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1.
Building nanocomposite architectures based on nanocarbon materials (such as carbon nanotubes and graphene nanosheets) and metal‐oxide nanoparticles is of great interests for electrochemical energy storage. Here, an ionic‐liquid‐assisted strategy is presented to mediate the in situ growth of TiO2 nanocrystals with controlled size on carbon nanotubes and graphene, and also reduce the modified carbon supports to recover the graphitic structure simultaneously. The as‐prepared nanocomposites exhibit a highly porous and robust structure with intimate coupling between TiO2 nanocrystals and carbon supports, which offers facile ion and electron transport pathway as well as high mechanical stability. When evaluated as electrode materials for lithium‐ion batteries, the nanocomposites manifest high specific capacity, long cycling lifetime, and excellent rate capability, showing their promising application in high‐performance energy storage devices.  相似文献   

2.
Multidimensional hierarchical architecturing is a promising chemical approach to provide unique characteristics synergistically integrated from individual nanostructured materials for energy storage applications. Herein, hierarchical complex hybrid architectures of CNT‐on‐OCNT‐Fe are reported, where iron oxide nanoparticles are encapsulated inside carbon nanotube (CNT) branches grown onto the ozone‐treated surface of 3D CNT internetworked porous structures. The activated surface of the 3D ozonated CNT (OCNT) interacts with the iron oxide nanoparticles, resulting in different chemical environments of inner and outer tubes and large surface area. The mixed phases of iron oxide nanoparticles are confined by full encapsulation inside the conductive nanotubes and act as catalysts to vertically grow the CNT branches. This unique hierarchical architecture allows CNT‐on‐OCNT‐Fe to achieve a reasonable capacity of >798 mA h g?1 at 50 mA g?1, with outstanding rate capability (≈72% capacity retention at rates from 50 to 1000 mA g?1) and cyclic stability (>98.3% capacity retention up to 200 cycles at 100 mA g?1 with a coulombic efficiency of >97%). The improved rate and cyclic capabilities are attributed to the hierarchical porosity of 3D OCNT internetworks, the shielding of CNT walls for encapsulated iron oxide nanoparticles, and a proximate electronic pathway for the isolated nanoparticles.  相似文献   

3.
High capacity cathode materials for long‐life rechargeable lithium batteries are urgently needed. Selenium cathode has recently attracted great research attention due to its comparable volumetric capacity to but much better electrical conductivity than widely studied sulfur cathode. However, selenium cathode faces similar issues as sulfur (i.e., shuttling of polyselenides, volumetric expansion) and high performance lithium‐selenium batteries (Li–Se) have not yet been demonstrated at selenium loading >60% in the electrode. In this work, a 3D mesoporous carbon nanoparticles and graphene hierarchical architecture to storage selenium as binder‐free cathode material (Se/MCN‐RGO) for high energy and long life Li–Se batteries is presented. Such architecture not only provides the electrode with excellent electrical and ionic conductivity, but also efficiently suppresses polyselenides shuttling and accommodates volume change during charge/discharge. At selenium content of 62% in the entire cathode, the free‐standing Se/MCN‐RGO exhibits high discharge capacity of 655 mAh g?1 at 0.1 C (97% of theoretical capacity) and long cycling stability with a very small capacity decay of 0.008% per cycle over 1300 cycles at 1 C. The present report demonstrates significant progress in the development of high capacity cathode materials for long‐life Li batteries and flexible energy storage device.  相似文献   

4.
The development of cost‐effective and high‐performance electrocatalysts for oxygen evolution reaction (OER) is essential for sustainable energy storage and conversion processes. This study reports a novel and facile approach to the hierarchical‐structured sheet‐on‐sheet sandwich‐like nanocomposite of CoNiO x /reduced graphene oxide as highly active electrocatalysts for water oxidation. Notably, the as‐prepared composite can operate smoothly both in 0.1 and 1.0 m KOH alkaline media, displaying extremely low overpotentials, fast kinetics, and strong durability over long‐term continuous electrolysis. Impressively, it is found that its catalytic activity can be further promoted by anodic conditioning owing to the in situ generation of electrocatalytic active species (i.e., metal hydroxide/(oxy)hydroxides) and the enriched oxygen deficiencies at the surface. The achieved ultrahigh performance is unmatched by most of the transition‐metal/nonmetal‐based catalysts reported so far, and even better than the state‐of‐the‐art noble‐metal catalysts, which can be attributed to its special well‐defined physicochemical textural features including hierarchical architecture, large surface area, porous thin nanosheets constructed from CoNiO x nanoparticles (≈5 nm in size), and the incorporation of charge‐conducting graphene. This work provides a promising strategy to develop earth‐abundant advanced OER electrocatalysts to replace noble metals for a multitude of renewable energy technologies.  相似文献   

5.
Fabricating free‐standing, three‐dimensional (3D) ordered porous graphene structure can service a wide range of functional materials such as environmentally friendly materials for antibacterial medical applications and efficient solar harvesting devices. A scalable solution processable strategy is developed to create such free‐standing hierarchical porous structures composed of functionalized graphene sheets via an “on water spreading” method. The free‐standing film shows a large area uniform honeycomb structure and can be transferred onto any substrate of interest. The graphene‐based free‐standing honeycomb films exhibit superior broad spectrum antibacterial activity as confirmed using green fluorescent protein labeled Pseudomonas aeruginosa PAO1 and Escherichia coli as model pathogens. Functional nanoparticles such as titanium dioxide (TiO2) nanoparticles can be easily introduced into conductive graphene‐based scaffolds by premixing. The formed composite honeycomb film electrode shows a fast, stable, and completely reversible photocurrent response accompanying each switch‐on and switch‐off event. The graphene‐based honeycomb scaffold enhances the light‐harvesting efficiency and improves the photoelectric conversion behavior; the photocurrent of the composite film is about two times as high as that of the pure TiO2 film electrode. Such composite porous films combining remarkably good electrochemical performance of graphene, a large electrode/electrolyte contact area, and excellent stability during the photo‐conversion process hold promise for further applications in water treatment and solar energy conversion.  相似文献   

6.
Lithium‐oxygen (Li‐O2) batteries are one of the most promising candidates for high‐energy‐density storage systems. However, the low utilization of porous carbon and the inefficient transport of reactants in the cathode limit terribly the practical capacity and, in particular, the rate capability of state‐of‐the‐art Li‐O2 batteries. Here, free‐standing, hierarchically porous carbon (FHPC) derived from graphene oxide (GO) gel in nickel foam without any additional binder is synthesized by a facile and effective in situ sol‐gel method, wherein the GO not only acts as a special carbon source, but also provides the framework of a 3D gel; more importantly, the proper acidity via its intrinsic COOH groups guarantees the formation of the whole structure. Interestingly, when employed as a cathode for Li‐O2 batteries, the capacity reaches 11 060 mA h g?1 at a current density of 0.2 mA cm?2 (280 mA g?1); and, unexpectedly, a high capacity of 2020 mA h g?1 can be obtained even the current density increases ten times, up to 2 mA cm?2 (2.8 A g?1), which is the best rate performance for Li‐O2 batteries reported to date. This excellent performance is attributed to the synergistic effect of the loose packing of the carbon, the hierarchical porous structure, and the high electronic conductivity of the Ni foam.  相似文献   

7.
Hybrid metal–organic frameworks (MOFs) demonstrate great promise as ideal electrode materials for energy‐related applications. Herein, a well‐organized interleaved composite of graphene‐like nanosheets embedded with MnO2 nanoparticles (MnO2@C‐NS) using a manganese‐based MOF and employed as a promising anode material for Li‐ion hybrid capacitor (LIHC) is engineered. This unique hybrid architecture shows intriguing electrochemical properties including high reversible specific capacity 1054 mAh g?1 (close to the theoretical capacity of MnO2, 1232 mAh g?1) at 0.1 A g?1 with remarkable rate capability and cyclic stability (90% over 1000 cycles). Such a remarkable performance may be assigned to the hierarchical porous ultrathin carbon nanosheets and tightly attached MnO2 nanoparticles, which provide structural stability and low contact resistance during repetitive lithiation/delithiation processes. Moreover, a novel LIHC is assembled using a MnO2@C‐NS anode and MOF derived ultrathin nanoporous carbon nanosheets (derived from other potassium‐based MOFs) cathode materials. The LIHC full‐cell delivers an ultrahigh specific energy of 166 Wh kg?1 at 550 W kg?1 and maintained to 49.2 Wh kg?1 even at high specific power of 3.5 kW kg?1 as well as long cycling stability (91% over 5000 cycles). This work opens new opportunities for designing advanced MOF derived electrodes for next‐generation energy storage devices.  相似文献   

8.
Potassium‐ion batteries (PIBs) are a promising alternative to lithium‐ion batteries because potassium is an abundant natural resource. To date, PIBs are in the early stages of exploration and only a few anode materials have been investigated. This study reports a cobalt sulfide and graphene (CoS@G) composite as anode electrode for PIBs for the first time. The composite features interconnect quantum dots of CoS nanoclusters uniformly anchored on graphene nanosheets. The coexistence of CoS quantum dot nanoclusters and graphene nanosheets endows the composite with large surface area, highly conductive network, robust structural stability, and excellent electrochemical energy storage performance. An unprecedented capacity of 310.8 mA h g?1 at 500 mA g?1 is obtained after 100 cycles, with a rate capability better than an equivalent sodium‐ion batteries (SIBs). This work provides the evidence that PIBs can be a promising alternative to SIBs, especially at high charge–discharge rates. The development of the CoS@G anode material also provides the basis of expanding the library of suitable anode materials for PIBs.  相似文献   

9.
Engineering of controlled hybrid nanocomposites creates one of the most exciting applications in the fields of energy materials and environmental science. The rational design and in situ synthesis of hierarchical porous nanocomposite sheets of nitrogen‐doped graphene oxide (NGO) and nickel sulfide (Ni7S6) derived from a hybrid of a well‐known nickel‐based metal‐organic framework (NiMOF‐74) using thiourea as a sulfur source are reported here. The nanoporous NGO/MOF composite is prepared through a solvothermal process in which Ni(II) metal centers of the MOF structure are chelated with nitrogen and oxygen functional groups of NGO. NGO/Ni7S6 exhibits bifunctional activity, capable of catalyzing both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) with excellent stability in alkaline electrolytes, due to its high surface area, high pore volume, and tailored reaction interface enabling the availability of active nickel sites, mass transport, and gas release. Depending on the nitrogen doping level, the properties of graphene oxide can be tuned toward, e.g., enhanced stability of the composite compared to commonly used RuO2 under OER conditions. Hence, this work opens the door for the development of effective OER/HER electrocatalysts based on hierarchical porous graphene oxide composites with metal chalcogenides, which may replace expensive commercial catalysts such as RuO2 and IrO2.  相似文献   

10.
Lithium–sulfur (Li–S) batteries present one of the most promising energy storage systems owing to their high energy density and low cost. However, the commercialization of Li–S batteries is still hindered by several technical issues; the notorious polysulfide shuttling and sluggish sulfur conversion kinetics. In this work, unique hierarchical Fe3‐xC@C hollow microspheres as an advanced sulfur immobilizer and promoter for enabling high‐efficiency Li–S batteries is developed. The porous hollow architecture not only accommodates the volume variation upon the lithiation–delithiation processes, but also exposes vast active interfaces for facilitated sulfur redox reactions. Meanwhile, the mesoporous carbon coating establishes a highly conductive network for fast electron transportation. More importantly, the defective Fe3‐xC nanosized subunits impose strong LiPS adsorption and catalyzation, enabling fast and durable sulfur electrochemistry. Attributed to these structural superiorities, the obtained sulfur electrodes exhibit excellent electrochemical performance, i.e., high areal capacity of 5.6 mAh cm?2, rate capability up to 5 C, and stable cycling over 1000 cycles with a low capacity fading rate of 0.04% per cycle at 1 C, demonstrating great promise in the development of practical Li–S batteries.  相似文献   

11.
Hierarchically porous composites with mesoporous carbon wrapping around the macroporous graphene aerogel can combine the advantages of both components and are expected to show excellent performance in electrochemical energy devices. However, the fabrication of such composites is challenging due to the lack of an effective strategy to control the porosity of the mesostructured carbon layers. Here an interface‐induced co‐assembly approach towards hierarchically mesoporous carbon/graphene aerogel composites, possessing interconnected macroporous graphene networks covered by highly ordered mesoporous carbon with a diameter of ≈9.6 nm, is reported. And the orientation of the mesopores (vertical or horizontal to the surface of the composites) can be tuned by the ratio of the components. As the electrodes in supercapacitors, the resulting composites demonstrate outstanding electrochemical performances. More importantly, the synthesis strategy provides an ideal platform for hierarchically porous graphene composites with potential for energy storage and conversion applications.  相似文献   

12.
High‐performance graphene microwave absorption materials are highly desirable in daily life and some extreme situations. A simple technique for the direct growth of graphene as absorption fillers in wave‐transmitting matrices is of paramount importance to bring it to real‐world application. Herein, a simple chemical vapor deposition (CVD) route for the direct growth of edge‐rich graphene (ERG) with tailored structures and tunable dielectric properties in porous Si3N4 ceramics using only methyl alcohol (CH3OH) as precursor is reported. The large O/C atomic ratio of CH3OH helps to build a mild oxidizing atmosphere and leads to a unique structure featuring open graphite nanosteps and freestanding nanoplanes, endowing the ERG/Si3N4 hybrid with an appropriate balance between good impedance matching and strong loss capacity. Accordingly, the prepared materials exhibit superior electromagnetic wave absorption, far surpassing that of traditional CVD graphene and reduced graphene oxide‐based materials, achieving an effective absorption bandwidth of 4.2 GHz covering the entire X band, with a thickness of 3.75 mm and a negligibly low loading content of absorbents. The results provide new insights for developing novel microwave absorption materials with strong reflection loss and wide absorption frequency range.  相似文献   

13.
Aqueous dual‐ion batteries (DIBs) are promising for large‐scale energy storage due to low cost and inherent safety. However, DIBs are limited by low capacity and poor cycling of cathode materials and the challenge of electrolyte decomposition. In this study, a new cathode material of nitrogen‐doped microcrystalline graphene‐like carbon is investigated in a water‐in‐salt electrolyte of 30 m ZnCl2, where this carbon cathode stores anions reversibly via both electrical double layer adsorption and ion insertion. The (de)insertion of anions in carbon lattice delivers a high‐potential plateau at 1.85 V versus Zn2+/Zn, contributing nearly 1/3 of the capacity of 134 mAh g?1 and half of the stored energy. This study shows that both the unique carbon structure and concentrated ZnCl2 electrolyte play critical roles in allowing anion storage in carbon cathode for this aqueous DIB.  相似文献   

14.
Lithium–sulfur battery is recognized as one of the most promising energy storage devices, while the application and commercialization are severely hindered by both the practical gravimetric and volumetric energy densities due to the low sulfur content and tap density with lightweight and nonpolar porous carbon materials as sulfur host. Herein, for the first time, conductive CoOOH sheets are introduced as carbon‐free sulfur immobilizer to fabricate sulfur‐based composite as cathode for lithium–sulfur battery. CoOOH sheet is not only a good sulfur‐loading matrix with high electron conductivity, but also exhibits outstanding electrocatalytic activity for the conversion of soluble lithium polysulfide. With an ultrahigh sulfur content of 91.8 wt% and a tap density of 1.26 g cm?3, the sulfur/CoOOH composite delivers high gravimetric capacity and volumetric capacity of 1199.4 mAh g?1‐composite and 1511.3 mAh cm?3 at 0.1C rate, respectively. Meanwhile, the sulfur‐based composite presents satisfactory cycle stability with a slow capacity decay rate of 0.09% per cycle within 500 cycles at 1C rate, thanks to the strong interaction between CoOOH and soluble polysulfides. This work provides a new strategy to realize the combination of gravimetric energy density, volumetric energy density, and good electrochemical performance of lithium–sulfur battery.  相似文献   

15.
Surface modification of carbon materials plays an important role in tailoring carbon surface chemistry to specify their electrochemical performance. Here, a surface modification strategy for graphene is proposed to produce LiF‐nanoparticle‐modified graphene as a high‐rate, large‐capacity pre‐lithiated electrode for high‐power and high‐energy lithium ion batteries. The LiF nanoparticles covering the active sites of the graphene surface provide an extra Li source and act as an effective solid electrolyte interphase (SEI) inhibiter to suppress LiFP6 electrolyte decomposition reactions, affect SEI components, and reduce their thickness. Consequently, the Li‐ion diffusion is greatly sped up and the thermodynamic stability of the electrode is significantly improved. This modified graphene electrode shows excellent rate capability and improved first‐cycle coulombic efficiency, cycling stability, and ultrahigh power and energy densities accessible during fast charge/discharge processes.  相似文献   

16.
Tin oxide‐based materials attract increasing attention as anodes in lithium‐ion batteries due to their high theoretical capacity, low cost, and high abundance. Composites of such materials with a carbonaceous matrix such as graphene are particularly promising, as they can overcome the limitations of the individual materials. The fabrication of antimony‐doped tin oxide (ATO)/graphene hybrid nanocomposites is described with high reversible capacity and superior rate performance using a microwave assisted in situ synthesis in tert‐butyl alcohol. This reaction enables the growth of ultrasmall ATO nanoparticles with sizes below 3 nm on the surface of graphene, providing a composite anode material with a high electric conductivity and high structural stability. Antimony doping results in greatly increased lithium insertion rates of this conversion‐type anode and an improved cycling stability, presumably due to the increased electrical conductivity. The uniform composites feature gravimetric capacity of 1226 mAh g?1 at the charging rate 1C and still a high capacity of 577 mAh g?1 at very high charging rates of up to 60C, as compared to 93 mAh g?1 at 60C for the undoped composite synthesized in a similar way. At the same time, the antimony‐doped anodes demonstrate excellent stability with a capacity retention of 77% after 1000 cycles.  相似文献   

17.
Sn‐based materials have triggered significant research efforts as anodes for lithium‐storage because of their high theoretical capacity. However, the practical applications of Sn‐based materials are hindered by low capacity release and poor cycle life, which are mainly caused by structural pulverization and large volume changes on cycling. Herein, a surfactant‐assisted assembly method is developed to fabricate 3D nanoarchitectures in which Sn‐based nanoparticles are encapsulated by a porous graphene network. More precisely, the graphene forms a 3D cellular network, the interstices of which only partially filled by the electroactive masses, thus establishing a high concentration of interconnected nanosized pores. While the graphene‐network itself guarantees fast electron transfer, it is the characteristic presence of nanosized pores in our network that leads to the favorable rate capability and cycling stability by i) accommodating the large volume expansion of Sn‐based nanoparticles to ensure integrity of the 3D framework upon cycling and ii) enabling rapid access of Li‐ions into Sn‐based nanoparticles, which are in addition prevented from agglomerating. As a result, the 3D Sn‐based nanoarchitectures deliver excellent electrochemical properties including high rate capability and stable cycle performance. Importantly, this strategy provides a new pathway for the rational engineering of anode materials with large volume changes to achieve improved electrochemical performances.  相似文献   

18.
Freestanding carbon‐based hybrids, specifically carbon nanotube@3D graphene (CNTs@3DG) hybrid, are of great interest in electrochemical energy storage. However, the large holes (about 400 µm) in the commonly used 3D graphene foams (3DGF) constitute as high as 90% of the electrode volume, resulting in a very low loading of electroactive materials that is electrically connected to the carbon, which makes it difficult for flexible supercapacitors to achieve high gravimetric and volumetric energy density. Here, a hierarchically porous carbon hybrid is fabricated by growing 1D CNTs on 3D graphene aerogel (CNTs@3DGA) using a facile one‐step chemical vapor deposition process. In this architecture, the 3DGA with ample interconnected micrometer‐sized pores (about 5 µm) dramatically enhances mass loading of electroactive materials comparing with 3DGF. An optimized all‐solid‐state asymmetric supercapacitor (AASC) based on MnO2@CNTs@3DGA and Ppy@CNTs@3DGA electrodes exhibits high volumetric energy density of 3.85 mW h cm?3 and superior long‐term cycle stability with 84.6% retention after 20 000 cycles, which are among the best reported for AASCs with both electrodes made of pseudocapacitive electroactive materials.  相似文献   

19.
On account of increasing demand for energy storage devices, sodium‐ion batteries (SIBs) with abundant reserve, low cost, and similar electrochemical properties have the potential to partly replace the commercial lithium‐ion batteries. In this study, a facile metal‐organic framework (MOF)‐derived selenidation strategy to synthesize in situ carbon‐encapsulated selenides as superior anode for SIBs is rationally designed. These selenides with particular micro‐ and nanostructured features deliver ultrastable cycling performance at high charge–discharge rate and demonstrate ultraexcellent rate capability. For example, the uniform peapod‐like Fe7Se8@C nanorods represent a high specific capacity of 218 mAh g?1 after 500 cycles at 3 A g?1 and the porous NiSe@C spheres display a high specific capacity of 160 mAh g?1 after 2000 cycles at 3 A g?1. The current simple MOF‐derived method could be a promising strategy for boosting the development of new functional inorganic materials for energy storage, catalysis, and sensors.  相似文献   

20.
A composite material made of graphene nanoribbons and iron oxide nanoparticles provides a remarkable route to lithium‐ion battery anode with high specific capacity and cycle stability. At a rate of 100 mA/g, the material exhibits a high discharge capacity of ~910 mAh/g after 134 cycles, which is >90% of the theoretical li‐ion storage capacity of iron oxide. Carbon black, carbon nanotubes, and graphene flakes have been employed by researchers to achieve conductivity and stability in lithium‐ion electrode materials. Herein, the use of graphene nanoribbons as a conductive platform on which iron oxide nanoparticles are formed combines the advantages of long carbon nanotubes and flat graphene surfaces. The high capacity over prolonged cycling achieved is due to the synergy between an electrically percolating networks of conductive graphene nanoribbons and the high lithium‐ion storage capability of iron oxide nanoparticles.  相似文献   

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