated. First-principle calculations of Density Functional Theory were performed on acetone's adsorption on different crystal planes of tungsten oxide. The results verify spontaneous and fast adsorption on the (010) crystal plane than on the (001) and (200) planes. Further characterizations indicate that WO2.72 nanourchins with (010) crystal facets contain more reactive sites with high surface energy, facilitating charge separation, increasing charge carrier mobility, and enabling the redox reactions to occur independently at different rates. Moreover, their richer electron-donor surface oxygen defects, smaller feature sizes, and higher surface area (SBET) with hierarchical porous structures, all contribute to the enhanced acetone sensing. Our work provides a strategy for improved acetone sensing based on optimizing the particle shape with different crystal facets and oxygen vacancy density. We further expect our strategy to be applicable in designing other sensor materials with efficient charge separation and fast surface redox reactions to detect toxic gases.

Dielectric properties and temperature dependence of holey graphene/resin composites

In order to enhance the survivability of fighter aircraft, it is crucial to develop microwave absorbing (MA) materials with a low dielectric-temperature dependence. Reduced graphene oxide (RGO) has potential for military stealth applications, but its wave absorbing properties are highly sensitive to temperature fluctuations due to significant conductivity loss. In this work, conductivity and polarization loss are balanced through microstructural design to disrupt the conductive pathways by creating holes on the graphene surface. The holey RGO aerogel/phenolic resin (HRGA/PF) composites with a hierarchical pore structure were synthesized through combining freeze-drying and PF infiltration. The results show that the HRGA/PF composites possess excellent X-band full frequency absorption performance in the temperature range of 25 °C–250 °C, and the reflection loss (RL) is optimized to −62.78 dB. This work expands feasible thoughts for the design of stable MA materials with wide temperature range.

Gelation-pyrolysis strategy for fabrication of advanced carbon/sulfur cathodes for lithium-sulfur batteries

The development of high-performance carbon-based composite hosts play decisive roles in the electrochemistry of lithium sulfur batteries. Herein, a novel metal-ion induced gelation self-assembly technology is reported to construct sodium alginate carbon (SAC) based polar hierarchical carbon composites with cross-linked network architecture and in-situ co-grown cross-linked polar nanoparticles. Interestingly, it shows high versatility to an extensive array of materials including metals, alloys, and metallic oxides. As a representative, NiCo alloy nanoparticles are chosen to obtain the SAC/NiCo composite host for sulfur in LSBs, which possess superior physical/chemical adsorption capabilities and catalytic conversion kinetics to polysulfide in virtue of synergistic interaction between the hierarchical pore structures and NiCo catalyst. The designed SAC/NiCo-S cathode shows superior electrochemical performance with excellent rate capacity (2 C: 693.5 mAh/g) and enhanced cycling stability (764.3 mAh/g at 0.1 C after 240 cycles). This work provides a straightforward approach for fabricating multifunctional carbon composites with adjustable component for advanced energy storage system.

One-step green synthesis of melamine-modified cellulose nanofiber composite aerogels for efficient removal of Pb(II) and Cu(II): Experiments and DFT calculations

A composite aerogel (CGMA) with high porosity (98.32 %) and multiple active sites was prepared for the adsorption of Pb(II) and Cu(II) by sol-gel combined with freeze-drying process using melamine and (3-Glycidyloxypropyl)trimethoxysilane as cellulose nanofiber modifying materials. Characterized by SEM-EDS, XPS, FTIR, BET, MIP and TG, CGMA has a hierarchical pore structure and abundant adsorption sites. At pH = 6, the adsorption reached equilibrium within 120 min, following the Pseudo second-order kinetic model and the Langmuir model, with maximum capacities of 268.1 mg/g for Pb(II) and 152.6 mg/g for Cu(II). The process was primarily governed by homogeneous chemisorption. The coexisting ion, organic matter, and water quality experiments confirmed the excellent anti-interference properties of CGMA. Competitive adsorption experiments showed that CGMA has excellent selective adsorption performance for Pb(II). After 5 cycles, Pb(II) and Cu(II) adsorption performance decreased to 79.21 % and 83.40 %, respectively. FTIR, XPS, DFT and RDG analysis showed that amino groups and oxygen-containing groups were the main sites of adsorption. CGMA forms coordination bonds and complexes with Pb(II) and Cu(II) via amine and oxygen groups and adsorbs via electron transfer, hydrogen bonding, and van der Waals forces, with Pb(II) being more selective. CGMA has good prospects for application in heavy metal ion treatment.

HNTs Improve Flame Retardant and Thermal Insulation of the PVA/CA Composite Aerogel.

Porous materials are widely used in construction, batteries, electrical appliances, and other fields. In order to meet the demand for flame-retardant and thermal insulation properties of organic porous materials, in this work, poly(vinyl alcohol)/calcium alginate/halloysite nanotube (PVA/CA/HNTs) aerogels with a hierarchical pore structure at micrometer-nanometer scales were prepared through freeze-drying using PVA as the substrate. The cross-linking reactions of PVA with H3BO3 and sodium alginate (SA) with CaCl2 constructed a double cross-linking network structure within the aerogel. And the HNTs were incorporated as reinforcing agents. The experimental results showed that the PVA/CA/HNTs aerogels had excellent flame-retardant and thermal insulation properties, and the heat release rate (HRR) and total heat release (THR) were effectively reduced compared to the PVA/CA aerogel. In addition, PVA/CA/HNTs aerogels had a high limiting oxygen index (LOI 60%) and low thermal conductivity (0.040 W/m·K). While their surface was subjected to a flame (800-1000 °C) for 25 min, the temperatures of the back surface were still lower than 80 °C. The low thermal conductivity of HNTs with hollow nanotube-like structures and the excellent flame-retardant properties of CA contributed to this phenomenon. The presence of HNTs and CA facilitated the formation of a dense carbon layer during combustion, enhancing the flame retardancy for PVA. In addition, the interpenetrating cross-linking network and the unique nanopores of HNTs collectively established a hierarchical pore structure within the gel, effectively impeding substance and heat exchange between the substrate and external environment. As the flame-retardant and thermal insulating material, PVA/CA/HNTs aerogels have a promising development prospect and potential in the fields of construction, transportation, electronics, and electrical appliances.

Solvent-free synthesis of highly dispersed zinc-doped porous carbons as efficient dibenzothiophene adsorbents

Designing efficient adsorbents for the deep removal of refractory dibenzothiophene (DBT) from fuel oil is vital for addressing environmental issues such as acid rain. Herein, zinc gluconate and urea-derived porous carbons SF-ZnNC-T (T represents the carbonization temperature) were synthesized without solvents. Through a temperature-controlled process of “melting the zinc gluconate and urea mixture, forming H-bonded polymers, and carbonizing the polymers,” the optimal carbon, SF-ZnNC-900, was obtained with a large surface area (2280 m2 g), highly dispersed Zn sites, and hierarchical pore structures. Consequently, SF-ZnNC-900 demonstrated significantly higher DBT adsorption capacity of 43.2 mg S g−1, compared to just 4.3 mg S g−1 for the precursor. It also demonstrated good reusability, a fast adsorption rate, and the ability for ultra-deep desulfurization. The superior DBT adsorption performance resulted from the evaporation of residual zinc species, which generated abundant mesopores that facilitated DBT transformation, as well as the formation of Zn-Nx sites that strengthened the host-guest interaction (ΔE = −1.466 eV). The solvent-free synthesized highly dispersed Zn-doped carbon shows great potential for producing sulfur-free fuel oil and for designing metal-loaded carbon adsorbents.

Biomimetic Channels Design in Metal-Organic Framework Enabling Highly Lithium-Ion Conduction for Lithium-Metal Batteries.

Solid-state electrolytes (SSEs) based on metal-organic frameworks (MOFs) are an ideal material for constructing high-performance lithium metal batteries (LMBs). However, the low ion conductivity and poor interface contact (especially at low temperatures) still seriously hinder its further application. Herein, inspired by the Na+/K+ conduction in biology systems, a series (NH2, OH, NH-(CH2)3-SO3H)-modified MIL-53-X as SSEs is reported. These functional groups are similar to anions suspended in biological ion channels, partially repelling anions while allowing cations to be effectively transported through pore channels. Subsequently, MIL-53-X with hierarchical pore structure (H-MIL-53-X) is obtained by introducing lauric acid as a regulator, and then the effects of structural design and morphology control on its performance are explored. The conductivity of H-MIL-53-NH-SO3Li with multi-level pore structure and modified by sulfonic acid groups reached 2.2×10-3Scm-1 at 25°C, lithium-ion transference number of 0.78. Besides, the H-MIL-53-NH-SO3Li still has an excellent conductivity of 10-4Scm-1 at -40°C. Additionally, LiFePO4/Li batteries equipped with H-MIL-53-NH-SO3Li SSEs could operate stably for over 200 cycles at 0.1C. The strategy of combining structural and morphological design of MOFs with biomimetic ion channels opens new avenues for the design of high-performance SSEs.

Defect-controlled confined growth of nano-MOFs to prepare materials with hierarchical micro/mesoporous structures for efficient CO2 capture

In recent years, nanoporous materials with special structure have been widely used in various fields. In view of the poor stability of MOFs materials and the poor mass transfer ability, in this study, we developed a simple method to restrict the growth of UiO-66-NH2 crystals in hollow silica by “vacuum evaporation” strategy, different kinds of acid regulators were introduced, to obtain a composite material with hierarchical pore structure. By characterizing the physical chemistry and microstructure of the composite adsorbent, and calculating the structural defects under different acid regulation, the adsorption and desorption performance and stability of the adsorbent for CO2 were comprehensively investigated. The mechanism of action on CO2 was further analyzed by in-situ infrared and other techniques. The results show that the change of coordination environment and coordination rate caused by the competition of organic acids, which increases the defects and reduces the nucleation and aggregation effect of UiO-66-NH2, promotes the formation of hierarchical pore structure of the composites. Among them, benzoic acid is the best regulating monocarboxylic acid, which makes UiO-66-NH2 have good dispersion in the cavity and suitable crystal size. The specific surface area of the composite material is 717.96 m2·g-1. At the same time, due to its excellent CO2 adsorption capacity (3.35mmol·g-1) at 298K and 1.06bar, it is 48.07% higher than the original UiO-66-NH2. In order to accomplish the goal of effective CO2 adsorption performance of composites, this study offers a novel approach for the synthesis and modification of MOFs-based composites.

A novel colorless flexible polymer aerogel with stable amine linkage enabled superior formaldehyde removal and multifunctional application

Massive formaldehyde emissions have seriously endangered environment and human health, while predictably polymer aerogel is a promising candidate for formaldehyde (FA) removal, whereas low FA adsorption capacity, high volume shrinkage, and mechanical brittleness restrict its further development. Herein, based on “rigid-soft combination” polycondensation strategy, trifunctional 1,3,5-benzenetricarboxaldehyde (BTC) and polyetheramine Jeffamine T403 are selected as building blocks to construct a novel amine-linked polymer aerogel (rBTA) with hierarchical micro-nano porous structure via mild sol-gel method and freeze-drying process. Stable amine linkages in rBTA are formed by NaBH4 reduction of imine bonds, improving acid/alkali resistance and chemical stability greatly, and creating numerous active amine sites for reaction with FA. Formation of robust 3D covalent network facilitates to simultaneously achieve ultra-low-shrinkage (5.4%), high specific compressive modulus (5.32 kN·m·kg-1), remarkable mechanical durability/fatigue-resistance, flexibility, and machinability. Benefiting from synergistic physical-chemical adsorption effect, FA adsorption capacity and removal ratio of rBTA reach as high as 459.84 mg·g-1 and 97.87%, respectively. Colorless rBTA is further ground into powders for preparing polyoxymethylene (POM)/rBTA composite without affecting its color and formaldehyde emission amount at 60/230°C effectively decreases by 66.87%/79.55%. Furthermore, rBTA exhibits hydrophobicity, low thermal conductivity, and high solar reflectance, being successfully applied in emulsion separation, thermal insulation, and energy-efficient buildings fields.

Solvent self-doping synthesis of nitrogen/oxygen co-doped porous carbon from cellulose as high performance material for multipurpose energy storage

Developing novel heteroatoms co-doped biomass porous carbon with low-cost, tunable physical/chemical properties, and environmental friendliness is an important candidate to face energy shortage and environmental pollution currently. Herein, a novel solvothermal avenue was designed using triethanolamine as self-doping solvent to treat rice straw powders with KOH. The rice straw with triethanolamine derived carbon (RSTCs-1) possessed hierarchical porous structure, N/O diatomic doping, and large specific surface area. The electrochemical energy storage performance of RSTCs-1 was evaluated in the systems of supercapacitors, aqueous zinc ion hybrid supercapacitors (AZHSs), and lithium-ion batteries (LIBs) respectively. As the results, the RSTCs-1 based symmetric supercapacitor exhibited the maximum energy density of ca. 98.4 Wh·kg−1 with the excellent cycling stability. Moreover, both RSTCs-1 AZHSs and RSTCs-1 LIBs achieved the relative high discharge specific capacities of ca. 407.1 and 1906.7 mAh·g−1 at current density of 0.1 A·g−1. These results highlighted the huge potential of the obtained with notable electrochemical performance acting as multifunctional electrode material for the different energy storage devices.

Effects of tree species pore structure characteristics and CO2 activation on the performance of their derived carbon electrode for supercapacitors

Herein, we investigated the effects of tree species selection on the specific surface area and electrochemical properties of wood-derived carbon electrodes. The SEM, Raman spectra and aperture distribution test results showed that compared with BCW and ZCW, CW had a more complex hierarchical porous structure and more defects. The N2 adsorption/desorption isotherms and electrochemical test results showed that CW had the largest specific surface area and the best electrochemical performance, with a specific surface area of 495.3 m2g−1 and an areal capacitance of 3079 mF cm−2 at 5 mA cm−2. The specific surface area and electrochemical properties of ACW, ABCW and AZCW electrodes obtained by CO2 activation were significantly improved compared with CW, BCW and ZCW electrodes. Among the activated electrodes, the ACW electrode had the highest specific surface area (558.4 m2g−1) and the highest areal capacitance (3727 mF cm−2 at 5 mA cm−2).

One-step pyrolysis route to N, O, S co-doped hierarchical carbon as multi-functional separator for lithium-sulfur batteries

Lithium-sulfur batteries have high theoretical energy density while their practical application is trapped because of severe shuttle effect and sluggish conversion kinetics of polysulfides. Here, a nitrogen, oxygen, and sulfur co-doped porous carbon (NOSAKC) is prepared by one-step pyrolysis of acesulfame potassium, which is employed as an efficient component on polypropylene separators to restrict the shuttle of polysulfides based on Lewis acid-base theory. The NOSAKC exhibits a hierarchical porous structure with high specific surface area and abundant adsorption/catalytic sites. The substantial mesoporous channels are conducive to rapid ion transfer, and the micropores minimize the polysulfide shuttle. The abundant heteroatoms doped in NOSAKC can achieve synergistic constraint and conversion of lithium polysulfides. So the Li-S battery with the NOSAKC separator displays distinguished electrochemical performance with a high discharge capacity of 1598 mAh g-1 at 0.2C and 1012 mAh g-1 at 1C. It maintains 84% of the initial capacity after 500 cycles with a stable coulombic efficiency of 99.8%. Moreover, the Li-S battery achieves a capacity retention of 67% after 200 cycles for a high sulfur loading of 4.33mgcm-2. This work reports a one-step preparation of hierarchical porous carbon with tri-doped heteroatoms for synergistic polysulfide adsorption and conversion.

Rice husk-based activated carbon/carbon nanotubes composites for synergistically enhancing the performance of lead-carbon batteries

Lead-carbon batteries (LCBs), an advanced form of lead-acid battery (LAB) technology, incorporate super-capacitive carbon materials into the negative electrode. Rice husk-based activated carbon (RHAC) is a promising additive for LCBs due to its favorable properties. However, RHAC's amorphous structure impedes electronic conduction, and its zigzag microporous channels hinder ion transport, leading to degraded high-rate performance. This study addresses these issues by growing carbon nanotubes (CNTs) in situ on RHAC through a one-step heat treatment, resulting in carbon nanotubes-loaded RHAC (CNTs/RHAC), and the electronic conductivity and ionic conductivity are simultaneously enhanced. When CNTs constitute 30 wt.% of CNTs/RHAC, the negative electrode achieves a cycle life of 4721 cycles at a 2C rate under 50% state of charge, which is 10.04 times that of the blank anode. The enhanced performance is attributed to the synergistic effects of CNTs and RHAC, where CNTs form long-range conductive networks among the negative electrode active material (NAM) and facilitate the diffusion and electro-deposition of Pb2+, while the high specific surface area (SSA) and hierarchical porous structure of RHAC enhance its capacitive function, leading to a stable lead-carbon composite structure.