Ultrahigh Specific Area Research Articles

Thermally-stable and flame-retardant metal-organic framework-based separator for high-performance lithium-ion batteries

Safety hazards hinder the development of lithium-ion batteries (LIBs), in which the failure of separator is a key point. However, commercial polyolefin separators display poor thermal stability and flame-retardant property. Aramid nanofiber (ANF) is a promising material for safer separators in batteries due to its excellent thermal stability and remarkable flame retardancy, but the pure ANF separator often shows low ionic conductivity because of the tightly packed fibers. Metal-organic framework (MOF) is a promising candidate for increasing the porosity and ionic conductivity of ANF separator due to its ultrahigh porosity and ultrahigh specific area. Herein, a thermally-stable and high-performance composite separator is fabricated by combining MOF pore-forming agent and ANF network skeleton. The MOF/ANF1composite separator with 10 wt% ANF shows excellent thermal-stability (melting-point above 300 °C and decomposition temperature above 500 °C) and remarkable flame-retardant property. And it exhibits high ionic-conductivity of 1.01 mS·cm−1, contributed to the superior long-term cycling performance of the coin cell with the capacity of 147.3 mAh·g−1 after 200 cycles at 1 C, almost 25.4 % higher than that of the coin cell with PP separator for LIBs. The strategy of this research provides new ideas for the design of high-safety LIBs.

Boosting bifunctional oxygen electrocatalysis with atomically dispersed Fe and Co dual-metal sites for flexible zinc-air batteries

Rechargeable zinc-air batteries (ZABs) hold enormous promise as energy conversion and storage system of the next generation. Here, through utilizing the Co/ZIF-8@F127 precursor and a coordinated strategy that includes ‘post-absorption’ and ‘dual-pyrolysis’, a Fe/CoNx-C possesses a hierarchical porous N-doped carbon with an ultrahigh specific area and rich defects to stabilize accessible dual metallic active sites. With a narrow potential gap of 0.71 V, the Fe/CoNx-C catalyst demonstrates excellent bifunctional electrocatalytic activity toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Noteworthily, scanning electrochemical microscopy (SECM) was used to visualize the local electrocatalytic ORR activity of CoNx-C and Fe/CoNx-C. For the applications of zinc-air batteries, the Fe/CoNx-C-based cathode provides a high peak power density of 134.97 mW cm−2 for aqueous ZABs. Moreover, quasi-solid-state ZABs (including flexible ZAB and cell ZAB)-based on Fe/CoNx-C as cathode catalyst demonstrate satisfying flexibility and durability. The theoretical calculation results further elucidate the synergistic effect that the engagement of Fe atoms in the electron transfer process of the FeN4@CoN4 system reduces the energy barrier of the rate-determining-step in ORR and OER, hence facilitating the reversible oxygen electrocatalytic kinetics.

Construction of UiO-66-NH2/BiOBr heterojunctions on carbon fiber cloth as macroscale photocatalyst for purifying antibiotics

Metal-Organic Frameworks (MOFs) as a novel semiconductor-like material with high adsorption were used to combine with other efficient semiconductors to enhance the adsorption capacity and photocatalytic activity for removing antibiotics from aqueous solutions. In addition, most of the efficient photocatalysts are in powder-shaped, making recycling problematic. To solve the above problems, with macroscale carbon fiber cloth (CFC) as the substrate, Zr-based MOFs (UiO-66-NH2) as a model material with ultra-high specific area and BiOBr as an efficient semiconductor with irregular sheet structure were synthesized sequentially by a solvothermal method and dip-coating process. The prepared CFC/UiO-66-NH2/BiOBr exhibits strong adsorption of 65.4% levofloxacin (LVFX) or 16.8% ciprofloxacin (CIP) within 60 min in dark, and excellent degradation of 92.2% LVFX or 86.4% CIP under visible-light irradiation over a period of 120min. Additionally, after 4 cycles of visible-light irradiation, the macroscale CFC/UiO-66-NH2/BiOBr exhibits stable removal efficiency of antibiotics. Using low-cost CFC as substrate, CFC/UiO-66-NH2/BiOBr shows high efficiency and recyclability in removing antibiotics from polluted wastewater, offering guidance for developing highly effective photocatalysts on a large scale through methods like calcination and sol-gel synthesis. Therefore, the macroscale CFC/UiO-66-NH2/BiOBr has great potential for purifying antibiotics under visible-light illumination, presenting a practical solution for sustainable development.

A graphitized hierarchical porous carbon as an advanced cathode host for alkali metal-selenium batteries

• One-step activation-free synthesis of hierarchical porous carbon is achieved by CO 2 erosion. • HPC possesses high electronic conductivity with controllable graphitization degree. • The excellent specific surface area and voids of HPC can buffer deposition and drastic volume breath. • HPC/Se shows high excellent electrochemical performance as cathode for alkali metal-selenium batteries. Selenium cathode, of high volumetric energy density and compatibility with safe/cheap carbonate electrolyte, are plagued by low active material utilization, limited rate capability and fast capacity fading. Therefore, a carbon host, capable of speeding electron transfer, facilitating Li + diffusion and buffering drastic volume breath, is greatly demanded. Herein, a graphitized hierarchical porous carbon is prepared by metallothermic reduction reaction of CO 2 , and employed as cathode host for alkali metal-Se batteries. With high electronic conductivity, ultrahigh specific area (1740 m 2 g −1 ) and abundant porosity (1.76 cm 3 g −1 ), this carbon host after Se infiltrating exhibits an initial capacity of 994 mAh g −1 and a reversible capacity of 538 mAh g −1 at 0.5C in the initial cycle for lithium-selenium batteries. In addition, a reversible capacity of 451 mAh g −1 can still be achieved at a current density of 2C, with a low capacity decay rate of about 0.037% per cycle in subsequent 800 cycles. In further tests, HPC/Se cathode also shows superior rate capabilities and stable cyclability for sodium-selenium batteries and potassium-selenium batteries.

Fe Single‐Atom Catalysts on MOF‐5 Derived Carbon for Efficient Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

AbstractThe development of Fe single‐atom catalysts (Fe SACs) with abundant, accessible Fe sites is a key step toward enhancing the efficiency of the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). In this study, Zn4O(1,4‐benzenedicarboxylate)3 (MOF‐5), which has a 3D microporous cubic structure, is used as the precursor to prepare highly‐porous carbon (denoted as C‐MOF‐5) with an ultrahigh specific surface area (2751 m2 g–1) and high external surface area (1651 m2 g–1). C‐MOF‐5 is demonstrated as an effective carbon support to yield Fe SAC‐MOF‐5 with a large amount of accessible FeNx sites (2.35 wt%). Fe SAC‐MOF‐5 delivers a half‐wave potential of 0.83 V (vs RHE) in a 0.5 m H2SO4 electrolyte, and achieves a peak power density of 0.84 W cm–2 in a 0.2 MPa H2‐O2 PEMFC. This excellent performance originates from the ultrahigh specific surface area of C‐MOF‐5 for the formation of a high density of single Fe atoms, and high external surface area for the increased exposure of active sites. This work may inspire the rational design of metal single‐atom catalysts derived from a wider range of MOF precursors with ultrahigh specific area to improve the performance of the oxygen reduction reaction in PEMFCs.

The synergistic effect of P-doping and carbon coating for boosting electrochemical performance of TiO2 nanospheres for sodium-ion batteries

P-doping is an effective way to modulate the electronic structure and improve the Na+ diffusion kinetics of TiO2, enabling enhanced electrochemical performance. However, it is a challenge to prepare TiO2 with a high P-doping concentration starting from TiO2 in a crystalline state. In this work, we design a novel two-step route for constructing a carbon-coated anatase P-doping TiO2 nanospheres (denote as (P-AnTSS)@NC) with high P-doping concentration, by utilizing amorphous TiO2 nanospheres with the ultra-high specific area as P-doping precursor firstly, and followed by carbon coating treatment. Experimental results demonstrate that P is successfully doped into the crystal lattice and carbon layer is well coated on the surface of TiO2, with P-doping and carbon-coating contents of ~13.5 wt% and 10.4 wt%, respectively, which results in the enhanced pseudocapacitive behavior as well as favorable Na+ and electron transferring kinetics. The (P-AnTSS)@NC sample shows excellent rate and cycle performance, exhibiting specific capacities of 177 and 115 mAh/g at 0.1 and 1.0 A/g after 150 and 2000 cycles, respectively.

N, S-Codoped Activated Carbon Material with Ultra-High Surface Area for High-Performance Supercapacitors.

The recycling of macromolecular biowastes has been a problem for the agriculture industry. In this study, a novel N, S-codoped activated carbon material with an ultrahigh specific area was produced for the application of a supercapacitor electrode, using tobacco stalk biowastes as the carbon source, KOH as the activating agents and thiourea as the doping agent. Tobacco stalk is mainly composed of cellulose, but also contains many small molecules and inorganic salts. KOH activation resulted in many mesopores, giving the tobacco stem-activated carbon a large specific surface area and double-layer capacitance. The specific surface area of the samples reached up to 3733 m2·g−1, while the maximum specific capacitance of the samples obtained was up to 281.3 F·g−1 in the 3-electrode tests (1 A·g−1). The doping of N and S elements raised the specific capacitance significantly, which could be increased to a value as high as 422.5 F·g−1 at a current density of 1 A·g−1 in the 3-electrode tests, but N, S-codoping also led to instability. The results of this article prove that tobacco stalks could be efficiently reused in the field of supercapacitors.

Heteroatom-doped ultrahigh specific area carbons from hybrid polymers with promising capacitive performance

Development of the high capacitive supercapacitors needs the design of innovative materials that combine high surface area, hierarchical porous structures with doping of appropriate elements to accelerate ion transport and elevated electrolyte permeability. Herein, a series of ultrahigh surface area with intrinsic multiple-heteroatom doped carbon materials with excellent electrochemical performance are prepared via a simple chemical foaming strategy during the pyrolysis process of poly (bisphenoxy)phosphazene (PBPP). Due to the synergistic effect of the self-blowing strategy under pyrolysis, the as-synthesized polyphosphazene carbons (PZCs) exhibit a large number of hierarchical pores with ultrahigh specific surface area (up to 3673 m2 g-1). The ideal pore structures and N, P, O co-doping endue the carbon with a high specific capacitance of 225.0 F g-1 in 6 M KOH at 0.5 A g-1 of symmetric cell. Two methods contain pre-treatment and post-treatment, introducing reduced graphite oxide (rGO) into the precursor and in-situ polymerizing polyaniline (PANI) on the carbon, are used to modify the obtained carbons for further enhancing the capacity. PANI/PZC5-600-3 exhibits two-electrode specific capacitance of 413.1 F g-1 in 1 M H2SO4 at 1 A g-1, which is significantly higher than PZC5-600-3 and PZC5/2%rGO-600-3, with 90% increment compared with PZC5-600-3.

Novel design of high-surface-area poly-hollow alumina spheres via a facile ball dropping method based on particle-stabilized emulsions

Herein, the preparation of millimeter-sized poly-hollow alumina spheres (PHASs) with high-surface-area is proposed via an innovative and facile ball dropping method based on particle-stabilized emulsions. The PHASs fabricated by this method possess high specific surface area because of their hierarchical pore structures and high porosity, and exhibit remarkable superiority over the commercially available active alumina materials with specific surface areas of 200–300 m2g-1. The resultant millimeter-sized PHASs have diameters in range of 2–6 mm, average mesoporous sizes of 4–8 nm, and excellent specific surface areas of 400–500 m2 g-1, which are achieved with oil-water volume ratio of 3:1, rotation speed of 900 rpm, and sintering temperature of 500 °C. These high-performance PHASs with ultra-high specific areas and hierarchical pore structures can potentially be useful in various applications.

High dielectric and breakdown properties achieved in ternary BaTiO3/MXene/PVDF nanocomposites with low-concentration fillers from enhanced interface polarization

Although high permittivity is achieved in barium titanate (BT) filled polymer nanocomposites, severely reduced insulation and breakdown properties are frequently found due to overload and agglomeration of BT nanoparticles with ultrahigh specific area. To simultaneously realize high permittivity and breakdown strength, in this work, unfunctionalized 2D Ti3C2 MXene nanosheets with 2 wt% weight concentration were introduced to prepare ternary BT/MXene/polymer nanocomposites by solution cast process. Employing low-concentration conductive MXene instead of high-concentration ferroelectric BT could lead to significant improvement of permittivity of ternary composites, ascribed to remarkably increased interface types and enhanced interface polarization. In comparison to binary BT/polymer composites, ternary composites could have slightly improved dielectric loss and conductivity as well as gracefully reduced breakdown strength, attributed to finely retained high interface compatibility and filler dispersion. Ternary composite containing 8 wt% BT and 2 wt% MXene had a permittivity of 77, loss of 0.15 at 100 Hz and breakdown strength of 220 MV m−1. This work might open the door to large-scale fabrication of promising composites with high permittivity and breakdown strength under low filler loading (~ 10 wt%).

Two dimensional XAs (X = Si, Ge, Sn) monolayers as promising photocatalysts for water splitting hydrogen production with high carrier mobility

Two dimensional (2D) materials are emerging as promising candidates for photocatalysts owing to their fascinating properties and ultra-high specific areas. Herein, using first principle calculations, we systematically investigated a new kind of 2D XAs (X=Si, Ge, Sn). After verifying their stabilities, we found that SiAs and SnAs monolayers possess direct band gaps of 2.35 and 1.69eV, while GeAs has an indirect band gap of 2.08eV by HSE hybrid functional with the inclusion of spin-orbit coupling (SOC) effect. Meanwhile, their exceptionally high and directionally anisotropic carrier mobilities (up to 8.98×103cm2V−1s−1 for SiAs) can be advantageous for the fast migration and separation of the photogenerated electron-hole pairs. Most importantly, their band gaps and band edge positions at neutral environment meet the requirement of water splitting. Moreover, the study of XAs heterobilayers (correspondingly stacking with GaS, GaSe and InSe monolayers) shows that they have type-II band alignment, enhanced optical absorption and proper CBM positions with respect to the reduction potential of water, indicating that they may have stronger driving force for the hydrogen evolution reaction. Finally, we explored the adsorption and decomposition of water as well as the subsequent generation of hydrogen on the surfaces of 2D SiAs and SiAs/GaS, which unravels the micro-mechanism of the photocatalytic hydrogen production process. Our finding shows that XAs monolayers can provide appealing alternatives for diverse nanodevices and be potential candidates for metal-free photocatalysts.

Novel Synergistic Strategy for Developing High-Performance Lithium Sulfur Batteries of Large Areal Sulfur Loading by SEI Modified Separator

As a crucial energy density determining factor, the areal sulfur loading is still low nowadays for practical applications of Li–S batteries. To address this issue, intensive research efforts have been devoted to development of sulfur-hosting materials with ultrahigh specific surface area. However, design and manufacturing processes for these materials are complicated. Herein, we report a novel and facile strategy for developing a high-performance cathode with high areal sulfur content using conventional sulfur hosts without ultrahigh specific area. This strategy features a dense blocking layer of solid electrolyte interface (SEI) on the separator to ensure cycle stability of the cathode with a high areal sulfur loading. Meanwhile, a nanoarray cathode structure (CNT array on carbon cloth) is adopted to guarantee high sulfur utilization and rate performance. With the synergistic effect of a dense blocking layer and CNT array structure, the cathode with 10 mg/cm2 sulfur (90.9% in CNT/S composite) shows good ...

Hierarchically porous nitrogen-doped carbon derived from the activation of agriculture waste by potassium hydroxide and urea for high-performance supercapacitors

Nitrogen-doped carbon with an ultra-high specific surface area and a hierarchically interconnected porous structure is synthesized in large scale from a green route, that is, the activation of bagasse via a one-step method using KOH and urea. KOH and urea play a synergistic effect for the enhancement of the specific surface area and the modification of pore size of the as-prepared material. Benefiting from the multiple synergistic roles originated from an ultra-high specific area (2905.4 m2 g−1), a high porous volume (2.05 mL g−1 with 75.6 vol% micropores, which is an ideal proportion of micropores for obtaining high specific capacitance), a suitable nitrogen content (2.63 wt%), and partial graphitization, the hierarchically interconnected porous N-doped carbon exhibits an excellent electrochemical performance with a high specific capacitance (350.8, 301.9, and 259.5 F g−1 at 1.0 A g−1 in acidic, alkaline, and neutral electrolytes, respectively), superior rate capability and excellent cycling stability (almost no capacitance loss up to 5000 cycles). Furthermore, the symmetric device assembled by this material achieves high energy densities of 39.1 and 23.5 Wh kg−1 at power densities of 1.0 and 20 kW kg−1, respectively, and exhibits an excellent long-term cycling stability (with capacitance retention above 95.0% after 10 000 cycles).

Ideal N-doped carbon nanoarchitectures evolved from fibrils for highly efficient oxygen reduction

Convenient and economic one-step nitrogenization of oxygen-rich fibril materials, such as absorbent cotton and facial tissue, under gaseous ammonia is used to synthesize various oxygen reduction catalysts. The surface nanoarchitectures of fibrils are remolded by this nitrogenization processing with multi-effects involving the doping of abundant active pyridinic and graphitic N in the carbon skeleton, creating a highly unique mesopore structure with an ultrahigh specific area as well as a high degree of graphitization. The joint optimization of these structure characteristics yields an ideal catalytic nanoarchitecture, which can execute an approximate 4e− oxygen reduction with an activity comparable to that of Pt/C. The durability and methanol tolerance of the catalyst are also essentially superior to that of commercial Pt/C on the basis of this ideal nanoarchitecture.

Synthesis of C8 -Functionalized Magnetic Graphene with a Polydopamine Coating for the Enrichment of Low-Abundance Peptides.

For the first time, C8 -functionalized magnetic graphene (magG) has been designed and synthesized with a polydopamine (PDA) coating. The magG prepared by a solvothermal reaction was encapsulated in a layer of PDA through the oxidative polymerization of dopamine in alkaline buffer, and C8 groups were grafted onto magG/PDA composites through a silanization method. The as-prepared material integrates the merits of graphene, magnetic microspheres, PDA, and C8 chains; thus possessing an ultrahigh specific area, strong magnetic responsiveness, excellent solubility, and an extraordinary enrichment capability. The C8 -functionalized magnetic composites were employed in the enrichment and identification of low-concentration standard peptides, peptides in standard protein digest solutions, and endogenous peptides in human urine. The enriched peptides were eluted and analyzed by MALDI-TOF MS. The MS results indicated that the C8 -functionalized material exhibited the distinguished ability to enrich hydrophobic peptides mainly through hydrophobic-hydrophobic interactions. Moreover, thanks to the enrichment approach based on magG@PDA@C8 , the limit of detection of the standard peptide decreased to as low as 50 pM. The experimental results demonstrate that the magG@PDA@C8 composite is a promising candidate for the enrichment of low-abundance peptides in biological samples.

Porous carbon with ultrahigh specific surface area derived from biomass rice hull

Ultrahigh specific surface area porous carbon was prepared from biomass rice hull by the combination of activation temperature program method and sodium hydroxide activation process. The effect of the preparatory conditions on the properties of the prepared samples has been analyzed. Detailed characterizations of the sample revealed that the surface characteristic of carbon change significantly with mix ratio and activation temperature program. The maximum surface area (3960m2g−1) and pore volume (up to 1.98cm3g−1) were obtained at mix ratio 3:1 and three sections' heating pattern. The result suggests that is a convenient yet promising method could be used to prepare porous carbon with ultrahigh specific area and highly developed microporous and small mesoporous structures.

Synthesis of Rhodium Colloidal Nano‐Coating Grafted Mesoporous Silica Composite and its Application as Efficient Environmentally Benign Catalyst for Heck‐Type Reaction of Arylboronic Acids

AbstractThe synthesis and characterization of rhodium colloidal layer grafted mesoporous SBA‐15 material, designated as SBA‐Rh, are presented. In the preparation of this new catalyst, SBA‐15 mesoporous material was used as support without any pretreatment. The SiH functional groups were introduced onto the surface which resulted in highly dispersed metal colloid layer both on the outer and inner surface of the supporting material. The material was investigated for Heck‐type coupling reactions of alkenes with ayboronic in organic/water solvent. The ultrahigh specific area, large pore opening, and highly dispersed catalyst species in SBA‐Rh material created one of the most active heterogeneous catalysts for such reactions. Rhodium element was not detected in the final mixture by ICP after reaction. The catalyst species showed very high stability against leaching from the matrix and can be recycled for repeated use.

New and efficient heterogeneous catalytic system for Heck reaction: palladium colloid layer in situ reduced in the channel of mesoporous silica materials

The synthesis and characterization of palladium colloid layer grafted mesoporous SBA-15 material, designated as Pd-SBA, are described. In the preparation of this new catalyst, the Si H functional groups were introduced into the channel of SBA-15 mesoporous materials resulting in highly dispersed metal colloid layer on the pore walls of the supporting material. The material is investigated for Heck coupling reactions with activated and non-activated aryl substrates. The ultrahigh specific area, large pore opening, and highly dispersed catalyst species in Pd-SBA material create one of the most active heterogeneous catalysts for Heck coupling reactions.