首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Ti‐doped FeOOH quantum dots (QD) decorated on graphene (GN) sheets are designed and fabricated by a facile and scalable synthesis route. Importantly, the Ti‐doped FeOOH QD/GN are successfully dispersed within bacterial cellulose (BC) substrate as bending anode with large loading mass for flexible supercapacitor. By virtue of its favorable architecture, this composite electrode exhibits a remarkable areal capacitance of 3322 mF cm?2 at 2 mA cm?2, outstanding cycle performance (94.7% capacitance retention after 6000 cycles), and excellent mechanical strength (68.7 MPa). To push the energy density of flexible supercapacitors, the optimized asymmetric supercapacitor using Mn3O4/GN/BC as positive electrode and Ti‐doped FeOOH QD/GN/BC as negative electrode can be cycled reversibly in the operating voltage range of 0–1.8 V and displays ultrahigh areal energy density of 0.541 mWh cm?2, ultrahigh volumetric energy density of 9.02 mWh cm?3, reasonable cycling performance (9.4% decay in specific capacitance after 5000 cycles), and good capacitive retention at bending state.  相似文献   

2.
It is very important to exploit low‐cost and efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts for the development of renewable‐energy conversion and storage techniques. Although much attention has been made to develop efficient catalysts for ORR and OER, it is still highly desired to create new bifunctional catalysts. In this study, Co3O4 hollow polyhedrons are synthesized as efficient bifunctional electrocatalysts for ORR and OER by simple one‐step annealing Co‐centered metal–organic frameworks (ZIF‐67). Due to the large specific surface areas and high porosity, the as‐prepared Co3O4 hollow polyhedrons exhibit excellent electrocatalytic activities for ORR and OER in alkaline media. Co3O4 hollow polyhedrons show higher peak current density (0.61 mA cm?2) with four‐electron pathway than Co3O4 particles (0.39 mA cm?2), better methanol tolerance and superior durability (82.6%) than commercial Pt/C electrocatalyst (58.6%) for ORR after 25 000 s. In addition, Co3O4 hollow polyhedrons also display excellent OER performances with smaller overpotential (536 mV) for 10 mA cm?2 than Co3O4 particles (593 mV) and superior stability (86.5%) after 25 000 s. This facile one‐step strategy based on metal–organic frameworks self‐sacrificed templates can be used to develop the promising well‐defined porous hollow metal oxides electrode materials for energy conversion and storage technologies.  相似文献   

3.
A simple sucrose-assisted combustion and subsequent high-temperature calcination route have been employed to prepare hierarchical porous ZnMn2O4 nanostructure. When used as an electrode for supercapacitor, the ZnMn2O4 electrode displays a high specific capacitance of 411.75 F g?1 at a current density of 1 A g?1, remarkable capacitance retention rate of 64.28 % at current density of 32 A g?1 compared with 1 A g?1, as well as excellent cycle stability (reversible capacity retention of 88.32 % after 4000 cycles). The outstanding electrochemical performances are mainly attributed to its hierarchical porous architecture, which provides large reaction surface area, fast ion and electron transfer, and good structure stability. All these impressive results demonstrate that ZnMn2O4 shows promise for its application in supercapacitors.  相似文献   

4.
Three-dimensional hierarchical Co3O4@C hollow microspheres (Co3O4@C HSs) are successfully fabricated by a facile and scalable method. The Co3O4@C HSs are composed of numerous Co3O4 nanoparticles uniformly coated by a thin layer of carbon. Due to its stable 3D hierarchical hollow structure and uniform carbon coating, the Co3O4@C HSs exhibit excellent electrochemical performance as an anode material for lithium-ion batteries (LIBs). The Co3O4@C HSs electrode delivers a high reversible specific capacity, excellent cycling stability (1672 mAh g?1 after 100 cycles at 0.2 A g?1 and 842.7 mAh g?1 after 600 cycles at 1 A g?1), and prominent rate performance (580.9 mAh g?1 at 5 A g?1). The excellent electrochemical performance makes this 3D hierarchical Co3O4@C HS a potential candidate for the anode materials of the next-generation LIBs. In addition, this simple synthetic strategy should also be applicable for synthesizing other 3D hierarchical metal oxide/C composites for energy storage and conversion.  相似文献   

5.
A flexible Co3O4 hollow microsphere/graphene/carbon nanotube hybrid film is successfully prepared through a facile filtration strategy and a subsequent thermally treated process. The composition, morphology, and structure of the as-prepared film are characterized by X-ray diffraction, X-ray photoelectron spectrometer, scanning electron microscopy, and transmission electron microscopy. Based on the morphology characterizations on the hybrid film, the Co3O4 hollow microspheres are uniformly and closely attached on three-dimensional (3D) graphene/carbon nanotubes (GR/CNTs) network, which decreases the agglomeration of Co3O4 microspheres effectively. In this hybrid film, the 3D GR/CNT network which enhances conductance as well as prevents aggregation is a benefit to help Co3O4 to exert its lithium storage capabilities sufficiently. When used as a binder-free anode material for lithium-ion batteries, the hybrid film delivers excellent electrochemical properties involving reversible capacity (863 mAh g?1 at a current density of 100 mA g?1) and rate performance (185 mAh g?1 at a current density of 1600 mA g?1).  相似文献   

6.
The development of smart structured cathode materials for supercapacitors (SCs) has sparked tremendous interest. However, the appropriate design to achieve high capacitance and energy density-based cathode materials remains a major problem for energy storage systems. This article describes the effective synthesis of self-supported 3D micro-flowers composed of ultrathin nanowires array of Co3O4 on Ni foam (NF) using hydrothermal conditions (Co3O4@NF). The mesoporous Co3O4@NF with a high surface area, providing a rich active state for the Faraday redox reaction and increasing the diffusion rate of the electrolyte ions. The optimized Co3O4@NF-16h electrode exhibited supreme electrochemical performance by delivering a high specific capacitance of 1878, (1127) and 1200 (720 C g−1) F g−1 at 1.0 and 20 A g−1, respectively. The Co3O4@NF electrode retained good capacitance stability of 91% over 10000 cycles at 20 A g−1 with excellent rate-performance of 67% at 20 folded high current values. The obtained results for the Co3O4@NF electrode are presented the enhanced pseudocapacitive performance, indicating the substantial potential for high-performance supercapacitor applications.  相似文献   

7.
A novel approach of double hydroxide-mediated synthesis of nickel cobaltite (NiCo2O4) electro-active material by the hydrothermal method is reported. The obtained NiCo2O4 electro-active material displays the spinel cubic phase and hexagonal-like morphology. Thermogravimetry analysis confirms the thermal stability of the electrode material. The functional groups and phase formation of NiCo2O4 have been confirmed by FT-IR and Raman spectral analysis. The modified NiCo2O4 electrode exhibits the highest specific capacitance of 767.5 F g?1 at a current density of 0.5 A g?1 in 3 M KOH electrolyte and excellent cyclic stability (94 % capacitance retention after 1000 cycles at a high current density of 5 A g?1). The excellent electrochemical performance of the electrode is attributed to the hexagonal-like morphology, which contributes to the rich surface electro-active sites and easy transport pathway for the ions during the electrochemical reaction. The attractive Faradic behavior of NiCo2O4 electrode has been ascribed to the redox contribution of Ni2+/Ni3+ and Co2+/Co3+ metal species in the alkaline medium. The symmetrical two-electrode cell has been fabricated using the NiCo2O4 electro-active material with excellent electrochemical properties for supercapacitor applications.  相似文献   

8.
3D reduced graphene oxide (rGO)‐wrapped Ni3S2 nanoparticles on Ni foam with porous structure is successfully synthesized via a facile one‐step solvothermal method. This unique structure and the positive synergistic effect between Ni3S2 nanoparticles and graphene can greatly improve the electrochemical performance of the NF@rGO/Ni3S2 composite. Detailed electrochemical measurements show that the NF@rGO/Ni3S2 composite exhibits excellent supercapacitor performance with a high specific capacitance of 4048 mF cm?2 (816.8 F g?1) at a current density of 5 mA cm?2 (0.98 A g?1), as well as long cycling ability (93.8% capacitance retention after 6000 cycles at a current density of 25 mA cm?2). A novel aqueous asymmetric supercapacitor is designed using the NF@rGO/Ni3S2 composite as positive electrode and nitrogen‐doped graphene as negative electrode. The assembled device displays an energy density of 32.6 W h kg?1 at a power density of 399.8 W kg?1, and maintains 16.7 W h kg?1 at 8000.2 W kg?1. This outstanding performance promotes the as‐prepared NF@rGO/Ni3S2 composite to be ideal electrode materials for supercapacitors.  相似文献   

9.
Porous electrode materials with large specific surface area, relatively short diffusion path, and higher electrical conductivity, which display both better rate capabilities and good cycle lives, have huge benefits for practical applications in lithium‐ion batteries. Here, uniform porous NiCo2O4 nanorods (PNNs) with pore‐size distribution in the range of 10–30 nm and lengths of up to several micrometers are synthesized through a convenient oxalate co‐precipitation method followed by a calcining process. The PNN electrode exhibits high reversible capacity and outstanding cycling stability (after 150 cycles still maintain about 650 mA h g?1 at a current density of 100 mA g?1), as well as high Coulombic efficiency (>98%). Moreover, the PNNs also exhibit an excellent rate performance, and deliver a stable reversible specific capacity of 450 mA h g?1 even at 2000 mA g?1. These results demonstrate that the PNNs are promising anode materials for high‐performance Li‐ion batteries.  相似文献   

10.
《Current Applied Physics》2019,19(7):794-803
Cobalt oxide and manganese oxides are promising electrode materials amongst the transition metal oxides (TMOs) for pseudocapacitors. The lack of reversibility and deterioration of capacitance at higher current densities is major flaw in Co3O4 as an electrode for supercapacitor while MnO2 suffers from low electrical conductivity and poor cycling stability. It is inevitable to bridge the performance gap between these two TMOs to obtain a high performance supercapacitor based on environmental benign and earth abundant materials. Herein, we fabricated a hybrid triple heterostructure high-performing supercapacitor based on hexagonal sheets of Co3O4, MnO2 nanowires and graphene oxide (GO) to form a composite structure of Co3O4/MnO2/GO by all hydrothermal synthesis route. The Co3O4 square sheets serves as an excellent backbone with good mechanical adhesion with the current collector providing a rapid electronic transfer channel while the integrated nanostructure of MnO2 NW/GO permits more electrolyte ions to penetrate capably into the hybrid structure and allows effective utilization of more active surface areas. A triple heterostructured device exhibits a high areal capacitance of 3087 mF cm−2 at 10 mV s−1 scan rate along with the exceptional rate capability and cycling stability having capacitance retention of ∼170% after 5000 charge/discharge cycles. The TMOs based pseudocapacitor with the conducting scaffolds anchoring based on graphene derivatives like this will pave an encouraging alternatives for next generation energy storage devices.  相似文献   

11.
《Current Applied Physics》2018,18(11):1399-1402
Nanorod films of cobalt oxide (Co3O4) have been grown by a unique oblique angle deposition (OAD) technique in an e-beam evaporator for supercapacitor electrode applications. This technique offers a non-chemical route to achieve large aspect ratio nanorods. The fabricated electrodes at OAD 80° exhibited a specific capacitance of 2875 F/g. The electrochemically active surface area was 1397 cm−2, estimated from the non-Faradaic capacitive current region. Peak energy and power densities obtained for Co3O4 nanorods were 57.7 Wh/Kg and 9.5 kW/kg, respectively. The Co3O4 nanorod electrode showed a good endurance of 2000 charge-discharge cycles with 62% retention. The OAD approach for fabricating supercapacitor nanostructured electrodes can be exploited for the fabrication of a broad range of metal oxide materials.  相似文献   

12.
Rechargeable Li‐O2 batteries are promising candidates for electric vehicles due to their high energy density. However, the current development of Li‐O2 batteries demands highly efficient air cathode catalysts for high capacity, good rate capability, and long cycle life. In this work, a hydrothermal‐calcination method is presented to prepare a composite of Co3O4 hollow nanoparticles and Co organic complexes highly dispersed on N‐doped graphene (Co–NG), which acts as a bifunctional air cathode catalyst to optimize the electrochemical performances of Li‐O2 batteries. Co–NG exhibits an outstanding initial discharge capacity up to 19 133 mAh g?1 at a current density of 200 mA g?1. In addition, the batteries could sustain 71 cycles at a cutoff capacity of 1000 mAh g?1 with low overpotentials at the current density of 200 mA g?1. Co–NG composites are attractive as air cathode catalysts for rechargeable Li‐O2 batteries.  相似文献   

13.
High-quality monodisperse multiporous hierarchical micro/nanostructured ZnCo2O4 microspheres have been fabricated by calcinating the Zn1/3Co2/3CO3 precursor prepared by urea-assisted solvothermal method. The as-prepared products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) measurement to study the crystal phase and morphology. When tested as anode material for lithium ion batteries, the multiporous ZnCo2O4 microspheres exhibit an initial discharge capacity of 1,369 mAh g?1 (3,244.5 F cm?3) and retain stable capacity of 800 mAh g?1 (1,896 F cm?3) after 30 cycles. It should be noted that the good electrochemical performances can be attributed to the porous structure composed of interconnected nanoscale particles, which can promote electrolyte diffusion and reduce volume change during discharge/charge processes. More importantly, this ZnCo2O4 3D hierarchical structures provide a large number of active surface position for Li+ diffusion, which may contribute to the improved electrochemical performance towards lithium storage.  相似文献   

14.
A dandelion-like mesoporous Co3O4 was fabricated and employed as anode materials of lithium ion batteries (LIBs). The architecture and electrochemical performance of dandelion-like mesoporous Co3O4 were investigated through structure characterization and galvanostatic charge/discharge test. The as-prepared dandelion-like mesoporous Co3O4 consisted of well-distributed nanoneedles (about 40 nm in width and about 5 μm in length) with rich micropores. Electrochemical experiments illustrated that the as-prepared dandelion-like mesoporous Co3O4 as anode materials of LIBs exhibited high reversible specific capacity of 1430.0 mA h g?1 and 1013.4 mA h g?1 at the current density of 0.2 A g?1 for the first and 100th cycle, respectively. The outstanding lithium storage properties of the as-prepared dandelion-like mesoporous Co3O4 might be attributed to its dandelion-like mesoporous nanostructure together with an open space between adjacent nanoneedle networks promoting the intercalation/deintercalation of lithium ions and the charge transfer on the electrode. The enhanced capacity as well as its high-rate capability made the as-prepared dandelion-like mesoporous Co3O4 to be a good candidate as a high-performance anode material for LIBs.  相似文献   

15.
The amorphous Co3O4 nanostructure, which adopted sodium hexametaphosphate as structure-directing agent, has been successfully synthesized in large scale via two steps: preparation of the precursor and the calcination process. The results of X-ray diffraction indicate that the prepared materials are mainly composed of Co3O4; the formless Co3O4 nanoplate with loose structures is observed by scanning electron microscopy. Cyclic voltammetry, chronopotentiometry, and electrochemical impedance measurements are applied in a mild aqueous electrolyte (2 mol L?1 KOH) to investigate the performance of the Co3O4, which show a high specific capacitance (SC) of 482.61 F g?1 at 5 mA cm?2. Besides, the SC degradation is only 10.05 % after 250 continuous charge–discharge cycles at 5 mA cm?2, indicating an excellent electrochemical stability. The improved performance is reasonably ascribed to their irregular structure for ionic transport during the electrochemical reaction, which presents as promising candidates for supercapacitors.  相似文献   

16.
A Co3O4/vapor-grown carbon fiber (VGCF) hybrid material is prepared by a facile approach, namely, via liquid-phase carbonate precipitation followed by thermal decomposition of the precipitate at 380 °C for 2 h in argon gas flow. The material is characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller specific surface area analysis, and carbon elemental analysis. The Co3O4 in the hybrid material exhibits the morphology of porous submicron secondary particles which are self assembled from enormous cubic-phase crystalline Co3O4 nanograins. The electrochemical performance of the hybrid as a high-capacity conversion-type anode material for lithium-ion batteries is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic discharge/charge methods. The hybrid material demonstrates high specific capacity, good rate capability, and good long-term cyclability, which are far superior to those of the pristine Co3O4 material prepared under similar conditions. For example, the reversible charge capacities of the hybrid can reach 1100–1150 mAh g?1 at a lower current density of 0.1 or 0.2 A g?1 and remain 600 mAh g?1 at the high current density of 5 A g?1. After 300 cycles at 0.5 A g?1, a high charge capacity of 850 mAh g?1 is retained. The enhanced electrochemical performance is attributed to the incorporated VGCFs as well as the porous structure and the smaller nanograins of the Co3O4 active material.  相似文献   

17.
Co3O4 nanoplate/graphene sheet composites were prepared through a two-step synthetic method. The composite material as prepared was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The platelet-like morphology of Co3O4 leads to a layer-by-layer-assembled structure of the composites and a good dispersion of Co3O4 nanoplates on the surface of graphene sheets. The electrochemical characteristics indicate that the specific capacitance of the composites is 337.8 F?g?1 in comparison with the specific capacitance of 204.4 F?g?1 without graphene sheets. Meanwhile, the composites have an excellent rate capability and cycle performance. The results show that the unique microstructure of the composites enhances the electrochemical capacitive performance of Co3O4 nanoplates due to the three-dimensional network of graphene sheets for electron transport increasing electric conductivity of the electrode and providing unobstructed pathways for ionic transport during the electrochemical reaction.  相似文献   

18.
ZnCo2O4 nanoflakes were directly grown on Ni foam via a two-step facile strategy, involving cathodic electrolytic electrodeposition (ELD) method and followed by a thermal annealing treatment step. The results of physical characterizations exhibit that the mesoporous ZnCo2O4 nanoflakes have large electroactive surface areas (138.8 m2 g?1) and acceptable physical stability with the Ni foam, providing fast electron and ion transport sites. The ZnCo2O4 nanoflakes on Ni foam were directly used as integrated electrodes for supercapacitors and their electrochemical properties were measured in 2 M KOH aqueous solution. The ZnCo2O4 nanoflake electrode exhibits a high capacitance of 1781.7 F g?1 at a current density of 5 A g?1 and good rate capability (62% capacity retention at 50 A g?1). Also, an excellent cycling ability at various current densities from 5 to 50 A g?1 was obtained and 92% of the initial capacitance maintained after 4000 cycles. The results demonstrate that the proposed synthesis route is cost-effective and facile and can be developed for preparation of electrode materials in other electrochemical supercapacitors.  相似文献   

19.
A facile strategy is developed to fabricate bicomponent CoO/CoFe2O4‐N‐doped graphene hybrids (CoO/CoFe2O4‐NG). These hybrids are demonstrated to be potential high‐performance anodes for lithium‐ion batteries (LIBs). The CoO/CoFe2O4 nanoplatelets are finely dispersed on the surface of N‐doped graphene nanosheets (CoO/CoFe2O4‐NG). The CoO/CoFe2O4‐NG electrode exhibits ultrahigh specific capacity with 1172 mA h g?1 at 500 mA g?1 and 970 mA h g?1 at 1000 mA g?1 as well as excellent cycle stability due to the synergetic effects of N‐doped graphene and CoO/CoFe2O4 nanoplatelets. The well‐dispersed bicomponent CoO/CoFe2O4 is responsible for the high specific capacity. The N‐doped graphene with high specific surface area has dual roles: to provide active sites for dispersing the CoO/CoFe2O4 species and to function as an electrical conducting matrix for fast charge transfer. This method provides a simple and efficient way to configure the hybridized electrode materials with high lithium storage capacity.  相似文献   

20.
3D vertically aligned carbon nanotubes (CNTs)/NiCo2O4 core/shell structures are successfully synthesized as binder‐free anode materials for Li‐ion batteries (LIBs) via a facile electrochemical deposition method followed by subsequent annealing in air. The vertically aligned CNTs/NiCo2O4 core/shell structures are used as binder‐free anode materials for LIBs and exhibit high and stable reversible capacity (1147.6 mAhg?1 at 100 mAg?1), excellent rate capability (712.9 mAh g?1 at 1000 mAg?1), and good cycle stability (no capacity fading over 200 cycles). The improved performance of these LIBs is attributed to the unique 3D vertically aligned CNTs/NiCo2O4 core/shell structures, which support high electron conductivity, fast ion/electron transport in the electrode and at the electrolyte/electrode interface, and accommodate the volume change during cycling. Furthermore, the synthetic strategy presented can be easily extended to fabricate other metal oxides with a controlled core/shell structure, which may be a promising electrode material for high‐performance LIBs.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号