Co-doped Carbon Nanosheets Research Articles

Mesoporous N-P Codoped Carbon Nanosheets as Superior Cathodic Catalysts of Neutral Metal-Air Batteries.

Development of high-efficiency oxygen reduction reaction (ORR) catalysts under neutral conditions has made little research progress. In this work, we synthesized a three-dimensional porous N/P codoped carbon nanosheet composites (CNP@PNS) by high-temperature thermal treatment of dicyandiamide, starch, and triphenylphosphine and subsequent porous structure-making treatment using the NaCl molten salt template. In the neutral solution, the electrocatalytic performance of the CNP@PNS-4 catalyst exhibits an onset potential of 0.98 V (vs reversible hydrogen electrode) and a half-wave potential of 0.91 V for ORR, which greatly surpasses commercial Pt/C (40%). Three kinds of neutral metal-air batteries (Zn-air, Al-air, and Fe-air) using the prepared samples as cathodic catalysts were constructed, corresponding to the maximum power density of 120.2, 78.3, and 18.9 mW·cm-2, respectively. Also, they reveal outstanding discharge stability under different current densities. The density functional theory calculation depicts the reduction of the free energy of the determining step and subsequent decline of the overpotential for ORR.

Preparation of Fe/N Co-Doped Hierarchical Porous Carbon Nanosheets Derived From Chitosan Nanofibers for High-Performance Supercapacitors

Abstract Due to the low specific capacitance and small specific surface area of conventional carbon materials used as electrode materials for double-layer capacitors, the search for more ideal materials and ingenious preparation methods remains a major challenge. In this study, fractional porous carbon nanosheets were prepared by co-doping Fe and N with chitosan as nitrogen source. The advantage of this method is that the carbon nanosheets can have a large number of pore structures and produce a large specific surface area. The presence of Fe catalyzes the graphitization of carbon in the carbon layer during carbonization process and further increases the specific surface area of the electrode material. This structure provides an efficient ion and electron transport pathway, which enables more active sites to participate in the REDOX reaction, thus significantly enhancing the electrochemical performance of SCs. The specific surface area of CS-800 is up to 1587 m2 g−1. When the current density is 1 A g−1, the specific capacitance of CS-800 reaches 319.5 F g−1 and remains 84.61% of the initial value after 10,000 cycles. The Coulomb efficiency of CS-800 is almost 100% after a long cycle, which indicates that CS-800 has more ideal double-layer capacitance and pseudo capacitance.

High-energy aqueous supercapacitors enabled by N/O codoped carbon nanosheets and “water-in-salt” electrolyte

A facile fabrication strategy is reported to obtain N/O codoped porous carbon nanosheets for purpose of ameliorating the charge transfer and accumulation in the concentrated LiTFSI (lithium bis(trifluoromethane sulfonyl)imide) electrolyte. By tunning the feed ratio of comonomers, the porous nanosheet structure is endowed with a significant ion-adsorption surface area (1630 m2/g) and interconnected hierarchical porosity; meanwhile, high-level N/O dopants (N: 3.58 at%, O: 12.91 at%) increase the effective contact area for electrolyte ions, and further facilitate rapid ion/electron transfer. Benefiting from the advantageous features, carbon nanosheets electrode reveal an enhanced specific capacitance (375 F/g) in three-electrode configuration and the H2SO4-based device yields a high gravimetric energy density of 11.4 Wh/kg. Particularly, the ion-diffusion highways in porous carbon nanosheets contribute to the 2.25 V LiTFSI-based symmetric device with a high energy delivery up to 33.1 Wh/kg. This work offers an inspiring strategy for facile fabrication of carbon nanosheets, and demonstrates their promising application in “water-in-salt” electrolyte-based supercapacitor systems.

Highly efficient electrochemical production of hydrogen peroxide over nitrogen and phosphorus dual-doped carbon nanosheet in alkaline medium

• N/P co-doped carbon nanosheet was prepared by pyrolysis of chitosan-phytic acid complex hydrogels. • High ORR activity with selective H 2 O 2 production benefits from 2D nanostructure and N/P co-doping. • High H 2 O 2 production rate of 223.4 mmol g catayst −1 h −1 with faradaic efficiency of 80% was achieved in H-cell. Electrochemical two-electron oxygen reduction reaction (ORR) is a promising green method for hydrogen peroxide (H 2 O 2 ) production, but the H 2 O 2 selectivity and productivity in alkaline medium have remained too low for economic viability of the process. In the present work, we reported the design and preparation of nitrogen and phosphorus dual-doped carbon nanosheet (NPCNS) through direct pyrolysis of supramolecular aggregates that resulted from the cross-linking reaction between nitrogen bio-functional groups of chitosan and phosphoric groups of phytic acid. The resultant NPCNS catalysts exhibited very high electrochemical ORR activity and selectivity toward H 2 O 2 production in alkaline medium due to the unique 2D nanostructure and the synergistic effect between nitrogen and phosphorus dopant. High practical H 2 O 2 production rate of 223.4 mmol g catayst −1 h −1 with high faradaic efficiency of 80% could be also achieved in home-made H-cell, indicating the potential applications of H 2 O 2 in the waste water treatment, pulp and paper industry.

N/S co-doped carbon nanosheet bundles as high-capacity anode for potassium-ion battery

N/S co-doped carbon nanosheet bundles as high-capacity anode for potassium-ion battery

Ultrafast Potassium Storage in F-Induced Ultra-High Edge-Defective Carbon Nanosheets.

Carbonaceous materials have been considered as promising anodes for potassium-ion batteries (PIBs) because of their high electronic conductivity, eco-friendliness, and structural stability. However, the small interlayer spacing and serious volume expansion caused by the repeated insertion/extraction of large K-ions restrict their potassium-ion storage performance. Herein, F and N codoped carbon nanosheets (FNCS) with rich-edge defects are designed to resolve these problems. The F doping is in favor of the formation of more edge defects in the carbon layer, offering strong K+ adsorption capability and promoting the K+ storage. The ultrathin carbon nanosheets can provide a large contact area for the electrochemical reactions and shorten the transportation pathways for both K-ions and electrons. Consequently, the FNCS anode shows a high reversible capacity (610 mAh g-1 at 0.1 A g-1) and ultrastable cyclability over 4000 cycles at 5 A g-1. Moreover, K-ion full cells (FNCS|K2FeFe(CN)6) display excellent cycling stability (128 mAh g-1 at 1 A g-1 after 500 cycles) and rate capability (93 mAh g-1 at 20 A g-1). This design strategy can be extended to design other electrode materials for high-performance energy storage, such as magnesium-ion batteries, supercapacitors, and electrocatalysis.

Cu Catalyst Supported on Nitrogen and Phosphorus Co-Doped Carbon Nanosheets for Homocoupling of Terminal Alkynes Using CO2 as a Soft Oxidant

A bifunctional role of carbon dioxide (CO2) was developed in this research as a medium for catalyst preparation and as a soft oxidant for the subsequent coupling reaction. A highly dispersed and lo...

From onion skin waste to multi-heteroatom self-doped highly wrinkled porous carbon nanosheets for high-performance supercapacitor device

Herein, we report the synthesis of N, S, P-self-doped porous and wrinkled graphene-like carbon nanosheets derived from the abundant waste onion skin via carbonization and activation strategy. The optimized onion skin derived carbon (OnC-900) exhibits highly wrinkled graphene-like morphology and multi-heteroatom doping without any external dopants is confirmed via field emission scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The OnC-900, acting as a supercapacitor electrode, exhibits excellent specific capacitance of 478 F g−1 at a current density of 1 A g−1 and maintains 241.7 F g−1 even at 6.7 A g−1 in the three-electrode cell indicating its excellent rate capability. The assembled symmetric supercapacitor device using aqueous neutral electrolyte (1 M Na2SO4) delivers outstanding specific energy of 17 Wh kg−1 with a wide potential window up to 1.4 V. The device also exhibits excellent cyclic stability by retaining 93% of initial capacitance over 10,000 cycles at a current density of 3 A g−1. This enhanced performance of the electrode is mainly due to the high specific surface area and the heteroatom co-doping that provides improved surface wettability by polarized surface, induced pseudocapacitance effect, and improved electronic conductivity. These results demonstrate that onion waste derived multi-heteroatom co-doped graphene-like carbon nanosheets have great potential for renewable and sustainable energy storage devices.

Nitrogen and phosphorus co-doped mesoporous carbon nanosheets derived from bagasse for lithium-ion batteries

N,P co-doped bagasse-based sheet-like mesoporous carbon (NP-BC) for lithium-ion battery anode material was prepared using bagasse and NH4H2PO4 as raw material. Compared with primary bagasse carbon (BC), the specific surface area and the lattice spacing of the NP-BC increased from 1307.21 to 2118.59 m2/g and from 0.34 to 0.385 nm, respectively. The first discharge specific capacity also increased from 1186.59 to 2347.56 mAh/g at 0.05 A/g, and the reversible capacity increased more than twice.

Sulfur and nitrogen co-doped carbon nanosheets for improved sodium ion storage

Heteroatom doping into specific nanostructure is believed as the leading solution for developing the advanced carbon materials for sodium ion batteries (SIBs), however, the preparation and understanding of heteroatoms co-doped carbon anodes are still challenging. Herein, the sulfur and nitrogen co-doped (weight content of 15.64% for N and 3.1% for S) carbon nanosheets (SNC) are prepared by treating nitrogen-rich carbon nanosheets with sublimation sulfur. The S, N co-doping is responsible for the enlarged interlamellar spacing of 0.38 nm and abundant defect-introduced active sites. These structure features combined with the advantage of nanosheet are significant for activating sodium ion storage properties, endowing SNC with high Na+ storage capacity of 270 mAh g−1 at 0.1 A g−1 and 100 mAh g−1 at 1 A g−1 after 1000 cycles. More importantly, the kinetic analysis is carried out to illustrate that S, N co-doping can improve the Na+ diffusion coefficient in carbon anode and enhance the ion storage. This work deepens the understanding on the boosting effect of heteroatoms dual-doping for the sodium ion storage of carbon materials, which conduces to development of advanced heteroatom doped carbon anodes for SIBs.

One-step synthesis of nitrogen and sulfur co-doped mesoporous graphite-like carbon nanosheets as a bifunctional material for tetracycline removal via adsorption and catalytic degradation processes: Performance and mechanism

In this study, nitrogen and sulfur co-doped mesoporous graphite-like carbon nanosheets (NS-MGCNS) were synthesized via a facile pyrolysis method. The as-prepared sample at a calcined temperature of 800 °C (NS-MGCNS-800) exhibited remarkably outstanding removal capacity for tetracycline (TC). About 94.5% of TC (20 mg/L) was removed within 60 min via the synergistic effect of adsorption and catalytic degradation processes. Pseudo-second-order adsorption plot and Langmuir models fitted well with the adsorption process. The maximum adsorption capacity of NS-MGCNS-800 was 91.57 mg/g through π-π interactions. Besides, NS-MGCNS-800 could activate persulfate (PS) for TC degradation with the pseudo-first-order degradation reaction rate constant of 0.144 min−1, which was 51.4, 24.0, and 1.3-fold as high as that over graphitic carbon nitride (CN), pure carbon (C), and nitrogen doped carbon nanosheets (N-CNS), respectively. Meanwhile, NS-MGCNS-800 possessed superior reusability for removing TC with the removal efficiency of over 87% after 5 cycles. Quenching tests, electron spin resonance spectroscopy (ESR), and electrochemical measurement revealed that radical and non-radical pathways were involved in the NS-MGCNS-800/PS/TC system. More importantly, by means of experimental methods and density functional theory (DFT) calculations, the introduction of sulfur could significantly adjust the electron density of the carbon lattice though the synergistic effect of nitrogen doped carbon nanosheests, promoting the TC adsorption and PS activation of NS-MGCNS-800. Finally, TC intermediates were detected and six possible degradation pathways of TC were proposed. Consequently, this study not only developed a high-performance bifunctional graphite-like carbon nanomaterial, but also provided a new direction for removing the trace antibiotics in environmental remediation.

Nitrogen and phosphorus co-doped ultrathin carbon nanosheets as superior cathode catalysts for Zn–air batteries

Nitrogen and phosphorus co-doped mesoporous ultrathin carbon nanosheets prepared by a NaCl template method present outstanding ORR activity and can be used as superior cathode catalysts for Zn–air batteries.

Co, Fe codoped holey carbon nanosheets as bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries.

Unique Co, Fe codoped holey carbon nanosheets with high surface area and abundant bimetal single atoms (CoFe@HNSs) exhibited remarkable bifunctional oxygen electrocatalytic activity (0.704 V) with very positive half-wave potential (0.897 V) for the ORR and small potential (1.601 V) to drive 10 mA cm-2 for the OER, outperforming commercial Pt/C and IrO2, respectively. Furthermore, as the air-cathode for rechargeable Zn-air batteries, the CoFe@HNS based device exhibits a high-power density of 131.3 mW cm-2 and long-term stability over 140 h, indicating the attractive potential of CoFe@HNSs applied in energy storage and conversion.

Ultrathin two-dimensional phosphorus and nitrogen Co-doped carbon nanosheet as efficient oxygen reduction electrocatalyst

Developing metal-free electrocatalysts with high performance towards oxygen reduction reaction (ORR) is critical for the commercialization of fuel cell technologies and metal-air batteries. Herein, we develop an effective and rational strategy to synthesize an ultrathin two-dimensional (2-D) carbon nanosheet (P–NCNS) with more exposed N and P doping sites as ORR electrocatalyst. This strategy adopts ice/salt dual-template to construct an ultrathin 2-D porous carbon nanosheet using gelatin as C/N precursor, and employs red P as P dopant to achieve controllable doping of heteroatoms. Red P also acts as a pore-forming agent to create abundant porosity on 2-D carbon surface through the activation of P-containing species. The resulting carbon nanosheet exhibits an ultrathin thickness of 1–2 nm, a large specific surface area (499.5 m2 g−1) and a well-defined micro/mesoporous structure, showing more exposed and abundant N, P doping sites that are accessible to the ORR reactants. As a result, P–NCNS shows an outstanding ORR performance both in alkaline and acidic electrolyte. More attractively, P–NCNS was used as the cathode electrocatalyst for a primary zinc-air battery showing good performance and long-term stability. This strategy offers a new insight for the design and synthesis of high-performance non-precious metal electrocatalyst for ORR.

CoMoP2 nanoparticles anchored on N, P doped carbon nanosheets for high-performance lithium-oxygen batteries

Transition metal phosphides with superior electrical conductivity and a large number of electrochemically active sites, have become a research hotspot in various energy-related research fields. However, CoMoP2-based materials were rarely reported, especially in the rechargeable batteries. Herein, CoMoP2 nanoparticles anchored on N, P co-doped carbon nanosheets (CoMoP2@NPC) were prepared through the simple pyrolysis of organic precursor in the presence of phosphoric acid. When used as electrode materials, the as-prepared CoMoP2@NPC electrode exhibited good electrocatalytic activities towards oxygen reduction and oxygen evolution reactions for Li-O2 batteries. With the unique structure, NPC nanosheets could not only improve electrical conductivity of the composite, but also relive volume changes during cycling to expose the active sites of CoMoP2 nanoparticles. This work introduces a highly-effective strategy for preparing carbon materials embedded bimetal phosphides for energy storage and conversion devices.

Enhanced performance of microbial fuel cells using Ag nanoparticles modified Co, N co-doped carbon nanosheets as bifunctional cathode catalyst

The slow kinetics of oxygen reduction reaction (ORR) and the formation of biofilm on cathode severely limited the performance of microbial fuel cells (MFCs). An efficient way to enhance the power-generation capacity and long-term stability of MFCs is to develop bifunctional catalyst by incorporating the efficient ORR catalysts with antibacterial ingredient. In this study, the Ag/Co-N-C nanosheets were designed and synthesized by decorating Ag nanoparticles (NPs) onto Co-N-C nanosheets, which were prepared from Zn/Co bimetallic metal-organic framework (ZIF-67/ZIF-8) precursor. The Zn/Co ratio, Ag doping amount and the calcination temperature of the precursor were systematically investigated. The optimum sample Ag/Co-N-C-30 revealed the excellent ORR performance with a half-wave potential of 0.80 V vs. RHE, which was slightly lower than that of Pt/C (0.82 V vs. RHE). The MFCs equipped with Ag/Co-N-C-30 cathode exhibited maximum power density of 548 ± 12.6 mW m−2 and superior durability even after 1600 h operation. Besides, the selective antimicrobial ability of Ag/Co-N-C-30 was further explored and the aerobic bacteria in cathode biofilm was found to be obviously inhibited by Ag/Co-N-C-30. The results suggested the Ag/Co-N-C nanosheets can serve as a promising cathode catalyst for practical applications of MFCs.

Liquid-phase exfoliation of layered biochars into multifunctional heteroatom (Fe, N, S) co-doped graphene-like carbon nanosheets

• Developing a liquid exfoliation strategy for delaminating multilayered biochars. • The graphene-like carbon nanosheets (Fe-N-S-CNS) had multi-heteroatom co-doping. • Fe-N-S-CNS showed multifunctional electrochemical activity. • A higher ORR activity was obtained than that of commercial Pt/C. • The ionic liquid-based supercapacitor delivered an energy density of 54.1 Wh kg −1 . We here report a liquid-phase exfoliation strategy to delaminate multilayered biochars into multi-heteroatom (Fe, N, S) co-doped graphene-like carbon nanosheets, in which the multilayered biochars derived from naturally evolved layer-by-layer precursors. This strategy provides the versatile capability to tailor the textural properties of the as-synthesized carbon nanosheets, such as obtaining a controllable specific surface area of up to 2491 m 2 g −1 . Thanks to the unique integration of graphene-like microstructures with a thickness of 4.3 nm, large specific surface area and hierarchical pores, homogenous co-doping of N, S, and Fe, and high electronic conductivity, the as-synthesized Fe-N-S co-doped carbon nanosheets could act as multifunctional electrodes for electrocatalytic process of oxygen reduction reaction (ORR) and capacitive energy storage. The optimized nanosheets showed a better ORR catalytic performance than commercial Pt/C catalyst, with a more positive onset potential (1.026 V) and half-wave potential (0.829 V), higher long-term stability, and outstanding methanol tolerance in alkaline mediums. Furthermore, the porous carbon nanosheets exhibited excellent supercapacitive performances which delivered a high energy density of 29.1 Wh kg −1 at a high power density of up to 39.5 kW kg −1 in an ionic liquid electrolyte. This liquid-phase exfoliation strategy will offer new inspiration for the synthesis of various biomass-derived graphene-like carbon nanosheets for multifunctional applications.

Optimized Kinetics Match and Charge Balance Toward Potassium Ion Hybrid Capacitors with Ultrahigh Energy and Power Densities.

Potassium ion hybrid capacitors (PIHCs) are of particular interest benefiting from high energy/power densities. However, challenges lie in the kinetic mismatch between battery-type anode and capacitive-type cathode, as well as the difficulty in achieving optimized charge/mass balance. These significantly sacrifice the electrochemical performance of PIHCs. Here, strategies including charge/mass balance pursuance, electrolyte optimization, and tailored electrode design, are employed, together, to address these challenges. The key parameters determining the energy storage properties of PIHCs are identified. Specifically, i) the good kinetic match between anode and cathode translates into the very small variation of cathode/anode mass ratio at various rates. This sets general rules for the pursuance of charge balance, and to maximize the electrochemical performance of hybrid devices. ii) A potassium bis(fluoroslufonyl)imide (KFSI)-based electrolyte promotes better electrode kinetics and allows for the formation of more stable and intact solid electrolyte interphase layer, with respect to potassium hexafluorophosphate (KPF6 )-based electrolyte. And iii) hierarchically porous N/O codoped carbon nanosheets (NOCSs) with enlarged interlayer spacing, disordered structure, and abundant pyridinic-N functional groups are advantageous in terms of high electronic/ionic transport dynamics and structural stability. All these together, contribute to the high energy/power density of the activated carbon//NOCSs PIHCs (113.4 Wh kg-1 , at 17,000 W Kg-1 ).

Multi-role graphitic carbon nitride-derived highly porous iron/nitrogen co-doped carbon nanosheets for highly efficient oxygen reduction catalyst

Pyrolyzing precursors containing iron, nitrogen and carbon elements is a commonly used process for synthesizing FeNC catalysts for oxygen reduction reaction (ORR). Generally, aggregation of iron-based species is prone to occur because of a lack of chemical bonds between iron-based species and carbon matrix and synthesizing highly porous FeNC catalysts is difficult because carbon skeleton is prone to collapse during pyrolysis. Herein, highly porous FeNC catalysts with fine iron-based species are synthesized by selecting glucose as carbon source, FeCl3 as iron source, and urea-derived g-C3N4 as nitrogen source, iron anchoring and stabilizing species, and pore-forming template. The multi-role g-C3N4-derived catalyst synthesized at 1100 °C (FeNC1100) has fine iron-based species, large specific surface area (737 m2 g−1), and extremely high pore volume (2.66 cm3 g−1). Accordingly, FeNC1100 shows a larger half-wave potential (E1/2 = 0.894 V), a higher stability (ΔE1/2 = 6 mV) after 10,000 potential cycles in alkaline media, and a higher peak power density (P = 152 mW cm−2) when employed as ORR catalyst of zinc-air battery, which are all superior to those of the commercial Pt/C catalyst (E1/2 = 0.864 V, ΔE1/2 = 30 mV, P = 134 mW cm−2). The present work brings a new method for synthesizing highly porous FeNC catalysts decorated with fine active sites for ORR.

Gas expansion-assisted preparation of 3D porous carbon nanosheet for high-performance sodium ion hybrid capacitor

Sodium ion hybrid capacitors (SIHCs) have attracted considerable attentions due to their high-energy density of batteries and high-power output of supercapacitors. However, the slow intercalation kinetics of anode and low specific capacity of cathode greatly hinder the high-performance output of the SIHCs. Herein, we develop a facile chemical gas expansion method with chemical etching to prepare 3D nitrogen and sulfur co-doped porous carbon nanosheet (PCNS). As an anode material of SIBs, the PCNS displays a high reversible capacity of 205 mAh g−1 at 0.5 A g−1, outstanding rate capability of 96 mAh g−1 at 20 A g−1, and excellent cycle performance of 180 mAh g−1 at 7 A g−1 after 10 000 cycles. Based on this good performance, a dual-carbon SIHC is assembled by battery-type anode material (PCNS) and capacitive-type cathode material (hierarchically porous carbon). This device exhibits high energy densities of 119 Wh kg−1 and 53 Wh kg−1 at power densities of 200 W kg−1 and 20 kW kg−1, respectively. Besides, it possesses a superior cycle life of 82% capacity retention after 8000 cycles. Moreover, this work provides a new idea for the synthesis of carbon materials as high-performance SIBs and SIHCs electrode materials.