N-doped Carbon Nanosheets Research Articles

Structure Manipulation of C1N1-Derived N-Doped Defective Carbon Nanosheets to Significantly Boost K-Storage Performance

Structure Manipulation of C₁N₁-Derived N-Doped Defective Carbon Nanosheets to Significantly Boost K-Storage Performance

Fullerene-Derived Porous and Defective N-Doped Carbon Nanosheets as Advanced Trifunctional Metal-Free Electrocatalysts.

Dopants and defects are crucial for multifunctional carbon-based metal-free electrocatalysts, but the rational design and facile production remain as a big challenge. Herein, we report a novel strategy using salt-assisted pyrolysis of derivatized fullerenes to fabricate defect-rich and N-doped carbon nanosheets. Molecular level modification of C60 via amination and hydroxylation gives rise to well-defined fullerol molecules bearing N-containing groups (FNG). Subsequent calcination of FNG and NaCl at 750 °C generates porous carbon nanosheets (FNCNs-750) and turns the N-containing groups into high-level N dopants (12.43 at.%). Further pyrolysis of FNCNs-750 at 900 °C (FNCNs-900) leads to a reduced N content populated by graphitic-N. Meanwhile, abundant intrinsic defects (e. g., topological defects and edges) are created due to the breakdown of fullerene cages and partial removal of edged N atoms. These structural features endow FNCNs-900 with outstanding trifunctional catalytic performance, better than or close to the noble metal-based benchmark catalysts.

Fabrication of Mo2C nanoparticles on N-doped carbon nanosheets as high-performance electrocatalyst

Molybdenum carbide is a promising material as electrocatalyst for hydrogen evolution reaction (HER). Herein, a facile strategy was proposed to prepare Mo-precursor by coordination of Mo with polysaccharide from natural biomass (jujube) at room temperature, which also acted as carbon and chelating agent. After the Mo-polysaccharide complex is carbonized, Mo2C nanoparticles (NPs) are highly dispersed on N-doped carbon matrix. In this process, nitrogen self-doping, lamellar carbon formation and molybdenum carbonization were achieved simultaneously, and particle aggregation is avoided. The results show that 2D carbon nanosheets-embedded Mo2C NPs is an excellent electrocatalyst for HER in alkaline medium. An overpotential of 124 mV at j = 10 mA cm−2 can be reached when the optimum Mo2C/NC-1.0 material as electrode material, and it is better than other Mo2C materials reported recently. The exceptional HER performance is originated from the 2D lamellar structure and rich-N atom from jujube source, which can accelerate electron transfer and change the electron density of Mo2C. This study opens a new avenue to design biomass-derived C/Mo2C used as catalyst in hydrogen-evolving reactions.

High synergetic transition metal phosphides@ nitrogen doped porous carbon nanosheets hybrids derived from silk fibroin and phytic acid self-assembly for ultra-high performance lithium storage

Transition metal phosphides (TMPs) have received widespread attention due to their high theoretical specific capacity and fast reaction kinetics. However, their poor conductivity and volume changes during the cycle limited their applications. Herein, we explore a facile and cost-effective way to prepare core–shell-like transition metal phosphides (TMPs: CoP, Ni 2 P, Cu 3 P) nanoparticles embedded into nitrogen doped porous carbon nanosheets (denoted as CoP@NDPCS, Ni 2 P@NDPCS, Cu 3 P@NDPCS) via biological material-driven assembly and self-template strategy. By self-assembled process, the amino and carbonyl groups in silk fibroin can chelate with metal ions, and then phytic acid added undergoes a coordination reaction with the metal components. Subsequently, core-shell TMPs nanoparticles supported by nitrogen doped porous carbon nanosheets were prepared by a one-step high-temperature calcination process. The obtained unique hybrid structure material with enough vacancy space to alleviate volume expansion exhibits ultra-high specific capacity and excellent cycling performance for the anode of lithium-ion batteries. The CoP@NDPCS, Ni 2 P@NDPCS and Cu 3 P@NDPCS electrodes exhibit the reversible capacities of 1014.2, 486.5 and 877 mAh g −1 at the current density of 500 mA g -1 , respectively. The remarkable lithium storage performance of TMP@NDPCS indicates that a reasonable structure designed by biological material-driven is an effective and promising method to enhance the lithium storage of transition metal phosphides. Core-shell transition metal phosphides supported by N-doped porous carbon nanosheets were prepared by one-step high temperature calcination process. The unique hybrid structure materials exhibit ultra-high specific capacity and excellent cycling stability for the anode of lithium-ion batteries, and the reasonable structure design by biological material-driven is very effective and universal method to enhance the lithium storage of transition metal phosphides. • Carbon nanosheets derived from silk fibroin can effectively alleviate the volume expansion of TMPs during the cycling process. • The TMP@NDPCS materials exhibit ultra-high specific capacity and excellent cycling stability for lithium-ion batteries. • The TMP@NDPCS hybrid materials were synthesized by one step phosphating.

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.

Active clusters ensemble effect of bimetallic RuCo alloys for efficient hydrogen production from ammonia borane

Bimetallic alloy nanoparticles (NPs) have proven to be an effective catalyst for hydrogen production from ammonia borane (AB) hydrolysis, but how to explain the relationship between bimetallic catalytic activity and the shape, size and dispersion of bimetallic components has always been a daunting challenge. In this paper, a trace Ru-based bimetallic RuCo alloy catalyst deposited on N-doped porous carbon nanosheets (NPC) was prepared through a simple impregnation reduction approach accompanied by the hydrolysis catalysis of AB. The activity of RuxCo1-x/NPC catalyst is mainly contingent on the composition of Ru and Co metals.The high catalytic activity of Ru0.075Co0.925/NPC can be ascribed to the fact that the active cluster ensemble effect of the bimetallic RuCo alloy exhibits the random stacking of rigid geometry and the structure of more d-electron layers without filling, which are conducive to its display of strange catalytic properties that bulk materials do not possess. Moreover, the co-alloying effect between Ru and Co NPs can dramatically improve the hydrolysis performance of AB. The present experimental study will provide a promising approach for high catalytic activity and have the potential of hydrolyzing hydrogen from chemical storage materials.

N-Doped Two-Dimensional Carbon Nanosheets with Micropore-Dominant Porosity for High-Performance Supercapacitors

N-doped two-dimensional (2D) porous carbon nanosheets (PCNs) have been developed for high-performance supercapacitors (SCs) through chemical crosslinking of biomass shell and γ-glutamic acid followed by pyrolysis and activation. The C and N recomposition and pore formation processes occur within the shell/γ-glutamic acid composite during pyrolysis. The enormous specific surface area of 2393 m2 g–1, unique 2D nanosheet, and rich microporous structure are only a few of the benefits of an optimized PCNs material. The rich oxygen/nitrogen functional groups and 2D nanosheet structure endow the materials with super hydrophilicity, and also provide extra pseudocapacitance. With these added structural advantages and the component synergy, the PCNs show superior performance for which the specific capacitance is 321 F g–1, and only with a 7% capacitance loss after 13,000 cycles in a three-electrode system. Furthermore, a PCNs-based symmetric SC displays a high specific energy of 9.7 W h kg–1.

Construction of 0D/1D/2D MXene nanoribbons-NiCo@NC hierarchical network and their coupling effect on electromagnetic wave absorption

The construction of MXene-based composites with rational hierarchical structures and networks has emerged as a promising candidate for high-performance electromagnetic wave (EMW) absorption, stemming from the unpredictable formation of multiple components and multiple interfaces. Herein, a stable and porous 0D/1D/2D MXene nanoribbons (NRs)-NiCo@NC hierarchical network consisting of 0D NiCo alloy embedded in nitrogen (N)-doped carbon (NiCo@NC), 1D Ti3C2Tx MXene nanoribbons, and 2D N-doped carbon nanosheets is rationally constructed for EMW absorption. The “shearing effect” of alkaline KOH can induce the formation of 1D MXene nanoribbons with staggered-connected nanoribbon network and macroporosity, which greatly increases the attenuation of multiple reflections of EMW. Meanwhile, MXene nanoribbons can serve as a structural network for the subsequent growth of 2D NiCo layered double hydroxide (LDH) ultrathin nanosheets as well as a conductive network for conduction loss. The 0D NiCo@NC derived from NiCo LDH nanosheets inherit excellent eddy current losses that contribute to magnetic loss and abundant N heteroatoms that contribute to dipole polarization. Furthermore, thanks to the coupling effect, 0D/1D/2D hierarchical network provides numerous interfaces that contribute to interfacial polarization and considerable exchange resonances that contribute to magnetic loss. As a result, 0D/1D/2D MXene nanoribbons-NiCo@NC hierarchical network exhibits robust EMW absorption performance with a reflection loss (RL) value of −57.1 dB at a thickness of 4.82 mm and a RL value of −33.19 dB at a thickness of only 1.4 mm. This study provides new inspiration for the future construction of EMW absorbers with hierarchical networks.

Cobalt clusters on g-C3N4 nanosheets for enhanced H2/H2O2 generation and NO removal

A one-step thermal polymerization method was developed to create homogeneous metallic cobalt (Co) clusters on graphitic carbon nitride (g-C3N4) nanosheets. The size (less than 3 nm) and distribution of Co clusters were controlled by a subsequent acid treatment. Because of the nanofluidic channels, efficient charge transfer, and enhanced light harvesting ability, optimized Co/g-C3N4 nanoarchitectonics by acid treatment revealed excellent photocatalytic activities. The visible-light photocatalytic H2 generation, H2O2 evolution and NO removal rate of the nanoarchitectonics were 82, 4, and 2 times of those of g-C3N4 nanosheets, respectively, suggesting that integrating transition metal clusters on g-C3N4 nanosheets is a novel strategy for NO removal and water splitting. Interestingly, Co/g-C3N4 nanoarchitectonics were further heat-treated at high temperature to create Co clusters decorated N-doped carbon nanosheets, in which ideal performance in hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction in alkaline solution were observed. This result supplied an efficient route to construct non-noble metal multifunctional catalysts.

Coordination polymer-derived non-precious metal catalyst for propane dehydrogenation: Highly dispersed zinc anchored on N-doped carbon

Highly dispersed non-precious metal catalysts supported on carbon have been intensively explored in the field of heterogeneous catalysis and material science owing to its low price, special electronic and geometric structure. However, their application and improvement of catalytic efficiency in alkane dehydrogenation were chronically limited due to spontaneous aggregation of metal atoms under the harsh conditions, low loading content and the complex preparation process. A new type of lamellar coordination polymer and a series of well-dispersed zinc-based catalyst anchored on N-doped carbon nanosheets were prepared via a facile combination of self-assembly and controlled pyrolysis. These carbonized composites showed superior initial activity (the propane conversion at 34% and the olefin selectivity at 80%) and acceptable catalytic stability (the deactivation rate of 0.082 h−1) in propane DDH reactions (600 °C, 2.4 kPa C3H8, He balance). The structure analysis results indicated the zinc loading in the optimized sample can be up to 19 wt%, which was also effectively retained after reactions. The systematic investigation on structure–function relations revealed that the catalytic activity originated from highly dispersed Zn, and the improvement of its performance could be ascribed to the mutual promotion between zinc loading and specific surface area. This work provided new guidelines to enable further development of the carbon-supported zinc-based catalyst in alkane dehydrogenation reactions and promoted the rational design of highly dispersed metal materials.

Schiff-base polymer derived FeCo-N-doped porous carbon flowers as bifunctional oxygen electrocatalyst for long-life rechargeable zinc-air batteries

Rational design and exploration of low-cost and robust bifunctional oxygen electrocatalysts are vitally important for developing high-performance zinc-air batteries (ZABs). Herein, we reported a facile yet cost-efficient approach to construct a bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) electrocatalyst composed of N-doped porous carbon nanosheet flowers decorated with FeCo nanoparticles (FeCo/N-CF). Rational design of this catalyst is achieved by designing Schiff-base polymer with unique molecular structure via hydrogen bonding of cyanuramide and terephthalaldehyde polycondensate in the presence of metal cations. It exhibits excellent activity and stability for electrocatalysis of ORR/OER, enabling ZAB with a high peak power density of 172 mW cm−2 and a large specific capacity of 811 mA h g−1Zn at large current. The rechargeable ZAB demonstrates excellent durability for 1000 h with slight voltage decay, far outperforming a couple of precious Pt/Ir-based catalysts. Density functional theory (DFT) calculations reveal that high activity of bimetallic FeCo stems from enhanced O2 and OH− adsorption and accelerated O2 dissociation by OO bond activation.

Ultrafine CoFe nanoparticles supported on nitrogen-doped carbon sheets boost oxygen electrocatalysis for Zn-air batteries

Efficient, durable and inexpensive electrocatalysts are urgently needed to mediate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Zn-air batteries (ZABs). Herein, ultrafine CoFe alloyed nanoparticles (NPs) homogeneously decorated on N-doped carbon nanosheets (CoFe@NCS) are synthesized by annealing the precursor of NCS supported CoFe-based Prussian-blue-analogues. The optimal CoFe@NCS delivers prominent electrocatalytic behaviors for both the ORR (0.88 V of half-wave potential) and OER (340 mV of overpotential at 10 mA cm−2) in an alkaline electrolyte. The outstanding bifunctional electrocatalytic activities are ascribed to the synergistic interplay of structural and compositional advantages, including the hierarchically porous structure as well as the strong coupling of ultrafine CoFe species and NCS. Simultaneously, the assembled flow ZAB with CoFe@NCS as the air-cathode catalyst manifests a superior battery performance to the device catalyzed by the noble-metal benchmark (Pt/C + RuO2). This work may pave an avenue for developing efficient bifunctional electrocatalysts and promoting the practical application of ZABs.

One-pot synthesis of N-doped carbon nanosheets from Victorian brown coal with enhanced lithium storage

We report a novel one-pot synthesis method of N-doped porous carbon nanosheets (NCNS) from Victorian brown coal (VBC), which puts forward a sustainable alternative method of utilizing these vast and low-cost resources. VBC and urea were used as the carbon and nitrogen sources in the synthesis process. Benefiting from the porous nanosheet structure and doped N atoms in the carbon matrix, the prepared NCNS at a VBC:urea ratio of 1:3 delivered a promising specific capacity of 604.7 mAh/g at the current density of 50 mA/g. After the cycling performance under 1000 cycles at 1000 mA/g, the reversible capacity remained at 303.6 mAh/g (capacity retention of 97.43%), suggesting a superior stability. Various analytical techniques were used to establish the formation mechanism of NCNS in the presence of urea as well as the charge storage behavior and mechanism in the developed NCNS. The proposed process has great potential for the efficient conversion of VBC into high-performance carbon anode materials for LIBs.

Bifunctional high-entropy alloys for sensitive nitrite detection and oxygen reduction reaction

Herein, a novel confinement growth strategy was proposed to synthesize nanostructured high-entropy alloys (HEAs) by using the carbon nitride (g-C3N4) as anchoring template and phenolic resin as coating layer. Through the high temperature treatment, the FeCoNiCuMn HEA nanoparticles (NPs) formed uniformly on g-C3N4 and phenolic resin derived two-dimensional (2D) N-doped carbon nanosheets (FeCoNiCuMn/NCNS). Due to the synergistic effects of each metal sites in HEAs, the FeCoNiCuMn/NCNS electrochemical sensors show a very sensitive response to nitrite, with a broad linear response range of 2–1000 μM, a high sensitivity of 553.43 µA mM−1 cm−2, a detection limit of 0.14 μM (S/N = 3), and a rapid response balance at 0.74 V (response time is 1.1 s). FeCoNiCuMn/NCNS exhibits extraordinary stability, favorable anti-interference and reproducibility, and offers good feasibility for the detection of nitrite in water. Besides, the FeCoNiCuMn/NCNS also indicate excellent electrocatalytic activity for ORR application in alkaline medium with a higher half-wave potential (E1/2) of 0.87 V, a lower Tafel slope of 48 mV dec−1 and electron transfer number (n) of approximately 3.9, when compared with the commercial Pt/C (0.85 V and 77 mV dec−1). These results suggest that FeCoNiCuMn/NCNS exhibits promising applications in the nitrite detection and oxygen reduction.

Enhanced oxygen reduction of porous N-doped carbon nanosheets with graphitic N and defects obtained from coal-based graphene quantum dots

Metal-free carbon-based electrocatalysts for oxygen reduction reaction (ORR) have received considerable attention owing to their abundance and low cost. However, designing carbon-based electrocatalysts with excellent performance in a facile manner remains a challenge. In this work, porous nitrogen-doped carbon nanosheet (PNCNs) catalysts with high contents of graphitic N and defects were readily prepared via a simple self-doping method, in which coal-based graphene quantum dots (GQDs) were used as the carbon and nitrogen resource. Based on the results, PNCNs-900 (obtained at 900 °C) displayed good ORR performance, with a half-wave potential (E1/2) of 0.80 V. It also exhibited high stability and methanol tolerance compared with commercial Pt/C. Experimental investigations and theoretical calculations prove that the increased ORR electrocatalytic activity of PNCNs-900 is due to the synergistic effect of a large number of defects and graphitic N. Furthermore, its higher electrocatalytic activity for ORR also benefits from the porous lamellar structure, which facilitates the mass transfer process. This study offers a novel approach for developing effective ORR catalysts and for the high value-added utilization of coal resources.

MoC nanocrystals confined in N-doped carbon nanosheets toward highly selective electrocatalytic nitric oxide reduction to ammonia

MoC nanocrystals confined in N-doped carbon nanosheets toward highly selective electrocatalytic nitric oxide reduction to ammonia

Synergistic Effects in Ultrafine Molybdenum-Tungsten Bimetallic Carbide Hollow Carbon Architecture Boost Hydrogen Evolution Catalysis and Lithium-Ion Storage.

Constructing hierarchical heterostructures is considered a useful strategy to regulate surface electronic structure and improve the electrochemical kinetics. Herein, the authors develop a hollow architecture composed of MoC1- x and WC1- x carbide nanoparticles and carbon matrix for boosting electrocatalytic hydrogen evolution and lithium ions storage. The hybridization of ultrafine nanoparticles confined in the N-doped carbon nanosheets provides an appropriate hydrogen adsorption free energy and abundant boundary interfaces for lithium intercalation, leading to the synergistically enhanced composite conductivity. As a proof of concept, the as-prepared catalyst exhibits outstanding and durable electrocatalytic performance with a low overpotential of 103 and 163mV at 10mA cm-2 , as well as a Tafel slope of 58 and 90mV dec-1 in alkaline electrolyte and acid electrolyte, respectively. Moreover, evaluated as an anode for a lithium-ion battery, the as-resulted sample delivers a rate capability of 1032.1mA h g-1 at 0.1 A g-1 . This electrode indicates superior cyclability with a capability of 679.1mA h g-1 at 5 A g-1 after 4000 cycles. The present work provides a strategy to design effective and stable bimetallic carbide composites as superior electrocatalysts and electrode materials.

N-doped carbon nanosheets derived from lignin as a novel bifunctional electrocatalyst for rechargeable zinc-air battery

New energy utilization devices have attracted great research interest as a sustainable route for clean energy production. However, the disadvantage of this process is the need to use high-cost precious metal catalysts. Hereby, N-doped carbon nanosheets (LNZ@GC) was prepared by ball milling-carbonization two step strategy using alkali lignin as carbon source and the gas-phase exfoliation with NH4Cl and ZnCl2 as pore-forming agents. We investigative the properties of LNZ@GC series and find that LNZ@GC exhibit the most excellent ORR performances with a half-wave potential up to 0.851 V, outstanding stability and methanol tolerance, which are all superior commercial Pt/C. Furthermore, the rechargeable zinc-air battery assembled by LNZ-800@GC shows excellent performance with a high power density of 841.8 Wh kg−1, a large specific capacity of 750.3 mA h g−1. This work not only provides a general strategy for the preparation of porous N-doped catalysts, but also provides technical support for the design and development of inexpensive catalysts using lignin as a carbon source.

Facile synthesis of hierarchical porous two-dimensional N-doped carbon nanosheets as bi-functional electrode for superior supercapacitor and photo-catalyst

The hierarchical porous nitrogen-doped two-dimensional carbon (HNGC) was prepared by simple calcination of magnesium sulfate (MgSO4) and self-synthesized nitrogen-doped two-dimensional graphene-like carbon at a mild temperature in oxygen. The influence MgSO4 on the morphology, structure and chemical composition of the prepared HNGC samples were studied using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, surface area analysis, X-ray photoelectron microscopy and elemental analyzer. HNGC-2 exhibited a uniform three-dimensional coral-like porous inter-connected structure, large specific surface area, high pore volume, and no loss of nitrogen content. HNGC-2 demonstrated an excellent rate capability of 62.8% at 20 A g−1, outstanding stability of 96.1% following 5000 cycles and the assembled symmetric supercapcitor achieved 12.5 Wh kg−1 at a 350 Wkg-1 and 7.5 Wh kg−1 at 3500 Wkg-1. The novel method was also found to be effective for facilitating the electrochemical performance of commercial biomass active carbon. In addition, HNGC-2 was used for the photo-catalytic degradation of methylene blue and over 99% of methylene blue was successfully degraded under 25-min visible irradiation in the presence of potassium persulfate. The enhanced electrochemical performance and the excellent photo-catalytic performance of HNGC-2 indicated that porous carbon can be successfully activated using an appropriate oxidation strategy.

Facile synthesis of carbon nanosheet arrays decorated with chromium-doped Co nanoparticles as advanced bifunctional catalysts for Zn-air batteries

The development of low-cost electrochemical catalytic nanomaterials for efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) through structural and composition control is a great challenge. Herein, a 3D hybrid structure is designed by an in-situ approach for growing 2D leaf-like nanosheet arrays on 1D electrospun nanofibers. The resultant catalysts composed of Cr-doped Co nanoparticle decorated N-doped carbon nanosheet and carbon nanofiber are synthesized by subsequent Cr3+ impregnation and heat treatment. The excellent properties of the as-prepared cathode benefit from the novel establishment of the 3D structure and the regulating mechanism of the electron density of Co after Cr doping, which simultaneously increases the mass and charge transfer process during the catalytic reaction. Consequently, Cr0.10-Co@NC exhibits excellent catalytic performance for the ORR (with a half-wave potential of 0.84 V) and OER (with an overpotential of 370 mV). When used in a homemade ZAB for evaluating their practical reversible performance, the device exhibits a higher open-circuit voltage (1.45 V) and a smaller potential gap (0.73 V) with excellent cycle durability of 110 h. This work offers a well-designed structure and development for synthesizing efficient and durable electrocatalysts in electrochemical energy conversion technologies.