Carbon Nanoflakes Research Articles

CdSe-nanoparticles-regulated synthesis of ZnCo-MOFs derived conductive porous carbon nanoflakes on carbon cloth for flexible sodium-ion supercapacitors

Porous carbon derived from metal-organic frameworks (MOFs) represents a novel class of carbonaceous materials with unique structural characteristics, conductivity, and chemical stability, rendering them suitable for electrodes in supercapacitors. Herein, a three-dimensional structure of conductive porous carbon nanoflakes (CPCN) is synthesized based on MOFs composed of organic ligands containing zinc and cobalt. Nanoscale CdSe particles serving as energy-storage materials are incorporated into CPCN (CdSe/CPCN@CC) to form the flexible electrode for sodium-ion supercapacitors. The electrochemical properties of CdSe/CC, CdSe/ZnCo-MOF@CC, Cd/CPCN@CC, and CdSe/CPCN@CC are studied in 1 M Na2SO4. The CdSe/CPCN@CC electrode shows an impressive specific capacitance of 893.52 F g-1 at a current density of 0.125 mA cm-2 and excellent cycling stability with 80.68% retention after 10,000 cycles in 1.0 M Na2SO4. The asymmetric supercapacitor constructed with CdSe/CPCN@CC and 1 M NaPF6 electrolyte shows a capacitance of 97.8 F g-1, an energy density of 139.10 Wh kg-1, and a power density of 589.82 W kg-1 at a current density of 1 mA cm-2. In addition, the capacitance retention is 88.45% after 10,000 cycles. The electrochemical properties of CdSe/CPCN@CC are improved due to the incorporation of more active materials as well as the synergistic effects of the CdSe nanoparticles and CPCN. Density-functional theory (DFT) calculations reveal a sodium ion adsorption energy of -1.0692 eV and large DOS near the Fermi level. More importantly, in spite of severe mechanical bending, the device continues to power an LED array boding well for flexible and wearable applications.

α-MnO2 composite with gold nanoparticles on carbon cloth modified with MOFs-derived porous carbon for flexible and activity-enhanced sodium-ion supercapacitors

Improving the catalytic activity of electrodes in a limited space is crucial to energy storage devices such as supercapacitors. Herein, the surface activity of the flexible electrode (Au-MnO2/CPCN@CC) is enhanced by combining gold particles (AuNPs) modified α-MnO2 with conductive porous carbon nanoflakes (CPCN) derived from the metal-organic framework (MOF) on carbon cloth (CC). The Au-MnO2/CPCN@CC electrode exhibits a higher specific capacity of 503.7 F/g at 0.125 mA/cm2 and retains 87.68% capacity after 10,000 cycles in 1 M Na2SO4, while the structure without AuNPs achieves 242.6 F/g and 61.07% capacity retention after 10,000 cycles. The high stability of Au-MnO2/CPCN@CC stems from the good pseudocapacitance ratio of 83.80% at 1 mV/s compared to 78.43% of MnO2/CPCN@CC and 40.88% of Au/CPCN@CC. The supercapacitor assembled with Au-MnO2/CPCN@CC as the positive electrode and activated carbon (AC) as the negative electrode in 1 M NaPF6 shows an excellent power density of 79.96 W/kg at 71.48 Wh/kg as well as 81.93% capacitance retention after 10,000 cycles. Density-functional theory (DFT) calculations of Au-MnO2/CPCN composite reveal a sodium-ion adsorption energy of 3.744 eV and a large DOS near Fermi level. Hence, Au nanoparticles (AuNPs) and MOFs-derived CPCN lead to enhanced surface electron transport of MnO2 and ultimately superior performance.

Application of a Fluctuating Charge Polarization Model to Large Polyaromatic Hydrocarbons and Graphene Nanoflakes.

We present a polarization model incorporating coupled fluctuating charges and point inducible dipoles that is able to accurately describe the dipole polarizabilities of small hydrocarbons and, for sufficiently large graphene nanoflakes, reproduce the classical image potential of an infinite conducting sheet. When our fluctuating charge model is applied to the hexagonal carbon nanoflake C60000 we attain excellent agreement with the image potential and induced charge distribution of a conducting sheet. With the inclusion of inducible dipole terms, the model predicts an image plane of zim = 1.3334 a0, which falls in line with prior estimates for graphene. We consider the case of two charges placed on opposite sides of C60000 and find that the fluctuating charge model reproduces classical electrostatics once again. By testing opposing and similar signs of the external charges, we conclude that an atomically thin molecule or extended system does not fully screen their interaction.

Efficient adsorption of bisphenol A by metal-organic frameworks-derived N-doped carbon nanoflakes: Adsorption performance and mechanism investigation

Carbon-based materials have attracted great attentions as one of the most efficient adsorbents for wastewater treatment owing to their outstanding merits of low cost and excellent stability. In this work, we synthesized a novel N-doped carbon nanoflakes (NCF600) with high BET surface area (1609.1 m2/g) via carbonization and etching using UiO-66 as a precursor. Batch experiments demonstrated that NCF600 exhibited a high adsorption capacity for high concentrations of bisphenol A (BPA) in aqueous solutions (200 mg/g for 40 mg/L BPA) within 15 min. Furthermore, NCF600 shown good stability and reusability (the declining efficiency 3.4% after five cycles), following the pseudo-second-order model and the Freundlich adsorption model. Combined with multiple characterizations and density functional theory (DFT) calculations, we observed that pyridinic N is the main adsorption site instead of pyrrolic N and graphitic N. Considering the presence of functional groups in BPA and their interaction with NCF600, along with the influence of solution pH on the adsorption capacity of BPA, it is anticipated that the primary adsorption mechanisms will involve hydrogen bonding and π-π interactions. The present work demonstrates that NCF600 presents broad practical application prospects and provides insights for the design of N-doped carbon-based adsorbents for the effective removal of pollutants.

N-doped carbon nanoflakes coordinate with amorphous Fe to activate ozone for degradation of p-nitrophenol

Due to their high catalytic performance, metal nitrogen-doped carbon materials are widely used in the field of environmental restoration of polluted water but there is limited research on metal nitrogen doped carbon composite materials as ozone catalysts. Herein, we report the preparation of amorphous iron-coordinated nitrogen-doped carbon nanosheets as a catalyst for ozone by the coordination of Fe-metal ions at the end of phenol chain in the lignin network. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (Raman), powder X-ray diffraction (XRD) and element mapping were used to characterize the Fe/D-NC composite material and investigate its morphology and composition. Highly uniform distribution of iron species was found through characterization. By exploring the degradation performance of composite materials of Fe/D-NC-T (700，800，900 ℃) prepared at different temperatures, it was found that the optimal Fe/D-NC-800 could effectively degrade p-nitrophenol (PNP) within 30 min. Quenching experiments and ESR analysis showed that both free and non-free radicals (•OH, O2•− and 1O2) and intrinsic Lewis acid sites (LAS) of the composite material Fe/D-NC-800 were involved and responsible for the degradation of PNP. This work not only offers new platforms for catalytic ozonation and may drive the development of metal-lignin-based catalytic ozonation for effective water treatment but also opens new avenues toward lignin valorization and biomass economy.

Alkali cations and H2 molecules on BN-doped carbon nanoflakes: Theoretical study

Non-covalent interactions of two cations (Li+ and Na+) and hydrogen molecules with coronene and hexagonal boron nitride models as well as their heterostructures (mBNC and pBNC) were studied by using a set of theoretical methods. It was shown that the shapes of boron nitride moieties in the graphene-like framework have a strong influence on the cation-π interactions. Decomposition of the interaction energy (Eint) was classified as consisting mainly of the inductive energy term (Eind), which is followed by the electrostatic term (Eel). Hydrogen adsorption, however, depends strongly on both these terms, and in the case of numerous adsorbed H2 molecules, the dispersion interactions (Edisp) are also of importance. The assessed hydrogen capacity of studied structures reaches 5.5 wt%. The present investigation explicitly shows that cation-π and, in some cases, hydrogen adsorption properties can be easily modified by a B and N atoms introduction in the carbon nanoflakes, and, hence, it establishes the route to the remarkable adsorbent materials.

Graphitic Carbon-Coated PtCoNi Alloys Supported on N-Doped Porous Carbon Nanoflakes for Sensitive Detection of Bisphenol A

As the raw material of polycarbonate and epoxy resins, bisphenol A (BPA) is widely employed in industrial production of commodities, such as plastic bottles and thermal paper. However, excessive amounts of BPA affect the immune system of the human body and damage the health. It is important to monitor BPA in environmental and industrial samples. Herein, a graphitic carbon-coated PtCoNi alloy supported on N-doped porous carbon nanoflakes (G-PtCoNi/N-PCFs) was successfully prepared by high-temperature pyrolysis. The characteristics (e.g., compositions and microstructure) of the G-PtCoNi/N-PCFs were characterized in detail, coupled by investigating the N-doping effect. Specifically, the well-dispersed PtCoNi alloy enhanced the catalytic activity, combined by inhibiting the poisoning effect of the species absorbed on the surface and improving the utilization of Pt with additional Co/Ni atoms. Moreover, the graphitic carbon shell further enhanced the catalytic stability of BPA. As a desirable electrode material, the G-PtCoNi/N-PCFs composite was applied for building an electrochemical sensor for the detection of BPA. Under optimal conditions, the resultant sensor exhibited outstanding catalytic activity and analytical performance with a wide linear range of 2.0–140.0 μM and a low limit of detection of 0.19 μM (S/N = 3), combined with the feasibility for detecting BPA in thermal paper and plastic bottles.

Gd2O3–Carbon Nanoflakes (CNFs) as Contrast Agents for Photon-Counting Computed Tomography (PCCT)

Gd2O3–Carbon Nanoflakes (CNFs) as Contrast Agents for Photon-Counting Computed Tomography (PCCT)

Polycyclic Aromatic Hydrocarbons as Anode Materials in Lithium-Ion Batteries: A DFT Study.

The structure and energetics of the interactive behavior of Li+ and Li with polycyclic aromatic hydrocarbons (PAHs) have been studied at the wB97XD/6-311G(d,p) level of DFT. The electron distribution in the PAHs, analyzed using the topology of the molecular electrostatic potential (MESP), led to the categorization of their aromatic rings into five types, viz Rs, Rn, Rd, Rb, and Re. Among the different rings, sextet-type Rs and naphthalene-type Rn rings showed the highest interaction with Li+. The change in MESP at the nucleus of Li+ (ΔVLi+) due to the formation of the complex Li+...PAH is found to be proportional to the adsorption energy (E1). In Li...PAH, the spin density on Li is close to zero, suggesting the formation of Li+...PAH•- due to the electron transfer from Li to PAH. The adsorption energy (E2) for Li...PAH does not correlate with the change in MESP at the nucleus of Li, whereas the dissociation energy (E3) of Li+...PAH•- to yield Li+ and PAH•- correlates well with the MESP data, ΔVLi. The study confirms that the change in MESP at the nucleus of Li+ due to complex formation gives a quantitative measure of the electronic effect of the cation-π binding. The cell potential (Vcell) is predicted for the lithium ion battery (LIB) using the Li+...PAH and Li...PAH adsorption energies. On the basis of the Vcell data, "carbon nanoflake"-type systems, viz coronene, circumbiphenyl, C42H16, and C50H18 are suggested as good anode materials for LIBs.

One-step high-value conversion of heavy oil into H2, C2H2 and carbon nanomaterials by non-thermal plasma

Non-thermal plasma is promising for cracking the abundant but low-quality heavy oil into value-add chemicals due to its wide feedstock adaptability and high conversion rate. In this work, heavy oil cracking characteristics by microsecond pulsed spark discharge plasma were investigated in terms of pulse voltage, pulse repetition frequency and discharge power. Experiment results indicate pulse voltage and pulse repetition frequency are the main factors to control product yields and distribution. Pulse voltage determines single pulse energy and influences discharge stability and gas temperature. Pulse repetition frequency determines discharge intervals and affects collision reactions and quenching process. The maximum heavy oil conversion rate was 50.4% and the mass yields of H2 and C2H2 were 3.3% and 19.7% with 10.1 W discharge power, and H2 and C2H2 production energy consumption were 25.2 kW·h/m3H2 and 55.4 kW·h/m3C2H2. Compared with thermal plasma, heavy oil conversion rate of this work increased 12% with above 95% reduction in discharge power, and this work has a significant advantage in H2 and C2H2 production energy consumption. Carbon nanomaterials composed of carbon nanoflakes and nanoparticles can be obtained while producing H2 and C2H2. Especially, there were few-layers graphene nanoflakes (GNFs) in the carbon nanomaterials, which realized the full utilization of heavy oil. The possible reaction mechanism of heavy oil cracking was discussed using saturates-nucleating-aromatics-flaking theory. This work provides an effective COx-free method for one-step production of H2, C2H2 and carbon nanomaterials, which has wide application prospects for heavy oil utilization.

Interfacial Engineering of Leaf-like Bimetallic MOF-Based Co@NC Nanoarrays Coupled with Ultrathin CoFe-LDH Nanosheets for Rechargeable and Flexible Zn-Air Batteries.

Exploring high-efficiency, low-cost, and long-life bifunctional self-supporting electrocatalysts is of great significance for the practical application of advanced rechargeable Zn-air batteries (ZABs), especially flexible solid-state ZABs. Herein, ultrathin CoFe-layered double hydroxide (CoFe-LDH) nanosheets are strongly coupled on the surface of leaf-like bimetallic metal-organic frameworks (MOFs)-derived hybrid carbon (Co@NC) nanoflake nanoarrays supported by carbon cloth (CC) via a facile and scalable method for rechargeable and flexible ZABs. This interfacial engineering for CoFe-LDHs on Co@NC improves the electronic conductivity of CoFe-LDH nanosheets as well as achieves the balance of oxygen evolution reduction (OER) and oxygen reduction reaction (ORR) activity. The unique three-dimensional (3D) open interconnected hierarchical structure facilitates the transport of substances during the electrochemical process while ensuring adequate exposure of OER/ORR active centers. When applied as an additive-free air cathode in rechargeable liquid ZABs, CC/Co@NC/CoFe-LDH-700 demonstrates high open-circuit potential of 1.47 V, maximum power density of 129.3 mW cm-2, and satisfactory specific capacity of 710.7 mAh g-1Zn. Further, the flexible all-solid-state ZAB assembled by CC/Co@NC/CoFe-LDH-700 displays gratifying mechanical flexibility and stable cycling performance over 40 h. More significantly, the series-connected flexible ZAB is further verified as a chain power supply for LED strips and performs well throughout the bending process, showing great application prospects in portable and wearable electronics. This work sheds new light on the design of high-performance self-supporting non-precious metal bifunctional electrocatalysts for OER/ORR and air cathodes for rechargeable ZABs.

Cellulose‐Derived Wearable Carbon Nanoflake Sensors Customized by Semiconductor Laser Photochemistry

AbstractMulti‐functional wearable electrical materials have been regarded as one of the most pivotal cornerstones for the booming internet of things (IoTs), biomimetic robotics/science, and sensory e‐skins. Nevertheless, customizable, high‐throughput, batch‐fabricated, function‐integrated wearable electronics remain technologically challenging to traditional material engineering. Hereby, a cellulose‐converted active amorphous carbon nanomaterial is developed via a transfer‐free, precursor‐free rapid laser synthesis method incorporating deformation‐tolerant waste papers. The lattice fringe spacing of laser‐synthesized carbon nanoflake is ≈0.305 nm topologically distinct from graphene or carbon dots. The nanostructured three‐dimensional (3D) carbon network exhibits desirable mechanical flexibility, high hygroscopicity/electrical conductivity, large ion storing capacity for Zn2+ or Na+, high sensitivity to pressure, and a natural microwave absorbing ratio (> 37 dB at the terahertz range). Abundant percolation pathways inside cellulose/carbon composite networks offered fast electrolyte diffusion and carrier mobility. A series of low‐cost highly‐deformable interdigitated supercapacitors, tactile sensors, electrical circuits, and functional coatings are experimentally fabricated and identified, enabling waste paper as a function‐magnified meta platform for e‐skins, wearable energy devices, or IoTs interfaces.

Hydrogen storage capacity of the niobium atom adsorbed on carbon and boron nitride planar nanoflakes

In the present work, we investigate the capacity of the niobium atom adsorbed on the carbon and boron nitride planar flakes to store hydrogen molecules. Specifically, the Nb adsorbed on the circumcoronene (Nb@C), hexagonal boron nitride (Nb@h − BN), and the h − BN with the central ring substituted by carbons (Nb@C6/h − BN). The Nb@C and Nb@C6/h − BN systems present a hybridization among the carbon and niobium orbitals, which implies higher binding energy between the Nb atom and the corresponding flake, contrasting with the observed for the Nb@h − BN cluster. All the Nb@flakes possess multiplicity different from one, reinforcing the importance of considering the various accessible spin-state. Despite the high number of adsorbed hydrogen molecules supported by the Nb@flakes, the stability of the whole system is affected as the number of molecular hydrogen increases. The Nb@C6/h − BN is the system that satisfies the conditions of stability and H2 storage capacity. We highlight that the storage capacity of a given system must be measured considering not only the number of hydrogen molecules supported by the structure but also taking into account how the presence of nH2 affects the stability of the whole material.

MOF-Derived Robust and Synergetic Acid Sites Inducing C-N Bond Disruption for Energy-Efficient CO2 Desorption.

Amine-based scrubbing technique is recognized as a promising method of capturing CO2 to alleviate climate change. However, the less stability and poor acidity of solid acid catalysts (SACs) limit their potential to further improve amine regeneration activity and reduce the energy penalty. To address these challenges, here, we introduce two-dimensional (2D) cobalt-nitrogen-doped carbon nanoflakes (Co-N-C NSs) driven by a layered metal-organic framework that work as SACs. The designed 2D Co-N-C SACs can exhibit promising stability, superhydrophilic surface, and acidity. Such 2D structure also contains well-confined Co-N4 Lewis acid sites and -OH Brønsted acid sites to have a synergetic effect on C-N bond disruption and significantly increase CO2 desorption rate by 281% and reduce the reaction temperatures to 88 °C, minimizing water evaporation by 20.3% and subsequent regeneration energy penalty by 71.7% compared to the noncatalysis.

Spontaneous synthesis of Ag nanoparticles on ultrathin Co(OH)2 nanosheets@nitrogen-doped carbon nanoflake arrays for high-efficient water oxidation

The slow four-electron transfer of the oxygen evolution reaction (OER) greatly limits the water splitting efficiency, so the development of high-efficiency and stable OER electrocatalysts is of great significance for large-scale alkaline water splitting. Herein, we reported an efficient self-supported OER electrocatalyst of Ag NPs decorated ultrathin Co(OH)2 nanosheets supported on nitrogen-doped carbon (NC) nanoflake arrays on carbon cloth (Ag/Co(OH)2@NC/CC). Our designed 3D unique electrode structure with heterointerfaces and hierarchical nanosheets endow Ag/Co(OH)2@NC/CC with outstanding OER electrocatalytic activity (300 and 350 mV at 50 and 100 mA/cm2, 79.8 mV/dec of Tafel slope) and good long-term durability in 1 M KOH. Furthermore, the related results of electrochemical tests show that the improved conductivity, increased electrochemical active sites and enhanced intrinsic active sites explain the superior OER performance. Our study will offer some new ideas in constructing new highly-active materials for various other energy conversion fields.

DFT Study on the Adsorption of Propylthiouracil on Si- and Ga-doped Carbon Nanoflake and Aluminum Nitride Nanosheets

DFT Study on the Adsorption of Propylthiouracil on Si- and Ga-doped Carbon Nanoflake and Aluminum Nitride Nanosheets

Cadmium-Sulfide Doped Carbon Nanoflakes Used for Sunlight-Assisted Selective Photodegradation of Indigo Carmine

Cadmium-Sulfide Doped Carbon Nanoflakes Used for Sunlight-Assisted Selective Photodegradation of Indigo Carmine

Facile fabrication of 2D porous carbon nano-flake electrodes for high-performance flexible on-chip micro-supercapacitors

Graphene has been continuously investigated as electrode material for flexible micro-supercapacitors (MSCs). However, owing to the lack of in-plane ion transport channels and low specific surface area caused by restacking of graphene sheets, its electrochemical performance is unsatisfactory. To solve this problem, herein, we present a novel strategy for preparing 2D porous carbon nano-flake (PCF) through simple chlorine-etching MXene (Ti3C2). Distinctly different from the commonly graphene sheets, the prepared PCF shows high specific surface area (1239 m2 g−1) and abundant ion transport channels in c-axis direction, thus enhancing electrochemical performance. When the prepared PCF is used as the electrode for MSCs, the MSCs behaves excellent electrochemical performances. The areal capacitance and the energy density is up to 102.1 mF cm−2 (at current density of 0.2 mA cm−2) and 13.2 μWh cm−2 (at 0.1 mW cm−2 power density), respectively, which, to the best of our knowledge, are both among the highest values reported for MSCs with the graphene electrodes. In addition, the fabricated MSCs also show excellent mechanical flexibility and easy-adjustment in the voltage and capacitance by connecting multiple MSCs in series and parallel. These results indicate that the prepared PCF has great application potential in micro electrochemical energy storage devices.

Biomass-derived graphene-like carbon nanoflakes for advanced supercapacitor and hydrogen evolution reaction

It is valuable that graphene-like carbon materials are prepared from the biomass resources due to their unique two-dimensional structure, heteroatom enriched, and high specific surface area. Herein, we use egg white and graphene oxides as precursor and employ post-hydrothermal carbonization approach, freeze-drying technique, carbonization, and activation methods by KOH to prepare the graphite carbon nanoflakes with Fe7C3 @graphite carbon nanoflakes hybrid materials. Morphology tests imply that the formation of graphite carbon nanoflakes are mainly depended by activation step, it implies that carbon flakes are exfoliated via introducing K+ into carbon layers and further destroying the van der Waals force (VDWF). As a result, this hybrid materials exhibit an attractive capacitance (528 mF·cm−2 @1 mA·cm−2) and durability (91 @10 mA·cm−2, 4000 cycles). For hydrogen evolution reaction (HER), the as-collected samples also deliver a low overpotential and remarkable stability. We believe that the as-obtained hybrid materials have a greatly application value in energy storage devices.

Zn-Metal-Organic Framework Derived Ordered Mesoporous Carbon-Based Nanostructure for High-Performance and Universal Multivalent Metal Ion Storage.

Metal-organic framework (MOF) derivatives promise great potential in energy storage and conversion because of their excellent tunability in both the active metal sites, organic links, and the overall structures down to atomic and up to mesoscale. Nevertheless, a big challenge is to precisely control and thoroughly understand the actual MOF-to-derivative conversion process to realize the template-free synthesis of the MOF-derived ordered mesoporous materials. Here, a class of ordered mesoporous N-doped carbon nanoflakes is presented with slit-shaped pores synthesized by one-step pyrolysis of Zn1 Cux -MOF, where the Cu doping plays a critically important direction-inducing function on the dissociation of organic ligands during the pyrolysis. Benefiting from the uniquely ordered mesoporous structure and large specific surface area (910 m2 g-1 ), the Zn1 Cux -MOF-derived ordered mesoporous carbon nanoflakes present outstanding electrochemical storage performance for multivalent metal ions, such as Mg2+ , Ca2+ , Co2+ , Ni2+ , Al3+ , and Zn2+ , demonstrating the universal nature of the slit-shaped pores in enabling the multivalent metal ions for energy storage. Moreover, the assembled flexible Zn-ion hybrid supercapacitor (ZHSC) delivers a high specific capacity of 134 mAh g-1 at 0.5 A g-1 , excellent cycling and mechanical stability, showing great application potential in the new generation energy storage devices.