碳化硅纳米材料及其衍生碳在超级电容器领域的应用

超级电容器由于充放电速度快、循环寿命长、成本低、环境友好等特性在众多储能器件中脱颖而出。在各类电极材料中,碳化硅(SiC)纳米材料及其衍生碳因其高稳定性、优异的导电性等优势被认为是极具应用前景的超级电容器电极材料。本文首先系统地阐述了SiC纳米材料及其衍生碳的常用制备方法;然后,详细综述了SiC纳米材料及其衍生碳在超级电容器应用中的研究进展,总结“高导电碳材料复合”、“杂原子掺杂”、“赝电容材料复合”、“多级孔结构的设计”、“化学活化”等电化学性能的提升策略;最后,对SiC纳米材料及其衍生碳在超级电容器储能领域中应用存在的挑战和机遇进行展望。

Microstructure and evolution of hafnium carbide whiskers via polymer-derived ceramics:A novel formation mechanism

Polymer-derived ultra-high-temperature ceramic(UHTC)nanocomposites have attracted growing attention due to the increasing demands for advanced thermal structure components in aerospace.Herein,hafnium carbide(HfC)whiskers are successfully fabricated in carbon fiber preforms via the polymer-derived ceramic(PDC)method.A novel carbon nanotube(CNT)template growth mechanism combined with the PDC method is proposed in this work,which is different from the conventional vapor–liquid–solid(VLS)mechanism that is commonly used for polymer-derived nanostructured ceramics.The CNTs are synthesized and proved to be the templates for fabricating the HfC whiskers,which are generated by the released low-molecular-weight gas such as CO,CO_(2),and CH4 during the pyrolysis of a Hf-containing precursor.The formed products are composed of inner single crystal HfC whiskers that are measured to be several tens of micrometers in length and 100–200 nm in diameter and outer HfC/HfO_(2)particles.Our work not only proposes a new strategy to prepare the HfC whiskers,but also puts forward a new thinking of the efficient utilization of a UHTC polymer precursor.

Si_(3)N_(4)nanowires@pyrolytic carbon nanolayers coupled withhydroxyapatite nanosheets as reinforcement for carbon matrixcomposites with boosting mechanical and friction properties

Extensive attention has been drawn to the development of carbon-matrix composites for application in the aerospace and military industry,where a combination of high mechanical strength and excellent frictional properties are required.Herein,carbon-matrix composites reinforced by Si_(3)N_(4)nanowires@pyrolytic carbon nanolayers(Si_(3)N_(4nws)@PyCnls)coupled with hydroxyapatite nanosheets is reported.The Si_(3)N_(4nws)@PyCnls(SP)with coaxial structure could increase the surface roughness of Si_(3)N_(4nws)and promote the stress transfer to the carbon matrix,whereas the porous hydroxyapatite nanosheets favor the infiltration of the carbon matrix and promote the interfacial bonding between the SP and carbon matrix.The carbon matrix composites reinforced by SP coupled with hydroxyapatite nanosheets(Si_(3)N_(4nws)@PyCnls-HA-C)exhibit excellent mechanical strength.Compare with the conventional Si_(3)N_(4nws)reinforced carbon composites,Si_(3)N_(4nws)@PyCnls-HA-C(SPHC)have 162%and 249%improvement in flexural strength and elastic modulus,respectively.Moreover,the friction coefficient and wear rate decreased by 53%and 23%,respectively.This study provides a co-reinforcement strategy generated by SP coupled with hydroxyapatite nanosheets for effective improvement of mechanical and frictional properties of carbon matrix composites that are used for aerospace and military industry applications.

Free-standing SnNb_(2)O_(6)@CSN film as flexible anode for high performance sodium-ion batteries

Free-standing electrodes are promising candidates for flexible rechargeable batteries, toward the application of flexible energy storage devices, due to their merits of additive-free, lightweight, and high energy density. Herein, we report a free-standing SnNb_(2)O_(6)@CSN flexible film with SnNb_(2)O_(6) encapsulated in 3D carbon skeleton nanofibers by electrospinning and carbonization processes as flexible anode for sodium-ion batteries(SIBs). The 3D carbon skeleton nanofibers serve as ion/electron transport pathway to improve the electrochemical reaction kinetics and meanwhile alleviate the volume changes of SnNb_(2)O_(6) during charge-discharge processes. The as-constructed half-cell(SnNb_(2)O_(6)@CSN‖Na) exhibits excellent cycling stability of 99.2 m Ah/g at 0.5 A/g after 950 cycles(coulombic efficiency of ~100%) and a high rate performance of 108.6 mAh/g at 10 A/g. In addition, the pouch cell can light up the LEDs at different bending angles(0°, 90°, 180°). This research shows a promising anode material for flexible energy storage electronics.

Flexible double-wall carbon foam/Cu-Co oxides based symmetric supercapacitor with ultrahigh energy density

Electrochemical supercapacitors are regarded as a promising electrochemical energy storage device,because of its fast chargeability,long cycle life,and high power density.The connection of porous carbon and extensive electroactive substances have significantly improved their performance.However,the unsuitable constructing strategy and unclear electrochemical mechanism lead to a mismatch between the fast double-layer effect and the sluggish Faradaic behavior at the electrode,degrading the energy density and capacitance performances.Herein,the construction strategy based on the double-wall carbon foam,carbon nanotubes and copper nanocubes provides enhanced electronic structure and ion transport path,resulting in accelerated proton transport and redox insertion/deinsertion processes,as well as surprising electrochemical behaviors of Cu-Co oxide on both positive and negative electrodes(927.9 and 427.0 F g^(−1)at 1 A g^(−1)).A flexible symmetric supercapacitor assembled with the SCF/CNT@Cu/Cu-Co-O delivers a extremely excellent performance.At 1 A g^(−1),the specific capacitance is 337.8 F g^(−1),the energy density hits 60 Wh kg^(−1)at the power density of 17.8 kW kg^(−1).At 10 A g^(−1),the energy density is up to 120.1 Wh kg^(−1),representing the top energy density of supercapacitors.Combining systematical structural optimization and mechanism study,this work broadens the fabricating strategy of hierarchical nanostructures and high-performance electrode materials for energy storage.

类普鲁士蓝空心微米管的通用性制备及其作为高性能非对称超级电容器的研究

在电化学储能领域,具有可控组成的一维空心结构纳米材料引起了人们的极大关注.本文以静电纺丝制备的聚丙烯腈(PAN)-醋酸钴(Co(Ac)2)纳米纤维为模板,首次采用简易的自模板法制备了一维铁氰化钴(CoHCF)空心微米管.PAN-Co(Ac)2纳米纤维模板与铁氰化钾溶液反应,合成了核壳结构的PAN-Co(Ac)2@CoHCF纳米纤维;随后,选择性溶解去除PAN-Co(Ac)2芯部,从而得到CoHCF空心微米管.得益于其独特的结构优势,CoHCF空心微米管电极在Na2SO4电解液中表现出优异的电化学性能,如高比电容(281.8 F g^-1@1 A g^-1),良好的速率性能和长时间循环稳定性(5000次循环后电容保持率为93%).由CoHCF为正极和活性炭(AC)为负极组装的非对称超级电容器,具有43.9 W h kg^-1的高能量密度、20 k W kg^-1的功率密度以及长的循环寿命.更重要的是,这种通用性的自模板合成策略可以推广到其他组成可控的一维空心普鲁士蓝(PB)及其类似物(PBA)材料,因而在很多领域具有广泛的应用前景.

Grow defect-rich bamboo-like carbon nanotubes on carbon black for enhanced microwave absorption properties in X band

Due to the limited electromagnetic wave(EMW)loss capacity and agglomeration,carbon black(CB)gradually fails to meet the increasingly harsh demanding conditions.Herein,defect-rich bamboo-like carbon nanotubes(CNTs)were grown on CB by the process of chemical vapor deposition.CNTs prepared in situ on CB can assist it to build a developed multilevel conductive network and introduce plentiful CB/CNTs nano-interfaces.What’s more,the defects that accompany the growth of CNTs endow CNTs with a moderate conductivity and good impedance matching,thereby causing an effective microwave absorption(MA).Meanwhile,the high-density defects on CNTs can induce dipole polarization to further strengthen the EMW loss ability.The influence of CNTs with different growth time on MA performance has been explored.Profiting from the structural merits,the synthesized CB-CNT with CNTs growth time of 40 min exhibits the optimal absorbing property,which has the minimum reflection loss of-53.6 d B and maximum effective absorption bandwidth of 4.1 GHz with the thickness of 2.7 mm,covering almost the entire X band.The introduction of defect-rich CNTs significantly enhances the EMW loss ability of CB,which provides a rational strategy for the design of high-efficient microwave absorption materials.

Effects of PyC shell thickness on the microstructure,ablation resistance of SiCnws/PyC-C/C-ZrC-SiC composites

SiC nanowires/pyrocarbon(SiCnws/PyC)core-shell structure toughenedC/C-ZrC-SiC composites were fabricated by CLVD process,and the influences of PyC shell thickness on the microstructure and ablation resistance of the composites were researched.The results presented that SiCnws/PyC core-shell structure had a linear shape,and the composites became dense with the increasing PyC thickness.When the thickness of PyC shell increased from 0 to 2.4μm,the density and thermal conductivity of the composites was improved gradually,but the coefficient of thermal expansion(CTE)decreased firstly and then increased.After the ablation test for 90 s,the ablation rates of the composites decreased continuously as the PyC thickness increased from 0 to 1.4μm,but increased when the PyC thickness was up to 2.4μm.Especially when the PyC thickness was 1.4μm,the linear and mass ablation rates of the composites were 71.25%and 63.01%lower than those of the composites without PyC shell.The reasons behind the remarkable improvement of anti-ablation property were that the proper PyC thickness could alleviate the CTE mismatch to promote the formation of complete oxide coating,improve the thermal conductivity to reduce heat corrosion and enhance the capability to limit the mechanical erosion.

NiCoLDH nanosheets grown on MOF-derived Co_(3)O_(4) triangle nanosheet arrays for high-performance supercapacitor

Hierarchical Co_(3)O_(4)@NiCoLDH nanosheets(NSs)were prepared on carbon cloth through a multistep method,containing Metal-organic frameworks(MOF)-templated thermal annealing and electrodeposition.The triangle-shaped Co_(3)O_(4 NSs)were firstly obtained by thermal treatment of MOF templates in air.Then,ultrathin NiCoLDH_(NSs)were in-situ electrodeposited on the surface of Co_(3)O_(4NSs),constructing a core-shell structure.Benefiting the unique hierarchical structure,high conductivity of Co_(3)O_(4 NSs)core and large surface area of NiCoLDHNSs shell,the Co_(3)O_(4)@NiCoLDH_(NSs)array served as supercapacitor electrode exhibits excellent electrochemical properties,such as high specific capacitance of 1708 F g^(-1)(850 C g^(-1))at a current density of 1 A g^(-1),good rate capability,and excellent cycling stability.Further,the asymmetric supercapacitor assembled by Co_(3)O_(4)@NiCoLDH_(NSs)and activated carbon,also displays superior electrochemical perfo rmance with high energy density and power density.Remarkably,the strategy of constructing core-shell structure based on MOF templates could be extended to other electrochemical fields.

Hierarchical,seamless,edge-rich nanocarbon hybrid foams for highly efficient electromagnetic-interference shielding

Lightweight,flexible,ultrahigh-performance electromagnetic-interfe rence(EMI)shielding materials are urgently required in the areas of aircraft/aerospace,portable and wearable electronics.Herein,1 D carbon nanotubes(CNT)and carbon nanofibers(CNF)with 2 D edge-rich graphene(ERG)are used to form a lightweight,flexible CNT-ERG-CNF hybrid foam.This foam was fabricated through a self-sacrificial templating chemical vapor deposition process,where nanocarbons bond through covalent bonding,forming a hierarchical 3 D hybridized carbon nanostructure.Multistage conductive networks and heterogeneous interfaces were constructed using edge-rich nanocarbons to increase the induced currents and interfacial polarization which makes great contributions to achieve high absorption electromagnetic shielding effectiveness(SEA).The CNT-ERG-CNF hybrid foam exhibits EMI shielding effectiveness(SE)exceeding55.4 dB in the X-band while the specific SE(SSE,SE divided by mass density)achieves 9200 dB cm^(3)g^(-1),which surpasses that of nearly all other carbon-based composite materials.Furthermore,the structural stability and durability of the flexible CNT-ERG-CNF hybrid foams is examined by measuring EMI SE after 10000 times cyclic bending.Remarkably,this work not only provides a new idea for preparing hierarchical carbon materials for a wide range of applications,but presents some fundamental insights for achieving higher absorption losses in EMI shielding materials.

A robust carbon coating of Na_(3)V_(2)(PO_(4))_(3)cathode material for high performance sodium-ion batteries

Na_(3)V_(2)(PO_(4))_(3)is a very prospective sodium-ion batteries(SIBs)electrode material owing to its NASICON structure and high reversible capacity.Conversely,on account of its intrinsic poor electronic conductivity,Na_(3)V_(2)(PO_(4))_(3)electrode materials confront with some significant limitations like poor cycle and rate performance which inhibit their practical applications in the energy fields.Herein,a simple two-step method has been implemented for the successful preparation of carbon-coated Na_(3)V_(2)(PO_(4))_(3)materials.As synthesized sample shows a remarkable electrochemical performance of 124.1 mAh/g at 0.1 C(1 C=117.6 mA/g),retaining 78.5 mAh/g under a high rate of 200 C and a long cycle-performance(retaining 80.7 mAh/g even after 10000 cycles at 20 C),outperforming the most advanced cathode materials as reported in literatures.

Construction of multi-structures based on Cu NWs-supported MOF-derived Co oxides for asymmetric pseudocapacitors

Cu@MOF core-shell nanowires are synthesized by introducing oxidizable and CTAB-modified metal nanowires as self-engaged templates and supporting MOFs for a one-dimension nanostructure.The following thermal process is controlled to obtain several one-dimension structure s ofCuCo-mixed materials,such as nanorods,single-shell and double-shell nanowires.The hollow structure for electrode materials enlarges the surface area,provides buffer space for electrolyte to accelerate the ion/charge transfers and for the structure to reduce injuries of volume expansion during cycling.Together with some other merits,such as adequate oxidation of the MOFs,small crystal grains of the material,and well-mixed Cu/Co oxides,the double-shell Cu@MOF nanowires(CuCo-DS5)applied for pseudocapacitors deliver advanced electrochemical performance with a specific capacitance of 563.8 F g^(-1)at 1 A g^(-1)as well as an outstanding cycling stability with a 92%retention after 3000 cycles at 5 A g^(-1).Meanwhile,an asymmetric pseudocapacitor constructed with the CuCo-DS5 and active carbon(AC)shows a high specific capacitance and energy density.

Metal-organic framework derived hierarchical NiCo_(2)O_(4) triangle nanosheet arrays@SiC nanowires network/carbon cloth for flexible hybrid supercapacitors

To overcome the disadvantages of traditional powder electrodes,such as the insufficient performance,the aggregation of active materials,and the complex fabrication process,rationally constructing free-standing electrode materials with hierarchical architecture is an effective and promising method,which could further improve the electrochemical properties.Herein,using metal-organic framework nanoarrays(MOFNAs)as self-sacrificial templates and SiC nanowires(SiCNWs)network as nanoscale conductive skeletons,we successfully fabricated the hierarchical core-shell SiCNWs@NiCo_(2)O_(4)NAs on carbon cloth(CC)substrate.Taking advantages of structural merits,such as hierarchical porous triangle-like NiCo_(2)O_(4)NAs,the interwoven SiCNWs network and conductive CC substrate,when evaluated as a binder-free supercapacitor electrode,the CC/SiCNWs@NiCo_(2)O_(4)NAs shows a high specific capacitance of 1604.7 F g^(-1)(specific capacity of 222.9 mA h g^(-1))at 0.5 A g^(-1),good rate performance,and excellent cycling stability.Significantly,the hybrid supercapacitor assembled with CC/SiCNWs@NiCo_(2)O_(4)NAs as the cathode and MOF derived CC/SiCNWs@CNAs as the anode,could deliver a high specific density of 49.9 W h kg^(-1) at a specific power of 800 W kg^(-1),stable cycling performance,and good flexibility.Impressively,this feasible strategy for fabricating hierarchical structure displays great potential in the field of energy storage.

Templated synthesis of spinel cobaltite MCo_(2)O_(4) (M¼Ni, Co and Mn) hierarchical nanofibers for high performance supercapacitors

Rational construction of transitional metal oxides electrode materials with suitable structure and composition is an effective strategy of improving their electrochemical performance.Herein,novel MCo_(2)O_(4) hierarchical nanofibers(H-MCo_(2)O_(4)NFs,M¼Ni,Co and Mn)were fabricated by a multi-step selftemplating method using electrospun nanofibers as precursors.Benefiting from the unique structure,such as numerous of vertically interlinked nanosheets on the surface and 1D interwoven nanofibers networks,the obtained HeNiCo_(2)O_(4)NFs electrode exhibits a high specific capacitance of 1750 F g1(At a current density of 0.5 A g1),good rate capability(Capacitance retention of 70%at 20 A g1),and outstanding cycling stability(Capacitance retention of 92%after 6000 cycles).Moreover,the solid-state hybrid supercapacitor assembled by HeNiCo_(2)O_(4)NFs and activated carbon(AC),delivers a high energy density of 38.4 Wh kg1 at a power density of 800 W kg1,and excellent cycling stability.Thus,the HeNiCo_(2)O_(4)NFs is a promising candidate material for supercapacitors electrode and this self-templating method in this work also provides a new path for the preparation of one-dimensional hierarchical metallic oxides.

Stable controlled growth of 3D CuO/Cu nanoflowers by surfactant-free method for non-enzymatic hydrogen peroxide detection

Sensitive, convenient and rapid detection of hydrogen peroxide（H2 O2） is highly desirable in fields like fundamental biological research, food industries, and clinical environmental analysis. Herein, a hierarchical porous CuO/Cu flower-like active electrode material for non-enzymatic H2 O2 sensor was synthesized via a low-cost and one-step chemical oxidation of Cu powder in water bath without surfactants. In order to discuss the growth mechanism of the product, products with different growth time length were fabricated. The electro-catalysis of all products were first exhibited by cyclic-voltammetry,and the product under 6 h reaction shows the best result. The detailed electro-catalytic behaviors of the best product（under 6 h reaction） are characterized by cyclic-voltammetry and amperometry under alkaline conditions. The materials have high sensitivity of 103 μA mM^（-1） cm^（-2）（R^2= 0.9979）, low detection limit of 2 μmol/L and wide concentration range（from 2 μmol/L to 19.4 mmol/L）. Large specific surface area and stabled nanostructure enabled good features, such as stability and sensitivity for the H2 O2 determination.

Two birds with one stone: Simultaneous fabrication of HfC nanowires and CNTs through efficient utilization of polymer-derived ceramics

Carbon nanotubes(CNTs) are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfC_(NWS)) through thermal pyrolysis of Hf-containing polymer precursor.The formed HfC_(NWS) are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C) composites and display perfect single crystal appearance.The pyrolysis of the Hf-containing organic precursor provides hafnium and carbon source for the growth of HfC_(NWS).The released waste gasses containing CO,CH4and CO_(2)are the main carbon source for the growth of CNTs.Specifically,the flexural strength of HfC_(NWS) reinforced carbon/carbon(HfC_(NWS)-C/C) composites is enhanced by ~105% compared with pure C/C,and the CNTs/carbon cloth also displays improved electrochemical performance with respect to capacitor applications.The present study introduces a novel sustainable and eco-friendly process related to polymer-derived ceramics to form advanced ceramic nanocomposites and proposes a deep understanding of the growth mechanism of CNTs.

Cu/Co mixed hierarchical tubular heterostructures for alkaline supercapacitors

The hierarchical hollow structures of electrode materials s of supercapacitors is effective for the large specific surface area and fast ions and charge transports.Cu nanowires as self-engaged templates provide sites and paths for the nucleation and growth of the ZIF-67.Meanwhile,Cu atoms can disperse into metal organic frameworks(MOFs)to form Cu-Co mixed oxides and construct heterostructures.In this case,Cu nanowires are used as a template and an activated part to improve the internal electronic structures.The electrochemical performance can be improved due to these features.Herein,Cu nanowires and MOFs are combined via a mild and efficient approach to fabricate Cu-Co-O/CuO electrode materials.This electrode exhibits excellent electrochemical performance with a specific capacitance of 834.1 F g^(-1) at 1 A g^(-1).The assembled asymmetric supercapacitor(ASC)shows an ultra-high energy density of 40.7 W h kg^(-1) at a power density of 915 W kg^(-1) and a good capacitance retention after 8000 cycles in a 2 M KOH aqueous solution.The results otained in this work indicate a strategy of the combination of reactive metals with metal organic frameworks used as electrode materials for electrochemical supercapacitors.