Nitrogen-doped Graphene-like Carbon Research Articles

Nitrogen-Doped Graphene-Like Carbon Intercalated MXene Heterostructure Electrodes for Enhanced Sodium- and Lithium-Ion Storage.

MXene is investigated as an electrode material for different energy storage systems due to layered structures and metal-like electrical conductivity. Experimental results show MXenes possess excellent cycling performance as anode materials, especially at large current densities. However, the reversible capacity is relatively low, which is a significant barrier to meeting the demands of industrial applications. This work synthesizes N-doped graphene-like carbon (NGC) intercalated Ti3C2Tx (NGC-Ti3C2Tx) van der Waals heterostructure by an in situ method. The as-prepared NGC-Ti3C2Tx van der Waals heterostructure is employed as sodium-ion and lithium-ion battery electrodes. For sodium-ion batteries, a reversible specific capacity of 305mAhg-1 is achieved at a specific current of 20mAg-1, 2.3 times higher than that of Ti3C2Tx. For lithium-ion batteries, a reversible capacity of 400mAhg-1 at a specific current of 20mAg-1 is 1.5 times higher than that of Ti3C2Tx. Both sodium-ion and lithium-ion batteries made from NGC-Ti3C2Tx shows high cycling stability. The theoretical calculations also verify the remarkable improvement in battery capacity within the NGC-Ti3C2O2 system, attributed to the additional adsorption of working ions at the edge states of NGC. This work offers an innovative way to synthesize a new van der Waals heterostructure and provides a new route to improve the electrochemical performance significantly.

Bottom-up self-assembly strategy to construct ternary MoxC/Ni3Fe@GL as efficient water splitting electrocatalyst

Efficient and robust bifunctional non-precious metal electrocatalysts, used for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), are crucial to develop water splitting commercial applications. Herein, a bottom-up self-assembly strategy is proposed to construct ternary electrocatalysts of nitrogen-doped graphene-like carbon layers encapsulated MoxC (x = 1, 2) and Ni3Fe alloy nanoparticles (MoxC/Ni3Fe@GL) for efficient water electrolysis. The optimized sample (0.27MoxC/Ni1.5Fe@GL, 0.27 represent the mass of ammonium molybdate in the precursor) requires overpotentials (η10) of 88 and 150, 265 mV in 0.5 M H2SO4 for HER and 1.0 M KOH for HER and OER, respectively. Furthermore, as a bifunctional electrocatalyst in a two-electrode cell, 0.27MoxC/Ni1.5Fe@GL requires only 1.523 V at 10 mA cm−2, which surpasses the noble metal RuO2(+)||Pt/C(−) in 1.0 M KOH electrolyte, and shows excellent stability by working at 20 mA cm−2 long as 150 h. The superior electrocatalytic performance can mainly originate from MoxC and Ni3Fe alloys synergistically effected results. The partial doping of Ni or Fe atoms into Mo2C optimizes the electronic structure, making the intrinsic activity enhanced. On the other hand, the incorporation of MoxC heterophases effectively inhibits the Ni3Fe nanoparticles agglomeration, benefitting to expose more active sites. Moreover, the protection of encapsulated thin N-doped graphene-like carbon layers for the nanoparticles against corrosion, guarantees the long-time durability. This work provides a potential general bottom-up self-assembly approach to construct high-performance electrocatalysts with multiphase heterostructures with enriched abundant active sites and enhanced intrinsic activity for energy coversion fields.

Two-Dimensional Metal Organic Framework derived Nitrogen-doped Graphene-like Carbon Nanomesh toward Efficient Electromagnetic Wave Absorption

Functional two-dimensional (2D) graphene-like carbon has the potential to be a good electromagnetic wave absorbing material due to its good electronic properties, but the preparation of 2D carbon via metal–organic frameworks (MOFs) derivation method is still a bottleneck. Herein, we fabricated ultrathin nitrogen-doped graphene-like carbon nanomesh (N-GN) via thermal exfoliation of 2D MOF (Zn-ZIF-L) directly. The species of the chloride salt that exfoliated Zn-ZIF-L have an effect on the nitrogen content, graphitization degree, pore size and specific surface area of N-GN. The Zn-ZIF-L derived N-GN exfoliated by KCl and LiCl simultaneously has the optimum reflection loss of −54 dB only with the thickness of 2.1 mm and the filler loading of 3 wt%. The excellent electromagnetic wave absorbing property is attributed to its favorable structure, micro-meso-macropores, N heteroatoms, abundant heterogeneous graphene-like carbon nanomesh interfaces and defects. Our simple and low-cost preparation process facilitates the large-scale production and application for electromagnetic wave absorbing material of functionalized graphene-like carbon.

Hierarchical porous nitrogen-doped carbon nanosheets derived from zinc-based bioMOF as flexible supercapacitor electrode

We propose an efficient and flexible supercapacitor electrode material based on hierarchically structured nitrogen-doped graphene-like carbon nanosheets (H-NCNs) with accordion-like shape. H-NCNs were obtained by pyrolyzing zinc-based biometal–organic frameworks (Zn-bioMOFs) and using urea as nitrogen source at high temperature (800 °C) under nitrogen atmosphere, and Zn-bioMOFs were synthesized using biomass molecules, i.e., curcumin. Inheriting from the features of Zn-bioMOF, H-NCNs showed hierarchical structures and unique accordion-like morphology. By changing the urea dosage, the nitrogen-doping degree and porosity of H-NCNs were regulated, optimizing the supercapacitive performance. H-NCNs-8 prepared with Zn-bioMOF/urea mass ratio of 1:8 exhibited high specific capacitance and superior rate capability (293 F g−1 at 0.25 A g−1 and 188 F g−1 at 50 A g−1). The H-NCNs-assembled symmetric supercapacitor offered long cycle life of over 40,000 cycles at 2 A/g and high energy density of 17.6 Wh kg−1 at 250 W kg−1, outperforming most carbon nanomaterial-related ones. Accordingly, the proposed flexible interdigital solid microsupercapacitor demonstrated high areal capacitance, high areal energy densities, and long cycle stability. The present work can provide promising application prospects of MOFs in the field of supercapacitors and flexible electronics.

The nitrogen-doped graphene-like carbon nanosheets: Confined construction and oxygen-limited oxidation for higher removal efficiency toward organic contaminants

Due to the excellent properties, including large specific surface area, stable structure, and strong adsorbability, mesoporous carbon material has captured a lot of attention and applied to various fields. Here, we proposed a facile approach to synthesize nitrogen-doped graphene-like carbon (NGLC) nanosheets and investigated the performance in wastewater decontamination. In this work, NGLC nanosheets were obtained via the combination of confined synthesis and low-temperature calcination in oxygen-limited condition. Such NGLC nanosheets were composed of several carbon layers with porous structure, which provided a large specific surface area (421.85 m2 g−1). Meanwhile, the NGLC was endowed with abundant active sites, including oxygen-contained groups and nitrogen species, via low-temperature calcination in oxygen-limited conditions. These properties allow the NGLC to be an excellent adsorbent for organic pollution treatment. The maximum adsorption capacities toward cationic dyes, the rhodamine B (RhB) and methylene blue (MB), reached as high as 1272.74 mg g−1 and 679.55 mg g−1, respectively, indicating the promising potential for the cationic contaminants treatment. The excellent reusability and wide pH suitability (2–10) were observed by batch adsorption experiments. The kinetic adsorption test showed that 98.97% of RhB could be adsorbed by NGLC-450 after 150 min contact time at 25 °C, while the RhB removal efficiencies from bulk polydopamine derived carbon material (denoted as PDA carbon) and NGLC-450-Ar (generated at argon atmosphere) were only 17.56% and 62.03%, respectively. The significant difference in adsorption performance implied the importance of confined synthesis with template-assistance and oxygen-limited oxidation. The adsorption process involved the pore filling & adsorption, electrostatic interaction, and π-π interaction, as well as the hydrogen bonding, which was demonstrated by experiment and Fourier transform infrared (FT-IR) & X-ray photoelectron spectroscopy (XPS) analysis.

Interface engineering of MoS2-based ternary hybrids towards reversible conversion of sodium storage

Sodium-ion batteries (SIBs) using conversion-type metal sulfides as anode materials have received a lot of attention. However, the irreversible conversion reaction is the major challenge for achieving long-life cycling performance. Herein, taking MoS2 as a representative material, conductive Co9S8 and three-dimensional porous nitrogen-doped graphene-like carbon are selected to promote its reaction kinetics through engineered interface. In the designed MoS2-based hybrids, MoS2 and Co9S8 form two-dimensional (2D) Mott-Schottky heterostructure via in-plane interface, lying on the surface of graphene-like carbon through horizontal interface. The 2D in-plane Mott-Schottky interface not only improves the electrical conductivity but also facilitates the Na+ adsorption and diffusion. The horizontal interface is beneficial for adsorbing and dispersing the discharged products. They lead to highly reversible conversion reaction. Therefore, the resultant hybrids show an excellent long-term cycling stability of 1,500 cycles at a high rate of 1 A/g. This work suggests that rational design of interface in conversion-type hybrids is a promising way for preparing highly reversible anodes of SIBs and provides a new approach to construct 2D metal sulfide-based heterostructures.

Optimized design of 3D nitrogen-doped graphene-like carbon derived from g-C3N4 encapsulated nano-Si as high-performance anode for lithium-ion batteries

Silicon anode is attracted enormous attention due to ultra-high theoretical capacity. However, the volume change of nearly 300% and poor conductivity stymie the application of silicon anodes. It is of fundamental importance and challenge to solve this problem. Here, the porous Si/nitrogen-doped carbon nanosheets (Si/NCNS) composites are successfully synthesized by in situ growth of nano-silicon on a graphene-like carbon. The in-situ growth of nano-SiO2 is introduced through the electrostatic interaction on the surface of g-C3N4 nanosheets (CNNS) by hydrolysis of tetraethyl orthosilicate (TEOS). Subsequently, SiO2 nanoparticles are reduced to porous Si and the nitrogen of CNNS is partially removed to form nitrogen-doped carbon nanosheets (NCNS) via a magnesiothermic reduction route. Importantly, NCNS not only provides rapid transferring channels for electrons and lithium ions but also relieves volumetric changes of Si, which contributes to ameliorating electrochemical performance. The optimal Si/NCNS-1 composite exhibits excellent electrochemical performances of 1106.7 mAh g−1 after 200 cycles with the capacity retentions of 93.6%, and the coulombic efficiency remains above 99.5%. This controllable synthesis method provides a potential building for the application of Si anode.

Nitrogen-doped graphene-like carbon from bio-waste as efficient low-cost electrocatalyst for fuel cell application

The development of metal-free carbon-based catalysts for alkaline fuel cells has been the subject of current interest, because of the low cost and improving fuel cell efficiency. Particularly, nitrogen-doped carbon shows prominent results. Here, we show an oxygen reduction reaction (ORR) activity of nitrogen-doped graphene-like carbon materials (N-GLC) prepared by heating bagasse-derived carbon and melamine in a 1:15 ratio. The N-GLC catalyst displays excellent electro-catalytic activity towards the ORR with an onset potential of 0.92 V vs. reversible hydrogen electrode (RHE) in alkaline media (0.1 M KOH). Moreover, the half-wave (E1/2) potential 0.83 V is almost the same compared to Pt-C (40 wt%) catalyst and the diffusion limiting current of 4 mA cm–2. The rotating ring disc experiment showed a four-electron pathway (n = 3.65) with the moderate peroxide ( $${{\rm HO}}^{-}_{2}$$ ) yield. Due to its promising ORR activity and long-term electrochemical stability, N-GLC catalyst is used in alkaline anion exchange membrane fuel cell (AEMFC) as a single cell, about 6 mW cm–2 peak power density was achieved at the load current density of ~20 mA cm–2. So the N-GLC can be a cheap alternative ORR catalyst for AEMFC applications.

Iron Carbide Dispersed on Nitrogen-Doped Graphene-like Carbon Nanosheets for Fast Conversion of Polysulfides in Li–S Batteries

The lithium–sulfur (Li–S) battery has drawn tremendous interest because of its superior theoretical specific capacity, while the shuttle effect of lithium polysulfides (LPSs) has greatly hindered i...

In situ integration of Co5.47N and Co0.72Fe0.28 alloy nanoparticles into intertwined carbon network for efficient oxygen reduction

Cost-effective electrocatalysts with excellent oxygen reduction reaction (ORR) activity are requisite for the commercial application fuel cells and zinc-air batteries. Herein, we prepare a series of carbon-based non-precious metal catalysts by simply carbonizing the mixture of FeCo-ZIF, melamine and soya-bean oil. The microstructure and electrochemical activity of the prepared catalysts highly depend on the adding amount of FeCo-ZIF. With proper addition, the FeCo-ZIF are transformed into Co5.47N and Co0.72Fe0.28 alloy nanoparticles, which are embedded in the in situ formed carbon network consisted of nitrogen-doped graphene-like carbon nanosheets and interwoven carbon nanotubes. The resulted catalyst (FeCo@NCs-0.15) with considerable specific surface area and high pore volume demonstrates a superior ORR catalytic activity than commercial Pt/C with a half-wave potential (E1/2) of 0.83 V (vs. RHE), onset potential (Eonset) of 0.97 V (vs. RHE) and 4-electron dominated reaction path. The durability and methanol resistance are also better than that of commercial Pt/C in alkaline solution. This study provides an inexpensive, facile and scalable strategy to simultaneously realize non-precious metal-based active sites, nitrogen-doping, porosity and highly conductive carbon matrix in one electrocatalyst by one step.

Liquid-to-gas transition derived cobalt-based nitrogen-doped carbon nanosheets with hierarchically porous for oxygen reduction reaction

Here, Co@CoOx-based three-dimensional nitrogen-doped graphene-like carbon nanosheets (denoted as 3D HPN-GCNS/Co@CoOx) are fabricated by controllable grading-pyrolysis strategy, in which they show 3D fluffy and hierarchically porous nanostructure in and out-of-plane; large numbers of Co@CoOx-based nanoparticles uniformly embedded on graphene-like C nanosheets and mesoporous active edge introduce more ORR active sites. When applied for ORR, hybrids exhibit a half-wave potential (E1/2) of 0.87 V and an onset potential (Eonset) of 0.92 V in 0.1 M KOH, comparable to that of commercial 20% Pt/C. The hybrids display better methanol tolerance and stability, with almost no change of ORR performance before and after 5000 cycles. H2O2 yield in ORR process is less than 5% and number of electron transfer is higher than 3.9. The remarkable features are mainly ascribed to synergistic enhancement effect, in which 3D fluffy and hierarchically porous nanostructure in and out-of-plane supplies large accessible specific activity area, allows species to efficiently participate in ORR and facilitates fast mass transfer; graphene-like C nanosheets with N-rich dopant promote O2 adsorption and assure fast electron transport; large numbers of Co@CoOx-based nanoparticles introduce more ORR active sites. All the advantages synergistically enhance the ORR efficiency and make it a highly efficient ORR catalyst.

Nitrogen-doped graphene-like carbon material derived via a simple, cost-effective method as an excellent adsorbent for methylene blue adsorption

Nitrogen-enriched graphene-like carbon materials were successfully prepared via pyrolysis of a mixture of melamine, ammonia chloride (NH4Cl) and polyvinyl pyrrolidone (PVP) at a mild temperature without inert gas protection. Different techniques were used to analyze the physical and chemical properties of the products. All the prepared materials showed excellent performance in methylene blue (MB) adsorption, In particular, the materials prepared with 3 g polyvinyl pyrrolidone (PVP) (NCG-2) exhibited the best performance, a very high maximum adsorption capacity of 348.2 mg/g, much larger than many reported materials. The high adsorption capacity of the Nitrogen-doped graphene-like carbon materials was possible due to its uniform porous structure, high specific surface area. Moreover, NCG-2 could be recycled and only a only slightly decreased in the removal efficiency were observed after 5 cycles.

Facile fabrication of ultrafine Pt nanoparticles supported on 3D macro-/oversized mesoporous N-doped carbon for efficient methanol oxidation

Limited by unsatisfactory mass diffusion and complex fabrication procedures, nanoporous carbons (NPCs) don't perform well, served as catalyst supports. Herein, utilizing nitrogen-doped carbon nanotubes (NCNTs) as spacers of nitrogen-doped graphene-like carbon nanosheets (NGs), a 3D nanoarchitecture (Co@NCNT-NG-900) is fabricated via a facile and eco-friendly approach. Physical characterizations manifest that the in situ-formed NCNTs make for improving graphitic degree, NGs contribute to increasing the specific surface area and the level of N-doping, meanwhile, the spacers effects of NCNTs promote the formation of opened macropores, what's more, Co@NCNT-NG-900 mainly consists of three-dimensional macropores and oversized mesoporous (3D macro-/oversized mesoporous), unlike conventional NPCs. Benefiting from improved charge transfer rate, enhanced N-doping level and dominant 3D macro-/oversized mesoporous, Co@NCNT-NG-900 is evaluated as an ideal Pt support for methanol oxidation reaction (MOR) in acid and alkaline medium. This work provides a facile synthetic method for NPCs and sheds directive light into the research of efficient catalysts for MOR.

Increased activity of nitrogen-doped graphene-like carbon sheets modified by iron doping for oxygen reduction

Rational design and synthesis of Fe-N-codoped carbon materials are promising for replacing commercial Pt/C for oxygen reduction reaction (ORR). Herein, we develop a simple two-step pyrolysis approach to synthesize highly active Fe-N-codoped graphene-like carbon sheets (FeNGC) with active Fe-N-based species for ORR. In this strategy, two-dimensional nitrogen-doped graphene-like carbon sheets (NGC) with a high N-doping level (8.1 at%) and abundant mesoporosity (3.8 nm) are firstly synthesized by co-pyrolysis of biomass carbon source and dicyandiamide, in which dicyandiamide simultaneously serves as a trifunctional role of in situ reaction template, nitrogen source and porogen. Secondly, FeNGCs are prepared by additional iron doping of NGC at high temperatures, in which sheet-like structure is in favor of increased accessibility of N-functional groups to more Fe atoms, thus giving rise to formation of high-density Fe-N-based active sites. The optimized catalyst synthesized at 950 °C (FeNGC-950) demonstrates significantly increased ORR activity with a dominant 4e− reduction process compared to pure NGC in alkaline and acidic solutions, which evidently shows the comparable activity to Pt/C due to the synergy of simultaneously optimized structures and multi-active sites. Moreover, FeNGC-950 has better long-term stability and methanol tolerance than Pt/C both in alkaline and acidic electrolytes. The present strategy paves a new venue to design and prepare various metal-doped carbon materials with great potentials in energy applications.

Nitrogen-doped graphene-like carbon nanosheets from commercial glue: morphology, phase evolution and Li-ion battery performance.

We report a two-step process to synthesize nitrogen-doped graphene-like carbon nanosheets (N-CNS), using commercially available ethyl cyanoacrylate based super glue as a carbon precursor. In this process, super glue is polymerized in aqueous NaCl solution, followed by carbonization at 1000 °C. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) studies show that the resultant material consists of micron-sized carbon nanosheets with a wrinkled morphology. HRTEM, X-ray diffraction (XRD), XPS and Raman spectroscopic studies confirm the formation of nanocrystalline and graphitic, nitrogen-doped carbon nanosheets. A detailed FTIR analysis of the degradation products of the polymeric precursor (polyethyl cyanoacrylate) at various heat treatment temperatures under an inert atmosphere reveals that the polymer undergoes a cyclization process similar to polyacrylonitrile (PAN) during carbonization to yield the N-CNS. The N-CNS used as an anode for a lithium-ion battery shows stable reversible capacities of 480 mA h g-1 for 100 cycles, which indicates that N-CNS are promising materials for lithium-ion battery applications. In a broader perspective, a unique chemical transformation of polyethyl cyanoacrylate to graphitic carbon may be useful to design new nanostructured carbons for a plethora of applications.

An extremely active and durable Mo2C/graphene-like carbon based electrocatalyst for hydrogen evolution reaction

The efficiency of hydrogen production from electrolysis of water is severely limited by the sluggish kinetics of hydrogen evolution reaction (HER). Here we report our findings in the development of a very active and durable HER electrocatalyst derived from a one-pot synthesis of highly porous molybdenum carbide (Mo2C) nanoparticles uniformly dispersed on nitrogen-doped graphene-like carbon. The nanocomposite catalyst displays excellent HER activity and durability in an acidic electrolyte among all non-noble-metal catalysts ever reported. The remarkable performance is attributed to the unique nanostructure of the Mo2C phase, the conductive nitrogen-doped graphene-like carbon network, the high porosity of the hybrid, and the synergistic effect between the Mo2C and the carbon substrate. Further, the facile and low-cost synthetic strategy for preparation of such nanostructures may open up opportunities for exploiting other high-performance electrocatalysts for various applications.

Reactive template synthesis of nitrogen-doped graphene-like carbon nanosheets derived from hydroxypropyl methylcellulose and dicyandiamide as efficient oxygen reduction electrocatalysts

Abstract Oxygen reduction reaction (ORR) plays a dominant role in proton exchange membrane fuel cells (PEMFCs). Thus, the design and preparation of efficient ORR electrocatalysts is of high importance. In this work, we successfully prepared a series of nitrogen-doped graphene-like carbon nanosheets (NCNSs) with large pore volumes of up to 1.244 cm 3 g −1 and high level of N dopants (5.3–6.8 at%) via a one-step, in-situ reactive template strategy by co-pyrolysis of hydroxypropyl methylcellulose (HPMC) and dicyandiamide (DICY) as the precursors at 1000 °C. The DICY-derived graphitic carbon nitride (g-C 3 N 4 ) nanosheets could act as the hard template for the confined growth of 2D carbon nanosheets, and the further increase in the pyrolysis temperature could directly remove off the g-C 3 N 4 template by complete decomposition and simultaneously dope N atoms within the carbon nanosheets. The pyridinic and graphitic nitrogen groups are dominant among various N functional groups in the NCNSs. The NCNS_1:10 prepared with the HPMC/DICY mass ratio of 1/10 can be used as the metal-free ORR electrocatalysts with optimal activity (onset potential: −0.1 V vs. SCE; limiting current density: 4.8 mA cm −2 ) in O 2 -saturated 0.1 M KOH electrolyte among the NCNSs. Moreover, the NCNS_1:10 demonstrates a dominant four-electron reduction process, as well as excellent long-term operation stability and outstanding methanol crossover resistance. The excellent ORR activity of the NCNS_1:10 should be mainly owing to high contents of pyridinic and graphitic N dopants, large pore volume, hierarchical structures, and microstructural defects.

Improved Electrochemical Performance of LiFePO4@N-Doped Carbon Nanocomposites Using Polybenzoxazine as Nitrogen and Carbon Sources.

Polybenzoxazine is used as a novel carbon and nitrogen source for coating LiFePO4 to obtain LiFePO4@nitrogen-doped carbon (LFP@NC) nanocomposites. The nitrogen-doped graphene-like carbon that is in situ coated on nanometer-sized LiFePO4 particles can effectively enhance the electrical conductivity and provide fast Li+ transport paths. When used as a cathode material for lithium-ion batteries, the LFP@NC nanocomposite (88.4 wt % of LiFePO4) exhibits a favorable rate performance and stable cycling performance.

Templated synthesis of nitrogen-doped graphene-like carbon materials using spent montmorillonite

This work provided a method that can recycle the spent montmorillonite and synthesize heteroatom-doped graphene-like materials.

One-step preparation of ultrathin nitrogen-doped carbon nanosheets with ultrahigh pore volume for high-performance supercapacitors

A facile one-step activation and nitrogen-doping combination method is developed for preparation of nitrogen-doped graphene-like carbon nanosheets (N-CNSs).