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1.
We report the synthesis of cobalt sulfide multi‐shelled nanoboxes through metal–organic framework (MOF)‐based complex anion conversion and exchange processes. The polyvanadate ions react with cobalt‐based zeolitic imidazolate framework‐67 (ZIF‐67) nanocubes to form ZIF‐67/cobalt polyvanadate yolk‐shelled particles. The as‐formed yolk‐shelled particles are gradually converted into cobalt divanadate multi‐shelled nanoboxes by solvothermal treatment. The number of shells can be easily controlled from 2 to 5 by varying the temperature. Finally, cobalt sulfide multi‐shelled nanoboxes are produced through ion‐exchange with S2? ions and subsequent annealing. The as‐obtained cobalt sulfide multi‐shelled nanoboxes exhibit enhanced sodium‐storage properties when evaluated as anodes for sodium‐ion batteries. For example, a high specific capacity of 438 mAh g?1 can be retained after 100 cycles at the current density of 500 mA g?1.  相似文献   

2.
Complex metal–organic frameworks used as precursors allow design and construction of various nanostructured functional materials which might not be accessible by other methods. Here, we develop a sequential chemical etching and sulfurization strategy to prepare well‐defined double‐shelled zinc–cobalt sulfide (Zn‐Co‐S) rhombic dodecahedral cages (RDCs). Yolk‐shelled zinc/cobalt‐based zeolitic imidazolate framework (Zn/Co‐ZIF) RDCs are first synthesized by a controlled chemical etching process, followed by a hydrothermal sulfurization reaction to prepare double‐shelled Zn‐Co‐S RDCs. Moreover, the strategy reported in this work enables easy control of the Zn/Co molar ratio in the obtained double‐shelled Zn‐Co‐S RDCs. Owing to the structural and compositional benefits, the obtained double‐shelled Zn‐Co‐S RDCs exhibit enhanced performance with high specific capacitance (1266 F g−1 at 1 A g−1), good rate capability and long‐term cycling stability (91 % retention over 10,000 cycles) as a battery‐type electrode material for hybrid supercapacitors.  相似文献   

3.
Unique triple‐shelled Mo‐polydopamine (Mo‐PDA) hollow spheres are synthesized through a facile solvothermal process. A sequential self‐templating mechanism for the multi‐shell formation is proposed, and the number of shells can be adjusted by tuning the size of the Mo‐glycerate templates. These triple‐shelled Mo‐PDA hollow spheres can be converted to triple‐shelled MoO2/carbon composite hollow spheres by thermal treatment. Owing to the unique multi‐shells and hollow interior, the as‐prepared MoO2/carbon composite hollow spheres exhibit appealing performance as an anode material for lithium‐ion batteries, delivering a high capacity of ca. 580 mAh g?1 at 0.5 A g?1 with good rate capability and long cycle life.  相似文献   

4.
TiO2?x with well‐controlled hollow multi‐shelled structures (HoMSs) were designed and synthesized, via a sequential templating approach (STA), to act as sulfur carrier materials. They were explored as physico‐chemical encapsulation materials. Particularly, the sulfur cathode based on triple‐shelled TiO2?x HoMSs delivered a specific capacity of 903 mAh g?1 with a capacity retention of 79 % at 0.5 C and a Coulombic efficiency of 97.5 % over 1000 cycles. The outstanding electrochemical performance is attributed to better spatial confinement and integrated conductivity of the intact triple‐shell that combine the features of physico‐chemical adsorption, short charge transfer path along with mechanical strength.  相似文献   

5.
Hierarchical hollow structures for electrode materials of supercapacitors could enlarge the surface area, accelerate the transport of ions and electrons, and accommodate volume expansion during cycling. Besides, construction of heterostructures would enhance the internal electric fields to regulate the electronic structures. All these features of hierarchical hollow heterostructures are beneficial for promoting the electrochemical properties and stability of electrode materials for high‐performance supercapacitors. Herein, CoO/Co‐Cu‐S hierarchical tubular heterostructures (HTHSs) composed of nanoneedles are prepared by an efficient multi‐step approach. The optimized sample exhibits a high specific capacity of 320 mAh g?1 (2300 F g?1) at 2.0 A g?1 and outstanding cycling stability with 96.5 % of the initial capacity retained after 5000 cycles at 10 A g?1. Moreover, an all‐solid‐state hybrid supercapacitor (HSC) constructed with the CoO/Co‐Cu‐S and actived carbon shows a stable and high energy density of 90.7 Wh kg?1 at a power density of 800 W kg?1.  相似文献   

6.
Hierarchical tubular structures composed of Co3O4 hollow nanoparticles and carbon nanotubes (CNTs) have been synthesized by an efficient multi‐step route. Starting from polymer‐cobalt acetate (Co(Ac)2) composite nanofibers, uniform polymer‐Co(Ac)2@zeolitic imidazolate framework‐67 (ZIF‐67) core–shell nanofibers are first synthesized via partial phase transformation with 2‐methylimidazole in ethanol. After the selective dissolution of polymer‐Co(Ac)2 cores, the resulting ZIF‐67 tubular structures can be converted into hierarchical CNTs/Co‐carbon hybrids by annealing in Ar/H2 atmosphere. Finally, the hierarchical CNT/Co3O4 microtubes are obtained by a subsequent thermal treatment in air. Impressively, the as‐prepared nanocomposite delivers a high reversible capacity of 1281 mAh g?1 at 0.1 A g?1 with exceptional rate capability and long cycle life over 200 cycles as an anode material for lithium‐ion batteries.  相似文献   

7.
Complex hollow structures of transition metal oxides, especially mixed metal oxides, could be promising for different applications such as lithium ion batteries. However, it remains a great challenge to fabricate well‐defined hollow spheres with multiple shells for mixed transition metal oxides. Herein, we have developed a new “penetration–solidification–annealing” strategy which can realize the synthesis of various mixed metal oxide multi‐shelled hollow spheres. Importantly, it is found that multi‐shelled hollow spheres possess impressive lithium storage properties with both high specific capacity and excellent cycling stability. Specifically, the carbon‐coated CoMn2O4 triple‐shelled hollow spheres exhibit a specific capacity of 726.7 mA h g?1 and a nearly 100 % capacity retention after 200 cycles. The present general strategy could represent a milestone in design and synthesis of mixed metal oxide complex hollow spheres and their promising uses in different areas.  相似文献   

8.
Oriented and penetrating molecular sieving membranes display enhanced separation performance. A polyimide (PI) solution containing highly dispersed ZIF‐7(III) sheets in CHCl3 was deposited on a glass side and subjected to flat‐scraping with a membrane fabricator. In this way we developed a novel oriented and penetrating ZIF‐7@PI mixed matrix membrane (MMM) with 50 wt. % ZIF‐7 loading. Because the height of the ZIF‐7 sheets (5 μm) is higher than the film thickness, every ZIF‐7 sheet penetrates both surfaces of the polyimide film. Since the ZIF‐7 channels are the dominant pathway for gas permeation, the ZIF‐7@PI MMM displays a high molecular sieve performance for the separation of H2 (0.29 nm) from larger gas molecules. At 100 °C and 2 bar, the mixture separation factors of H2/CO2 and H2/CH4 are 91.5 and 128.4, with a high H2 permeance of about 3.0×10?7 mol m?2 s?1 Pa?1, which is promising for hydrogen separation by molecular sieving.  相似文献   

9.
PDMAEMA‐b‐PMAA block copolymers were prepared by the sequential RAFT polymerization of DMAEMA and tBMA, followed by hydrolysis. Phosphotungstic acid (HPW) was anchored to the PDMAEMA blocks through electrostatic interactions and the as‐obtained HPW/PDMAEMA‐b‐PMAA was added to the synthesis of ZIF‐8. During the formation of ZIF‐8, the PMAA blocks coordinated to the Zn2+ ions through their carboxy groups, along with the HPW groups that were anchored to the PDMAEMA blocks. In this way, the block copolymer could consolidate the interactions between HPW and ZIF‐8 and prevent the leakage of HPW. Finally, the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 ternary lamellar composite was obtained and the structure of the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 hybrid material was characterized by using powder X‐ray diffraction (PXRD), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). As a photocatalyst, the HPW/PDMAEMA‐b‐PMAA/ZIF‐8 ternary lamellar composite showed excellent photoactivity for the degradation of methylene blue (MB). The rate of degradation of MB was 0.0240 min?1, which was 7.5‐times higher than that of commercially available P25 (0.0032 min?1). In the presence of H2O2, the kinetic degradation parameters of the composite reached 0.0634 min?1, which was about 19.8‐times higher than that of P25.  相似文献   

10.
The electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance owing to preferential catalyst–H formation and the consequential hydrogen evolution reaction (HER). Now, the Pt/Au electrocatalyst d‐band structure is electronically modified using zeolitic imidazole framework (ZIF) to achieve a Faradaic efficiency (FE) of >44 % with high ammonia yield rate of >161 μg mgcat?1 h?1 under ambient conditions. The strategy lowers electrocatalyst d‐band position to weaken H adsorption and concurrently creates electron‐deficient sites to kinetically drive NRR by promoting catalyst–N2 interaction. The ZIF coating on the electrocatalyst doubles as a hydrophobic layer to suppress HER, further improving FE by >44‐fold compared to without ZIF (ca. 1 %). The Pt/Au‐NZIF interaction is key to enable strong N2 adsorption over H atom.  相似文献   

11.
The facile synthesis of a porous carbon material that is doped with iron‐coordinated nitrogen active sites (FeNC‐70) is demonstrated by following an inexpensive synthetic pathway with a zeolitic imidazolate framework (ZIF‐70) as a template. To emphasize the possibility of tuning the porosity and surface area of the resulting carbon materials based on the structure of the parent ZIF, two other ZIFs, that is, ZIF‐68 and ZIF‐69, are also synthesized. The resulting active carbon material that is derived from ZIF‐70, that is, FeNC‐70, exhibits the highest BET surface area of 262 m2 g?1 compared to the active carbon materials that are derived from ZIF‐68 and ZIF‐69. The HR‐TEM images of FeNC‐70 show that the carbon particles have a bimodal structure that is composed of a spherical macroscopic pore (about 200 nm) and a mesoporous shell. X‐ray photoelectron spectroscopy (XPS) reveals the presence of Fe‐N‐C moieties, which are the primary active sites for the oxygen‐reduction reaction (ORR). Quantitative estimation by using EDAX analysis reveals a nitrogen content of 14.5 wt. %, along with trace amounts of iron (0.1 wt. %), in the active FeNC‐70 catalyst. This active porous carbon material, which is enriched with Fe‐N‐C moieties, reduces the oxygen molecule with an onset potential at 0.80 V versus NHE through a pathway that involves 3.3–3.8 e? under acidic conditions, which is much closer to the favored 4 e? pathway for the ORR. The onset potential of FeNC‐70 is significantly higher than those of its counterparts (FeNC‐68 and FeNC‐69) and of other reported systems. The FeNC‐based systems also exhibit much‐higher tolerance towards MeOH oxidation and electrochemical stability during an accelerated durability test (ADT). Electrochemical analysis and structural characterizations predict that the active sites for the ORR are most likely to be the in situ generated N? FeN2+2/C moieties, which are distributed along the carbon framework.  相似文献   

12.
Carbon aerogels (CAs) with 3D interconnected networks hold promise for application in areas such as pollutant treatment, energy storage, and electrocatalysis. In spite of this, it remains challenging to synthesize high‐performance CAs on a large scale in a simple and sustainable manner. We report an eco‐friendly method for the scalable synthesis of ultralight and superporous CAs by using cheap and widely available agarose (AG) biomass as the carbon precursor. Zeolitic imidazolate framework‐8 (ZIF‐8) with high porosity is introduced into the AG aerogels to increase the specific surface area and enable heteroatom doping. After pyrolysis under inert atmosphere, the ZIF‐8/AG‐derived nitrogen‐doped CAs show a highly interconnected porous mazelike structure with a low density of 24 mg cm?3, a high specific surface area of 516 m2 g?1, and a large pore volume of 0.58 cm?3 g?1. The resulting CAs exhibit significant potential for application in the adsorption of organic pollutants.  相似文献   

13.
Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one‐step direct carbonization of cobalt‐containing zeolitic imidazolate framework‐67 (ZIF‐67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp2‐bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge–discharge measurements. Our NPC is very promising for efficient electrodes for high‐performance supercapacitor applications. A maximum specific capacitance of 238 F g?1 is observed at a scan rate of 20 mV s?1. This value is very high compared to previous works on carbon‐based electric double layer capacitors.  相似文献   

14.
The unique features of high porosity, shape selectivity, and multiple active sites make metal–organic frameworks (MOFs) promising as novel stationary phases for high‐performance liquid chromatography (HPLC). However, the wide particle size distribution and irregular shape of conventional MOFs lead to lower column efficiency of such MOF‐packed columns. Herein, the fabrication of monodisperse MOF@SiO2 core–shell microspheres as the stationary phase for HPLC to overcome the above‐mentioned problems is reported. Zeolitic imidazolate framework 8 (ZIF‐8) was used as an example of MOFs due to its permanent porosity, uniform pore size, and exceptional chemical stability. Unique carboxyl‐modified silica spheres were used as the support to grow the ZIF‐8 shell. The fabricated monodisperse ZIF‐8@SiO2 packed columns (5 cm long × 4.6 mm i.d.) show high column efficiency (23 000 plates m?1 for bisphenol A) for the HPLC separation of endocrine‐disrupting chemicals (bisphenol A, β‐estradiol, and p‐(tert‐octyl)phenol) and pesticides (thiamethoxam, hexaflumuron, chlorantraniliprole, and pymetrozine) within 7 min with good relative standard deviations for 11 replicate separations of the analytes (0.01–0.39, 0.65–1.7, 0.70–1.3, and 0.17–0.91 % for retention time, peak area, peak height, and half peak width, respectively). The ZIF‐8@SiO2 microspheres combine the advantages of the good column packing properties of the uniform monodisperse silica microspheres and the separation ability of the ZIF‐8 crystals.  相似文献   

15.
Multi‐wall Sn/SnO2@carbon hollow nanofibers evolved from SnO2 nanofibers are designed and programable synthesized by electrospinning, polypyrrole coating, and annealing reduction. The synthesized hollow nanofibers have a special wire‐in‐double‐wall‐tube structure with larger specific surface area and abundant inner spaces, which can provide effective contacting area of electrolyte with electrode materials and more active sites for redox reaction. It shows excellent cycling stability by virtue of effectively alleviating pulverization of tin‐based electrode materials caused by volume expansion. Even after 2000 cycles, the wire‐in‐double‐wall‐tube Sn/SnO2@carbon nanofibers exhibit a high specific capacity of 986.3 mAh g?1 (1 A g?1) and still maintains 508.2 mAh g?1 at high current density of 5 A g?1. This outstanding electrochemical performance suggests the multi‐wall Sn/SnO2@ carbon hollow nanofibers are great promising for high performance energy storage systems.  相似文献   

16.
To reduce the charge‐transfer resistance of supercapacitors and achieve faster reversible redox reactions, ternary Ni‐Co‐Fe layered double hydroxide was prepared by using the urea method and then calcined to give NiCoFe oxide (NiCoFeO). To enhance conductivity, a polyaniline (PANI) conductive layer was assembled on the surface of the NiCoFeO particles by in situ oxidative polymerization of aniline monomers. The as‐prepared NiCoFeO/PANI composite was successful employed as a supercapacitor electrode. It was found that the NiCoFeO/PANI composite displayed good cycling stability, with a capacity loss of only 29.54 % after 5000 cycles. Furthermore, the NiCoFeO/PANI composite also exhibited excellent supercapacitor performance, with a high specific capacity of 843 F g?1 at a current density of 2 A g?1, whereas NiCoFeO showed a specific capacity of only 478 F g?1. This result was attributed to the synergistic effect between NiCoFeO and PANI. The facile synthesis strategy and excellent electrochemical performance suggest that NiCoFeO/PANI is a promising economical electrode material for applications in supercapacitors.  相似文献   

17.
Two‐dimensional nanosheets with high specific surface areas and fascinating physical and chemical properties have attracted tremendous interests because of their promising potentials in both fundamental research and practical applications. However, the problem of developing a universal strategy with a facile and cost‐effective synthesis process for multi‐type ultrathin 2 D nanostructures remains unresolved. Herein, we report a generalized low‐temperature fabrication of scalable multi‐type 2 D nanosheets including metal hydroxides (such as Ni(OH)2, Co(OH)2, Cd(OH)2, and Mg(OH)2), metal oxides (such as ZnO and Mn3O4), and layered mixed transition‐metal hydroxides (Ni‐Co LDH, Ni‐Fe LDH, Co‐Fe LDH, and Ni‐Co‐Fe layered ternary hydroxides) through the rational employment of a green soft‐template. The synthesized crystalline inorganic nanosheets possess confined thickness, resulting in ultrahigh surface atom ratios and chemically reactive facets. Upon evaluation as electrode materials for pseudocapacitors, the Ni‐Co LDH nanosheets exhibit a high specific capacitance of 1087 F g?1 at a current density of 1 A g?1, and excellent stability, with 103 % retention after 500 cycles. This strategy is facile and scalable for the production of high‐quality ultrathin crystalline inorganic nanosheets, with the possibility of extension to the preparation of other complex nanosheets.  相似文献   

18.
《化学:亚洲杂志》2017,12(21):2790-2793
We successfully fabricate a well‐defined inorganic/organic hybrid Cu2O@Cu/Co‐ZIF (ZIF=zeolitic imidazolate frameworks) by use of growth of dual‐metal Cu/Co‐ZIF on the obtained Cu2O hollow spheres. The key point of the strategy is coupling the in situ self‐sacrificing template. Cu2O and the coordination of metal ions (Cu+ and Co2+) with 2‐methylimidazole. This new hybrid was characterized by powder X‐ray diffraction, (scanning) transmission electron microscopy, energy‐dispersive spectroscopy mapping, in situ FT‐IR spectroscopy, UV/Vis diffuse reflection spectroscopy, N2 sorption measurements, and electron spin resonance. It was evidenced that Cu/Co‐ZIF nanocrystals have been assembled to continuous shells surrounding the Cu2O cores as well as in the voids between layers and inner pores. Cu2O@Cu/Co‐ZIF exhibits visible light responsiveness and holds potential as narrow band gap semiconductor and visible photocatalyst.  相似文献   

19.
Voltage decay and capacity fading are the main challenges for the commercialization of Li‐rich Mn‐based layered oxides (LLOs). Now, a three‐in‐one surface treatment is designed via the pyrolysis of urea to improve the voltage and capacity stability of Li1.2Mn0.6Ni0.2O2 (LMNO), by which oxygen vacancies, spinel phase integration, and N‐doped carbon nanolayers are synchronously built on the surface of LMNO microspheres. Oxygen vacancies and spinel phase integration suppress irreversible O2 release and help lithium ion diffusion, while N‐doped carbon nanolayer mitigates the corrosion of electrolyte with excellent conductivity. The electrochemical performance of LMNO after the treatment improves significantly; the capacity retention rate after 500 cycles at 1 C is still as high as 89.9 % with a very small voltage fading rate of 1.09 mV cycle?1. This three‐in‐one surface treatment strategy can suppress the voltage decay and capacity fading of LLOs.  相似文献   

20.
The electrochemical nitrogen reduction reaction (NRR) offers an energy‐saving and environmentally friendly approach to produce ammonia under ambient conditions. However, traditional catalysts have extremely poor NRR performances because of their low activity and the competitive hydrogen evolution reaction. The high catalytic activity of nanoporous gold (NPG) and the hydrophobicity and molecular concentrating effect of the zeolitic imidazolate framework‐8 (ZIF‐8) were incorporated in the NPG@ZIF‐8 nanocomposite so that the ZIF‐8 shell could weaken hydrogen evolution and retard reactant diffusion. A highest Faradaic efficiency of 44 % and an excellent rate of ammonia production of (28.7±0.9) μg h?1 cm?2 were achieved, which are superior to traditional gold nanoparticles and NPG. Moreover, the composite catalyst shows high electrochemical stability and selectivity (98 %). The superior NRR performance makes NPG@ZIF‐8 one of the most promising water‐based NRR electrocatalysts for ammonia production.  相似文献   

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