Interconnected Carbon Nanosheets Research Articles

Nitrogen, Sulfur, Phosphorous Co‐doped Interconnected Porous Carbon Nanosheets with High Defect Density for Enhancing Supercapacitor and Lithium‐Ion Battery Properties

AbstractPorous carbon nanosheets with open 2D nanostructure have been considered a desirable and high‐efficient energy‐storage material. Herein, N, S, P co‐doped interconnected porous carbon nanosheets (CPCNs) with high defect density and open 2D ultrathin nanostructure are prepared by using a cork‐shaped soybean aerogel as carbon source. A reasonable design of the preparation technology controls the formation of the distinctive and ordered structure of intermediates during the synthetic process. The as‐prepared CPCN material is made of interconnected nanosheets with a thickness of 4.9 nm and have a maximum N‐dopant content of 5.83 at. % and a high specific surface area of 3586 m2 g−1. Due to the synergistic effects of the features, the CPCN electrode for supercapacitors has a high capacitance of 427 F g−1 with a long cycling stability of 97.42 % after 10 000 cycles. For lithium‐ion batteries, the CPCN material also exhibits an excellent capacity of 1220 mAh g−1 at 100 mA g−1 with a high rate capability and cycling stability. Moreover, a scenario through using CPCN to enhance the electrochemical performance of nano‐inorganic material proves a high scalability in the application for the products.

Construction of 3D Carbon Nanostructure: Carbon Nanosheets Decorated Carbon Nanofiber As a Three-Dimensional Carbon Hybrid for High Performance Lithium-Sulfur Battery

Among the emerging energy storage methods, lithium-sulfur battery (LiS) has drawn plenty of attentions due to its high theoretical energy density (2600 Wh kg-1),1 economical cost and environmental benignity. Nevertheless, the insulating nature of sulfur and notorious polysulfides shuttling result in a low sulfur utilization and short cycling life.2 To address these problems, carbon material has been confirmed as an ideal sulfur host to promote LiS’s performance because of their low cost, high conductivity and controllable structure such as carbon spheres, carbon nanotube/fibers and carbon nanosheets. For example, one-dimensional carbon nanotube can increase the sulfur utilization by providing better electrical conductivity. However, its “open-to-electrolyte” structures cannot effectively prevent shuttling effect.3 As for zero-dimension carbon materials, core/yolk shell carbon spheres in particular, are less capable of establishing conductive networks, which in turns, compromise the sulfur utilization and rate capability.4 Thus, it is of great necessity to develop three-dimensional (3D) carbon materials with multiple functions in order to achieve high-performance lithium-sulfur batteries. Along this line, we prepared a three-dimensional carbon nanosheets modified carbon nanofiber (3DCNF) as high porosity sulfur host. After decorated with vertically aligned carbon nanosheets, the surface area of pristine carbon nanofiber was dramatically increased from 30 m2/g to 500 m2/g due to the expanded dimension. Although both 1D nanofiber and 2D nanosheets cannot effectively prevent polysulfides shuttling by themselves, the delicate combination of them endows new functions, where 3D carbon hybrid is capable of accommodating sulfur expansion and deterring polysulfides dissolution by the hierarchical porous structure and interconnected carbon nanosheets. At the same time, the 3D porous carbon nanofiber can also form conductive network that allows rapid electron transfer. With the structural advantages, the 3DCNF and sulfur composite delivered a capacity as high as 1266, 977 mAh/g at 0.1 and 0.5 C, respectively. After 500 cycles at 0.5 C, it still retains a capacity of 607 mAh/g (0.07% capacity fading per cycle), exhibiting excellent cycling capability. Reference M. K. Song, E. J. Cairns and Y. Zhang, Nanoscale, 2013, 5, 2186-2204.Y. Yang, G. Zheng and Y. Cui, Chem. Soc. Rev., 2013, 42, 3018-3032.X. Liang, Z. Wen, Y. Liu, H. Zhang, J. Jin, M. Wu and X. Wu, J. Power Sources, 2012, 206, 409-413.Y. J. Hong, J.-K. Lee and Y. Chan Kang, J. Mater. Chem. A, 2017, 5, 988-995. Figure 1

Battery-supercapacitor hybrid device based on agarics-derived porous nitrogen-doped carbon and 3D branched nanoarchitectures CNTs/Ni(OH)2

Design and fabrication of electrochemical energy storage systems with both high energy and power densities are of great importance. The battery-supercapacitor hybrid device (BSH), as one of these systems, has attracted enormous attentions. In this study, a battery-supercapacitor hybrid device was successfully fabricated by using the resultant 3D branched nanoarchitectures carbon nanotubes/Ni(OH)2 (CNTs/Ni(OH)2) as a positive electrode and the hierarchically porous, nitrogen-doped, interconnected carbon nanosheets (HPN-CNS) as the negative electrodes, respectively. HPN-CNS were prepared from agaric through simultaneous carbonization, activation, and nitrogen-doping method, while 3D branched nanoarchitectures CNTs/Ni(OH)2 were prepared by deposited Ni(OH)2 nanosheets on the highly conductive CNTs by a single-step chemical bath deposition. Because of their unique structure, both of the two materials exhibited excellent electrochemical performance. The as-assembled BSH delivered a high energy density of 34 W h kg-1 along with power density of 0.8 kW kg−1, even at the power density of 16 kW kg−1, energy density still hold at 22.2 W h kg-1 with the high potential window of 1.6 V. Furthermore, the device showed a good cycling stability with capacitance retention of 75% after 2000 cycles. Such results showed that HPN-CNS and CNTs/Ni(OH)2 could be expected to serve as promising candidates for assembling high-performance BSH devices.

Electrostatic interaction in electrospun nanofibers: Double-layer carbon protection of CoFe2O4 nanosheets enabling ultralong-life and ultrahigh-rate lithium ion storage

There are crucial demands for high power density and long-term cycling performance of Li-ion batteries (LIBs), and the development of stable electrode material operating at high current densities still remains a challenge. Here we develop a novel strategy for the synthesis of flexible N-doped carbon nanofiber/CoFe2O4 film (CoFe2O4@N-CNF) with a double-layer carbon protection by electrospinning, which possesses stable carbon shell and honeycomb-like core with CoFe2O4 nanosheets embedded into conductive and interconnected carbon nanosheets. The unique structure is beneficial for providing robust structural stability upon long-term cycling, and offering nitrogen-rich interconnected mesoporous and conductive carbon matrix for fast charge and ion transport. As a consequence, the optimized CoFe2O4@N-CNF exhibits a high reversible capacity of 858 mAh g−1 at 0.1 A g−1, excellent rate capability (306 mAh g−1 at 30 A g−1), and superior cycling stability up to 10,000 cycles with almost no capacity loss at 10 A g−1. We believe that this proposed methodology has a profound impact on drastic improvements of various flexible energy storage devices.

Self N-Doped Porous Interconnected Carbon Nanosheets Material for Supercapacitors

Self N-Doped Porous Interconnected Carbon Nanosheets Material for Supercapacitors

Template-free synthesis of interconnected carbon nanosheets via cross-linking coupled with annealing for high-efficiency triiodide reduction

A facile and template-free strategy was developed for the synthesis of interconnected carbon nanosheets with a power conversion efficiency of 8.71% as a counter electrode, outperforming a Pt reference (7.24%).

Self-templated synthesis of interconnected porous carbon nanosheets with controllable pore size: Mechanism and electrochemical capacitor application

Interconnected porous carbon nanosheets (IPCNs) are promising candidates for use as the electrode materials of electrochemical capacitors, as adsorbents, and as catalytic supports because of their high surface area, efficient ion transport, and three-dimensional (3D) structure. Herein, IPCNs with easily adjustable pore-size distributions, ranging from micro- to mesoporous, are synthesized by the carbonization of alkali metal citrates in a single-step self-templating process. Microporous, mesoporous, and hierarchical micro/mesoporous IPCNs are produced by empolying potassium citrate, sodium citrate, and their mixtures, respectively. Particularly, the hierarchical micro/mesoporous IPCNs derived from the mixture of potassium and sodium citrates in a weight ratio of 8:2 exhibit good electrochemical performance, including high specific capacitance (∼200 F/g at 5 mV/s) and excellent rate capability and cyclability. In addition, the structural changes in the carbon materials produced using pyrolysis are thoroughly studied, and the mechanism of IPCN formation is elucidated. The study on the synthetic mechanism of IPCNs provides an important guidance for designing superb porous carbon materials possessing desirable pore structures and particle morphologies for a variety of applications.

Controlled Fabrication of Interconnected Porous Carbon Nanosheets for Supercapacitors with a Long Cycle Life

AbstractThe pursuit of promising precursors and simple preparation approaches boosts the development of sustainable carbon‐related energy systems. In this work, a relatively low‐cost and eco‐friendly ternary precursor system is presented for the fabrication of interconnected sheet‐structured porous carbon materials by the combination of template‐assisted pyrolysis and post‐activation. The variation of effect factors permitted the formation of tunable microstructures with multilevel pore channels, and the optimized sample (APC3‐700) with multiple desired properties (such as, large surface area, hierarchical interconnected pores, and nitrogen doping) was successfully synthesized. Due to the large electrode/electrolyte interface, short pathway for mass/charge transfer, high electrochemical activity, and low transport resistance, APC3‐700 proved to be a favorable material with high capacitance (225 F g−1 at 1 A g−1) and a high rate profile (remaining 91 % at 20 A g−1). In particular, the symmetrical supercapacitor assembled demonstrated a long cycle life with almost no capacitance decaying over 20 000 cycles. The method used may be employed for the widespread development of nanosheet‐connected carbon materials from different sources for efficient enhancement of energy storage.

Top-down synthesis of interconnected two-dimensional carbon/antimony hybrids as advanced anodes for sodium storage

Nanoparticle-based electrode materials have sparked enormous excitement in the sodium-ion battery community because of potentially fast transport kinetics. However, they may suffer from many challenging static and dynamic problems, such as agglomeration of nanoparticles, high contact resistance, volume change, and instability of solid electrolyte interphase. Herein, we develop inter-connected 2D carbon nanosheets in which ultrasmall 0D Sb nanodots are embedded homogenously through a previously unexplored “top-down” strategy. Starting from the laminar structure K3Sb3P2O14, H3Sb3P2O14 nanosheets are exfoliated by ion exchange and then serve as templates for the synthesis of carbon sheets and Sb nanodots. Such combination of multi-dimensional and multi-scale nanostructures in the electrode materials lead to excellent electron/ion transport kinetics and pronounced integrity of the electrode structure on cycling, providing a promising pathway for developing advanced electrode materials in terms of reversibility, rate capability and cycle life.

Ultrasmall Fe2GeO4 nanodots anchored on interconnected carbon nanosheets as high-performance anode materials for lithium and sodium ion batteries

Poor intrinsic conductivity and huge volume expansion during charge/discharge process greatly limit the development of Ge-based ternary oxide as anode material for both lithium-ion batteries and sodium-ion batteries. To alleviate these issues, an ideal strategy is developed to achieve active particle nanocrystallization and composite with conductive carbon materials, simultaneously. Therefore, ultrasmall Fe2GeO4 nanodots (∼4.6nm) uniformly and tightly anchored on 3D interconnected N-doped ultrathin carbon nanosheets (3D Fe2GeO4/N-CNSs) were constructed via one-step high temperature calcination process. This unique hybrid nanostructure can not only effectively enhance electron conductivity but also restrict the aggregation and volume fluctuation of Fe2GeO4 during the charge/discharge process. As a result, the 3D Fe2GeO4/N-CNSs electrode exhibited excellent electrochemical performances for both lithium-ion and sodium-ion battery anodes. When utilized for lithium-ion battery anode, the electrode delivered a highly reversible specific capacity (1280mAhg−1 at 0.4Ag−1 after 180 cycles). It is the first time that Fe2GeO4 was applied for sodium-ion battery anode, which showed a remarkable rate capability (350mAhg−1 at 0.1Ag−1 and 180mAhg−1 at 22.8Ag−1), and ultralong cycling stability (∼86% reversible capacity retention after 6000 cycles).

Flower-like molybdenum disulfide nanosheets grown on carbon nanosheets to form nanocomposites: Novel structure and excellent electrochemical performance

A nanocomposite containing three-dimensional (3D) flower-like MoS2 nanosheets and two-dimensional (2D) interconnected carbon nanosheets was successfully prepared by a facile hydrothermal method. The nanocomposite (MC-2) containing 6% surface-functional carbon nanosheets are beneficial to inhabit the restacking of MoS2 nanosheets and form curved MoS2 nanosheets, which are grown along the vertical orientation on the carbon nanosheets. The curved MoS2 nanosheets could provide more suitable ion transport channels. The carbon nanosheets can enhance the electronic conductivity and keep the integrity of the nanocomposites. MC-2 exhibits the highest specific capacitance of 381 F/g at the current density of 1 A/g, as well as superior cyclic stability with 92% capacitance retention over 3000 cycles in KOH electrolyte. The excellent electrochemical performance of MC-2 as supercapacitor electrode is attributed to the 3D/2D structure and the synergistic effects between MoS2 nanosheets and carbon nanosheets.

Interconnected Phosphorus and Nitrogen Codoped Porous Exfoliated Carbon Nanosheets for High-Rate Supercapacitors.

Carbon-based supercapacitors have high power density and long cycle life; however, they are known to suffer from problems related to low energy density and high inner resistance. Here, we report a novel hierarchically porous functional carbon that is made up of interconnected exfoliated carbon nanosheets with thickness of a few nanometers. Notably, these porous carbon nanosheets are doped with abundant nitrogen (N) dopants in the basal plane and phosphorus (P) functional groups at the edge of the graphene lattice. The specific surface chemistry and pore structure of the synthesized sample, combined with its large specific surface area, make it a high-performance active material for supercapacitor electrode. The obtained supercapacitor made with the optimized sample showed a high specific capacitance (265 F g-1 at 0.5 A g-1) as well as long-term stability (94% capacitance retention after 5000 cycles). Particularly, the enhanced electrochemical characteristics were maintained even at high electrode mass loading (time constant (τ0) is 1.10 s for an electrode mass loading of 12.38 mg cm-2 compared to 1.61 s for a mass loading of 4.17 mg cm-2 for commercial activated carbon), which is important for a high packing factor of the capacitor.

Interconnected open-channel carbon nanosheets derived from pineapple leaf fiber as a sustainable active material for supercapacitors

The interconnected open-channel carbon nanosheets were prepared from the agro-waste pineapple leaf fiber using a simple hydrothermal technique and KOH chemical activation under heat treatment in Ar atmosphere. The obtained activated carbon showed amorphous structure with porous graphitized carbon nanosheets and a high specific surface area of 1681m2g−1. When used as an active material for supercapacitor, such natural fiber-derived carbon nanosheets revealed a high electrochemical performance (the specific capacitance was as high as 202Fg−1 at 5mVs−1 in 1M H2SO4) and a superb cycling stability even after 10,000 cycles of operation. The carbon nanosheets reported herein, therefore, represent a green energy material that combine the benefit of sustainability of an active component and the promise of high-performance energy storage device.

Synthesis of Hierarchically Porous Nitrogen‐Doped Carbon Nanosheets from Agaric for High‐Performance Symmetric Supercapacitors

Hierarchically porous, nitrogen‐doped, and interconnected carbon nanosheets (HPN‐CS) have been prepared from agaric through a one‐step method, that is, simultaneous carbonization, activation, and nitrogen‐doping. Potassium hydroxide infiltrated into the cell walls of agaric acts as an in‐built activating agent to induce a unique architecture of the resultant material. HPN‐CS have average pore diameter of 2.6 nm, specific surface area of 1565.6 m2 g−1, and high volume fraction of macro/mesopores (71.7%). It is noted that a lot of micropores with the simple pore structure are homogeneously distributed on the interconnected carbon nanosheets. The symmetric supercapacitor based HPN‐CS achieve a high operation voltage of 2.0 V and energy density of 27.2 Wh kg−1 (at a power density of 1 kW kg−1) in aqueous electrolyte of 2 m Li2SO4. Even at the power density of 50 kW kg−1 (50 times increase, a full charge–discharge within 3.2 s), energy density still holds at 20.8 Wh kg−1, indicating an excellent energy storage/release performance. In addition, the single device is able to easily light 60 light‐emitting diodes (working voltage 2.0–2.2 V) in parallel after charging for only 10 s, showing an outstanding potential in the practical applications.

Rich sulfur doped porous carbon materials derived from ginkgo leaves for multiple electrochemical energy storage devices

Based on the unique multilayered structure of ginkgo leaves, interconnected carbon nanosheets with rich micro/meso pores have been fabricated, showing excellent electrochemical performance in multiple energy storage devices.

Facile Preparation of 3D Nanostructured O/N co-Doped Porous Carbon Constructed by Interconnected Carbon Nanosheets for Excellent-Performance supercapacitors

A facile and readily scalable approach to prepare O/N co-doped 3D nanostructured foam-like porous carbon composed of interconnected carbon nanosheets (NFPCs) has been successfully explored. The NFPCs are synthesized from normal reagents including melamine resin, coal tar pitch, magnesium acetate and KOH, and firstly found that the KOH exerts a vital role in constructing the 3D foam-like nanostructure. The 3D foam-like porous carbon possesses continuous macropores, high surface area, interconnected 8nm thick carbon nanosheets, especially, a good deal of nanosized fissures in carbon nanosheets and high content of oxygen/nitrogen heteroatoms, which endow NFPCs with superior capacitive performance. The NFPC0.4-0.4Y-700 exhibits a high specific capacitance of 302Fg−1 at 5Ag−1 and high rate capability (92% retention from 5 to 50Ag−1) in 6M KOH. The NFPC0.4-0.4Y-700 symmetrical supercapacitor has presented a high energy density of 21 Wh kg−1 at 865Wkg−1 in 1M Na2SO4 electrolyte. The simple, cost-effective and scalable synthesis strategy to produce advanced nanostructured carbon materials from industrialized reagent provides a new protocol for fabricating excellent performance supercapacitors.

Hemp-Derived Activated Carbons for Electrochemical Energy Storage

Electrochemical double layer capacitors have many potential applications, including portable electronics, load leveling, and engine start-stop systems.1 Major goals in the development of electrochemical capacitors include the fabrication of devices which feature high capacitance, high power performance, long cycle life, and are suitable for applications under a variety of operational conditions. Activated carbonaceous materials which have high surface area, suitable pore volume, and tailorable pore size are promising candidates as electrode materials for electrochemical capacitors. Cost is one important issue affecting the application of high-performance activated carbonaceous materials to electrochemical energy storage applications. Hydrothermal processing, followed by either chemical or physical activation is an efficient and economical strategy to prepare activated carbonaceous materials with attractive properties. Hemp, which is an easily grown crop in certain climates, including Kentucky, is a useful industrial raw material for preparing activated carbons. Hemp bast fiber has already been utilized as a precursor for the hydrothermal process to prepare interconnected carbon nanosheets which show excellent high rate performance in electrochemical capacitors.2 Only the outside part of the hemp stem (or bast) which makes up a minor percentage of the entire hemp stem was systematically investigated.2A major portion of the hemp stem (or hurd) was not used. Moreover, a variety of synthesis parameters in the whole approach (both hydrothermal processing and activation) can influence the electrochemical performance properties of the activated carbons, especially when raw biomass is utilized as the precursor. In this study, the entire raw hemp stem is taken into full use; both activated bast (the outside fibrous part of the stem) and activated hurd (inside pulp of the stem) were prepared and demonstrated as high-performance activated carbons for electrochemical capacitors utilizing both hydrothermal and non-hydrothermal methods. Various processing factors were found to play important roles in the morphology, surface properties, and electrochemical performance of the activated carbons, i.e. hydrothermal solution, pre-hydrothermal treatment, ratio of KOH/carbon, and activation temperatures. Using a systematic study of the preparation conditions, we are able to control and tune the properties of the activated carbons and achieve excellent performance when used as electrode materials in electrochemical capacitors. This simple processing route presents great potential for preparing energy storage materials from raw biomass. In this work, activated carbonaceous materials were prepared through both hydrothermal and non-hydrothermal processing conditions, followed by either physical or chemical activation processes.3,4 Activated carbon materials having high surface area and high mesoporosity, perform well as active electrode materials in electrochemical capacitors (Figures 1a and 1b). The activated hurd achieved excellent electrochemical performance metrics, including a specific capacitance of 160 F/g, and a high energy density of 19.8 Wh/kg at a power density of 21 kW/kg. In addition, one activated hurd sample achieved > 80% specific capacitance at a discharge rate of 80 A/g, relative to the baseline achieved at 1 A/g, demonstrating the high power performance achievable with activated carbons derived from hemp.4 References 1) Winter, M.; Brodd, R. J. Chemical Reviews. 2004, 104, 4245. 2) Wang, H., et al. ACS Nano. 2013, 7 , 5131. 3) Sun, W.; Lipka, S. M.; Yang, F. “Activated Carbon Derived from hemp and Its Use in Electrochemical Capacitors.” Presented at the 228thMeeting of the Electrochemical Society, Phoenix, AZ, October 2015 (ECS abstract MA2015-02, 587). 4) Sun, W.; Lipka, S. M.; Swartz, C. R.; Williams, D.; Cheng, Y. T.; Yang, F. Hemp-derived activated carbons for supercapacitors. Carbon. 2016, 103, 181. Figure 1

Construction of nitrogen-doped porous carbon buildings using interconnected ultra-small carbon nanosheets for ultra-high rate supercapacitors

A nitrogen-doped porous carbon building (N-PCB) was constructed using interconnected ultra-small carbon nanosheets through the carbonization of biomass (Auricularia).

Nitrogen-doped interconnected carbon nanosheets from pomelo mesocarps for high performance supercapacitors

Here, we report a novel type of nitrogen-doped porous interconnected carbon nanosheets derived from an easily gained and green plant-waste (pomelo mesocarps) by simultaneous activation, carbonization and nitrogen-doped processes using CaCl2 as activating agent and urea as nitrogen source. The nitrogen-doped pomelo mesocarps-based nanosheet carbon (N-PMNC) displays an interconnected sheet-like morphology, a high specific surface area (974.6m2g−1), a porous architecture and a high nitrogen doping content (9.12wt%). The N-PMNC based supercapacitor exhibited superior electrochemical performance with high specific capacitance of 245Fg−1 at 0.5Ag−1 and excellent rate capability (72% capacitance retention ratio even at 20Ag−1) in 2molL−1 KOH electrolyte. Furthermore, N-PMNC based symmetric supercapacitor possesses high specific energy of 14.7Whkg−1 at a power density of 90Wkg−1 operated in the wide voltage range of 1.8V in aqueous neutral Na2SO4 electrolyte, and shows outstanding cyclic stability.

Nitrogen and sulfur co-doped porous carbon nanosheets derived from willow catkin for supercapacitors

A facile one-step pyrolysis and activation synthesis method is utilized to convert a common biomass of willow catkin into interconnected porous carbon nanosheets (PCNs), and then followed by effective nitrogen and sulfur co-doping. Owing to the unique hollow and multilayered structure of willow catkin fiber, the pore structure of obtained carbons can be controlled by adjusting the mass ratio of raw material to alkali. As a result, the nitrogen and sulfur co-doped PCNs demonstrate a high specific capacitance of 298Fg−1 at 0.5Ag−1 and 233Fg−1 at 50Ag−1, revealing excellent rate performance. In addition, the electrode demonstrates superb cycling stability with only 2% capacitance loss after 10,000 cycles. Furthermore, the assembled symmetric cell with a wide voltage range of 1.8V yields a remarkable specific energy of 21.0Whkg−1 at 180Wkg−1. These exciting results exhibit a green and low-cost design of electrode materials for high performance supercapacitors.