Nitrogen-doped Hollow Carbon Nanospheres Research Articles

Short-Chain Sulfur Confined into Nitrogen-Doped Hollow Carbon Nanospheres for High-Capacity Potassium Storage.

Carbon-based materials are one of the ideal negative electrode materials for potassium ion batteries. However, the limited active sites and sluggish diffusion ion kinetics still hinder its commercialization process. To address these problems, we design a novel carbon composite anode, by confining highly reactive short-chain sulfur molecules into nitrogen-doped hollow carbon nanospheres (termed SHC-450). The formation process involves the controlled synthesis of hollow polyaniline (PANI) nanospheres as precursors via an Ostwald ripening mechanism and subsequent sulfuration treatment. The high content of constrained short-chain sulfur molecules (20.94 wt%) and considerable N (7.15 wt%) ensure sufficient active sites for K+ storage in SHC-450. Accordingly, the SHC-450 electrode exhibits a high reversible capacity of 472.05 mAh g-1 at 0.1 A g-1 and good rate capability (172 mAh g-1 at 2 A g-1). Thermogravimetric analysis shows that SHC-450 has impressive thermal stability to withstand a high temperature of up to 640 °C. Ex situ spectroscopic characterizations reveal that the short-chain sulfur provides high capacity through reversible formation of K2S. Moreover, its special hollow structure not only provides ample space for highly active short-chain sulfur reactants but also effectively mitigates volume expansion during the sulfur conversion process. This work offers new perspectives on enhanced K+ storage performance from an interesting anode design and the space-limited domain principle.

Optimizing Electron Spin-Polarized States of MoSe2 /Cr2 Se3 Heterojunction-Embedded Carbon Nanospheres for Superior Sodium/Potassium-Ion Battery Performances.

The principal challenges faced by sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) revolve around identifying suitable host materials capable of accommodating metal ions with larger dimensions and addressing the issue of sluggish chemical kinetics. Herein, a MoSe2 /Cr2 Se3 heterojunction uniformly embedded is fabricated in nitrogen-doped hollow carbon nanospheres (MoSe2 /Cr2 Se3 @N-HCSs) as an electrode material for SIBs and KIBs. Cr2 Se3 exhibits spontaneous antiparallel alignment of magnetic moments. Mo2+ doping is employed to regulate the electron spin states of Cr2 Se3 . Moreover, the MoSe2 and Cr2 Se3 heterojunctions induce a lattice mismatch at the heterostructure interface, resulting in spin-polarized states or localized magnetic moments at the interface, potentially contributing to spin-polarized surface capacitance. MoSe2 /Cr2 Se3 @N-HCSs demonstrate a high capacity of 498 mAh g-1 at 0.1 A g-1 with good cycling stability (capacity of 405 mAh g-1 and a coulombic efficiency of 99.8% after 1000 cycles). Additionally, density functional theory (DFT) calculations simulate the accumulation of spin-polarized charges at the MoSe2 /Cr2 Se3 @N-HCSs heterojunction interface, dependent on the surface electron density of the antiferromagnetic Cr2 Se3 and the surface spin polarization near the Fermi level. After regulating the electron spin states through Mo-doping, the band gap of the material decreases. These significant findings provide novel insights into the design and synthesis of electrode materials with exceptional performance characteristics for batteries.

Cooperative regulation of hard template and emulsion self-assembly to the synthesis of N/O co-doped mesoporous hollow carbon nanospheres for supercapacitors

Hollow carbon nanospheres have attracted more and more attention as supercapacitor materials due to their excellent electrical conductivity, high theoretical surface area, high accumulation and rapid ion transfer and diffusion. In this work, we employed the Stöber method to create silica as a template, and then applied self-assembly and dopamine polymerization on the surface of the template to form SiO2@TMB-F127-PDA micelles. Then the nitrogen-doped mesoporous hollow carbon nanospheres (N-MHCNs) were prepared by carbonization and etching on the formed carbon precursors. The effect of dopamine amount on the structure and properties of N-MHCNs was systematically studied. Microstructural characterization results reveal that the morphology of N-MHCNs can be changed from sheet to sphere, and the particle size of N-MHCNs can be 33.8–225.7 nm, the specific surface area is distributed in the range of 175.9–430.1 m2 g−1. Due to the N,O heteroatomic co-doping and Porous spherical structure (with a small particle size of 33 nm, and a large specific surface area of 430.1 m2 g−1), typical sample N-MHCNS-2 shows excellent electrochemical performance in supercapacitors. And it has the highest specific capacitance (241 F g−1) at 0.5 A g−1 current density, excellent rate performance (capacity retention rate of 79 % when current density increases from 0.5 to 10 A g−1) and good cycling ability (capacity retention rate of 90.4 % after 3000 cycles), indicating that it shows great potential in energy storage. This approach provides new opportunities for the controllable synthesis of hollow mesoporous nanospheres and it can be extended to other systems such as hollow metals, metal oxide nanomaterials and carbon-based hybrids.

Organic-Inorganic Hybrid Interfaces Enable the Preparation of Nitrogen-Doped Hollow Carbon Nanospheres as High-Performance Anodes for Lithium and Potassium-Ion Batteries.

An abundant hollow nanostructure is crucial for fast Li+ and K+ diffusion paths and sufficient electrolyte penetration, which creates a highly conductive network for ionic and electronic transport. In this study, we successfully developed a molecular-bridge-linked, organic-inorganic hybrid interface that enables the preparation of in situ nitrogen-doped hollow carbon nanospheres. Moreover, the prepared HCNSs, with high nitrogen content of up to 10.4%, feature homogeneous and regular morphologies. The resulting HCNSs exhibit excellent lithium and potassium storage properties when used as electrode materials. Specifically, the HCNS-800 electrode demonstrates a stable reversible discharge capacity of 642 mA h g-1 at 1000 mA g-1 after 500 cycles for LIBs. Similarly, the electrode maintains a discharge capacity of 205 mA h g-1 at 100 mA g-1 after 500 cycles for KIBs. Moreover, when coupled with a high-mass-loading LiFePO4 cathode to design full cells, the HCNS-800‖LiFePO4 cells provide a specific discharge capacity of 139 mA h g-1 at 0.1 C. These results indicate that the HCNS electrode has promising potential for use in high-energy and environmentally sustainable lithium-based and potassium-based batteries.

Constructed a self-powered sensing platform based on nitrogen-doped hollow carbon nanospheres for ultra-sensitive detection and real-time tracking of double markers

Acute myocardial infarction (AMI) is acute necrosis of a portion of the myocardium caused by myocardial ischemia, which seriously threatens people's health and life safety. Its early diagnosis is a difficult problem in clinical medicine. Research has found that the abnormal expression of microRNA-199a (miR-199a) and microRNA-499 (miR-499) was closely related to AMI disease. In this work, we took advantage of the structural advantages of nitrogen-doped hollow carbon nanospheres (N-HCNSs) to design an ultra-sensitive, portable real-time monitoring visual self-powered biosensor system, which based on dual-target miRNAs triggered catalytic hairpin assembly (CHA) for sensitive detection of miR-199a and miR-499. In addition, the capacitor and the smartphone are introduced into the system to realize the secondary improvement of system sensitivity and portable real-time visual monitoring. Under optimized conditions, in the linear range of 0.1–100000 aM, the detection limits of miR-199a and miR-499 are 0.031 and 0.027 aM, respectively. At the same time, the ultra-sensitive detection of miRNAs is realized in the serum sample, and the recovery rate of miR-199a and miR-499 are 98.0–106.0% (RSD: 0.6–8.1%) and 94.0–109.7% (RSD: 1.8–7.7%), respectively. The method is simple, sensitive and can be used for real-time tracking and portable monitoring of related diseases.

Steric-hindrance effect and self-sacrificing template behavior induced PDA@SnO2-QDs/N-doped carbon hollow nanospheres: Enhanced structural stability and reaction kinetics for long-cyclic Li-ion half/full batteries

Tin-based anode materials with high theoretical specific capacity are subject to huge volume expansion and poor reaction reversibility, leading to degradation of battery performance. Herein, the steric-hindrance effect and self-sacrificing template behavior of polydopamine were firstly developed to induce the formation of hollow nanospheres assembled by ultrafine SnO2 quantum dots (SnO2-QDs) and nitrogen-doped carbon (NC), containing residual polydopamine (PDA) cores. The PDA@SnO2-QDs/NC hollow nanospheres could effectively accommodate the volume expansion and maintain structural stability. More importantly, the PDA core could capture oxygen free radicals produced by the charge/discharge process and be involved in the evolution of the SEI layer, achieving enhanced electrochemical reaction kinetics. The optimized PDA@SnO2-QDs/NC anode shows a specific capacity of 898 mAh g−1 after 300 cycles at 0.3 A g−1, and scarcely capacity attenuation after 1500 cycles at 1 A g−1. The long-cyclic life is up to 3000 cycles at 3 A g−1. Even after 200 cycles, the anode in the PDA@SnO2-QDs/NC||LFP full battery gives a reversible capacity of 489 mAh g−1 at 0.3 A g−1, with a capacity retention of 77 %. This work casts new light on tin-based anode materials and interface optimization.

Regulating The Shell Thickness of Nitrogen-Doped Hollow Carbon Nanospheres for Enhanced Electrochemical Performance

The shell thickness of hollow carbon spheres (HCs) plays a vital role in the electrochemical performance due to its direct influence on the transport kinetics of lithium ions. However, it is a tough task to ascertain the contribution solely from the changes of shell thickness but not from the synergistic effect of chemical compositions, pore structures and specific surface area. Herein, a simple one-pot method is developed to synthesize N-doped hollow carbon nanospheres (NHCs) with different shell thickness (6, 10 and 13 nm) while retaining other parameters almost same, such as chemical components, pore structure and specific surface area. The NHCs-1 sample with shell thickness of 6 nm, exhibits initial charge capacity of 1320.1 mA h g−1 at low current density (50 mA g−1) and retains capacity of 862.1 mA h g−1 after 500 cycles at high current density (500 mA g−1), obviously higher than those of NHCs-2 (717.1 mA h g−1) and NHCs-3 (588.9 mA h g−1) with the shell thickness of 10 and 13 nm, respectively. The capacity dependent on the shell thickness is detailedly addressed considering the changes of mass transfer coefficient of Li-ion across the wall. Also, the outstanding electrochemical properties of the NHCs can be ascribed to the unique hollow structure, N-doping and high specific surface. Furthermore, the calculation based on oxidation peaks of NHCs samples indicates that the reaction energy barrier gradually reduces with decreasing the shell thickness, which validates the enhancement of Li-ion transfer. The strategy developed for the preparation of hollow carbon spheres with different shell thickness via a simple one-pot method, provides a promising alternative to devise new carbonaceous materials as superior electrode material in the field of energy storage.

Mediating heterogenized nickel phthalocyanine into isolated Ni-N3 moiety for improving activity and stability of electrocatalytic CO2 reduction

The poor stability of heterogenized nickel phthalocyanine (NiPc) has hindered its application as a desirable catalyst for electrocatalytic carbon dioxide reduction. Herein, the electrocatalytic stability of heterogenized NiPc on nitrogen-doped hollow carbon nanospheres (NiPc@NHCSs) can be optimized via mediating NiPc into Ni-NC moiety (Ni-NC/NHCSs-Y) to construct a stable Ni catalytic unit. Different from the poor activity of NiPc@NHCSs (CO Faradaic efficiency, FECO< 80%, stability < 1200 s), the optimal catalyst (Ni-NC/NHCSs-600) with unsaturated Ni-N3 nitrogen-vacancy structure, displays FECO of 98.57% and CO turnover frequency of 3.75 s−1 at − 0.87 V vs. RHE, and stable operation over 14 h (−0.82 V vs. RHE). The stabilization mechanism and the temperature effect on the structure-activity relationship are systematically explored, which successfully steers the design of stable Ni-NC catalytic unit on different carbon substrate, while a zinc-CO2 rechargeable battery is constructed, displaying a peak power density of 0.64 mW cm−2 and FECO of 91.45%.

Nitrogen doped hollow carbon nanospheres as efficient polysulfide restricted layer on commercial separators for high-performance lithium-sulfur batteries

The polysulfide shuttle limits the development of lithium-sulfur (Li-S) batteries with high energy density and long lifespan. Herein, nitrogen doped hollow carbon nanospheres (NHCS) derived from polymerization of dopamine on SiO2 nanospheres are employed to modify the commercial polypropylene/polyethylene/polypropylene tri-layer separators (PP/PE/PP@NHCS). The abundant nitrogen heteroatoms in NHCS exhibit strong chemical adsorption toward polysulfides, which can effectively suppress the lithium polysulfides shuttle and further enhance the utilization of active sulfur. Lithium-sulfur batteries employing the PP/PE/PP@NHCS deliver an initial discharge capacity of 1355 mAh/g and retain high capacity of 921 mAh/g after 100 cycles at 0.2 C. At a high rate of 2 C, the lithium-sulfur batteries exhibit capacity of 461 mAh/g after 1000 cycles with a capacity fading rate of 0.049% per cycle. This work demonstrates that the NHCS coated PP/PE/PP separator is promising for future commercial applications of lithium-sulfur batteries with improved electrochemical performances.

Micro–mesoporous nitrogen-doped hollow carbon nanospheres as anodes for lithium-ion batteries with high-rate capability and outstanding cycling performance

Hollow porous carbon spheres have realized widespread applications as anodes in lithium-ion batteries. This study investigates micro–mesoporous nitrogen-doped hollow carbon nanospheres (NHCs) with outstanding lithium storage performance, which are derived from their phenolic analogues via a simple one-pot reaction. The as-prepared NHCs demonstrate an initial irreversible capacity of 949.3 mA h g −1 and still retain a high irreversible capacity of 539.0 mA h g −1 at 1000 mA g −1 . The NHCs also exhibits an excellent reversible capacity (717.2 mA h g −1 at 500 mA g −1 ) after 500 cycles. The high-performance of the NHC electrode can be ascribed to the unique structures of NCSs featuring small uniform size, nitrogen dopant, thin shell thickness and rich mesoporous structure.

NiCo2S4 nanosheets decorated on nitrogen-doped hollow carbon nanospheres as advanced electrodes for high-performance asymmetric supercapacitors

Taking advantage of both Faradaic and carbonaceous materials is an efficient way to synthesize composite electrodes with enhanced performance for supercapacitors. In this study, NiCo2S4 nanoflakes were grown on the surface of nitrogen-doped hollow carbon nanospheres (NHCSs), forming a NiCo2S4/NHCS composite with a core–shell structure. This three-dimensionally confined growth of NiCo2S4 can effectively inhibit its aggregation and facilitate mass transport and charge transfer. Accordingly, the NiCo2S4/NHCS composite exhibited high cycling stability with only 9.2% capacitance fading after 10 000 cycles, outstanding specific capacitance of 902 F g−1 at 1 A g−1, and it retained 90.6% of the capacitance at 20 A g−1. Moreover, an asymmetric supercapacitor composed of NiCo2S4/NHCS and activated carbon electrodes delivered remarkable energy density (31.25 Wh kg−1 at 750 W kg−1), excellent power density (15003 W kg−1 at 21.88 Wh kg−1), and satisfactory cycling stability (13.4% capacitance fading after 5000 cycles). The outstanding overall performance is attributed to the synergistic effect of the NiCo2S4 shell and NHSC core, which endows the composite with a stable structure, high electrical conductivity, abundant active reaction sites, and short ion-transport pathways. The synthesized NiCo2S4/NHCS composite is a competitive candidate for the electrodes of high-performance supercapacitors.

Nitrogen-doped hollow carbon nanospheres as highly efficient electrocatalysts for detection of triclosan

Nitrogen-doped hollow carbon (N-HC) nanospheres were fabricated by in-situ pyrrole polymerization on the hard template of ferroferric oxide nanospheres followed by acid treatment and calcination. The morphology, microstructure, surface composition and electroactivity for triclosan detection of as-prepared N-HC nanospheres were investigated. These N-HC nanospheres own single or double shells (shell thickness ≈ 20 nm, average diameter ≈ 250 nm). X-ray photoelectron spectroscopy measurement shows that the doped nitrogen in N-HC nanospheres is mainly graphitic and pyridinic nitrogen. N-HC nanospheres modified glassy carbon electrode (GCE) exhibits excellent electrochemical activity for electrooxidation of triclosan, resulting in the high efficiency for triclosan detection. The detection limit of triclosan is 30 nM and the limit of quantification is 100 nM, while a good linear response is obtained from 0.09 to 20 μM under the optimal detection conditions. In addition, the N-HC nanospheres decorated GCE shows great stability, reproducibility, and applicability for triclosan detection in real waters, including tap water, lake water, and river water from Hangzhou, China. The wide linear range and lower cost of N-HC based sensor synthesized in this work point to promising properties for further study and testing for potential practical application in water environment.

Self-Template Synthesis of Nitrogen-Doped Hollow Carbon Nanospheres with Rational Mesoporosity for Efficient Supercapacitors.

Rational design and economic fabrication are essential to develop carbonic electrode materials with optimized porosity for high-performance supercapacitors. Herein, nitrogen-doped hollow carbon nanospheres (NHCSs) derived from resorcinol and formaldehyde resin are successfully prepared via a self-template strategy. The porosity and heteroatoms in the carbon shell can be adjusted by purposefully introducing various dosages of ammonium ferric citrate (AFC). Under the optimum AFC dosage (30 mg), the as-prepared NHCS-30 possesses hierarchical architecture, high specific surface area up to 1987 m2·g−1, an ultrahigh mesopore proportion of 98%, and moderate contents of heteroatoms, and these features endow it with a high specific capacitance of 206.5 F·g−1 at 0.2 A·g−1, with a good rate capability of 125 F·g−1 at 20 A·g−1 as well as outstanding electrochemical stability after 5000 cycles in a 6 M KOH electrolyte. Furthermore, the assembled NHCS-30 based symmetric supercapacitor delivers an energy density of 14.1 W·h·kg−1 at a power density of 200 W·kg−1 in a 6 M KOH electrolyte. This work provides not only an appealing model to study the effect of structural and component change on capacitance, but also general guidance to expand functionality electrode materials by the self-template method.

Amorphous CoP nanoparticle composites with nitrogen-doped hollow carbon nanospheres for synergetic anchoring and catalytic conversion of polysulfides in Li-S batteries

The commercial viability of Li-S batteries was obstructed by short cycle life and poor capability owing to slow redox kinetics and polysulfide shuttle effect. To tackle these challenges, the amorphous CoP anchored on N-doped carbon nanospheres with hollow porous structures (CoP/HCS) has been synthesized as a superior sulfur host via a facial pyrolysis approach. The debilitating effect would be hampered during the cycling processing resulting from two reasons:(1) the powerful chemical anchoring between unsaturated Co and Li-polysulfides, (2) the remarkable adaption of volume variation originating from the hollow porous architectures. The amorphous CoP nanoparticles not only catalyze the transformation of lithium polysulfides as electrocatalyst, but also acquired a high sulfur loading as sulfur host materials. More importantly, the synergistic incorporation of CoP and HCS improved the inherit low conductivity by anchoring on the N-doped carbon hollow, thus leading to excellent performance for Li-S batteries. Benefiting from these advantages, the amorphous CoP/HCS-based sulfur electrodes exhibited outstanding rate performance (685.6 mAh g−1 at 3C), excellent long-cycling stability with a low capacity decay of only 0.03% per cycle over 1000 cycles at 2C, and a high areal capacity of 5.16 mAh cm−2 under high sulfur loading.

Engineered nitrogen-doped hollow carbon nanospheres adhered by carbon nanotubes for capacitive potassium-ion storage

Hollow carbon materials are promising candidates when evaluated as anode for potassium ion batteries (PIBs) due to high capacity, available pore structure, excellent surface properties and unique structural for buffering the destructive volume expansion. However, the unsatisfactory electrical conductivity and structural stability caused by amorphous carbon structure hinder its further practical application of accommodating potassium ions. Herein, nitrogen-doped hollow carbon nanospheres (NHCSs) are synthesized by using acetone discriminatively dissolving the interior part of 3-aminophenol-formaldehyde resin nanospheres and then interconnected with carbon nanotubes (CNTs) to prepare the CNTs-NHCSs composite as advanced anode for PIBs. Owing to the long-range order graphitized structure introduced by CNTs and unique cavity structure provided by NHCSs, the integrity of the connection between NHCSs and CNTs can be confirmed to boost electron transport and buffer volume changing synergistically. Accordingly, the CNTs-NHCSs electrode delivers high reversible capacity of 228 and 165.2 mAh g−1 over 100 cycles at 100 mA g−1 and 1000 cycles at 1000 mA g−1 respectively, indicating superior reversible potassium storage capacity and excellent rate capability. The successful construction of advanced CNTs-NHCSs composite in this work provides a new avenue in structural design and function optimization for the development of PIBs electrode materials.

Ultrafine Copper Oxide Particles Dispersed on Nitrogen-Doped Hollow Carbon Nanospheres for Oxidative Esterification of Biomass-Derived 5-Hydroxymethylfurfural.

One-pot synthesis of furan-2,5-dimethylcarboxylate (FDMC) from 5-hydroxymethylfurfural (HMF) is highly demanding for the commercial production of polyethylene furanoate (PEF). Herein, a direct synthesis of FDMC is reported from oxidative esterification of HMF using ultrafine CuO particles dispersed on nitrogen-doped hollow carbon nanospheres (CuO/N-C-HNSs) as a catalyst and tert-butyl hydroperoxide (TBHP) as an oxidizing and methylating reagent. The CuO/N-C-HNSs was prepared through a template protection-sacrifice strategy using SiO2 as a sacrificial template and histidine as the precursor for N and C. N-doping facilitated a strong interaction between the support and copper species, affording formation of CuO nanoparticles of less than 10 nm in size. By virtue of the highly dispersed CuO nanoparticles and a high BET surface area 373 m2 /g, the CuO/N-C-HNSsshows excellent catalytic performance in the selective conversion of HMF into FDMC affording 93 % yield of the desired product with a TON value of 49. Furthermore, the oxidative esterification involving SP3 C-H bond functionalization is also demonstrated using the same catalyst.

Amino-1H-tetrazole-regulated high-density nitrogen-doped hollow carbon nanospheres for long-life Zn-air batteries.

High-density nitrogen-doped porous carbon catalysts have been regarded as promising alternatives to precious metals in proton-exchange membrane fuel cells (PEMFC) and metal–air batteries based on the oxygen reduction reaction (ORR). We herein synthesized high-density pyridinic and graphitic N-doped hollow carbon nanospheres (G&P N-HCS) using a high-yield amino-1H-tetrazole (ATTZ) via a self-sacrificial-template method. The synthesized G&P N-HCS shows a high N content (15.2 at%), in which pyridinic (Pr) and graphitic (Gr) N are highly reactive for the ORR catalysis. We found that the half-wave potential and limiting current density of G&P N-HCS are comparable to the state-of-the-art Pt/C, whereas its cyclic durability is much superior to that of Pt/C. Experimental results indicate that an optimal ratio (1 : 1) between Gr N and Pr N in G&P N-HCS exhibits the highest ORR performances, rather than Gr N-dominated N-HCS or Pr N-dominated N-HCS. Notably, N-HCS containing only Gr N and Pr N has poor catalytic performance for ORR in alkaline electrolytes. Density functional theory (DFT) simulations untangle the catalytic nature of Pr and Gr N and decipher the relations between the N type(s) and total N content required for the ORR catalysis. This study provides a new way to design efficient N-doped porous carbon-enriched active sites, and solves the cathode catalyst in the commercialization of PEMFC and metal–air batteries.

Modulation of Single Atomic Co and Fe Sites on Hollow Carbon Nanospheres as Oxygen Electrodes for Rechargeable Zn-Air Batteries.

Efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are required for metal air batteries, to replace costly metals, such as Pt and Ir/Ru based compounds, which are typically used as benchmarks for ORR and OER, respectively. Isolated single atomic sites coordinated with nitrogen on carbon supports (M-N-C) have promising performance for replacement of precious metal catalysts. However, most of monometallic M-N-C catalysts demonstrate unsatisfactory bifunctional performance. Herein, a facile way of preparing bimetallic Fe and Co sites entrapped in nitrogen-doped hollow carbon nanospheres (Fe,Co-SA/CS) is explored, drawing on the unique structure and pore characteristics of Zeolitic imidazole frameworks and molecular size of Ferrocene, an Fe containing species. Fe,Co-SA/CS showed an ORR onset potential and half wave potential of 0.96 and 0.86 V, respectively. For OER, (Fe,Co)-SA/CS attained its anodic current density of 10 mA cm-2 at an overpotential of 360 mV. Interestingly, the oxygen electrode activity (ΔE) for (Fe,Co)-SA/CS and commercial Pt/C-RuO2 is calculated to be 0.73 V, exhibiting the bifunctional catalytic activity of (Fe,Co)-SA/CS. (Fe,Co)-SA/CS evidenced desirable specific capacity and cyclic stability than Pt/C-RuO2 mixture when utilized as an air cathode in a homemade Zinc-air battery.

Facile synthesis of nitrogen-doped mesoporous hollow carbon nanospheres@NiCo2O4 for high-performance supercapacitors

Highly performance composite material nitrogen-doped mesoporous hollow carbon nanospheres and Ni-Co coordination polymer metal precursor (N-MHCNS700@Ni-Co-MOF) obtained by using hydrothermal reaction Ni-Co coordination polymer metal precursor to assist hollow carbon nanospheres as templates. Then the composite material (N-MHCNS700@Ni-Co-MOF) is calcined under nitrogen to obtain nitrogen-doped mesoporous hollow carbon nanospheres and nickel cobalt metal oxide (N-MHCNS700@NiCo2O4). Material characterization is used to analyze the morphology and structure of the material. The hybrid materials exhibit high specific capacitance (166 mAh g−1 at 1 A g−1) and great cyclic stability (approximately 85.6% retained after 5,000 cycles at 10 A g−1). The composite material also have outstanding power density of composite (624.9 W kg−1) and the energy density (42.8 Wh kg−1). Therefore, composite materials can be applied to electrode materials for high-performance supercapacitor.

Controlled fabrication of orchid-like nitrogen-doped hierarchical porous carbon and hollow carbon nanospheres

Flower-like porous carbon has fascinated significant attention due to its outstanding and exceptional properties. However, controlled synthesis of porous carbon with adjustable morphology, highly active sites and cross-linked pore channels remains still a great challenge. Herein, an inimitable dissolution–reassembly anisotropic growth strategy was firstly demonstrated for the fabrication of idiographic orchid-like hierarchical porous carbon with ultra-thin multilayer carbon sheets, high specific surface area (1063 m2 g−1), large pore volume (0.82 cm3 g−1) and rich nitrogen content (7.6 wt%). Highly reactive phloroglucinol and EDA aggregated magically and SiO2 acted as a pore former. Ingeniously, acetone acted as a “surgical knife,” which cut the composite of SiO2@phloroglucinol–EDA into many tiny units and further anisotropic growth into orchid-like polymers. The width and thickness of the carbon petals can be effectively controlled with the diversification of acetone concentration. Intriguingly, monodisperse hollow carbon nanospheres could be harvested with silicon-deficient system, which may offer new insight into the construction of functionalized carbon materials with hollow architecture. Owing to the unmatched superstructures, orchid-like carbon materials can be employed as an ideal drug carrier and dye adsorbent. Figure Schematic illustration of solid carbon nanosphere, hollow carbon nanosphere and OHPC-25. For the first time, a novel dissolution–reassembly route based on strong hydrogen-bonding interaction was developed to prepare unique orchid-like hierarchical porous carbon, in which phloroglucinol acted as a carbon precursor and EDA both as a base catalyst and as a nitrogen precursor. The critical step to this synthetic approach was the ingeniously employed acetone as a “surgical knife” to cut the composite of SiO2@phloroglucinol–EDA into many tiny units, and these units were reassembled into orchid-like polymers. After adding acetone, the morphology of carbon materials has changed from solid nanospheres to hollow nanospheres. This strategy did not use any template as the cavity, which may offer a new insight into the comprehension of synthesized functionalized carbon materials with hollow architecture.