Hierarchical Porous Carbon Nanosheets Research Articles

Scalable synthesis of strutted nitrogen doped hierarchical porous carbon nanosheets for supercapacitors with both high gravimetric and volumetric performances

Porous carbon nanosheets with high specific surface area have become the most promising electrode materials for supercapacitor, but their high pore volume leads to relatively low density and poor volumetric capacitance. In this work, strutted nitrogen doped hierarchical porous carbon nanosheets (SNPCNS), featuring three-dimensional nonaggregated architecture braced by struts have successfully been scalably synthesized via a novel calcium d-gluconate-exploding technique. The pyrolysis temperature and duration, and the mass ratio of calcium d-gluconate and urea formaldehyde resin are regulated for optimizing the specific surface area, pore volume and capacitive performance of SNPCNS. The optimized SNPCNS displays high specific surface area (539 m2 g−1), rich surface heteroatoms (8.1 at.% for N) and high density (1.11 g cm−3). Therefore, the supercapacitor assembled by SNPCNS electrodes presents very high gravimetric/volumetric capacitances of 286 F g−1/317 F cm−3 (in 6 M KOH) and 355 F g−1/394 F cm−3 (in 1 M H2SO4). Importantly, high gravimetric/volumetric energy densities of 40.5 W h kg−1/44.9 W h L−1 (in ionic liquid) are achieved, which are superior to those of previously reported carbon nanosheets based symmetric supercapacitors. This work provides a new strategy for the mass and low-cost production of high-performance porous carbon nanosheets for energy storage.

Bio-inspired construction of electrocatalyst decorated hierarchical porous carbon nanoreactors with enhanced mass transfer ability towards rapid polysulfide redox reactions

Li-S batteries are considered as a highly promising candidate for the next-generation energy storage system, attributing to their tremendous energy density. However, the two-dimensional island nucleation-growth process of lithium sulfide leads to a thick insulating film covering the electrode, inducing slow electrons transfer and mass-transfer of ions and liquid sulfur species in working Li-S cells. Here, we demonstrate a bio-inspired strategy of constructing ant-nest-like hierarchical porous ultrathin carbon nanosheet networks with the implants of metallic nanoparticles electrocatalysts (HPC-MEC) as efficient nanoreactors enabling rapid mass transfer, via a simple and green NaCl template. Such nanoreactors with a large active surface area could effectively anchor polysulfides for mitigating the shuttle effect, facilitating uniformly thin Li2S film, and promoting the mass transfer for fast sulfur species conversions. This helps contribute to a continuously high sulfur utilization in Li-S batteries with the HPC-MEC reactors. As a typical exhibition, cobalt embedded hierarchical porous carbon (HPC-Co) could realize to deliver a remarkably high specific capacity of 1,540.6 mAh·g−1, an excellent rate performance of 878.8 mAh·g−1 at 2 C, and high area capacity of 11.6 mAh·cm−2 at a high sulfur load of 10 mg·cm−2 and low electrolyte/sulfur ratio of 5 µL·mg−1.

Molten salt template-assisted synthesis of N, S-codoped hierarchically porous carbon nanosheets for efficient energy storage

To enrich the type of carbons for double-layer supercapacitors and optimize their electrochemical performances, N/S co-doped hierarchical porous carbons (KISPCs) with well-balanced pore characteristic have been prepared by taking ginkgo leaf as carbon source and KCl/K2CO3 molten-salt as template/activation agent. The as-obtained carbons possess a well-developed interconnected sheet-like structure, accompanying with high N, S and O contents, conductive to abundant ions transport channels and exposure of more ions-accessible active sites. Moreover, the types and contents of surface functional groups of hierarchical porous carbon could also be adjusted by K2CO3 content. A symmetrical supercapacitor was assembled to validate its electrochemical performance. The KISPCs electrodes manifest a specific capacitance of 215.2 F g−1 at 0.05 A g−1, splendid capacitance retention of 78.9 % (169.8 F g−1 at 20 A g−1) and exceptional cycling stability with only 1.6 % capacity decay after 10000 charge/discharge cycles. This work can afford promising new tactics for the preparation of hierarchical porous carbon nanosheets and offer insights into the application of energy storage fields.

Carbon coated SiO nanoparticles embedded in hierarchical porous N-doped carbon nanosheets for enhanced lithium storage

Carbon coated SiO nanoparticles embedded in N-doped carbon nanosheets were synthesized via a scalable and cost-effective route, and exhibited enhanced cyclability and rate capability as an anode for lithium-ion batteries.

Ultrahigh surface area biomass derived 3D hierarchical porous carbon nanosheet electrodes for high energy density supercapacitors

A simple one step activation method is used to achieve an ultra-high specific surface area of 2943 m2 g−1, and abundant pore volume of 1.83 cm3 g−1 with a rational micro/meso/macro pore size distributed activated carbon nanosheets from Prosopis Juliflora wood carbon waste blocks. A superior electrochemical performance has been achieved with a specific capacitance of 588 F g-1 at 0.5 A g−1 with an excellent stability (retention 92.5% after 6000 cycles) in 6 M KOH electrolyte for a three-electrode approach. The assembled symmetric supercapacitor device outperformed in a neutral aqueous electrolyte compared to an alkaline electrolyte, such as with a gravimetric capacitance of 403 and 426 F g−1 and superior energy density of 32.9 W h kg−1 (at 172.7 W kg−1) and 56.7 W h kg−1 (at 248.8 W kg−1), and a large electrochemical window of 0–1.4 V in 6 M KOH and 0–2 V in 1 M Na2SO4 electrolyte, respectively. The electrochemical performance has been enhanced by the degree of graphitization, surface functional groups, surface area and pore structure/volume. This work provides a trustworthy approach to produce higher energy density devices from renewable biomass carbon wastes for various energy storage applications.

Template-Free Preparation of Hierarchical Porous Carbon Nanosheets for Lithium-Sulfur Battery.

Porous carbon nanosheets have the advantages of longitudinal continuity, transverse ultrathin, high specific surface area, and surface atomic activity, as well as the synergistic effect of micro and nanoproperties, so the research on their preparation, structure, and properties has attracted wide attention. A series of ultrathin hierarchical porous carbon nanosheets (HPCNs) is fabricated through carbonization of precursors obtained through the Friedel-Crafts reaction-assisted loading of polystyrene on graphene oxide. Hierarchical pore structures consist of three parts: (1) the micropores (1.3 nm), which were provided by porous polystyrene through the Friedel-Crafts reaction; (2) the mesopores (3.8 nm), which were provided by slab pores from the stack of carbon nanosheets; and (3) the pores (>5 nm) formed from the random stack of carbon nanosheets. Controlling the carbonization time and temperature adds to a prominent increase in specific surface area from 405.8 to 1420 m2 g-1. It was found that excessive carbonization would destroy the hierarchical pore structure. These porous carbon materials were used as cathode materials for lithium-sulfur battery and showed good performance. HPCN/sulfur cathode has good rate performance and cycle performance, and the capacity retention rate is 87% after the current density rises from 1 to 3 C and 91% after 200 cycles.

In Situ Formation of Prussian Blue Analogue Nanoparticles Decorated with Three-Dimensional Carbon Nanosheet Networks for Superior Hybrid Capacitive Deionization Performance.

Capacitive deionization (CDI) is considered to be an alternative water purification technology because of its low cost and low driven energy. However, the desalination performance of traditional CDI still cannot meet the requirement of actual operations, which is the limited adsorption capacity of carbon electrodes. Here, we report a feasible and simple strategy for the synthesis of a three-dimensional hierarchical composite with homogeneous Prussian blue analogue nanoparticles, decorating hierarchical porous carbon nanosheet networks (NiHCF@3DC-2) as a redox-active intercalation electrode material for hybrid capacitive deionization (HCDI). The interconnected network structure, accompanied by its unique porous characteristic and uniform NiHCF nanoparticles, endows the prepared NiHCF@3DC-2 with enough straining space for alleviating the effect of volume change upon the regeneration process and guarantees fast transmission kinetics for both electrons and salt ions. As a consequence, an HCDI cell with NiHCF@3DC-2 and activated carbon showed superior desalination ability with a high ion removal capacity of 47.8 mg g-1 (107.5 mg g-1 NiHCF@3DC-2) and good cyclic regenerative performance. Moreover, the Na+ ions storage mechanism and the interfacial synergy of the NiHCF@3DC-2 were also explored by structure and electrochemistry analyses during the CDI process. Our work provides a promising redox-active intercalation electrode material to highly efficient hybrid capacitive deionization for brine.

One-Step Synergistic Effect to Produce Two-Dimensional N-Doped Hierarchical Porous Carbon Nanosheets for High-Performance Flexible Supercapacitors

Porous carbon-based supercapacitor has been regarded as a promising candidate for powering wearable electronics. To improve its energy density and mechanical flexibility, great efforts have been ma...

Keratin-derived functional carbon with superior charge storage and transport for high-performance supercapacitors

This work reports a scalable method to synthesize hierarchically porous, hetero-atom doped activated carbon nanosheet from waste biomass−human hair, and demonstrates the use of this carbon as an ultra-high performance electrode material for supercapacitor applications. Microscopic analyses reveal that sheet size ranges from 50 to 200 nm having a thickness of 15–27 nm. As-synthesized, carbon nanosheets possess a hierarchical porous structure having a specific surface area of 1548 m2 g−1. Heteroatom concentration (nitrogen, oxygen, and sulfur) of around 25% is confirmed from XPS analysis. Therefore, the novel interconnected hierarchical porous nanosheets structure enables fast adsorption and transportation of ions during electrochemical processes. Also, the abundant chemically available electroactive heteroatom species in the material enhance the wettability of ions and contribute to pseudocapacitance. The electrochemical analyses through cyclic voltammetry and galvanostatic charge-discharge measurements in 6 M KOH reveal the quasi-EDLC behavior of the activated carbons due to the presence of heteroatoms. A reprensentative KOH activated carbon shows an excellent specific capacitance value of 999 F g−1 at a current density of 1 A g-1. The symmetrically assembled two-electrode device also delivers a maximum energy density of 32 W h Kg-1 at a power density of 325 W Kg-1. In addition, excellent cyclic stability of 98% capacitance retention is observed after 10,000 continuous GCD cycles even at a high current density of 5 A g−1. Symmetric flexible supercapacitor device using KOH-PVA-K3FeCN6 as redox gel polymer electrolyte shows a synergistic specific capacitance of 145 mF cm−1 at a current density of 0.8 mA cm−1 exhibiting very less deviation in bending mode. Therefore, this waste biomass derived heteroatom doped hierarchical porous carbon nanosheets can be a promising material for cost-effective high- performance supercapacitor.

Green synthesis of nitrogen, sulfur-co-doped worm-like hierarchical porous carbon derived from ginger for outstanding supercapacitor performance

Herein, we report a low cost, green synthesis of unique hierarchical worm-like porous co-doped thin carbon nanosheets from ginger as biomass source using non-toxic NaCl/KCl salt mixture as activation media (unlike conventional toxic activation agents like KOH) for high performance supercapacitor application. The optimized synthesis of Nitrogen, Sulfur-doped activated ginger carbon (DAGC) exhibits micro-meso-macro porous structure, facilitating efficient electrolyte diffusion, appropriate graphitization degree, enhanced surface wettability, and synergistic effects between co-doped heteroatoms for rapid ion transfer. Transmission electron microscope (TEM) and Raman spectroscopy studies reveal the partially graphitized walls of carbon and graphitization degree respectively. The DAGC electrode exhibits an excellent specific capacitance of 456 F g−1 at 0.3 A g−1 in three-electrode cell. The assembled symmetric DAGC//DAGC supercapacitor delivers an outstanding specific energy of 48.3 Wh Kg−1 at 400 W kg−1 in comparison to other reported porous carbon with traditional activation method. Moreover, the DAGC supercapacitor device works in high potential region (0–1.4 V) with 1 M Na2SO4 as supporting electrolyte, exhibiting an excellent rate capability and high cyclic stability of 95% after 10000 cycles. All these features of DAGC electrode material make it environment friendly and a competitive entrant for electroactive materials in wide range of applications.

Mass fabrication of oxygen and nitrogen co-doped 3D hierarchical porous carbon nanosheets by an explosion-assisted strategy for supercapacitor and dye adsorption application

The mass fabrication of heteroatom-doped 3D hierarchical porous carbon nanosheets plays an important role in developing high-performance supercapacitor electrode materials and dye adsorbent. In this work, a simple and feasible explosion-assisted strategy was proposed, in which only glucose and magnesium nitrate were used as a reactant to fabricate a series of heteroatom-doped 3D hierarchical porous carbon nanosheets (HPCNS) on a large scale. The obtained HPCNS-1.0 possesses abundant porous structure as well as an ultrahigh oxygen content (16.08 at. %) and an outstanding specific surface area (SSA, 1378 m2 g−1). As an active electrode material, the specific capacitance for HPCNS-1.0 is 253 F g−1 at the current density of 1 A g−1 and 168 F g−1 at 20 A g−1, demonstrating its high rate capability (66%). The specific capacitance only loses 1.3% after 5000 cycles at 10 A g−1, indicating its outstanding cycle stability. As an adsorbent for dye adsorption, the HPCNS-1.0 shows good adsorption capability towards various types of dyes, especially methylene blue with the uptake of 561 mg g−1 at 25 °C. Our work provides a cheap and efficient way to develop high performance 3D hierarchical porous heteroatom-doped carbon nanosheets on a large scale.

Ingenious preparation of N/NiOx co-doped hierarchical porous carbon nanosheets derived from chitosan nanofibers for high-performance supercapacitors

It is still a key challenge to find suitable materials and methods to obtain super capacitors (SCs) with high specific capacitance due to the difficulty of balancing low theoretical capacity of conventional carbon materials and the poor ion transportability of transition metal oxide. In this work, N Ni dual-doped porous carbon nanosheets (NiOx-NCNSs) are prepared through a novel way using original N-doped chitosan nanofibers and nickel nitrate to form honeycomb layered structure constructed by 2D fiber network as precursors. NiOx-NCNS exhibits a high specific surface area of 1847.4 m2 g−1 with a rich N content of up to 5.16 wt% and shows a higher specific capacitance of 614.6 F g−1 at a current density of 1 A g−1 than that of carbon nanosheets of undoped Ni (NCNS) (427.5 F g−1). More specifically, the SC assembled using NiOx-NCNS electrodes achieves a high energy density of 20.3 W h kg−1 at a power density of 240.9 W kg−1, which is superior to most of the CNS-based SCs that have been reported. After 10 000 cycles, the symmetric SC retains approximately 85.61% of the initial capacitance. The strategy provided in this work probes the feasibility of high-performance SCs.

Nitrogen and oxygen co-doped broccoli-like porous carbon nanosheets derived from sericin for high-performance supercapacitors

Broccoli-like porous carbon nanosheets with high levels of heteroatoms doping was successfully synthesized from the wasted sericin via an environmental friendliness and cost-effective strategy. The hierarchical porous carbon nanosheets was formed from chemical expansion and activation by Mg2(OH)2CO3·xH2O simultaneously. Benefiting from the elaborate structure of NPCN-4, the prepared material shows the satisfactory energy storage ability in electrical double-layer capacitors (EDLCs) area with an outstanding specific capacitance of 214.5 F g−1 at 0.5 A g−1 in an alkaline solution and high capacitance retention of 87% at 10 A g−1 after 10000 cycles.

Production of hierarchical porous carbon nanosheets from cheap petroleum asphalt toward lightweight and high-performance electromagnetic wave absorbents

Developing efficient and cheap electromagnetic wave absorption (EWA) materials is highly desirable in modern information society. Herein, based on the abundant and low-cost petroleum asphalt, hierarchical porous carbon nanosheets (PCNs) have been rationally fabricated via one-step carbonization process by using water-removable NaCl templates. The NaCl can provide crystal planes for the growth of graphitized carbon layers, and promote the formation of interconnected porous architectures. The porous nanosheets structures realize the multiple reflections and scattering in the void space. The presence of dipole polarization and interfacial polarization in PCNs facilitates the dielectric loss. Remarkably, the EWA performance of optimized PCNs with a low filler content of 20 wt% reaches a strong reflection loss of −53.7 dB and a broad absorption bandwidth of 5.3 GHz at a thin thickness of 1.8 mm. This encouraging performance considerably outperforms most of reported dielectric materials, which also meets the demands of thin, light weight, strong and broad features for new-type EWA materials. Therefore, our strategy may open up new avenues for development of promising EWA materials and realizing the high value-added utilization of petroleum asphalt by considering the facile process and low production cost.

Rationally exfoliating chitin into 2D hierarchical porous carbon nanosheets for high-rate energy storage

Two-dimensional (2D) carbon nanomaterials with hierarchical porous structure and heteroatoms doping are highly desirable in the fields of energy storage because of their rich active surface and open ion diffusion channels. However, the scalable preparation of carbon materials simultaneously possessing ultrathin 2D feature and hierarchical pores remains a considerable challenge. Herein, a facile one-step method to massively fabricate 2D porous chitin nanosheets (coded as PCNs) via a phytic acid assisted top-down exfoliation of bulk chitin under hydrothermal treatment was presented. Subsequently, 2D carbon nanosheets with extra-thin thickness (3.6 nm), well-defined hierarchical porosity, high specific surface area (855 m2·g-1), as well as abundant self-doped heteroatoms (N, O, P) were fabricated by carbonizing the PCNs, and was named as HPCNs. The as-obtained HPCNs demonstrated remarkable electrochemical performance as electrode material for supercapacitors. The symmetric supercapacitors (SSCs) based on HPCNs exhibited a high specific capacitance of 79 F·g-1 (316 F·g-1 for single electrode) in 6 M KOH aqueous electrolyte solution, as well as a remarkable energy density of 23.8 W·h·kg-1 by using 1 M Li2SO4 as electrolyte. It is also demonstrated that HPCNs/PCNs hybrid dispersions can be used as inks to fabricate conductive films and energy devices with high strength and superior flexibility. This work paves a new avenue for the economical and large-scale synthesis of 2D hierarchically porous carbon materials for energy storage related applications.

Graphene-like nitrogen-doped porous carbon nanosheets as both cathode and anode for high energy density lithium-ion capacitor

Carbon materials have unique stability and controllable structure for all-carbon lithium-ion capacitors (LICs) electrode materials. In this paper, we used chitosan as a carbon source and self-doped nitrogen source, zinc nitrate as a templating agent. Hierarchical porous carbon nanosheets (PCNS) materials with graphene-like structure and abundant nitrogen doping were prepared through a one-step carbonization process. The PCNS materials were used as both capacitor-type cathode and battery-type anode for LICs. Due to the multi-mesoporous and ultrathin nanosheets structure, a large specific surface area (1321.3 m2 g−1) was obtained of PCNS materials, which ensures a high specific discharge capacity of 65.8 mAh g−1 at 3 A g−1 for the capacitor-type cathode. The interconnected graphene-like structure not only provides a large adsorbable area but also reduces the diffusion distannce of ions between the surface of the electrode and electrolyte. When the PCNS materials used as an anode for LIC, it also appeared a high specific discharge capacity of 285.0 mAh g−1 at a big current density of 20 A g−1. Finally, all-carbon symmetric LIC with a broad voltage window of 0.01–4.5 V was constructed successfully. The symmetric LIC shows a high energy density of 146 Wh kg−1 (at a power density of 1125 W kg−1) and an excellent capacity retention rate of 84.5% (10,000 cycles at 5 A g−1).

Hierarchical porous structure carbon nanosheets derived from sodium lignosulfonate for high-performance supercapacitors

Because of the special lamellar structure, numerous pores, and large effective specific surface area, the two-dimensional porous carbon material is very beneficial for the storage and transmission of energy.

Porous 2D carbon nanosheets synthesized via organic groups triggered polymer particles exfoliation: An effective cathode catalyst for polymer electrolyte membrane fuel cells

The synthesis of two-dimensional (2D) porous carbon materials has attracted much attention due to their widespread applications. In this work, Fe/N doped hierarchical porous carbon nanosheets are developed through thermal activation step based on organic groups triggered polymer particles exfoliation. Polymer nanoparticles are exfoliated by the reaction between the phenolic hydroxyl groups and the amino groups. The gas produced from dicyandiamide then blows polymer fragments into ultrathin flexible carbon nanosheets under pyrolysis process, along with nitrogen doping. The Fe–N–C catalyst exhibits half-wave potential (E1/2) at 0.852 V (vs. RHE) in 0.1 M KOH and at 0.686 V (vs. RHE) in 0.5 M H2SO4 for oxygen reduction reaction. Additionally, the polymer electrolyte membrane fuel cell that employs the catalyst at the cathode exhibits good durability without showing significant degradation after 96 h continuous operation. Furthermore, this method can be generalized to synthesize carbon nanosheets by using various polymer precursors. This work provides a new and general strategy for preparing porous carbon or metal/carbon nanosheets, which paves the way for the mass production of effective 2D carbon materials in many important applications.

Sustainable recycling of waste polystyrene into hierarchical porous carbon nanosheets with potential applications in supercapacitors

Herein, polystyrene waste was carbonized into mesoporous carbon nanosheets (CNS) using the template method. The pore structure of the obtained CNS was further tuned by KOH activation, resulting in the formation of hierarchical porous carbon sheets with a specific surface area of 2650 m2 g−1 and a pore volume of 2.43 cm3 g−1. Benefiting from these unique properties, in a three electrode system, the hierarchical porous carbon sheets displayed a specific capacitance of 323 F g−1 at 0.5 A g−1 in a 6 M KOH electrolyte, good rate capability (222 F g−1 at 20 A g−1) and cycle stability (92.6% of capacitance retention after 10 000 cycles). More importantly, an energy density of 44.1 Wh kg−1 was also displayed with a power density of 757.1 W kg−1 in an organic electrolyte. In this regard, the present strategy demonstrates a facile approach for recycling plastic waste into high value-added products, which will potentially pave the way for the treatment of plastic waste in the future.

Facile synthesis of 2D ultrathin and ultrahigh specific surface hierarchical porous carbon nanosheets for advanced energy storage

Two dimensional (2D) porous carbon nanosheets (CNS) have attracted tremendous research interests in energy storage and conversion, such as supercapacitors (SCs) and lithium-sulfur batteries, because of their unique micromorphology, chemical stability and high specific surface area (SSA). Rational design and facile scalable synthesis of CNS with high SSA, low cost and ultrathin nanosheet structure is highly desired but hitherto remains a big challenge. Here, we report a novel synthesis method of 2D hierarchical porous CNS with ultrahigh SSA (2687 m2 g−1) and ultrathin structure by directly pyrolysing and activating a unique and abundant biomass sheet. The electrochemical characterisations show that the prepared CNS-4-1 materials as electrodes creates a good energy-storage capability, with the energy density being 91 Wh kg−1 for symmetric SCs in ionic liquids, which is the highest in the reported biomass-derived CNS materials for SCs applications so far. Besides, the CNS-5-1 also exhibits a high initial capacity of 1078 mAh g−1 at 0.1 C when it acted as a sulfur hosting material for lithium-sulfur batteries. More importantly, it also shows a 586 mAh g−1 reversible capacity and an approaching 100% coulombic efficiency after 500 cycles at a high rate of 1 C. These superior electrochemical properties of the CNS are mainly attributed to their unique 2D ultrathin nanosheet structure, large SSA, and reasonable hierarchical porous structure. This work not only provides a new strategy to fabricate the ultrathin CNS in large scale and low cost but also enlarges CNS materials potential applications in energy storage.