Hexagonal boron nitride (h‐BN) has lately received great attention in the oxidative dehydrogenation (ODH) reaction of propane to propylene for its extraordinary olefin selectivity in contrast to ...metal oxides. However, high crystallinity of commercial h‐BN and elusive cognition of active sites hindered the enhancement of utilization efficiency. Herein, four kinds of plasmas (N2, O2, H2, Ar) were accordingly employed to regulate the local chemical environment of h‐BN. N2‐treated BN exhibited a remarkable activity, i.e., 26.0 % propane conversion with 89.4 % selectivity toward olefins at 520 °C. Spectroscopy demonstrated that “three‐boron center” N‐defects in the catalyst played a pivotal role in facilitating the conversion of propane. While the sintering effect of the “BOx” species in O2‐treated BN, led to the suppressed catalytic performance (12.4 % conversion at 520 °C).
Plasma (N2, O2, H2, Ar) regulated h‐BN with distinct local environment were obtained and employed for ODH of propane: N2 treated BN containing more three‐boron center nitrogen‐defects exhibited remarkable propane conversion of 26.0 % with olefin selectivity of 89.4 % at 520 °C. O2 treated BN showed deactivation due to the sintering effect of “BOx”. N‐H and B‐H generated during H2 treatment, may be unable to facilitate the reaction activity.
Hard carbon attracts considerable attention as an anode material for sodium‐ion batteries; however, their poor rate capability and low realistic capacity have motivated intense research effort toward ...exploiting nanostructured carbons in order to boost their comprehensive performance. Ultramicropores are considered essential for attaining high‐rate capacity as well as initial Coulombic efficiency by allowing the rapid diffusion of Na+ and inhibiting the contact of the electrolyte with the inner carbon surfaces. Herein, hard carbon nanosheets with centralized ultramicropores (≈0.5 nm) and easily accessible carbonyl groups (CO)/hydroxy groups (OH) are synthesized via interfacial assembly and carbonization strategies, delivering a large capacity (318 mA h g−1 at 0.02 A g−1), superior rate capability (145 mA h g−1 at 5.00 A g−1), and approximately 95% of reversible capacity below 1.00 V. Notably, a new charge model favoring fast capacitive sodium storage with dual potential plateaus is proposed. That is, the deintercalation of Na+ from graphitic layers is manifested as the low‐potential plateau region (0.01−0.10 V), contributing to stable insertion capacity; meanwhile, the surface desodiation process of the CO and OH groups corresponds to the high‐potential plateau region (0.40−0.70 V), contributing to a fast capacitive storage.
Hard carbon nanosheets with centralized ultramicropores (≈0.5 nm), accessible functional CO/OH groups, and large graphitic layer spacings exhibit excellent sodium‐storage properties. The desodiation process from graphitic layers and CO/OH groups results in a new sodium‐storage characteristic with dual‐potential plateaus during the charge process, which favors a high output of 95%, realistic capacity, and rapidly capacitive sodium storage.
While lithium-sulfur batteries are poised to be the next-generation high-density energy storage devices, the intrinsic polysulfide shuttle has limited their practical applications. Many recent ...investigations have focused on the development of methods to wrap the sulfur material with a diffusion barrier layer. However, there is a trade-off between a perfect preassembled wrapping layer and electrolyte infiltration into the wrapped sulfur cathode. Here, we demonstrate an in situ wrapping approach to construct a compact layer on carbon/sulfur composite particles with an imperfect wrapping layer. This special configuration suppresses the shuttle effect while allowing polysulfide diffusion within the interior of the wrapped composite particles. As a result, the wrapped cathode for lithium-sulfur batteries greatly improves the Coulombic efficiency and cycle life. Importantly, the capacity decay of the cell at 1000 cycles is as small as 0.03% per cycle at 1672 mA g
.To suppress the polysulfide shuttling effect in Li-S batteries, here the authors report a carbon/sulfur composite cathode with a wrapping layer that overcomes the trade-off between limiting polysulfide diffusion and allowing electrolyte infiltration, and affords extraordinary cycling stability.
Oxidative dehydrogenation of propane to olefins is a promising alternative route to industrialized direct dehydrogenation, but encounters the difficulty in selectivity control for olefins because of ...the overoxidation reactions that produce a substantial amount of undesired CO2. Here we report edge‐hydroxylated boron nitride, a metal‐free catalyst, that efficiently catalyzed dehydrogenation of propane to propylene with superior selectivity (80.2 %) but with only negligible CO2 formation (0.5 %) at a given propane conversion of 20.6 %. Remarkable stability was evidenced by the operation of a 300 h test with steady conversion and product selectivity. The active BNO. site, generated dynamically through hydrogen ion of B−OH groups by molecular oxygen, triggered propane dehydrogenation by selectively breaking the C−H bond but simultaneously shut off the pathway of propylene overoxidation towards CO2.
Olefin generation without a metal: Edge‐hydroxylated boron nitride shows superior selectivity for the oxidative dehydrogenation of propane to propylene with only negligible CO2 formation. The dynamically generated active BNO. site triggers propane dehydrogenation by selectively breaking the C−H bond by concomitantly avoiding propylene oxidation to CO2.
We report engineered hollow core–shell interlinked carbon spheres that consist of a mesoporous shell, a hollow void, and an anchored carbon core and are expected to be ideal sulfur hosts for ...overcoming the shortage of Li–S batteries. The hollow core–shell interlinked carbon spheres were obtained through solution synthesis of polymer spheres followed by a pyrolysis process that occurred in the hermetical silica shell. During the pyrolysis, the polymer sphere was transformed into the carbon core and the carbonaceous volatiles were self-deposited on the silica shell due to the blocking effect of the hermetical silica shell. The gravitational force and the natural driving force of lowering the surface energy tend to interlink the carbon core and carbon/silica shell, resulting in a core–shell interlinked structure. After the SiO2 shell was etched, the mesoporous carbon shell was generated. When used as the sulfur host for Li–S batteries, such a hierarchical structure provides access to Li+ ingress/egress for reactivity with the sulfur and, meanwhile, can overcome the limitations of low sulfur loading and a severe shuttle effect in solid carbon-supported sulfur cathodes. Transmission electron microscopy and scanning transmission electron microscopy images provide visible evidence that sulfur is well-encapsulated in the hollow void. Importantly, such anchored-core carbon nanostructures can simultaneously serve as a physical buffer and an electronically connecting matrix, which helps to realize the full potential of the active materials. Based on the many merits, carbon–sulfur cathodes show a high utilization of sulfur with a sulfur loading of 70 wt % and exhibit excellent cycling stability (i.e., 960 mA h g–1 after 200 cycles at a current density of 0.5 C).
This review focuses on the synthesis, protection, functionalization, and application of magnetic nanoparticles, as well as the magnetic properties of nanostructured systems. Substantial progress in ...the size and shape control of magnetic nanoparticles has been made by developing methods such as co‐precipitation, thermal decomposition and/or reduction, micelle synthesis, and hydrothermal synthesis. A major challenge still is protection against corrosion, and therefore suitable protection strategies will be emphasized, for example, surfactant/polymer coating, silica coating and carbon coating of magnetic nanoparticles or embedding them in a matrix/support. Properly protected magnetic nanoparticles can be used as building blocks for the fabrication of various functional systems, and their application in catalysis and biotechnology will be briefly reviewed. Finally, some future trends and perspectives in these research areas will be outlined.
Particularly attractive: Magnetic nanoparticles can be prepared and protected against corrosion in a variety of ways (Scheme: polystyrene (PS) coating of MnFe2O4 particles by atom‐transfer radical polymerization). The protected magnetic nanoparticles can be further functionalized for many applications including catalysis and biotechnology.
The atmospheric CO2 concentration continues a rapid increase to its current record high value of 416 ppm for the time being. It calls for advanced CO2 capture technologies. One of the attractive ...technologies is physical adsorption‐based separation, which shows easy regeneration and high cycle stability, and thus reduced energy penalties and cost. The extensive research on this topic is evidenced by the growing body of scientific and technical literature. The progress spans from the innovation of novel porous adsorbents to practical separation practices. Major CO2 capture materials include the most widely used industrially relevant porous carbons, zeolites, activated alumina, mesoporous silica, and the newly emerging metal‐organic frameworks (MOFs) and covalent‐organic framework (COFs). The key intrinsic properties such as pore structure, surface chemistry, preferable adsorption sites, and other structural features that would affect CO2 capture capacity, selectivity, and recyclability are first discussed. The industrial relevant variables such as particle size of adsorbents, the mechanical strength, adsorption heat management, and other technological advances are equally important, even more crucial when scaling up from bench and pilot‐scale to demonstration and commercial scale. Therefore, we aim to bring a full picture of the adsorption‐based CO2 separation technologies, from adsorbent design, intrinsic property evaluation to performance assessment not only under ideal equilibrium conditions but also in realistic pressure swing adsorption processes.
Divide and conquer: This Review discusses the recent advances in adsorption‐based CO2 separation technology, from porous materials synthesis, adsorbents’ intrinsic property evaluation to performance assessments not only in view of the ideal equilibrium conditions but also in critically practical perspective.
Novel multifunctional composites composed of highly dispersed nanosized Fe2O3 particles, a tubular mesoporous carbon host, and a conductive polypyrrole (PPy) sealing layer are hierarchically ...assembled via two facile processes, including bottom‐up introduction of Fe2O3 nanoparticles in tubular mesoporous carbons, followed by in situ surface sealing with the PPy coating. Fe2O3 particles are well‐dispersed within the carbon matrix and PPy is spatially and selectively coated onto the external surface and the pore entrances of the Fe2O3@C composite, thereby bridging the composite particles together into a larger unit. As an anode material for Li‐ion batteries (LIBs), the PPy‐coated Fe2O3@C composite exhibits stable cycle performance. Additionally, the PPy‐coated Fe2O3@C composite also possesses fast electrode reaction kinetics, high Fe2O3 use efficiency, and large volumetric capacity. The excellent electrochemical performance is associated with a synergistic effect of the highly porous carbon matrix and the conducting PPy sealing layer. Such multifunctional configuration prevents the aggregation of NPs and maintains the structural integrity of active materials, in addition to effectively enhancing the electronic conductivity and warranting the stability of as‐formed solid electrolyte interface (SEI) films. This nanoengineering strategy might open new avenues for the design of other multifunctional composite architectures as electrode materials in order to achieve high‐performance LIBs.
Novel multifunctional composites composed of highly dispersed nanosized Fe2O3 particles, a tubular mesoporous carbon host, and a conductive polypyrrole sealing layer are hierarchically assembled according to the different functions of each component, which are nanoengineered to improve the reversible capacity and cycle stability of Fe2O3‐based anodes.
Adsorptive separation is an appealing technology for propylene and propane separation; however, the challenge lies in the design of efficient adsorbents which can distinguish the two molecules having ...very similar properties. Here we report a kinetically amplified separation by creating wiggling mesopores in structurally robust carbon monoliths. The wiggling mesopores with alternating wide and narrow segments afford a surface area of 413 m2 g−1 and a tri‐modal pore size distribution centered at 1.5, 4.2 and 6.6 nm, respectively. The synergistically kinetic and equilibrium effects were observed and quantitatively assessed, which together ensured a remarkable propylene/propane selectivity up to 39. This selectivity outperformed not only the available carbon adsorbents but also highly competitive among the dominated crystalline porous adsorbents. In addition, the wiggling mesoporous carbon adsorbent showed excellent dynamical separation stability, which ensured its great potential in practical molecular separations.
Wiggling mesopores in monolithic carbon adsorbents lead to synergistic kinetic and equilibrium effects, allowing highly selective C3H6/C3H8 separation under practical dynamic conditions.
Microporous carbon sheets with precisely controlled thickness, narrow pores, short diffusion paths, high electrical conductive networks, and good wettability are synthesized using very low amounts of ...graphene sheets as a shape‐directing agent via an ionic liquid‐assisted surface coating method. When used as the electrode for supercapacitors, the sheets demonstrate excellent rate capability, good cycle stability, high specific capacitance, and high energy/power density.
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