Carbon Nanosheet Networks Research Articles

Interfacial Mo-N bonding enhancement of N-doped carbon nanosheets-stabilized ultrafine MoS2 enable ultrafast and durable sodium ion half/full batteries

The structural stability and Na+ diffusion kinetics of two-dimensional layered materials are critical to deliver efficient Na+ storage. Here, few-layer MoS2 nanocrystals were anchored on N-doped carbon nanosheets (MoS2@NCs), which realizes fast Na+ storage and long cycle life. The tight chemical bonding (Mo-N-C bonds) of N atom to MoS2 nanocrystals and carbon nanosheets improves the electronic conductivity and the structural stability of MoS2@NCs, while the carbon nanosheets network supports the MoS2@NCs structure to reduce the volume effect and provides a surface-dominated mechanism for fast Na+ diffusion. Density functional theory results show that the low diffusion barrier of MoS2@NCs with Mo-N-C bonds accelerates the Na+ transfer kinetics. Consequently, MoS2@NCs possesses superior rate capability of 307 mA h g−1 at 20 A/g and excellent long-term stability over 3,000 cycles. The reversible Na+ (de)insertion behavior is elucidated through in-situ EIS and ex-situ XRD technology.In addition, the assembled MoS2@NCs//Na3V2(PO4)3/C full cell also exhibits a high reversible capacity and good cycle stability. This work opens a new route for optimizing two-dimensional layered materials that can be used for high energy density rechargeable SIBs.

Mo2N quantum dots decorating N-doped carbon nanosheets for kinetics-enhanced Li-S batteries

Lithium-sulfur (Li-S) batteries face two main challenges, which are the severe shuttle effect of lithium polysulfides (LiPSs) and the slow redox kinetics of LiPSs. Herein, monodispersed Mo2N quantum dots decorating N-doped carbon nanosheets (Mo2N@NCNS) are rationally engineered via a simple and cost-effective method and used as an effective host for sulfur in high-performance Li-S batteries. Mo2N@NCNS presents enhanced intrinsic conductivity, superior catalytic capability, and improved LiPSs redox kinetics. The 3D N-doped carbon nanosheet networks endowed with abundant catalytic sites can heighten physically confined and chemically adsorptive LiPSs by strongly polar-polar interactions, further regulating the disordered motion of LiPSs. In the meanwhile, the highly dispersed Mo2N quantum dots with powerful adsorptive-catalytic properties anchor the soluble LiPSs and facilitate high-efficiency diffusion-conversion kinetics for the nucleation and deposition of Li2S2/Li2S, thus promoting the complete utilization of sulfur and the overall enhancement of electrochemical performance. Owing to these fascinating features, the Mo2N@NCNS-based sulfur cathodes demonstrate substantial enhancement in electrochemical performance, including remarkable capacity performance (1221 mAh g−1 at 0.2 C) and exceptional cyclability over 800 cycles at 2 C with a minimal decay rate (0.03 % per cycle). This work highlights the great potential of rational design of advanced composite materials for promoting the practical viability of Li-S batteries in energy storage systems.

Unique hierarchical porous carbon nanosheet network for supercapacitors: Ultra-long cycling stability and enhanced electroactivity of oxygen at high temperature

Porous carbon-based supercapacitors (SCs) are promising electrochemical energy storage devices. However, the unreasonable design of porous carbon leads to poor energy density and unsatisfactory high-temperature cycling stability of SCs. Herein, we synthesize a hierarchical porous carbon nanosheet network by combining self-templated pyrolysis and KOH activation strategies. This carbon nanosheet network exhibits an extremely large active ion-accessible pore volume (V0.76–6 nm=1.654 m3 g−1) and a considerable supermesopore volume (V6–50nm 0.413 m3 g−1), which provide abundant active sites and fast diffusion channels for electrolyte ions, respectively. Futhermore, the enhanced electroactivity of oxygen at high temperature is demonstrated, which provides additional active sites. Inspiringly, the as-constructed EMIMBF4-based SCs can be well serviced at the high temperature of 80 °C with ultra-high energy/power density of 122.23 Wh kg−1/40.6 kW kg−1 and superior durability (81.1% retention after 8000 cycles at 20 A g−1). This work provides insights into the effect of temperature on the electroactivity of oxygen, as well as the construction of porous carbon-based high-temperature SCs with desired performance metrics.

Hierarchically porous N-doped carbon nanosheet networks with ultrafine encapsulated Fe3C and Fe-Nx for oxygen reduction reaction in alkaline and acidic media

The electrocatalytic oxygen reduction reaction (ORR) plays an important role in renewable energy storage and conversion systems such as polymer electrolyte membrane fuel cells. However, design of high-performance cathode electrocatalysts is still required to speed up the sluggish kinetics of ORR. In this work, we develop a facile strategy to synthesize hierarchically porous N-doped carbon nanosheet networks with ultrafine encapsulated Fe3C and Fe-Nx for ORR by consideration of thermodynamic (intrinsic and support effect) and kinetic (diffusion effect) parameters. The synthetic process is straightforward and sustainable and the hierarchically porous materials can be synthesized directly starting from raw materials and without any additional template. The as-designed catalyst exhibits excellent ORR catalytic performance in both acidic and basic media with much positive half-wave potential and good stability, which is comparable to commercial Pt/C. The excellent ORR performance may result from highly active Fe-Nx sites and ultrafine encapsulated Fe3C, and the hierarchically porous nanosheet structure for accelerating mass diffusion and increasing exposure of the active site. This work provides a facile strategy for rational design and synthesis of highly active, hierarchically porous non-precious metal electrocatalysts.

An ant-nest like hierarchical nanoreactor for highly efficient sulfur species redox reactions

The main challenge in the practical exploitation of lithium-sulfur (Li-S) batteries is to resolve the problems of the sluggish liquid-solid conversions and the diffusion loss of liquid polysulfides especially at high sulfur loading. Herein, a novel bio-inspired reactor with ant-nest like architecture was tailored for Li-S electrochemistry, which combines abundant active nickel nanoparticles with hierarchical porous carbon-nanosheets network (HPCN/Ni). The nanoreactor provides multiple functions including strong trapping efficiency with polysulfides, fast transfer of ions/electrons and liquid sulfur species, and sufficient catalytic activity. The cooperative effects could accelerate Li-S redox reactions and improve sulfur utilization. Enhanced by the highly efficient HPCN/Ni naonoreactor, Li-S cells demonstrate a high specific capacity of 1437.9 mAh g−1 at 0.1 C, remarkable rate performances such as 900 mAh g−1 at 2 C, and exellent cycling stability with a high capacity retention of 734.2 mAh g−1 after 300 cycles at 1 C. Even at a high sulfur area loading of 5.63 mg cm−2, a high area capacity of 4.75 mAh cm−2 could be achieved. This contribution affords a fesible approach to design and construct nanoreactors with high efficiency for Li-S batteries and the analogous applications.

Hierarchically Porous N-Doped Carbon Nanosheet Networks with Ultrafine Encapsulated Fe <sub>3</sub>C and Fe-N <sub>x</sub> for Oxygen Reduction Reaction in Alkaline and Acidic Media

Hierarchically Porous N-Doped Carbon Nanosheet Networks with Ultrafine Encapsulated Fe <sub>3</sub>C and Fe-N <sub>x</sub> for Oxygen Reduction Reaction in Alkaline and Acidic Media

Data-driven design and controllable synthesis of Pt/carbon electrocatalysts for H2 evolution

SummaryTo achieve net-zero emissions, a particular interest has been raised in the electrochemical evolution of H2 by using catalysts. Considering the complexity of designing catalyst, we demonstrate a data-driven strategy to develop optimized catalysts for H2 evolution. This work starts by collecting data of Pt/carbon catalysts, and applying machine learning to reveal the importance of ranking various features. The algorithms reveal that the Pt content and Pt size have the greatest impact on the catalyst overpotentials. Following the data-driven analysis, a space-confined method is used to fabricate the size-controllable Pt nanoclusters that anchor on nitrogen-doped (N-doped) mesoporous carbon nanosheet network. The obtained catalysts use less platinum and exhibit better catalytic activity than current commercial catalysts in alkaline electrolytes. Moreover, the data formed in this work can be used as feedback to further improve the data-driven model, thereby accelerating the development of high-performance catalysts.

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.

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.

Nitrogen-doped mesoporous carbon nanosheet network entrapped nickel nanoparticles as an efficient catalyst for electro-oxidation of glycerol

The design and synthesis of nitrogen-doped (N-doped) carbon nanosheets network offer a tremendous electro-catalytic activity due to their high surface area and tunable porous structures for the development of direct alcohol fuel cells (DAFCs). In this work, nickel (Ni) nanoparticles entrapped onto the N-doped mesoporous carbon nanosheets network such as Ni–C-1, Ni–C-2, and Ni–C-3 are fabricated and characterized using SEM, TEM, XRD, XPS, and electrochemical methods. The physicochemical characterization of synthesized nanocomposite material confirmed that sodium chloride (NaCl) plays a major role in the formation of porous nanostructure during carbonization process. Under optimized conditions, all the above carbon samples are tested as potential electro-catalyst towards the electro-oxidation of glycerol for DAFCs application. Among them, the Ni–C-2 catalyst displays enhanced catalytic current density (~2.6 mA) and low onset oxidation potential (0.11 V) for electro-oxidation of glycerol than the Ni–C-1, and Ni–C-3 catalysts in alkaline electrolyte. In addition, the mesoporous carbon network structure containing Ni nanoparticles delivers substantial longer durability/robustness when compared to the conventional Pt/C-catalyst towards stable- and efficient electro-oxidation of glycerol for the first time. Thus, the obtained electro-catalytic performance revealed that Ni–C-2 is considered as a promising earth abundant non-noble low-cost catalyst material for DAFCs application.

Ultrathin MoS2 anchored on 3D carbon skeleton containing SnS quantum dots as a high-performance anode for advanced lithium ion batteries

Transition metal sulfides have high abundance and large theoretical capacities are considered to be an effective candidate for advanced electrodes of lithium ion batteries (LIBs). Here, a large-scale and controllable method was used in synthesizing ultrathin MoS2 nanosheets anchored on 3D hierarchical nanohybrids with SnS quantum dots, which are decorated on a carbon nanosheet network (MoS2@SnS-QDs/CNN). The 3D cross-linked carbon nanosheet not only could prevent SnS from being directly exposed to the electrolyte but also retained the structural stability of the electrode. Moreover, the MoS2 nanosheets exposed active sites to carry lithium ions. A heterojunction was formed at the interface owing to the close contact between molybdenum disulfide and SnS and greatly increased charge carrying and lithium storage capacities. Benefiting from these structural advantages, the MoS2@SnS-QDs/CNN electrodes showed outstanding electrochemical and long-term cycling performance owing to their unique structures and amazing synergies. As a half-cell anode material, MoS2@SnS-QDs/CNN-2 provided a reversible capacity of 713 mAh g−1 after 1000 cycles at a current density of 2 A g−1. When assembled into a full battery, it still provided 491 mAh g−1 at a current density of 1 A g−1 after 100 cycles. At the same time, a small LED bulb was lit for a while. This advanced material has great potential in other applications, such as supercapacitors, catalysis, and sensors.

Carbon Coated Core-Shell FeSiCr/Fe3C Embedded in Carbon Nanosheets Network Nanocomposites for Improving Microwave Absorption Performance

Development of microwave absorbing materials with tunable thickness and bandwidth is particularly important for practical applications, but its realization remains a great challenge. Here, we report carbon coated core-shell FeSiCr/Fe3C embedded in two-dimensional carbon nanosheets network (FeSiCr/Fe3C@C/C) nanocomposites fabricated by plasma arc-discharging method. FeSiCr/Fe3C@C/C has the best microwave absorption properties in which the minimum calculated reflection loss (RL) can reach [Formula: see text][Formula: see text]dB at 11.5[Formula: see text]GHz with a coating thickness of 2.4[Formula: see text]mm and the efficient absorption bandwidth (RL[Formula: see text][Formula: see text]dB) almost covers 4.5–18[Formula: see text]GHz range by adjusting the coating thicknesses from 1.3 to 5.0[Formula: see text]mm. The improved microwave absorption properties could be ascribed to the optimized impedance matching and enhanced polarization loss, conduction loss and internal reflections of the propagated microwave.

Cobalt nanoparticles intercalated nitrogen-doped mesoporous carbon nanosheet network as potential catalyst for electro-oxidation of hydrazine

Developing an efficient low-cost and high performance electrocatalyst for electro-oxidation of hydrazine is one of the key challenges in the prospect of direct hydrazine fuel cell (DHFC) application. In this work, a series of nitrogen doped three-dimensional porous Co3O4/carbon nanosheet network catalysts are synthesized (Co-NPC NNs-x), and simultaneously characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and electrochemical methods. Among them, Co-NPC NNs-2 is found to be a potential electrocatalyst towards highly efficient electro-oxidation of hydrazine. The electrochemical results clearly display that Co-NPC NNs-2 catalyst shows enhanced electro-oxidation (low-onset oxidation potential, higher catalytic current response), and higher cycling stability (catalytic response retained even after 120 successive cycles) toward hydrazine when compared to Co-NPC NNs-1, Co-NPC NNs-3, and NPC NNs catalysts modified electrodes. The existence of large active surface area, higher active catalytic sites, and synergetic activity between NPC NNs and Co3O4 NPs (Co-NPC NNs-2) are vital factors mainly attributes to the superior electro-oxidation response of hydrazine. Further, the Co-NPC NNs-2 catalyst demonstrated longer durability towards the electro-oxidation of hydrazine, which is highly comparable with commercially available Pt/C catalyst. Such an efficient low-cost electrocatalyst nanomaterial can enable the use of hydrazine as a promising energy carrier for DHFCs, which increases its practicality for upcoming energy storage and conversion applications.

Monodispersed FeS nanoparticles confined in 3D interconnected carbon nanosheets network as an anode for high-performance lithium-ion batteries

Transition metal sulfides as the most prominent candidates with high theoretical capacities; however, serious agglomeration and enormous volumetric variation limit its application in lithium-ion batteries. Herein, a chemical blowing strategy for the synthesis of FeS nanoparticles encapsulated into 3D porous carbon framework via chemical vapor deposition method and subsequent sulfidation process. In the constructed architecture, the monodispersed FeS nanoparticles are fully encapsulated in graphitic carbon, simultaneously, confined in 3D architecture composed of 2D graphitic carbon nanosheets. The unique architecture provides a facilitated transport pathway, enhances electron conductivity and buffers the volumetric expansion of FeS. Consequently, the composite delivers a high reversible capacity of 1084.2 mAh g−1 at 0.1 A g−1, excellent rate capability (723.5 mAh g−1 at 1 A g−1), and outstanding cycling stability (a specific capacity of 848.3 mAh g−1 without decay is achieved at 0.5 A g−1). Therefore, the present work suggests that the novel design of 3D FeS/C material provides a strategy for achieving high-performance anodes in lithium-ion batteries. Uniformly monodispersed FeS nanoparticles confined in 3D interconnected carbon network was synthesized by using chemical vapor deposition method and subsequent sulfidation process. The hybrid electrode exhibits excellent performance with a reversible capacity of 1084.2 mAh g−1 at 0.1 A g−1 as well as outstanding cycling stability performance of 848.3 mAh g−1 at 0.5 A g−1 after 170 cycles.

N,S dual-doped carbon nanosheet networks with hierarchical porosity derived from biomass of Allium cepa as efficient catalysts for oxygen reduction and Zn–air batteries

Efficient metal-free electrocatalysts for oxygen reduction reactions (ORR) have been actively pursued in recent years to promote the application of fuel cells and metal–air batteries. In this work, hierarchically porous nitrogen and sulfur dual-doped carbon nanosheet networks (N,S-HPC) were facilely synthesized by pyrolysis of Allium cepa chips impregnated with thiourea and KOH. The as-prepared N,S-HPC featured high content of N and S dopants (5.32 at.% for N and 2.23 at.% for S, respectively), abundant catalytically active sites, unique hierarchically porous architecture, large surface area (1859 m2 g−1) and exhibited remarkable electrocatalytic activity toward ORR with positive onset/half-wave potential and large limiting diffusion current. In addition, N,S-HPC showed much better long-time stability and resistance to methanol crossover than Pt/C did. When used as the cathodic catalysts of Zn–air battery, N,S-HPC outperformed Pt/C in terms of the open-circuit potential, discharge current density, peak power density, specific capacity and rate performance, showing promise as an alternative to Pt/C for application in fuel cells and metal–air batteries.

Anion-regulated selective growth ultrafine copper templates in carbon nanosheets network toward highly efficient gas capture

Controlling micropore size is the core for synthesizing highly efficient adsorbents for gas adsorption and separation engineering. Porous carbon prepared by traditional methods usually lacks competitiveness due to the random micropore size or complex process. Herein, we report a novel strategy for synthesizing nitrogen doped carbons nanosheets (Cu-NDPCs) with unimodal ultra-micropore based on the metal-organic covalency and the anion regulated in situ copper template. The thickness of single Cu-NDPCs is about 4.2 nm. In the presence of Cl−, the porosity of Cu-NDPCs can be tuned at 4.1–4.8 Å by adjusting the pyrolysis temperature. Among them, Cu-NDPC-800 has unique carbon nanosheets networks structure, ultrahigh surface area (2150 m2 g−1), large micropore volume (0.92 cm3 g−1) and abundant surface N doping (5.33%). As an adsorbent, it exhibits superhigh C2H2, C2H6, C3H8 and CO2 uptakes (6.7, 7.0, 11.4 and 4.4 mmol g−1) and corresponding x/CH4 or CO2/N2 IAST selectivities (12.9, 17.8, 468.6, 4.3 and 17.1) under ambient conditions. Meanwhile, the Cu-NDPC-800 possesses excellent cyclic stability.

Improving the electrochemical performance of Si-based anodes by co-compositing LiF and double carbon layer composed of graphite and three-dimensional PM

In order to improve the electrochemical performance of Si-based electrodes, Nano Si, lithium fluoride (LiF) and graphite (G) were combined with three-dimensional interconnected porous carbon nanosheets network embedded with multi-walled carbon nanotubes (PM). MWCNTs provide a good conductive path that promotes electron transport and maintains structural integrity. The three-dimensional interconnect structure of PM facilitates rapid electrical/ion transport and good electrolyte penetration. The intercalation of nano-Si in layered porous matrix effectively alleviated the serious volume expansion of Si during discharge/charge and prevent the pulverization of Si particles. The addition of LiF can compensated for the L+ consume in the formation of the SEI layers and enhanced the stability of SEI membrane. The electrochemical tests shown that the initial coulombic efficiency (ICE) of the SPM/G/7.5%LiF (SPMG-7.5%LiF) electrode reached approximately 75.2%. The capacity of the SPMG-7.5% LiF electrode hold 1057 mAh g−1 after 500 cycles with a coulombic efficiency (CE) of about 100%. The SPMG electrode exhibited a good rate performance and cycle performance.

Synergistically enhanced oxygen reduction electrocatalysis by atomically dispersed and nanoscaled Co species in three-dimensional mesoporous Co, N-codoped carbon nanosheets network

Metal-nitrogen-codoped carbon (M-N-C) nanostructures are promising electrocatalysts for oxygen reduction reaction (ORR). Despite the great progress that has been achieved, synthesizing three-dimensional porous nanoarchitectures derived from Co-N-C nanosheets or related nanohybrids with high content (> 5 wt%) of exposed single-atom sites remains a challenge. Herein, novel three-dimensional mesoporous Co-N-C nanosheets network enwrapping small amount of Co nanoparticles nanohybrids are fabricated by molten-salt template-assisted pyrolysis of Co-folic acid precursors and chemical etching. In the obtained nanohybrids, the content of single-atom-like Co (SA-Co%) is 7.4 wt% < SA-Co%<19.4 wt%. Due to the unique mesoporous nanosheets network structure and efficient synergy of atomic and nanoscaled Co species, such nanohybrids manifest enhanced ORR activity with a half-wave potential of 0.85 V, outperforming pure Co-N-C, Pt/C and most of other reported catalysts. Moreover, their stability exceeds that of Pt/C. This work will lead to the optimization of M-N-C nanostructures and accelerate their applications in fuel cells.

Synthesis of NiCo Alloy Nanoparticle-Decorated B,N-Doped Carbon Nanosheet Networks via a Self-Template Strategy for Bifunctional Oxygen-Involving Reactions

Developing nonprecious metal catalysts for oxygen electrocatalysis is vital for next-generation energy conversion devices. Herein, a uniform distribution of NiCo alloy nanoparticles wrapped by B,N-...

Hierarchically porous nanosheets-constructed 3D carbon network for ultrahigh-capacity supercapacitor and battery anode

An advanced hierarchically porous nanosheets-constructed three-dimensional (3D) carbon material (HPNSC) is prepared by using low-cost agricultural waste-nelumbium seed-pods as the precursor, and potassium hydroxide (KOH) as the activator. The as-prepared HPNSC material has a hierarchically porous nanosheets-constructed structure with 3D carbon nanosheet network morphology, which can enable fast and efficient transfer of Li+/Na+/H+ during charge–discharge process. The assembled HPNSC//HPNSC symmetric supercapacitors exhibit an improved energy density of 41.3 W h kg−1 with a power density of 180 W kg−1 in 1 mol l−1 Na2SO4 electrolyte. The energy density can still be maintained at 16.3 W h kg−1 even if the power density is increased to 9000 W kg−1. When acting as the reversible electrode for lithium ion batteries, this HPNSC material can achieve a high specific capacity of 1246 mA h g−1 at 0.1 A g−1. Moreover, sodium ion battery with HPNSC electrode exhibits excellent cycling performance of 161.8 mA h g−1 maintained even after being cycled 3350 times. The electrochemical performances clearly indicate that the HPNSC developed in this work is a very promising energy storage electrode material, and can further provide new insights for designing and developing highly porous materials for energy storage in other fields.