Nitrogen-doped Porous Carbon Nanosheets Research Articles

PdCoNi nanoparticles supported on nitrogen-doped porous carbon nanosheets for room temperature dehydrogenation of formic acid

Abstract The development of cost-effective heterogeneous catalysts for the dehydrogenation of formic acid (FA) is the key challenge for the commercialization of FA as a hydrogen-storage medium. Herein, PdCoNi nanoparticles (NPs) with different element ratios supported on N-doped carbon nanosheets (N-CN) were designed, which exhibit excellent catalytic dehydrogenation performance for FA. Compared with PdCoNi NPs loaded on the carbon nanosheets (CN), the introduction of pyrrolic N to CN induces the formation of ultrafine, monodispersed and amorphous Pd 0.6 Co 0.2 Ni 0.2 NPs with a size of 1.60 nm, which significantly increases the number of active sites and the instant contact between FA and catalysts. The as-prepared Pd 0.6 Co 0.2 Ni 0.2 /N-CN catalyst shows more than 99% conversion and 100% H 2 selectivity at room temperature, with a record-high initial turnover frequency (TOF initial ) of 1249.0 h −1 among non-noble containing Pd-based catalysts, which demonstrates the high potential of Pd 0.6 Co 0.2 Ni 0.2 /N-CN as a practical catalyst for the hydrogen generation from FA.

Synthesis of Biomass-Derived Nitrogen-Doped Porous Carbon Nanosheests for High-Performance Supercapacitors

Graphene-like two-dimensional carbon nanosheets with properly modulated compositions and porosity are of particular importance for robust capacitance harvesting. Nevertheless, the large-scale and cost-effective production of such nanostructures still remains a great challenge. Herein, we innovatively produce nitrogen-doped porous carbon nanosheets using pine nut shells, an abundant biomass waste, as the precursor, under the synergetic effect of KOH and melamine during the activation process. The sole activation of the precursors with KOH can produce only traditional activated carbon particles of several micrometers, while interestingly, the extra introduction of melamine results in nitrogen-doped porous carbon nanosheets possessing high tunability. By construction of a two-electrode configuration, the supercapacitors with optimal nanosheets as the electrode materials can deliver a superior specific capacitance of 324 F g –1 at 0.05 A g–1, outstanding rate capability of 258 F g–1 at 20 A g–1, and extraordi...

Assembling Carbon Pores into Carbon Sheets: Rational Design of Three-Dimensional Carbon Networks for a Lithium-Sulfur Battery.

The conversion reaction-based lithium-sulfur battery features an attractive energy density of 2600 W h/kg. Nevertheless, the unsatisfied performance in terms of poor discharge capacity and cycling stability still hinders its practical applications. Recently, porous carbon materials have been widely reported as promising sulfur reservoirs to promote the sluggish reaction kinetics of sulfur conversion, tolerate volume expansion of sulfur, and suppress polysulfide shuttling. However, porous carbon with a simply designed nanostructure is hard to satisfy all of these aspects simultaneously. Herein, we have applied a dual-template strategy that assembles carbon pores into carbon sheets to prepare three-dimensional (3D) nitrogen-doped porous carbon nanosheets (N-PCSs) as the multifunctional sulfur host for the Li-S battery. By arranging carbon pores within an interconnected 3D architecture, the porous carbon sheets enable rapid electron/ion transfer. Moreover, the micro/mesopores and nitrogen dopant in N-PCS provide both physical and chemical restrictions to polysulfide species. With these advances, the N-PCS/S cathode delivers a large initial discharge capacity of 1360 mA h/g at 0.1 C. When performed at 0.5 C for 1000 cycles, the cathode can still remain ∼50% of its capacity with a low decay rate of 0.05% per cycle, showing the important role of the 3D carbon material in the Li-S battery.

Porous Carbon Nanosheets Prepared from Plastic Wastes for Supercapacitors

With the rise of living standards, non-biodegradable waste, especially waste plastics, has caused serious environmental problems. Herein, we prepare nitrogen doped porous carbon nanosheets (N-PCNs) using magnesium hydroxide [Mg(OH)2] sheets, which are modified by Zn and Co bimetallic zeolitic imidazolate framework nanoparticles as templates and polystyrene (PS) as a carbon precursor. During the high-temperature pyrolysis process, PS pyrolyzes into small organic molecule gases, which can be converted into graphene-like carbon material under the catalyst magnesia (MgO) and Co species. Nitrogen is introduced into the carbon material in situ by the pyrolysis of imidazole ligands, and the evaporation of Zn helps increase the surface area. The obtained N-PCNs with porous structure and large specific surface area can be used as electrode material for supercapacitors, exhibiting excellent capacitance of 149 F g−1 at the current density of 0.5 A g−1, an excellent cycling stability of 97.6% for up to 5000 cycles.

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

Superhierarchical Cobalt-Embedded Nitrogen-Doped Porous Carbon Nanosheets as Two-in-One Hosts for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries, based on the redox reaction between elemental sulfur and lithium metal, have attracted great interest because of their inherently high theoretical energy density. However, the severe polysulfide shuttle effect and sluggish reaction kinetics in sulfur cathodes, as well as dendrite growth in lithium-metal anodes are great obstacles for their practical application. Herein, a two-in-one approach with superhierarchical cobalt-embedded nitrogen-doped porous carbon nanosheets (Co/N-PCNSs) as stable hosts for both elemental sulfur and metallic lithium to improve their performance simultaneously is reported. Experimental and theoretical results reveal that stable Co nanoparticles, elaborately encapsulated by N-doped graphitic carbon, can work synergistically with N heteroatoms to reserve the soluble polysulfides and promote the redox reaction kinetics of sulfur cathodes. Moreover, the high-surface-area pore structure and the Co-enhanced lithiophilic N heteroatoms in Co/N-PCNSs can regulate metallic lithium plating and successfully suppress lithium dendrite growth in the anodes. As a result, a full lithium-sulfur cell constructed with Co/N-PCNSs as two-in-one hosts demonstrates excellent capacity retention with stable Coulombic efficiency.

Synthesis of N-doped carbon nanosheets with controllable porosity derived from bio-oil for high-performance supercapacitors

Nitrogen-doped porous carbon nanosheets were fabricated by carbonization and subsequent KOH activation of bio-oil derived polymers.

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.

Nitrogen-doped nanostructured porous carbon derived from monosodium glutamate for high-performance lithium sulfur battery

Carbon host materials play an important role in improving the electrochemical performances of lithium-sulfur batteries. In this work, we have successfully prepared nitrogen-doped porous carbon nanosheets (NPCN) by using low-cost raw materials (monosodium glutamate) via a facile carbonization approach without any activation process. The obtained NPCN-800 possesses a special micro/mesoporous structure, with a relatively high BET surface area and appropriate nitrogen doping. By employing the NPCN-800 as a reservoir to impregnate sulfur as the cathode material of lithium-sulfur batteries, the resulting sulfur/carbon composite with 65.5 wt% sulfur exhibits an initial discharge capacity of 1070 mAh g−1 at 0.2 C and enhanced capacity retention of 680 mAh g−1 after 150 cycles. Moreover, a capacity of 452 mAh g−1 at 0.5 C is achieved over 200 cycles with 98.6% Coulombic efficiency. The superior electrochemical performance is attributed to the synergistic effect of the hierarchical porous structure (physisorption) and N-doping (chemisorption).

Nitrogen-Doped Porous Carbon Nanosheets Derived from Coal Tar Pitch as an Efficient Oxygen-Reduction Catalyst

High value-added processing and manufacturing of coal tar pitch (CTP), an abundant and cheap byproduct of the coal industry, is a crucial issue worldwide. Herein, novel nitrogen-doped porous carbon nanosheets (N-PCN) were fabricated by selecting CTP and ferric chloride (FeCl3) as the carbonaceous source and mild activating agent, respectively. Due to the synergistic effects of the unique flaky graphitic structure, hierarchical porosity, high nitrogen-doping contents, and trace of Fe-containing sites, N-PCN exhibited excellent oxygen-reduction (ORR) electrocatalytic activity in alkaline medium. Linear sweep voltammetry (LSV) testing results for N-PCN showed that the diffusion-limited current density was as high as 5.8 mA cm–2 and the half-wave potential was 0.85 V (vs RHE), both better than commercial 20 wt % Pt/C. Moreover, N-PCN showed an ideal methanol tolerance and catalytic stability, indicating its potential application as cathode catalysts in direct methanol fuel cells (DMFCs).

Proline-derived in situ synthesis of nitrogen-doped porous carbon nanosheets with encaged Fe2O3@Fe3C nanoparticles for lithium-ion battery anodes

The homogeneous incorporation of heteroatoms into two-dimensional C nanostructures, which leads to an increased chemical reactivity and electrical conductivity as well as enhanced synergistic catalysis as a conductive matrix to disperse and encapsulate active nanocatalysts, is highly attractive and quite challenging. In this study, by using the natural and cheap hydrotropic amino acid proline—which has remarkably high solubility in water and a desirable N content of ~12.2 wt.%—as a C precursor pyrolyzed in the presence of a cubic KCl template, we developed a facile protocol for the large-scale production of N-doped C nanosheets with a hierarchically porous structure in a homogeneous dispersion. With concomitantly encapsulated and evenly spread Fe2O3 nanoparticles surrounded by two protective ultrathin layers of inner Fe3C and outer onion-like C, the resulting N-doped graphitic C nanosheet hybrids (Fe2O3@Fe3C-NGCNs) exhibited a very high Li-storage capacity and excellent rate capability with a reliable and prolonged cycle life. A reversible capacity as high as 857 mAh•g–1 at a current density of 100 mA•g–1 was observed even after 100 cycles. The capacity retention at a current density 10 times higher—1,000 mA•g–1—reached 680 mAh•g–1, which is 79% of that at 100 mA•g–1, indicating that the hybrids are promising as anodes for advanced Li-ion batteries. The results highlight the importance of the heteroatomic dopant modification of the NGCNs host with tailored electronic and crystalline structures for competitive Li-storage features. Open image in new window

Molybdenum Carbide-Embedded Nitrogen-Doped Porous Carbon Nanosheets as Electrocatalysts for Water Splitting in Alkaline Media.

Molybdenum carbide (Mo2C) based catalysts were found to be one of the most promising electrocatalysts for hydrogen evolution reaction (HER) in acid media in comparison with Pt-based catalysts but were seldom investigated in alkaline media, probably due to the limited active sites, poor conductivity, and high energy barrier for water dissociation. In this work, Mo2C-embedded nitrogen-doped porous carbon nanosheets (Mo2C@2D-NPCs) were successfully achieved with the help of a convenient interfacial strategy. As a HER electrocatalyst in alkaline solution, Mo2C@2D-NPC exhibited an extremely low onset potential of ∼0 mV and a current density of 10 mA cm-2 at an overpotential of ∼45 mV, which is much lower than the values of most reported HER electrocatalysts and comparable to the noble metal catalyst Pt. In addition, the Tafel slope and the exchange current density of Mo2C@2D-NPC were 46 mV decade-1 and 1.14 × 10-3 A cm-2, respectively, outperforming the state-of-the-art metal-carbide-based electrocatalysts in alkaline media. Such excellent HER activity was attributed to the rich Mo2C/NPC heterostructures and synergistic contribution of nitrogen doping, outstanding conductivity of graphene, and abundant active sites at the heterostructures.

Nitrogen-Doped Porous Carbon Nanosheets from Eco-Friendly Eucalyptus Leaves as High Performance Electrode Materials for Supercapacitors and Lithium Ion Batteries.

Nitrogen-doped porous carbon nanosheets were prepared from eucalyptus tree leaves by simply mixing the leaf powders with KHCO3 and subsequent carbonisation. Porous carbon nanosheets with a high specific surface area of 2133 m2 g-1 were obtained and applied as electrode materials for supercapacitors and lithium ion batteries. For supercapacitor applications, the porous carbon nanosheet electrode exhibited a supercapacitance of 372 F g-1 at a current density of 500 mA g-1 in 1 m H2 SO4 aqueous electrolyte and excellent cycling stability over 15 000 cycles. In organic electrolyte, the nanosheet electrode showed a specific capacitance of 71 F g-1 at a current density of 2 Ag-1 and stable cycling performance. When applied as the anode material for lithium ion batteries, the as-prepared porous carbon nanosheets also demonstrated a high specific capacity of 819 mA h g-1 at a current density of 100 mA g-1 , good rate capability, and stable cycling performance. The outstanding electrochemical performances for both supercapacitors and lithium ion batteries are derived from the large specific surface area, porous nanosheet structure and nitrogen doping effects. The strategy developed in this paper provides a novel route to utilise biomass-derived materials for low-cost energy storage systems.

Natural Silk Cocoon Derived Nitrogen-doped Porous Carbon Nanosheets for High Performance Lithium-Sulfur Batteries

There is an ever-increasing interest in utilization of natural biomass for rational design and fabrication of advanced carbon materials towards energy-related storage/conversion application. In this work, we successfully prepared an in-situ nitrogen-doped porous carbon nanosheet (NPCN) materials derived from renewable silk cocoon via a facile simultaneous activation and carbonization approach using metal salt FeCl3 and ZnCl2 as chemical activating agent. The as-prepared carbon materials were fully characterized to determine their morphology and structure features, and it was found that the obtained NPCN has a unique interconnected sheet-like morphology and a hierarchically porous structure with a relatively high specific surface area of 1540m2g−1 and a large pore volume of 1.85cm3g−1. Owing to the inherent nitrogen-containing functional groups existing in the silk cocoon, in-situ doping of nitrogen heteroatom can be realized by the carbonization treatment, which can efficiently boost the electrical conductivity of the porous carbon nanosheets. By employing the NPCP as a reservoir to impregnate sulfur for lithium-sulfur batteries, the resulting carbon/sulfur composite (NPCN/S) shows a remarkably improved rate performance and superior long-term cycling stability with an extremely low decay rate (0.1% per cycle) up to 300 cycles at a high rate of 2C (3350mAg−1). What is more, a Coulombic efficiency of approximatively 100% is obtained. Taking into consideration various factors including sustainable development, low-cost carbon source, and facile mass production, this work shows a great scientific significance and promising prospect in scalable preparation of advanced carbon-based host matrix for the efficient immobilization of sulfur towards developing high performance lithium-sulfur batteries.

Carbon Nanosheets: Nitrogen-Doped Porous Carbon Nanosheets Templated from g-C3 N4 as Metal-Free Electrocatalysts for Efficient Oxygen Reduction Reaction (Adv. Mater. 25/2016).

T. Zhang and co-workers report the synthesis of nitrogen-doped porous carbon nanosheets with extremely high nitrogen content and high surface areas using graphitic carbon nitride (g-C3 N4 ) as template, nitrogen source, and porogen. As described on page 5080, the nanosheets exhibit outstanding oxygen reduction catalytic activities which are comparable to commercial Pt/C catalysts in alkaline media.

Hierarchically Porous N-Doped Carbon Nanosheets Derived From Grapefruit Peels for High-Performance Supercapacitors

In this work, the low-cost hierarchically porous nitrogen-doped carbon nanosheets (PNCNs) were prepared via one-step carbonization and KOH activation process of grapefruit peels. The prepared PNCNs exhibit higher specific surface area due to the inducement of the KOH-assisted carbonization compared to directly carbonized grapefruit peels (DCGPs). The PNCNs exhibit excellent electrochemical performances with high specific capacitance up to 311 F g−1, superior cycling stability over 10000 cycles with only 5.95 % capacitance degradation, high energy density of 17.7 W h kg−1 and power density of 1100 W kg−1 in 1 mol L−1 H2SO4 electrolyte. All these electrochemical data are significantly better than the comparative DCGPs material. Moreover, the assembled symmetric supercapacitor in 1 mol L−1 Na2SO4 aqueous electrolyte exhibits a high energy density of 34.05 W h kg−1 at a power density of 180 W kg−1 and retains 14.25 W h kg−1 even at 5400 W kg−1.

Nitrogen-Doped Porous Carbon Nanosheets Templated from g-C3 N4 as Metal-Free Electrocatalysts for Efficient Oxygen Reduction Reaction.

Nitrogen-doped porous carbon nanosheets (N-CNS) are synthesized by hydrothermal carbon coating of g-C3 N4 nanosheets followed by high-temperature treatment in N2 . g-C3 N4 serves as a template, nitrogen source, and porogen in the synthesis. This approach yields N-CNS with a high nitrogen content and comparable oxygen reduction reaction catalytic activities to commercial Pt/C catalysts in alkaline media.

Two‐Dimensional Core‐Shelled Porous Hybrids as Highly Efficient Catalysts for the Oxygen Reduction Reaction

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have drawn much attention due to their unique physical and chemical properties. Using TMDs as templates for the generation of 2D sandwich-like materials with remarkable properties still remains a great challenge due to their poor solvent processability. Herein, MoS2 -coupled sandwich-like conjugated microporous polymers (M-CMPs) with high specific surface area were successfully developed by using functionalized MoS2 nanosheets as template. As-prepared M-CMPs were further used as precursors for preparation of MoS2 -embedded nitrogen-doped porous carbon nanosheets, which were revealed as novel electrocatalysts for oxygen reduction reaction with mainly four-electron transfer mechanism and ultralow half-wave potential in comparison with commercial Pt/C catalyst. Our strategy to core-shelled sandwich-like hybrids paves a way for a new class of 2D hybrids for energy conversion and storage.

Nitrogen-doped porous carbon nanosheets derived from poly(ionic liquid)s: hierarchical pore structures for efficient CO2capture and dye removal

Nitrogen-doped porous carbon nanosheets were synthesizedviaan activation- or post-treatment-free approach, which delivered high CO2and dye adsorption capacities.

Graphene supported nitrogen-doped porous carbon nanosheets derived from zeolitic imidazolate framework for high performance supercapacitors

A nitrogen-doped porous carbon nanosheet/graphene composite (NPCN/G) with layer-by-layer structure is facilely synthesized on a large scale via pyrolysis of a zeolitic imidazolate framework (ZIF-8)/graphene (2D) mixture.