Two-dimensional Porous Carbon Nanosheets Research Articles

Graphene/metal-organic framework nano-sandwiches derived N, P-codoped porous carbon nanosheets as robust material for electrochemical analysis

Construction of novel two-dimensional porous carbon nanosheets with superior electrochemical activity is of great challenge. Here, graphene/ZIF-8 nano-sandwiches derived N, P-codoped porous carbon nanosheets (N, P-codoped PCN) was easily obtained by sequential room temperature self-assembly and high-temperature carbonization method. Relative to the widely used physically exfoliated graphene nanosheets (GN) and graphene/ZIF-8 derived N-doped porous carbon nanosheets (N-doped PCN), N, P-codoped PCN displayed larger active surface, faster electron transport ability and stronger physical adsorption ability, which can be ascribed to the dual doping effect of heteroatoms N and P. As a result, N, P-codoped PCN exhibited remarkable oxidation signal enhancement for tumor marker (8-hydroxy-2′-deoxyguanosine), analgesic and antipyretic drug (acetaminophen) and organic pesticide (benomyl). Besides, the limits of detection were measured as low as 1.58 nM, 7.50 nM and 2.10 nM with sensitivity of 270.00 μA μM−1 cm−2, 757.14 μA μM−1 cm−2 and 272.86 μA μM−1 cm−2 for 8-hydroxy-2′-deoxyguanosine, acetaminophen and benomyl, respectively. Basing on this, a novel and highly sensitive electrochemical sensing platform was developed. It is believed that the reported two-dimensional N, P-codoped PCN with unique structure and composition is highly valuable for the development of carbon-based electrochemical sensors.

Synergistically coupling of WC-WP/NC hybrid catalyst for electrocatalytic hydrogen production

WC-based materials are considered as a promising alternative electrocatalyst to Pt because of its similar electronic structure to Pt at Fermi level, low cost and good corrosion resistance. However, the shortcomings of easy agglomeration of WC at high temperature and its own strong WH bond leaded to its low catalytic performance. Herein, the hybrid catalyst of WC-WP/NC was prepared by a simple melting salt-assisted simultaneous phosphorylation and carbonization strategy. Excitingly, the hydrogen evolution overpotential of WC-WP/NC is much lower than that of WC/NC and WP/NC in acidic and alkaline conditions, and the stability of WC-WP/NC is significantly better than 20% Pt/C. The excellent performance is mainly attributed to the synergistically coupling of WC and WP hybrids, the rapid transfer of interface charges has changed the electronic structure of the catalyst. Furthermore, the nitrogen doped two-dimensional porous carbon nano sheets can not only increase the conductivity of the catalyst and prevent the agglomeration of nano particles, but also effectively promote the contact between electrolyte and catalyst, accelerating the HER (Hydrogen Evolution Reaction) kinetic reaction. This work provides an effective strategy for constructing a good dispersive multi-interface hybrid catalyst.

Preparation of Dual-Doped N/P Two-Dimensional Porous Carbon Nanosheets for High-Performance Alkaline Supercapacitors

Preparation of Dual-Doped N/P Two-Dimensional Porous Carbon Nanosheets for High-Performance Alkaline Supercapacitors

Embedding tin disulfide nanoparticles in two-dimensional porous carbon nanosheet interlayers for fast-charging lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have attracted significant attention for their high specific capacity, non-toxic and harmless advantages. However, the shuttle effect limits their development. In this work, small-sized tin disulfide (SnS2) nanoparticles are embedded between interlayers of two-dimensional porous carbon nanosheets (PCNs), forming a multi-functional nanocomposite (PCN-SnS2) as a cathode carrier for Li-S batteries. The graphitized carbon nanosheets improve the overall conductivity of the electrode, and the abundant pores not only facilitate ion transfer and electrolyte permeation, but also buffer the volume change during the charge and discharge process to ensure the integrity of the electrode material. More importantly, the physical confinement of PCN, as well as the strong chemical adsorption and catalytic reaction of small SnS2 nanoparticles, synergistically reduce the shuttle effect of polysulfides. The interaction between a porous layered structure and physical-chemical confinement gives the PCN-SnS2-S electrode high electrochemical performance. Even at a high rate of 2 C, a discharge capacity of 650 mA h g−1 is maintained after 150 cycles, underscoring the positive results of SnS2 based materials for Li S batteries. The galvanostatic intermittent titration technique results further confirm that the PCN-SnS2-S electrode has a high Li+ transmission rate, which reduces the activation barrier and improves the electrochemical reaction kinetics. This work provides strong evidence that reducing the size of SnS2 nanostructures is beneficial for capturing and reacting with polysulfides to alleviate their shuttle effect in Li-S batteries.

Synthesis of two-dimensional porous carbon nanosheets for high performance supercapacitors

• Two-dimensional porous carbon nanosheets was prepared by a simple way. • The optimized electrode shows good electrochemical performance. • The symmetric supercapacitor delivers high energy density. Two-dimensional (2D) porous carbon nanosheets (PCNs) have drawn tremendous concern due to they possess large specific surface area, reduced ion transportation resistance and shorten ion diffusion distance. However, the traditional template method is complex and time-consuming. Here, we reported a convenient strategy to synthesize 2D PCNs derived from cationic starch using graphene oxide (GO) as template through an electrostatic self-assembly strategy with KOH activation. Due to the unique 2D highly interconnected nanosheet-like porous framework with suitable specific surface area, the as-prepared PCNs-1 electrode delivers high specific capacitance (232.1 F g −1 at 2 mV s −1 ) and impressive electrochemical stabilization (100.3% retention after 10,000 cycles) in 6 M KOH aqueous electrolyte. Meanwhile, the constructed PCNs-1//PCNs-1 symmetrical supercapacitor shows an energy density of 19.2 Wh kg −1 and remarkable electrochemical stabilization (93.7% retention after 10,000 cycles) in 1 M Na 2 SO 4 aqueous electrolyte. The strategy provides a novel and convenient approach to construct porous carbon nanosheets for supercapacitors.

Molten metal chloride salt template synthesis of N/S co-doped porous carbon nanosheets for supercapacitors

Two-dimensional carbon nanosheets have recently become spotlight in the electrochemical energy storage fields. Herein, an effective and environmental-friendly strategy was developed to prepare ginkgo leaf derived N/S co-doped porous carbon nanosheets (PCNSs) using CaCl2/KCl molten salt as activating/template agent. The CaCl2/KCl as a green and non-toxic template can regulate the pore structure and microstructure of carbon materials. Benefiting from interconnected sheet-like morphology and plenty of heteroatoms (N, S, O) doping, the fabricated carbon-based supercapacitor exhibit good specific capacitance of 150.4 F g−1 at 0.05 A g−1 and splendid cycling performance with 94.2% capacity retention after 10,000 charge-discharge cycles at 1 A g−1.This facile and environmental-friendly activation strategy provides a new way of thinking for developing N, S-doped two-dimensional porous carbon nanosheets for high-performance energy storage devices.

Improving the electrochemical performance of lithium Si batteries by multilayer porous carbon nanosheets/multi-walled carbon nanotubes composite inert nano-Ag

In this paper, two-dimensional porous carbon nanosheets (PC)/one-dimensional multi-walled carbon nanotubes (MWCNTs) (PM) were used as carbon source supports, and AgNO3 was used as precursor. Si/Ag/PM composite was obtained by water bath reduction and calcination. The loading of nano-Ag improves the conductivity and stability of the Si-based anode. Inert metal nano-Ag can also catalyze the charging and discharging process of nano-Si. The three-dimensional interconnect structure of PM facilitates rapid electrical/ion transport and good electrolyte penetration, exhibits a highly Si-containing layered porous structure, and effectively enhances the physical constraints on soluble polysilicide. In addition, the three-dimensional interconnected layered porous structure and conductive network play a sufficient buffering role, and also help to inhibit the agglomeration of the nano-Ag particles. The lithium storage function of nano-Si is improved. The Initial coulombic efficiency (ICE) of the Si/Ag/PM electrode reached 78.9% at a current density of 0.1 A/g and maintained a specific discharge capacity of 706 mAh/g at a current density of 1 A/g with a capacity retention ratio of 68.6% after 300 cycles.

Two-dimensional porous carbon nanosheets from exfoliated nanopaper-like biomass

Two-dimensional porous carbon nanosheet materials are of increasing importance. Many examples for their synthesis exist, but they generally show some common requirements, such as rigid reaction conditions, high cost and complicated multiple synthetic steps. Here we report a facile and cost-effective way to prepare porous carbon nanosheets by using an exfoliated nanopaper-like biomass, i.e., melaleuca bark as precursor. It is found that just after a simple carbonization treatment, the nanopaper-like barks can be directly transformed into two-dimensional carbon nanosheets with a unique hierarchical porous structure. A high BET surface area of 1397 m2/g can be reached for the obtained carbon materials without any extra activation process. Tuning of nanostructures could be facilely accomplished by varying carbonization treatment conditions. The as-prepared porous carbon nanosheet serves well as the sulfur host materials for lithium-sulfur battery.

Engineering Pore Architecture into 2D Morphology: Synthesis of Multifunctional Nitrogen-Doped Porous Carbon Nanosheets Towards Long Calendar Life Lithium-Sulfur Battery

Owing to its high theoretical capacity, lithium-sulfur battery (Li-S) is considered as one of the leading alternatives to conventional lithium-ion batteries (LIBs) for electrical vehicles and grid-scale energy storage systems. The sulfur cathode has a theoretical capacity of 1675 mAh/g, accounting for an energy density as high as 2600 Wh/kg when coupled with lithium metal anode.1 Nevertheless, Li-S still need to overcome several challenges before being implemented in practical applications. The major issues include the low conductivity of sulfur, large volume change and severe polysulfide shuttling.2 In the recent reports, carbon material have been considered as an efficient sulfur host material to promote Li-S’s performance. However, it is difficult to solve all the problems simultaneously by a simple carbon material design. For instance, carbon nanotube has the advantages of its excellent conductivity, large surface area to volume ratio and prominent mechanical strength. However, it lacks porous sulfur reservoir to store the active sulfur, which makes their dissolution into electrolyte inevitable.3 Therefore, it is of great importance to develop multi-functional carbon materials for high-performance Li-S. Porous carbon materials have been intensively studied as the sulfur host due to its tunable porosity, large pore volume and controllable morphologies.4 The micro/meso pores can not only provide enough void space for sulfur volume expansion but also squeeze the cyclic sulfur molecules into short chain sulfur species and hence physically immobilize them from detrimentally shuttling to the anode side. To these aspects, we applied a dual-template strategy to synthesize nitrogen-doped two-dimensional porous carbon nanosheets (N-PCS). During the synthesis, we successfully integrating carbon pores into rational-designed secondary structure. The 2D carbon skeleton can effectively form conductive pathway for rapid electron/ion transfer. Moreover, when further doped with nitrogen, the carbon matrix enables a significantly improved conductivity and stronger interaction with polysulfides species due to the chemical bonding. With the advantages, when using N-PCS and sulfur composite as active material, an initial discharge capacity of 1360 mAh/g can be achieved at 0.1 C, showing a sulfur utilization as high as 81%. After 1000 cycles at 0.5 C, the cell can still retain ~50% of its initial capacity. At 1 C rate, N-PCS/S cathode is capable of delivering a high discharge capacity of 996 mAh/g, indicating its excellent electron conductivity and rate 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.S. Niu, W. Lv, G. Zhou, Y. He, B. Li, Q. H. Yang and F. Kang, Chem Commun (Camb), 2015, 51, 17720-17723. Figure 1

A Two-Dimensional Porous Carbon-Modified Separator for High-Energy-Density Li-S Batteries

Summary Lithium-sulfur (Li-S) batteries are a promising next-generation energy-storage system due to their high theoretical energy density and low cost. However, the rapid capacity fading of high-sulfur-loading cathodes caused by the shuttle of soluble polysulfide intermediates between two electrodes heavily hinders the development of high-energy-density Li-S batteries. We develop in this work a powerful functional separator to suppress the polysulfide shuttle by coating two-dimensional nitrogen-doped porous carbon nanosheets on one surface of a commercial polypropylene separator. The high surface area, high content of nitrogen dopants, and close-packing laminar structure of the two-dimensional porous carbon nanosheets make them ideal to fabricate a lightweight and thin separator for high-energy-density Li-S batteries. The separator reported in this work endows the high-sulfur-loading cathodes made of commercial carbon materials with significantly enhanced performances that are comparable with or even superior to the state-of-the-art sulfur composite cathodes, opening up new opportunities for designing practical high-energy-density Li-S batteries.

Facile synthesis of mesoporous hematite/carbon nanosheet for superior photodegradation

For large-scale fabrication of highly efficient photocatalysts, a facile modified solution combustion method is utilized to synthesize novel mesoporous α-Fe2O3/carbon hybrid nanosheets of highly photocatalytic activities. Such unique two-dimensional porous carbon nanosheets that are intimately contacted with homogeneous α-Fe2O3 nanoparticles present superior photocatalytic activity (complete degradation within 30min) and excellent long-term stability towards degradation of methylene blue, rhodamine B and methyl orange under simulated sunlight irradiation. The associated photocatalytic mechanism based on tailoring the holes and radicals has been discussed, indicating the synergistic effect of the exclusive porous carbon nanosheets and α-Fe2O3 nanoparticles on the dramatically enhanced photocatalytic activity. The results suggest that the scalable fabrication of novel carbon/α-Fe2O3 hybrid nanosheets holds tremendous potential for photodegradation of organic dyes and various applications in other fields.

Spinel MnCo2O4 nanoparticles cross-linked with two-dimensional porous carbon nanosheets as a high-efficiency oxygen reduction electrocatalyst

Catalysts for the oxygen reduction reaction (ORR) play an important role in fuel cells. Alternative non-precious metal catalysts with comparable ORR activity to Pt-based catalysts are highly desirable for the development of fuel cells. In this work, we report for the first time a spinel MnCo2O4/C ORR catalyst consisting of uniform MnCo2O4 nanoparticles cross-linked with two-dimensional (2D) porous carbon nanosheets (abbreviated as porous MnCo2O4/C nanosheets), in which glucose is used as the carbon source and NaCl as the template. The obtained porous MnCo2O4/C nanosheets present the combined properties of an interconnected porous architecture and a large surface area (175.3 m2·g-1), as well as good electrical conductivity (1.15 × 102 S·cm-1). Thus, the as-prepared MnCo2O4/C nanosheets efficiently facilitate electrolyte diffusion and offer an expedite transport path for reactants and electrons during the ORR. As a result, the as-prepared porous MnCo2O4/C nanosheet catalyst exhibits enhanced ORR activity with a higher onset potential and current density than those of its counterparts, including pure MnCo2O4, carbon nanosheets, and Vulcan XC-72R carbon. More importantly, the porous MnCo2O4/C nanosheets exhibit a comparable electrocatalytic activity but superior stability and tolerance toward methanol crossover effects than a high-performance Pt/C catalyst in alkaline medium. The synthetic strategy outlined here can be extended to other nonprecious metal catalysts for application in electrochemical energy conversion.

Carbon-coated Ni3Sn2 nanoparticles embedded in porous carbon nanosheets as a lithium ion battery anode with outstanding cycling stability

Carbon-coated Ni3Sn2 nanoparticles uniformly embedded in two-dimensional porous carbon nanosheets (2D Ni3Sn2@C@PGC) as superior lithium ion battery anode material were fabricated by a facile and scalable method, which involves in situ synthesis of 2D Ni@C@PGC and chemical vapor transformation processes from 2D Ni@C@PGC to Ni3Sn2@C@PGC.