Two-dimensional Carbon Nanosheets Research Articles

Mo2C-Co heterostructure with carbon nanosheets decorated carbon microtubules: Different means for high-performance lithium-sulfur batteries

The practical applications of lithium sulfur batteries (LSBs) are hindered by notorious shuttle effect and sluggish conversion kinetics of intermediate polysulfides. Herein, Mo2C-Co heterogeneous particles decorated two-dimensional (2D) carbon nanosheets grown on hollow carbon microtubes (CCC@MCC) are synthesized. Three-dimensional (3D) carbon framework with Mo2C-Co heterogeneous particles combines the conductivity, adsorption and catalysis, effectively trapping and accelerating the conversion of polysulfides. As evidenced experimentally, the hetero-structured Mo2C-Co with high Li+ diffusion coefficient enables uniform precipitation and complete oxidation of Li2S. Meanwhile, CCC@MCC is found to have multiple application possibilities for lithium-sulfur batteries. As an interlayer, the cells deliver an excellent capacity of 881.1 mAh/g at 2C and still retain 438.2 mAh/g after 500 cycles under the low temperature of 0 ℃. As a sulfur carrier, the cell with a sulfur loading of 7.0 mg cm−2 exhibits a high area capacity of 5.3 mAh cm−2. This work provides an effective strategy to prepare heterostructured material and imaginatively exploit the application potential of it.

Integrating single Ni site and PtNi alloy on two-dimensional porous carbon nanosheet for efficient catalysis in fuel cell

Integrating single Ni site and PtNi alloy on two-dimensional porous carbon nanosheet for efficient catalysis in fuel cell

Ultra-wideband electromagnetic wave absorption property with bimetallic Co6W6C/carbon

Binary dielectric materials, particularly carbide/carbon composites, have garnered considerable attention for their promising electromagnetic wave (EMW) absorption property. In this work, bimetallic carbide and carbon composite (Co6W6C/C) was successfully prepared through hydrothermal method and pyrolysis process. Characterization results reveal the growth of Co6W6C nanoparticles on two-dimensional carbon nanosheets. The mass ratio of glucose (C6H12O6) to Co6W6C was found to significantly impact the EMW absorption performance. When 150 mg C6H12O6 and 100 mg CoWO4 were added, the CWCC-2 composite exhibited an ultra-high effective absorption bandwidth of 7.49 GHz (10.51–18 GHz). In the far-domain circumstance, the highest radar cross-section acreage reached 21.24 dB m2. The exceptional EMW absorption performance can be attributed to the synergistic effects of impedance matching, electrical losses, and magnetic losses. The Co6W6C/carbon composite, synthesized through a facile approach, showcases a broad electromagnetic wave absorption bandwidth, paving the way for a breakthrough in materials science with wide-band and high-efficiency absorption capabilities.

Ice/salt assisted synthesis of ultrathin two-dimensional nitrogen doped carbon nanosheets for fast lithium storage

Two-dimensional carbon nanosheets have garnered considerable interest as promising anode materials in energy storage devices due to their large specific surface area and excellent conductivity. The efficient synthesis of ultrathin nitrogen-doped carbon nanosheets is achieved with the aid of cysteine, employing a green ice/salt-assisted strategy. Ice influences the growth direction of salt crystals and determines the distribution of sodium lignosulfonate on the surfaces of both ice and salt crystals. The introduction of methionine incorporates heteroatoms, altering the electronic structure and chemical activity of the material, thereby effectively enhancing its lithium storage performance. The initial charge capacity of the optimized sample reached 766.4 mA h g−1 at a current density of 0.2 A g−1, maintaining a capacity of 571.1 mA h g−1 after 100 cycles. This study presents an innovative method for fabricating ultrathin carbon nanosheets using eco-friendly, cost-effective sodium lignosulfonate, showcasing a promising candidate for lithium-ion batteries and future energy storage technologies.

Molten salts etching route driven construction of C@Ni nanoparticles loaded carbon nanosheet as high-performance electrocatalyst for hydrogen evolution reaction

Developing earth-abundant, low-cost, high-efficiency electrocatalysts for hydrogen evolution reaction (HER) by structure design is still a grand challenge. Herein, we fabricated Ni nanoparticles encapsulated by carbon loaded in two-dimensional carbon nanosheets (2D Ni@C@SU) using a molten salt (NaCl)-assisted pyrolysis method. Because of the large specific surface area (262.35 m²/g) and high electrical conductivity, the prepared 2D Ni@C@SU-0.75 electrocatalyst exhibits excellent HER electrocatalytic activity with the overpotential of −105 mV at −10 mA cm−2 and −367 mV at −200 mA cm−2, which is close to the commercial benchmark Pt/C (η200= −339 mV). Besides, the catalyst displays incredible durability in the electrocatalytic HER. This research indicates that the green solid-state synthetic strategy provides a new window for designing new Ni-based composite catalysts for electrocatalytic HER.

Crystallization-induced formation of two-dimensional carbon nanosheets derived from sodium lignosulfonate for fast lithium storage

Sodium lignosulfonate, an abundant natural resource, is regarded as an ideal precursor for the synthesis of hard carbon. The development of high-performance, low-cost and sustainable anode materials is a significant challenge facing lithium-ion batteries (LIBs). The modulation of morphology and defect structure during thermal transformation is crucial to improve Li+ storage behavior. Synthesized using sodium lignosulfonate as a precursor, two-dimensional carbon nanosheets with a high density of defects were produced. The synergistic influence of ice templates and KCl was leveraged, where the ice prevented clumping of potassium chloride during drying, and the latter served as a skeletal support during pyrolysis. This resulted in the formation of an interconnected two-dimensional nanosheet structure through the combined action of both templates. The optimized sample has a charging capacity of 712.4 mA h g−1 at 0.1 A g−1, which is contributed by the slope region. After 200 cycles at 0.2 A g−1, the specific charge capacity remains 514.4 mA h g−1, and a high specific charge capacity of 333.8 mA h g−1 after 800 cycles at 2 A g−1. The proposed investigation offers a promising approach for developing high-performance, low-cost carbon-based anode materials that could be used in advanced lithium-ion batteries.

Dual Activation for Tuning N, S Co-Doping in Porous Carbon Sheets Toward Superior Sodium Ion Storage.

Porous carbon has been widely focused to solve the problems of low coulombic efficiency (ICE) and low multiplication capacity of Sodium-ion batteries (SIBs) anodes. The superior energy storage properties of two-dimensional(2D)carbon nanosheets can be realized by modulating the structure, but be limited by the carbon sources, making it challenging to obtain 2D structures with large surface area. In this work, a new method for forming carbon materials with high N/S doping content based on combustion activation using the dual activation effect of K2SO4/KNO3 is proposed. The synthesized carbon material as an anode for SIBs has a high reversible capacity of 344.44mAhg-1 at 0.05Ag-1. Even at the current density of 5Ag-1, the capacity remained at 143.08mAhg-1. And the ICE of sodium-ion in ether electrolytes is ≈2.5 times higher than that in ester electrolytes. The sodium storage mechanism of ether/ester-based electrolytes is further explored through ex-situ characterizations. The disparity in electrochemical performance can be ascribed to the discrepancy in kinetics, wherein ether-based electrolytes exhibit a higher rate of Na+ storage and shedding compared to ester-based electrolytes. This work suggests an effective way to develop doubly doped carbon anode materials for SIBs.

A study on photocatalytic Janus membrane reactor for direct conversion of low concentration carbon dioxide in air to methane: Effects of combination of two-dimensional carbon nanosheets

Large CO2 emissions cause the greenhouse effect, which threatens human survival. Directly converting CO2 in the air into energy and valuable resources is the most effective way to address the greenhouse effect. Currently, the main problem with CO2 conversion is the poor conversion efficiency owing to low CO2 concentrations in the air. In this study, a Janus membrane with the functions of concentrating CO2 (gas separation layer) and photocatalytic reaction (photocatalytic reaction layer) was fabricated. The Janus membrane directly converted extremely low concentrations of CO2 in the air into CH4. Amine-functionalized graphene oxide was added to regulate the CO2 conversion efficiency and the structure of the gas separation layer. Graphene was added to the photocatalytic reaction layer to suppress electron-hole recombination and increase the probability of excited electrons colliding with CO2. The experimental results showed that the modification of the gas separation layer or the photocatalytic reaction layer effectively increased the CH4 yield of the Janus membrane. By maintaining a balance between the selectivity and permeability coefficients of the gas separation layer, the highest methane yield (8.9 ppm) was obtained. The CH4 yield of the Janus membrane was further improved (8.9 ppm to 11.1 ppm) by modifying the photocatalytic reaction layer with graphene. This study proposes a feasible method for improving the efficiency of the Janus membrane for converting low-concentration CO2 in air to CH4.

Solvent-free synthesis of ZrO2 nanoparticles/nitrogen-rich two-dimensional carbon nanosheet composites as efficient catalysts for ORR

An innovative, high-performance, non-noble-metal-based oxygen reduction reaction (ORR) catalyst must be developed utilizing a new and cost-effective technique. ZrO2 has the merits of high stability, low toxicity, good catalytic activity, and low enthalpy for atomic oxygen adsorption. However, the poor conductivity restricts its application as an ORR catalyst. Here, we successfully prepared ZrO2 nanoparticles / nitrogen-rich two-dimensional carbon nanosheet composites as ORR catalysts using a straightforward, solvent-free, one-step pyrolysis approach. Due to the unique component and structure characteristics, ZrO2@N-C-900 demonstrates remarkable ORR performances in alkaline electrolytes, such as high half-wave potential (0.82 V vs. RHE), higher current density (JL = 6.4 mA cm−2), and outstanding long term stability (95 % for 36,000 s). Especially, when used in a Zn-air battery, ZrO2@N-C-900 exhibited a power density of 148 mW cm−2, exceeding that of 20 % Pt/C.

NiSe nanoparticles decorated corn stalk derived 2D carbon nanosheet as separator modifier for high-performance lithium-sulfur batteries

Lithium-sulfur (Li–S) batteries are considered as the most promising successors of lithium-ion batteries, however, the shuttle effect and sluggish reaction kinetics are the biggest obstacles hindering their commercialization. In this work, a kind of NiSe nanoparticles embedded in corn stalk-derived two-dimensional (2D) porous carbon nanosheet (NiSe@CSC) is constructed as a separator modifier for advanced Li–S batteries. The rich pore structure of the corn stalk-derived carbon nanosheets enables uniform distribution of NiSe and provides more deposition sites for lithium polysulfides (LiPS). Electrochemical analyses show that NiSe increases the affinity for LiPS to suppress the shuttle effect, thereby effectively preventing the corrosion of polysulfide on the lithium anode. NiSe@CSC is found to accelerate the redox conversion of sulfur species in the kinetic study. Consequently, the assembled Li–S cells with NiSe@CSC coating layer exhibit a high-rate performance of 710 mAh g−1 at 3 C and a low capacity attenuation rate of 0.046% per cycle after 800 cycles at 1 C. Furthermore, it can still maintain 2.8 mAh cm−2 at 0.5 C in near-commercial application scenarios of 4.1 mg cm−2 sulfur loading. The NiSe@CSC-based Li–Li symmetric cells also demonstrate stability and low overpotential in protecting the lithium anode. This combination of renewable biomass-based carbons and transition metal selenides enriches the exploration of biomass materials in separators and provides new ideas for designing practical Li–S batteries.

MoS2/WS2 quantum dots co-doped two-dimensional carbon nanosheets with high lithium ion conductivity

MoS2/WS2 quantum dots co-doped two-dimensional carbon nanosheets with high lithium ion conductivity

Co-Ru alloy nanoparticles decorated onto two-dimensional nitrogen doped carbon nanosheets towards hydrogen/oxygen evolution reaction and oxygen reduction reaction

Constructing highly-efficient electrocatalysts toward hydrogen evolution reaction (HER)/oxygen evolution reaction (OER)/oxygen reduction reaction (ORR) with excellent stability is quite important for the development of renewable energy-related applications. Herein, Co-Ru based compounds supported on nitrogen doped two-dimensional (2D) carbon nanosheets (NCN) are developed via one step pyrolysis procedure (Co-Ru/NCN) for HER/ORR and following low-temperature oxidation process (Co-Ru@RuOx/NCN) for OER. The specific 2D morphology guarantees abundant active sites exposure. Furthermore, the synergistic effects arising from the interaction between Co and Ru are crucial in enhancing the catalytic performance. Thus, the resulting Co-Ru/NCN shows remarkable electrocatalytic performance for HER (70 mV at 10 mA cm−2) in 1 M KOH and ORR (half-wave potential E1/2 = 0.81 V) in 0.1 M KOH. Especially, the Co-Ru@RuOx/NCN obtained by oxidation exhibits splendid OER performance in both acid (230 mV at 10 mA cm−2) and alkaline media (270 mV at 10 mA cm−2) coupled with excellent stability. Consequently, the fabricated two-electrode water-splitting device exhibits excellent performance in both acidic and alkaline environments. This research provides a promising avenue for the advancement of multifunctional nanomaterials.

Carbon Nanosheets-Based Supercapacitor Materials: Recent Advances and Prospects.

The need for inexpensive and ecologically sustainable energy storage technologies is rising rapidly along with the severity of the world's environmental challenges as well as with the rising demand for portable electronics and hybrid vehicles. Supercapacitors have drawn a lot of attentions lately in this regard because of their ultrahigh power density, outstanding electrochemical stability, and environmental friendliness. Due to various advantages, carbon materials are the choice of designer for developing commercial electrodes for various applications including devising supercapacitors. Two-dimensional (2D) carbon nanosheets (CNSs) with a large surface area and excellent electronic transport properties have fired up the interest of researchers due to their unique properties and potential applications in energy storage. Such engineered 2D porous CNS may significantly improve the energy storage performance of supercapacitor by enabling fast ion transport and charge transfer kinetics. This article summarizes the most recent and significant advances in the area of activated, porous, graphene-based various CNSs and their composites with a special focus on their use as supercapacitor electrodes. A succinct overview about their syntheses and key characterizations regarding their different structural aspects have been discussed. The present challenges and prospects in using CNS in supercapacitor applications are highlighted.

RuCo alloy nanoparticles embedded within N-doped porous two-dimensional carbon nanosheets: a high-performance hydrogen evolution reaction catalyst

RuCo alloy nanoparticles embedded within N-doped porous two-dimensional carbon nanosheets: a high-performance hydrogen evolution reaction catalyst

Effect of the TiO2-carbon interface on charge transfer and ethanol photo-reforming

Carbonaceous materials have been widely used in photocatalysis to solve the drawback of rapid electron-hole recombination rate of semiconductors such as titania. To further understand the charge separation mechanism and its effect on the ethanol photoreforming hydrogen production, two types of carbon-titania hybrid material systems were studied. One of them is multi-walled carbon nanotube-titania nanoparticles (MWCNT-TiO2) prepared by a sol-gel synthesis method, which according to previous studies should facilitate the migration of electrons from TiO2 to MWCNT. The second system is based on a two-dimensional carbon (exfoliated carbon, 2DC) and titania nanosheet (TNS), synthesized through a hydrothermal route that enabled the formation of strong interaction between the carbon and the {001} facets of the TNS. Our results demonstrate that this unique design promotes the migration of the photogenerated holes from the TNS to the expanded carbon. Steady state photoluminescence studies indicate that the recombination rate in both cases decreases benefiting from the spatial separation of photogenerated carriers, resulting in enhanced photocatalytic activity. The present study provides a comprehensive understanding of the charge separation mechanism and its effect on ethanol photoreforming hydrogen production in carbon-titania hybrid material systems and clearly highlights the need for further research to investigate the charge transfer in these kinds of hybrid materials.

NaCl-assisted synthesis of 2D hexagonal FeNC nanosheets as efficient oxygen reduction catalyst for metal-air batteries

Iron coordinated with nitrogen (FeNx) sites hosted in the micropores of carbon substrate offer excellent performance for the oxygen reduction reaction (ORR). Achieving a highly exposed and dispersed FeNx sites accessible for ORR is still challenging to date. In this work, two-dimensional hexagonal carbon nanosheets supported FeNx moieties (FeNC-NaCl-T) were synthesized via a molten NaCl-assisted pyrolysis strategy. Benefit from the high specific surface area (1371.635 m3·g−1) and highly dispersed FeNx sites, the optimized FeNC-NaCl-900 exhibits superior ORR activity with a high half-wave potential of 0.90 V in alkaline electrolyte. Impressively, with FeNC-NaCl-900 as the cathode catalyst in aqueous zinc–air battery, achieving a remarkable performance with a high peak power density of 177 mW·cm−2 and competitive durability (200 h). Furthermore, the Al-air battery equipped with FeNC-NaCl-900 attained an ultrahigh specific capacity of 2257.48 mAh·g−1 at a large discharge current of 100 mA cm−2. These findings provide guidance for the development of high performance FeNC catalysts and their applications in metal-air batteries.

Two-dimensional carbon nanosheets loaded with NiCo bimetallic catalysts for efficient electrocatalytic reduction of nitrogen to ammonia

Ammonia, one of the most produced chemicals, is mainly produced by the Haber Bosch process, under high-temperature, high-pressure, and energy-intensive conditions. Therefore, electrocatalytic nitrogen reduction is an attractive alternative method under ambient conditions. In this paper, two-dimensional carbon nanosheets (CNS) are firstly prepared by a modified Hummer method, and then Co and Ni bimetal load on CNS are prepared by a hydrothermal method to investigate their electrocatalytic nitrogen reduction reaction (NRR) properties. CNS has a porous sheet structure, and the NiCo oxide nanoflower structure with zigzag folding grows on the surface of CNS, which is beneficial to improve the contact area of the catalyst with N2, increasing the number of active sites, and better improve the performance of N2 reduction NH3 synthesis. At −0.34 V, the NH3 yield reaches a maximum of 22.18 μg·h−1·mg−1, and the Faradaic efficiency (FE) is 4.50 %, both of which are about twice as high as that of pure CNS, which is superior to other metal-doped electrocatalysts used for N2 reduction. This study provides an effective method for the design of electrocatalysts with high N2 reduction performance for ammonia synthesis. The catalytic mechanism is further explored by the theoretical calculations of DFT.

High-loading Cu single-atom nanozymes supported by carbon nitride with peroxidase-like activity for the colorimetric detection of tannic acid

The design of nanozymes with high metal atom loading is of great significance to improve enzyme activity and is also the key to furthering the construction of highly sensitive colorimetric sensors. In this work, a colorimetric sensor for the quantitative analysis of tannic acid (TA) was developed based on two-dimensional carbon nanosheet carbon nitride (CN)-supported Cu single-atom nanozymes (Cu/CN). Cu/CN was synthesized by supramolecular preorganization and calcination, with an ultrathin nanosheet structure and a high density of Cu active sites, with a Cu loading of up to 14.3 wt%. Benefiting from the above characteristics, Cu/CN exhibits peroxidase-mimicking activity and excellent catalytic performance. Therefore, a colorimetric sensor was constructed for the fast and sensitive quantitative analysis of TA with good linearity in the range of 0.09–3.2 μM and a low detection limit of 30 nM. Furthermore, the sensor was successfully applied to the analysis of TA in tea samples of different varieties. This work sheds new light on the design of nanozymes with a high density of active sites and the analysis of TA in real environments.

Two-Dimensional Nitrogen-Doped Carbon Nanosheets Derived from g-C3N4 /ZIF-8 for Solid-Phase Microextraction in Exhalation of Esophageal Cancer Patients

Here, two-dimensional (2D) nitrogen-doped carbon nanosheets (CNSs) were prepared through carbonizing MOFs (ZIF-8) in-situ grown using graphitic carbon nitride (g-C3N4) as a template. The developed ZIF-8 CNS was then used as solid-phase microextraction (SPME) fiber coating for beneficiation of five biomarkers in exhalation of patients with esophageal cancer and in gas chromatography-mass spectrometry (GC-MS) for determination. The ZIF-8 CNS fiber exhibits satisfactory enrichment factors (3490-5631), wide linearity (5-1000 μg L-1), and low detection limits (0.26-0.96 μg L-1). The relative standard deviations (RSDs) for six replicate extractions of the same ZIF-8 CNS fiber were between 2.0-3.9% (intra-day) and 2.8-5.2% (inter-day). The reproducibility of three fibers prepared by the same approach was in the range 6.8-12.3% (RSD). The developed ZIF-8 CNS fiber can persist in 120 SPME cycles with no prominent loss of extraction efficiency and precision. The high enrichment factors of the 2D ZIF-8 CNS coatings are attributed to the high specific surface area, ultrathin thickness, and nano-pore or interlayer channels; moreover, nitrogen doping also endows the π system with a strong electron absorption ability, which will enhance the π-π interaction between the ZIF-8 CNS and the aromatic ring. Ultimately, the self-made ZIF-8 CNS-coated SPME fiber was applied to the analysis of exhaled breath samples. The recoveries of spiked analytes are between 84 and 105%.

Pt Nanoparticles Confined in a 3D Porous FeNC Matrix as Efficient Catalysts for Rechargeable Li-CO2/O2 Batteries

The cathodic product Li2CO3, due to its high decomposition potential, has hindered the practical application of rechargeable Li-CO2/O2 batteries. To overcome this bottleneck, a Pt/FeNC cathodic catalyst is fabricated by dispersing Pt nanoparticles (NPs) with a uniform size of 2.4 nm and 8.3 wt % loading amount into a porous microcube FeNC support for high-performance rechargeable Li-CO2/O2 batteries. The FeNC matrix is composed of numerous two-dimensional (2D) carbon nanosheets, which is derived from an Fe-doping zinc metal-organic framework (Zn-MOF). Importantly, using Pt/FeNC as the cathodic catalyst, the Li-CO2/O2 (VCO2/VO2 = 4:1) battery displays the lowest overpotential of 0.54 V and a long-term stability of 142 cycles, which is superior to batteries with FeNC (1.67 V, 47 cycles) and NC (1.87 V, 23 cycles) catalysts. The FeNC matrix and Pt NPs can exert a synergetic effect to decrease the decomposition potential of Li2CO3 and thus enhance the battery performance. In situ Fourier transform infrared (FTIR) spectroscopy further confirms that Li2CO3 can be completely decomposed under a low potential of 3.3 V using the Pt/FeNC catalyst. Impressively, Li2CO3 exhibits a film structure on the surface of the Pt/FeNC catalysts by scanning electron microscopy (SEM), and its size can be limited by the confined space between the carbon sheets in Pt/FeNC, which enlarges the better contacting interface. In addition, density functional theory (DFT) calculations reveal that the Pt and FeNC catalysts show a higher adsorption energy for Li2CO3 and Li2CO4 intermediates compared to the NC catalyst, and the possible discharge pathways are deeply investigated. The synergetic effect between the FeNC support and Pt active sites makes the Li-CO2/O2 battery achieve optimal performance.