Carbon Nanoframes Research Articles

Synthesis of Newly Discovered Carbon Nanoframes: A Self‐Assembly Strategy Based on DTAB @ NaCl

AbstractCarbon nanomaterials have attracted much attention in the field of science and technology for their excellent properties; however, developing a simple, environmentally friendly, and versatile synthesis strategy for the preparation of carbon nanomaterials with novel structures remains a great challenge. Herein, a surfactant @ salt (dodecyltrimethylammonium bromide DTAB @ NaCl) self‐assembly strategy for the synthesis of carbon nanomaterials with novel structures, i.e., carbon nanoframes is reported. The synthesis differs from the traditional template method in that it is characterized by the introduction of surfactants for separation and protection, and the salt can be recycled. In addition, the carbon frame size in this system can be adjusted on demand by simply adjusting the concentration of surfactant, thus realizing that the carbon nanoframe size is adjustable in the range of 232.58–322.51 nm. Impressively, the carbon nanoframe has purple, blue, and green PL emission behavior. It is anticipated that this research will provide new insights into the development of novel carbon nanomaterials.

Facile Synthesis of Vertical Layered Double Hydroxides Nanosheets on Co@Carbon Nanoframes as Robust Bifunctional Oxygen Electrocatalysts for Rechargeable Zn–Air Batteries

The development of efficient and low‐cost bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative but remains challenging in rechargeable zinc–air batteries. Herein, a metal oxidation‐assisted approach is developed for the facile synthesis of a highly efficient bifunctional catalyst (Co@NC@LDHs) which is composed of layered double hydroxides (LDHs) nanosheets in situ vertically grown on the surface of hollow carbon nanoframes encapsulating Co nanoparticles (Co@NC). Specifically, the vertical LDHs distributing on the carbon surface ensure the maximized number of accessible active sites and the interaction between LDHs with the carbon matrix. The hierarchically structured bifunctional Co@NC@LDHs display an overpotential of 0.33 V at 10 mA cm−2 for OER and a half‐wave potential of 0.88 V for ORR. The potential gap (ΔE) of Co@NC@LDHs is calculated to be 0.68 V, outperforming the mixed Pt/C + RuO2 catalysts (ΔE = 0.77 V), manifesting its superior bifunctional electrocatalysis performance. Moreover, the Zn–air batteries based on Co@NC@LDHs electrocatalyst exhibit a high peak power density (185.2 mW cm−2) and excellent durability (5.0 mA cm−2 over 500 h). This work may provide a facile strategy for the fabrication of LDHs on carbon substrate, acting as efficient catalysts for broad energy‐related applications.

A macroporous carbon nanoframe for hosting Mott-Schottky Fe-Co/Mo2C sites as an outstanding bi-functional oxygen electrocatalyst.

Simultaneously optimizing the d-band center of the catalyst and the mass/charge transport processes during the oxygen catalytic reaction is an essential but arduous task in the pursuit of creating effective and long-lasting bifunctional oxygen catalysts. In this study, a Fe-Co/Mo2C@N-doped carbon macroporous nanoframe was successfully synthesized via a facile "conformal coating and coordination capture" pyrolysis strategy. As expected, the resulting heterogeneous electrocatalyst exhibited excellent reversible oxygen electrocatalytic performance in an alkaline medium, as demonstrated by the small potential gap of 0.635 V between the operating potential of 1.507 V at 10 mA cm-2 for the oxygen evolution reaction and the half-wave potential of 0.872 V towards the oxygen reduction reaction. Additionally, the developed Zn-air battery employing the macroporous nanoframe heterostructure displayed an impressive peak power density of 218 mW cm-2, a noteworthy specific capacity of 694 mA h gZn-1, and remarkable charging/discharging cycle durability. Theoretical calculations confirmed that the built-in electric field between the Fe-Co alloy and Mo2C semiconductor could induce advantageous charge transport and redistribution at the heterointerface, contributing to the optimization of the d-band center of the nanohybrid and ultimately leading to a reduction in the reaction energy barrier during catalytic processes. The exquisite macroporous nanoframe facilitated the rapid transport of ions and charges, as well as the smooth access of oxygen to the internal active site. Thus, the presented unique electronic structure regulation and macroporous structure design show promising potential for the development of robust bifunctional oxygen electrodes.

Facet-selective growth of MOF-on-MOF heterostructures enables etching-free synthesis of highly-open Co/N-doped carbon nanoframes for efficient catalysis

Facet-selective growth of MOF-on-MOF heterostructures enables etching-free synthesis of highly-open Co/N-doped carbon nanoframes for efficient catalysis

Double salt-template strategy for the growth of N, S-codoped graphitic carbon nanoframes on the graphene toward high-performance electromagnetic wave absorption

The increasingly serious electromagnetic radiation urgently call for high performance electromagnetic wave (EMW) absorbers. Hollow carbon nanostructures are promising for lightweight EMW absorbers. However, due to lack of sufficient polarization centers, the EMW absorption property of hollow carbon nanosturctures is still unsatisfactory. Herein, we develop a double-salt template method for fabrication of N, S-codoped graphitic carbon nanoframes (GF) that anchored on the graphene sheets (GS). The GFs in the sample (N, S-GF/GS) have a width of about 51 nm and a wall thickness of only 4.8 nm. Furthermore, the graphene plane in the GF is perpendicular to the graphene plane in the GS, leading to the formation of numerous interfaces between the graphene planes perpendicular to each other. Theoretical calculations indicate that the interfaces can induce the interfacial polarization loss, and the N, S co-doping can cause dipole polarization loss, both of which enhance the EMW absorption performance of the N, S-GF/GS. The minimal reflection loss and efficient absorption width of the N, S-GF/GS at a low filler ratio of 10 wt% are -45.64 dB at the matching thickness of 2.3 mm and 4.35 GHz with the thickness of 1.5 mm, respectively, superior to most of carbon-based absorbers. Our proposed method opens a promising way for high-performance EMW absorbers.

Designing Hierarchically Porous Single Atoms of Fe-N5 Catalytic Sites with High Oxidase-like Activity for Sensitive Detection of Organophosphorus Pesticides.

Recently, single-atom catalysts (SACs) have been used to construct biosensors for the determination of organophosphorus pesticides (OPs). However, most nanozymes including SACs are peroxidase-like enzymes and require highly toxic and unstable hydrogen peroxide (H2O2) as a co-reactant to generate reactive oxygen species. Inspired by the heme site of cytochrome c oxidases (Ccos), the construction of Fe-N5-coordinated SACs by introducing axial N ligands is expected to bind O2 to generate active metal-oxygen intermediates. Herein, a SAC with an Fe-N5 active center confined by hierarchically porous carbon nanoframes (Fe SAs/N5-pC-4) was prepared by a polymerization-pyrolysis-evaporation-etching strategy, and its underlying enzyme-like mechanism was uncovered through experiments and density functional theory calculations. The 100% metal atom utilization, increased accessible active sites, accelerated mass transfer, excellent hydrophilicity, and an electron-driven mechanism of axial N endow the SAC with enhanced oxidase-like activity. Notably, its catalytic rate constant (0.398 s-1) is 569 times greater than that of the commercial Pt/C catalyst. Similar to the catalytic mechanism of Ccos, O2 can be converted into reactive oxygen species, avoiding the use of co-reactant H2O2 effectively. In addition, based on the inhibitory effect of thiols on the active site of Fe SAs/N5-pC-4, a biosensor was constructed and applied to the colorimetric analysis of OPs. This provides a facile, cost-effective method for efficient OP screening at sites to help control their contamination.

Fabrication of electrocatalytically active, cobalt-embedded nitrogen-doped ordered macroporous carbon for sensitive detection of nitrobenzene

Zeolitic imidazole framework-67 can be converted into metal compounds, and N-doped carbon nanomaterials, under suitable pyrolysis conditions. N-doped carbon materials have attracted much attention due to their high specific surface area, controllable framework structure, and significant synergy between carbon and transition metal nanocrystals. We successfully synthesized Co-NC by using PS nanospheres as templates and immersing the ZIF-67 precursor solution into the PS sphere template gap, and then carbonizing directly at different temperatures. The obtained Co-NC-800 shows excellent electrochemical activity because of its uniform and unique porous structure, as well as the uniform distribution of metal and nitrogen atoms in the carbon nanoframe. The Co-NC exhibits enhanced electrochemical sensing of nitrobenzene, with a wide linear detection range (0.1 μM–0.863 mM), lower detection limit (0.086 µM, S/N = 3), excellent stability and better selectivity. Therefore, the developed Co-NC electrocatalyst represents a promising catalyst for electrochemical analysis.

Fe-doped MOF-derived N-rich porous carbon nanoframe for H2 S cataluminescence sensing.

Metal-doped porous carbon matrix composites are considered as outstanding H2 S cataluminescence sensing materials for their good sulfur tolerance and high cataluminescence activity. In this work, an Fe-doped MOF-derived N-rich porous carbon nanoframe was successfully fabricated using the pyrolysis of Fe-doped ZIF-8 in an Ar atmosphere at a temperature of 900°C, and used for H2 S cataluminescence sensing. Along with zinc volatilization, the obtained porous carbon nanoframe not only had high specific surface area and abundant voids, but also had well dispersed Fe species doped in the skeleton. Compared with Fe2 O3 /ZnO composites derived from the same precursor but different pyrolysis terms, this as-prepared Fe-doped N-rich porous carbon presented a three times increase in the cataluminescence intensity towards H2 S, attributed to the porous carbon skeleton that is indispensable for dispersing catalytic active sites and providing more absorptive surface and voids. Comparably, this proposed sensor demonstrated high sensitivity and good selectivity, with the detection range of 1.57-19.58 μg·ml-1 and detection limit of 0.13 μg·ml-1 towards H2 S. This work may provide a new pathway for preparing catalysts for cataluminescence sensing with better metal distribution, higher specific surface area, and richer pores than ever before.

Well-dispersed ZIF-derived N-doped carbon nanoframes with anchored Ru nanoclusters as HER electrocatalysts

Nano-structuring and metal-support interactions are effective methods to improve the electrocatalytic activity of heterogeneous catalysis. In this study, we synthesized nitrogen-doped porous carbon substrates by using a SiO2-protected calcination strategy with ZIF-8 as a precursor. The experimental results revealed the prepared porous nitrogen-doped carbon (PNC) to have high dispersion, large specific surface area, and rich pore structure, allowing high exposure of active sites. The carbon support showed optimum characteristics to deposit precious metals with small particle sizes. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) showed that the N groups on the PNC substrates served as coordination sites for Ru, allowing the formation of ultrafine nanoclusters. The Ru clusters showed good metal dispersion, exposing more active sites and improving the utilization of the precious metal. At a current density of 10 mA/cm2, Ru/PNC showed a minimum overpotential of 40 mV. This work provided a simple and effective method for the preparation of excellent carbon substrates and the synthesis of metal clusters with small particle sizes.

Hollow Fe/Ni–CoTe@NCFs nanoarchitecture derived from MOF@MOF as high-efficiency electrocatalysts for boosting oxygen evolution reaction

To improve the oxygen evolution reaction (OER) catalytic efficiency of non-noble-metal-based catalysts, researchers have made great endeavors to adjust the compositions, morphologies and configuration of material. In this work, a dual-metal-organic frameworks (MOFs)-assisted fabrication hierarchical and hollow N-doped carbon nanoframes (NCFs) decorated with Fe/Ni-codoped CoTe nanocomposite catalyst (Fe/Ni–CoTe@NCFs) is reported. Starting from MOF-in-MOF composite precursors, the design and fabrication of Fe/Ni–CoTe by the strategies: i.e, hydrothermal precipitation, chemical etching and low-temperature tellurization, and high-temperature pyrolysis steps. Newly designed catalyst (Fe/Ni–CoTe@NCFs) performs superior OER catalytic activity to afford 10 mA cm−2 at the overpotential of 287 mV with a small Tafel slope of 52.3 mV dec−1. The frame-like hollow core-shell nanostructures with ample channels into the internal volume and high double-layer capacitance provide the large catalytic active surface area and increase more actives sites. The cooperative effects between alloy and metal telluride, as well as hollow carbon shell promote the activity of OER. Therefore, this study offers a catalyst with great potential for OER and provides the possibility for the application of transition metal tellurides in electrocatalysis.

Combine etching-doping sedimentation strategy and carbonization to design double-deck petal-like NiO/CoO nanoporous carbon composite for methyl parathion detection

Designing efficient and rapid methods for detection of pesticide residue is one of the prerequisites to reduce its negative health influences. Herein, we constructed an electrochemical sensor for efficient detection of Methyl parathion (MP) using a double-deck petal-like NiO/CoO nanoporous carbon composite (Z-NiO/CoO@CC). The Z-NiO/CoO@CC was fabricated through etching-doping sedimentation strategy and carbonized conversion. The elaborate electrocatalyst not only created the structural advantages to offer more activities sites for the target analyte, but also had compositional virtues by combining the carbon nano-frame (originating from zeolitic imidazolate framework, ZIF-67) and bimetal oxides to enhance electrochemical performances. Besides, the electro-catalysis mechanism and detection performance of the prepared electrode were also detailly studied through different electrochemical techniques. Under optimized conditions, the prepared Z-NiO/CoO@CC showed favorable performance for MP detection with linear range from 10 ng/mL to 10 μg/mL, high sensitivity of 12.8 μA μM−1 cm−2 and low detection limit of 3.6 ng/mL (S/N = 3). Moreover, the practical feasibility of the Z-NiO/CoO@CC was also verified through monitoring MP in tap water and grape samples. This work has explored a novel method for construction of high-performance electrochemical MP sensors.

Facile synthesis of N-doped carbon nanoframes encapsulated by CoP nanoparticles for hydrogen evolution reaction

Development of high-performance, economic, and stable non-noble metal catalysts is a still formidable challenge in hydrogen evolution reaction (HER) that must be overcome to alleviate the energy and environmental crisis. Herein, we designed and fabricated N-doped carbon nanoframes encapsulated by CoP nanoparticles (CoP-NCN). The 3D porous structure of the ZIF-67-derived N-doped carbon shortened the charge and mass transport pathways, contributing to enhanced electrocatalytic performance. Moreover, the synergistic effects of excellent conductivity, abundant mesopores, and high-activity CoP nanoparticles led to remarkable electrocatalytic activity toward HER with an extremely low overpotential of 120 mV at 10 mA cm−2 and long-term stability. We further indicate that the fantastic HER catalytic ability of CoP-NCN is attributed to the good conductivity and the abundant active sites. The present study provides a promising avenue toward the design of cost-effective HER electrocatalysts.

ZIF-Derived Carbon Nanoframes as a Polysulfide Anchor and Conversion Mediator for High-Performance Lithium-Sulfur Cells.

Improving the redox kinetics of sulfur species, while suppressing the "shuttle effects" to achieve stable cycling under high sulfur loading is an inevitable problem for lithium-sulfur (Li-S) cells to commercialization. Herein, the three-dimensional Zn, Co, and N codoped carbon nanoframe (3DZCN-C) was successfully synthesized by calcining precursor which protected by mesoporous SiO2 and was used as cathode host for the first time to improve the performance of Li-S cells. Combining the merits of strong lithium polysulfides (LiPSs) anchoring and accelerating the conversion kinetics of sulfur species, 3DZCN-C effectively inhibit the shuttling of LiPSs and achieves excellent cyclability with capacity fading rate of 0.03% per cycle over 1000 cycles. Furthermore, the Li-S pouch cell has been assembled and has been shown to operate reliably with high energy density (>300 Wh kg-1) even under a high sulfur loading of 10 mg cm-2. This work provides a simple and effective way for the promotion and commercial application of Li-S cells.

Copper Isolated Sites on N-Doped Carbon Nanoframes for Efficient Oxygen Reduction

In recent years, metal isolated site catalysts with the high exposure and maximized availability of metal species provide a new route to boost the oxygen reduction performance. However, in the absence of clusters and nanoparticles, the synthesis of this catalyst with metal high-loading, especially for copper, is still a big challenge. In this work, a metal isolated site catalyst with high copper content (1.12 wt %), copper isolated sites anchored on N-doped carbon materials (donated as Cu ISs/NC-1000), was prepared by the pyrolysis of copper acetylacetone within the metal–organic framework (ZIF-8) at 1000 °C. The successful preparation of products can be demonstrated by high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption spectra. With the merits of the atomically dispersed surface metal atoms and abundant ORR-favored copper active sites, the present Cu ISs/NC-1000 exhibits an excellent ORR electrochemical activity with a half-wave potential of 0.855 V (vs RHE) and a limiting current density of 5.2 mA cm–2 in the electrochemical tests, superior to the results from commercial Pt/C and previously reported Cu-based materials. For the durability, the negligible activity decay after 10,000 continuous potential cycles and good resistance to methanol crossover can be noted. The outstanding catalytic activity from the present Cu ISs/NC-1000 demonstrates the superiority of metal isolated sites as electrocatalytic centers.

Embedded PdFe@N-carbon nanoframes for oxygen reduction in acidic fuel cells

Carbon-supported metal nanoparticles are widely used as electrocatalysts in polymer electrolyte membrane fuel cells (PEMFCs), but still suffer from deactivation because of metal leaching and sintering at high temperature. Herein, we propose a novel and scalable metal coordination-polymer strategy for the facile synthesis of bimetallic PdFe nanoparticles embedded nitrogen-doped carbon (PdFe@N-C) nanoframes as a Mott-Schottky electrocatalyst to efficiently catalyze the oxygen reduction reaction (ORR) in PEMFCs. The metal coordination-polymer is formed through metal ions (Pd and Fe) mediated self-polymerization of 1-naphthylamine (NA), which allows alloy nanoparticles to bind tightly with N-carbon nanoframes after pyrolysis. It is found that PdFe nanoparticles with very small particle-size are uniformly embedded in the porous N-carbon nanoframes and physically separated from each other by the carbon matrix. Profited from the unique structure and composition merits, the half-wave potential of the developed PdFe@N-C nanoframes towards ORR is positively shifted by 30 and 50 mV compared to those of Pd@N-C and Pd/C, respectively. Importantly, the PdFe@N-C nanoframes derived acidic PEMFC delivers a high-power density of 0.91 W cm−2 together with remarkable operational stability after 10 h discharging. Such good performances make the metal-NA coordination-polymer an attractive precursor to design and synthesize high-performance electrocatalysts for fuel cells.

Metal–organic framework-derived mesoporous carbon nanoframes embedded with atomically dispersed Fe–Nx active sites for efficient bifunctional oxygen and carbon dioxide electroreduction

Metal–organic frameworks (MOFs) can be utilized as superior precursors to pyrolytically achieve the single-atom catalysts. However, most of the atomic active sites are buried inside the microporous carbon matrix, which severely impedes the accessibility of active sites and limits mass transport. Herein, the mesoporous carbon nanoframes with hierarchical pore size distribution and atomically dispersed Fe–Nx active sites were synthesized from Fe-doped MOF precursors. The dense Fe atoms within the nanostructures are dispersed in single-atom level with metalloporphyrin-like Fe–N4 configuration. The introduction of plentiful large mesopores into the nanoframes would not only enhance the accessibility of abundant single-atom active sites, but also boost mass and charge transports. Such distinctive nanostructure led to exceptional bifunctional electrocatalytic performances for oxygen reduction reaction, with more positive onset potential (1.01 V vs. 0.97 V) and half-wave potential (0.89 V vs. 0.82 V) compared with the commercial Pt/C, and electrochemical carbon dioxide reduction.

Cobalt encapsulated within porous MOF-derived nitrogen-doped carbon as an efficient bifunctional electrocatalyst for aprotic lithium-oxygen battery

In energy storage and conversion field, it is an eternal theme to develop effective and stable catalysts. Carbon composites with embedded metal/metal oxides as electrochemical catalysts has attracted extensive research attention. However, severe carbon evaporation causes the aggregation of metal particles during the pyrolysis synthesis, which directly leads to poor dispersion of the active sites and a decrease in catalytic stability. To solve this issue, cobalt encapsulated within porous nitrogen-doped carbon nano-frame (Co, N–CNF) is prepared by template-induced calcinations strategy using mental organic framework (MOF) as precursor and mesoporous SiO2 as template. This strategy leverages the template to capture volatile carbon and nitrogen species and retains the structure of the MOF precursor after pyrolysis. The prepared Co, N–CNF catalyst has a multi-layered spherical graphite shell with sp2 hybrid orbital and metallic cobalt core with fully exposed catalytic active site. Li–O2 batteries based on this core-shell structured cobalt-encapsulated catalyst show excellent electrochemical performance, including high specific capacity (5288 mA h g-1) and remarkable cycle stability without significant voltage attenuation after 500 cycles. These excellent properties are attributed to the unique core-shell structure, as well as the fully exposed metallic cobalt active sites.

Sub-5 nm palladium nanoparticlesin situembedded in N-doped carbon nanoframes: facile synthesis, excellent sinter resistance and electrocatalytic properties

N-carbon nanoframes embedded with sub-5 nm Pd nanoparticles are prepared through a 1-naphthylamine-driven pyrolysis strategy and exhibit excellent bifunctional electrocatalytic performance.

Well-defined carbon nanoframes containing bimetal-N-C active sites as efficient bi-functional electrocatalysts for Li-O2 batteries

Design and fabrication of framework-structured porous precursors have been regarded as a prospective albeit challenging strategy to obtain bimetal/NC-enriched bifunctional elecrocatalysts. In this work, an effective bottom-up approach involving solution-based self-assembly and a post-annealing process was developed to confine (Co, Zn)-N-C active sites into N-enriched graphitic carbon nanocages. This novel architecture containing N-doped-C stabilized bimetallic nanoparticles derived from ZIF precursors was well-studied by a series of characterization and analysis techniques. Details were given that these well-dispersed (Co, Zn) nanoparticles were encapsulated into the pyridinic-N-dominated graphitic carbon nanocage with a total metal loading of approximately 7.4 at.%. This favorable hierarchical structure not only enhances the electron conductivity, but also owns a sufficient BET surface area facilitating the gas-liquid-solid triphase reaction and producing more space to store discharge products. Importantly, results infer that the interesting nanoframes manifests a satisfying ORR/OER activity and enhanced cell performance whether liquid or solid-state electrolytes are used. As such, our work rationalizes that this type of cage-shaped bimetal-N-C material is promising for high-performance Li-O2 batteries.

A New Non-Enzymatic Amperometric Sensor Based on Nickel Decorated ZIF-8 Derived Carbon Nanoframe for the Glucose Determination in Blood Samples

The present study demonstrated a highly sensitive non-enzymatic glucose biosensor in real blood samples based on simple evaluated nickel deposited on N-doped porous carbon modified glassy carbon el ...