Influence of La-dopant on the material characteristics and supercapacitive performance of MnO<Subscript>2</Subscript> electrodes

Manganese dioxide was synthesized by electrodeposition method with Mn (CH3COO)2?4H2O as a raw material. La(NO3)3?6H2O was doped in electroyte during the preparing process to improve the performance of MnO2 electrodes. The micrographs, crystal structure and element content of electrodes were analyzed by SEM, XRD and atomic absorption spectroscopy, respectively. It is found that the La content ratio in the dioxide can be easily controlled by adjusting the composition of the plating solution. Appropriate amoun...     

Structural and electrochemical performances of <Emphasis Type="Italic">α</Emphasis>-MnO<Subscript>2</Subscript> doped with tin for supercapacitors

To improve the electrochemical performances of α-MnO₂ as electrode materials for supercapacitors, Sn-doped α-MnO₂ in the presence of the doping amount of 1%-4% was successfully synthesized by hydrothermal method. As-prepared α-MnO₂ presents nanorod shape and no other impurities exist. By ultraviolet-visible absorption spectroscopy, it is convinced that the band gaps of α-MnO₂ decrease with increasing Sn-doping amount. Cyclic voltammetry investigation indicates that undoped and doped α-MnO₂ all have regular capacitive response. As the scan rate enlarged, the profiles of curves gradually deviate from rectangle. Compared with undoped α-MnO₂, doped α-MnO₂ has larger specific capacitance. The specific capacitance of 3% doped α-MnO₂ reaches 241.0 F/g while undoped α-MnO₂ only has 173.0 F/g under 50 mA/ g current density in galvanostatical charge-discharge measurement. Enhanced conductivity by Sn-doping is considered to account for doped sample’s enhanced electrochemical specific capacitance.     

Optimal electrochemical performances of CO2 activated carbon aerogels for supercapacitors

Activated carbon aerogels（ACAs） derived from sol-gel polycondensation of resorcinol （R） and formaldehyde （F） were pyrolyzed under Ar flow and activated in CO2 atmosphere. The morphology of ACAs was characterized by scanning electron microscopy （SEM） and the structural properties were determined by N2 adsorption at 77 K. The results show that ACAs have a typical three-dimensional nanonetwork structure composing of cross-linking of carbon nanoparticles. The specific surface area and the total pore volume remarkably increase with increasing activation time while the previous porous structure still remains. The specific capacitance of the 950-10-ACA electrode can reach up to 212.3 F/g in 6 mol/L KOH electrolyte. The results of constant-current charge-discharge testing indicate that the ACAs electrodes present fast charge- discharge rate and long cycle life （about 98% capacitance retained after 3000 charge-discharge cycles at 1.25 mA/cm2）. Lower internal resistances can be achieved for 950-10-ACA electrode in KOH electrolyte. Our investigations are very important to improve the wettability and electrochemical performance of electrode for supercapacitors.     

Hybrid supercapacitor based on polyaniline doped with lithium salt and activated carbon electrodes

Polyaniline(PANI) nanofiber was synthesized by interfacial polymerization utilizing the interface between HCl and CCl₄. The hybrid type supercapacitors (PLi/C) based on Li-doping polyaniline and activated carbon electrode were fabricated and compared with the redox type capacitors (PLi/PLi) based on two uniformly Li-doping polyaniline electrodes. The electrochemical performances of the two types of supercapacitors were characterized in non-aqueous electrolyte. PLi/C supercapacitors have a wider effective energy storage potential range and a higher upper potential. At the same time, the PLi/C supercapacitor exhibits a specific capacity of 120.93 F/g at initial discharge and retains 80% after 500 cycles. The ohmic internal resistance (R _ES) of PLi/C supercapacitor is 5.0 Ω, which is smaller than that of PLi/PLi capacitor (5.5 Ω). Moreover, it can be seen that Et₄NBF₄ organic solution is more suitable for using as organic electrolyte of PLi/C capacitor compared with organic solution containing LiPF₆. Foundation item: Project(2008AA03Z207) supported by the National High-Tech Research and Development Program of China     

Supercapacitors based on high-surface-area graphene

Exfoliated graphite oxide was prepared by an improved Hummers method and was then reduced to graphene with hydrazine in the presence of ammonium hydroxide.N2adsorption–desorption measurement showed that graphene so obtained had a specific surface area as high as 818 m2/g.Galvanostatic charge/discharge curves demonstrated that the as-prepared graphene exhibited a specific capacitance of 186.9 F/g at a current density of 0.1 A/g and that about 96%of the specific capacitance was retained after 2000 cycles at a current density of 5 A/g.     

Preparation and electrochemical properties of Pb-0.3wt%Ag/Pb-WC composite inert anodes

We prepared Pb-0.3wt%Ag/Pb-WC(WC stands for tungsten carbide,the same below) composite inert anodes by double-pulse electrodeposition on the surface of Pb-0.3wt%Ag substrates,and investigated the electrochemical properties of the composite inert anodes,which were obtained under different forward pulse average current densities from 2 A/dm~2 to 5 A/dm~2 and WC concentrations from 0 g/L to 40 g/L in bath.The kinetic parameters of oxygen evolution,corrosion potential and corrosion current of the composite inert anodes were obtained in a synthetic zinc electrowinning electrolyte of 50 g/L Zn~(2+) and 150 g/L H_2SO_4 at 35 ℃,by measuring the anodic polarization curves,Tafel polarization curves and cyclic voltammetry curves.The results show that Pb-0.3wt% Ag/Pb-WC composite inert anodes obtained under forward pulse average current density of 3 A/dm~2 and WC concentration of 30 g/L in an original acid plating bath,possess higher electrocatalytic activity of oxygen evolution,lower overpotential of oxygen evolution,better reversibility of electrode reaction and corrosion resistance in [ZnSO_4+H_2SO_4] solution.The overpotential of oxygen evolution of the composite inert anode is 0.926 V under 500 A/m~2 in [ZnSO_4+H_2SO_4] solution,and 245 mV lower than that of Pb-1% Ag alloy;the corrosion current of the composite inert anode is 0.95×10~(-4)A which is distinctly lower than that of Pb-1%Ag alloy,showing the excellent corrosion resistance.     

Synthesis and Characterization of a Proton-transfer Complex of 1,2,4,5-benzenetetracarboxylic Acid with 1,10-phenanthroline

1Introduction Uptonow,manyproton transfercomplexesofaro maticcarboxylicacidsandLewisbaseshavebeen reported[19].Theproton transferfromorganicacidsto aminesmaytakeplacereadilywithaverylowactivation energyincontrastwiththeattackoftheaminetothecar bonylcarbon…     

Preparation and properties of pitch carbon based supercapacitor

Using the mesophase pitch as precursor, KOH and CO2 as activated agents, the activated carbon electrode material was fabricated by physical-chemical combined activated technique for supercapacitor. The influence of activated process on the pore structure of activated carbon was analyzed and 14 F supercapacitor with working voltage of 2.5 V was prepared. The charge and discharge behaviors, the properties of cyclic voltammetry, specific capacitance, equivalent serials resistance (ESR), cycle properties, and temperature properties of prepared supercapacitor were examined. The cyclic voltammetry curve results indicate that the carbon based supercapacitor using the self-made activated carbon as electrode materials shows the desired capacitance properties. In 1 mol/L Et4NBF4/AN electrolyte, the capacitance and ESR of the supercapacitor are 14.7 F and 60 m?, respectively. The specific capacitance of activated carbon electrode materials is 99.6 F/g; its energy density can reach 2.96 W·h/kg under the large current discharge condition. There is no obvious capacitance decay that can be observed after 5000 cycles. The leakage current is below 0.2 mA after keeping the voltage at 2.5 V for 1 h. Meanwhile, the supercapacitor shows desired temperature property; it can be operated normally in the temperature ranging from -40 ℃ to 70 ℃.     

Preparation and electrochemical characterization of C/PANI composite electrode materials

1 INTRODUCTIONRecently , surpercapacitor has attracted greatattention for its unique power performance[1 ,2],while electrode materials ,as one key factor to de-termine the performance of supercapacitor , nowbecome the focus of many researches . The super-capacitor materials can be categorized into threetypes :carbon electrode materials[3], metal oxide e-lectrode materials[4]and conductive polymer elec-trode materials[5].Conductive polymer electrode materials havehigher capacitance than tha…     

Preparation of polyaniline/TiO2 composite nanotubes for photodegradation of AZO dyes

Polyaniline （PANI） composite nanotubes （90-130 nm in diameter） containing titanium dioxide （TiO2） nanoparticles （about 10 nm in diameter） were synthesized through a self-assembly process in the presence of a-naphthalenesulfonic acid （a-NSA） as the dopant. It was found that PANI-TiO2 composites and PANI nanotubes both behaved with significant photocatalytic activities towards AZO dyes, during 2 h photocatalytic processes under natural light, the degradation ratio was 94.2% and 97.2% respectively （methyl orange and orange II）. The morphology of such products was characterized by SEM. The specific surface area of such composite nanotubes was 14.7 m2/g compared to normal polyaniline which was 0.27 m2/g. IR and X-ray diffraction characterizations showed that the chemical chain of the composite nanotubes was identical to that of the doped PANI. It may provide a new way for photodegradation of organic contaminants by using conjugated polymer with dimensional structure.     

Ethylene Polymerization by a Novel Dinuclear Heter-oligated Titanium Complex with the Ligand of （Salicylaldiminato） （β-enaminoketonato）

The condensation of acetylacetone （CH3COCH2COCH3） with benzdine （H2N-C6H4-C6H4-NH2） yielded diimine ligand 1 [HOC（Me）C（H）（Me）C=N（p-C6H4）（C6H4-p）N= C（Me）C（H）C（Me）OH）], which was converted into sodium salts. And then the sodium salts reacted with monosalicylaldiminato titanium complex 2{[3,5-di-But′2-（O）C6H2CHN（PH）]TiCl3（THF）} in dried dichloromethane to give a new benzdine-bridged binuclear complex 3{[3,5-di-Bu′-2-（O）C6H2CHN（PH）]2 [OC（Me）C（H）（Me）C=N（p-C6H4）-（C6H4-p）N=C（Me）C（H） C（Me）]Ti2Cl4}. The complex 3 was characterized by ^1HNMR and elemental analysis. In the presence of MAO（methylaluminoxane）, the complex 3 in toluene was effective to catalyze polymerization, affording moderately high catalytic activity 1.93 × 10^5 g PE/（mol.Ti.h）]and high molecular weight polyethylene [5.63× 10^5 g/moll. The high temperature gel permeation chromatography （GPC） curve of polyethylene obtained revealed a single peak, but the molecular weight distribution （MWD = 3.21） is obviously broader than that of the similar mononuclear titanium complex. The melting points of the obtained polyethylene reaches 138 ℃, indicating that the polyethylene is of high crystallinity.     

Adsorption of methylene blue from aqueous solution onto hydrochloric acid-modified rectorite

H+-rectorite clay,which was prepared by modifying the raw rectorite with 10% hydrochloric acid at 60 °C for 24 h,was used as an absorbent for removal of methyl blue (MB) from aqueous solutions.The morphology and the structure and crystallinity of the pristine rectorite and the H+-rectorite were characterized by scanning electron microscopy (SEM) technique and X-ray diffraction (XRD) technique,respectively.The results showed that the H+-rectorite exhibited high adsorption ability than the raw rectorite,and it was found that the removal percentage of MB increased with increasing in adsorbents dose,whereas the adsorption amount qe (mg/g) decreased.The equilibrium was attained within 30 min in adsorption process,and the maximum adsorption capacity of H+-rectorite for methylene blue reached as high as 37 mg/g.Besides,the effect of temperature on the adsorption of MB with H+-rectorite was investigated and the equilibrium data were well fitted to Freundlich equations.The H+-rectorite absorbent saturated with MB can be regenerated by calcinating at 400 °C for 2 h and the regenerated absorbent still showed higher percentage removal of MB.     

Influence on performance and structure of spinel LiMn2O4 for lithium-ion batteries by doping rare-earth Sm

The spinel LiMn₂O₄ used as cathode materials for lithium-ion batteries was synthesized by mechano-chemistry fluid activation process, and modified by doping rare-earth Sm. Thesting of X-ray diffraction, cyclic voltammograms, charge-discharge and SEM was carried out for LiMn₂O₄ cathode materials and the modified materials. The results show that the cathode materials doped rare earth Li _x Mn_2−y Sm _z O₄ (0.95⩽x⩽1.2, 0⩽y⩽0.3, 0⩽z⩽0.2) exhibit standard spinel structure, high reversibility of electrochemistry and excellent properties of charge-discharge. In EC: DMC(1 : 1)+1 mol/L LiPF₆ electrolyte with discharge capacity more than 130 mA · h/g, and its capacity is deteriorated less than 15% after 300 cycles at room temperature and less than 20% after 200 cycles at 55°C. At the same time, Crystal Field Theory was applied to explain the function and mechanism of doped rare earth element. Foundation item: Project (02JJY2081) supported by the Natural Science Foundation of Hunan Province     

Electrochemical performance of LiFePO4/（C＋Fe2P） composite cathode material synthesized by sol-gel method

A LiFePO4/(C+Fe2P) composite cathode material was prepared by a sol-gel method using Fe(NO3)3·9H2O,LiAc·H2O,NH4H2PO4 and citric acid as raw materials,and the physical properties and electrochemical performance of the composite cathode material were investigated by X-ray diffractometry(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM) and electrochemical tests.The Fe2P content,morphology and electrochemical performance of LiFePO4/(C+Fe2P) composite depend on the calcination tempera...     

氮掺杂石墨烯/聚苯胺复合凝胶的制备与性能

为了拓展石墨烯凝胶在超级电容器方面的应用,采用氨水与水合肼作为掺杂剂和还原剂,通过与氧化石墨烯的水热反应制备了氮掺杂石墨烯凝胶,并进一步运用原位聚合的方法在氮掺杂石墨烯凝胶上负载聚苯胺,得到氮掺杂石墨烯/聚苯胺复合凝胶. 利用X射线衍射、扫描电子显微镜对产物的结构和微观形貌进行表征,采用循环伏安、恒电流充放电等方法测试其电化学性能. 结果表明,氮掺杂石墨烯/聚苯胺复合凝胶与纯氮掺杂石墨烯凝胶相比,电化学性能有显著的提高. 当扫描速率为10 mV/s时,复合凝胶的比电容约为500 F/g;在恒电流充放电实验中,当电流密度增加到10 A/g时,复合凝胶的比电容仍然保持在约400 F/g. 当循环伏安扫描1 000圈后,比电容的保持率达到80%. 这些表明氮掺杂石墨烯/聚苯胺复合凝胶拥有突出的电化学性能,也表明了氮掺杂石墨烯/聚苯胺在超级电容器方面将会有很好的应用前景.     

金属有机框架在超级电容器中的应用

成功制备了金属有机框架M3(BTC)2·12H2O(M=Ni和Co),并将其应用于超级电容器电极材料中,通过X线衍射(XRD)表征发现,这些化合物具有同类型的结构,在6 mol/L电解液中,采用循环伏安法和1 000次充放电循环测试其电化学性能.实验表明:Ni3 (BTC)2·12H2O电极材料在扫描速率5 mV/s下,比电容达到了430 F/g;在高扫描速率200 mV/s下,比电容为154 F/g;在扫描速率5 mV/s下1 000次充放电测试其循环寿命后发现,比电容保持率为86％.     

Adsorption of Pb^2＋ on macroporous weak acid adsorbent resin from aqueous solutions： Batch and column studies

The adsorption properties of a novel macroporous weak acid resin (D152) for Pb²⁺ were investigated with chemical methods. The optimal adsorption condition of D152 resin for Pb²⁺ is at pH 6.00 in HAc-NaAc medium. The statically saturated adsorption capacity is 527 mg/g at 298 K. Pb²⁺ adsorbed on D152 resin can be eluted with 0.05 mol/L HCl quantitatively. The adsorption rate constants determined under various temperatures are k _{288 K}=2.22×10⁻⁵ s^t-1, k _{298 K}=2.51×10⁻⁵ s⁻¹, and k _{308 K}= 2.95×10⁻⁵ s⁻¹, respectively. The apparent activation energy, E _a is 10.5 kJ/mol, and the adsorption parameters of thermodynamics are ΔH ^Θ=13.3 kJ/mol, ΔS ^Θ=119 J/(mol·K), and ΔG ^Θ 298 K =−22.2 kJ/mol, respectively. The adsorption behavior of D152 resin for Pb²⁺ follows Langmuir model. Foundation item: Project(2008F70059) supported by the Scientific and Technological Research Planning of Zhejiang Province, China     

Electrochemical behavior of K3Fe（CN）6 in water-in-oil microemulsion

A water-in-oil (W/O) microemulsion composed of Triton X-100, n-hexanol, n-hexane and water solution with hydrochloric acid was prepared. K₃Fe(CN)₆ was added in as a water-soluble electroactive probe, and its electrochemical behavior was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It is found that the H⁺ concentration of the water phase has a great effect on the conductivity of the W/O microemulsion, and hence influences the electrochemical behavior of K₃Fe(CN)₆. When the pH value of water phase is about 7, the electrical conductivity of the W/O microemulsion is only 1.2×10⁻⁶ S/cm, and K₃Fe(CN)₆ almost cannot react at the glassy carbon electrode. But when the H⁺ concentration is more than 3 mol/L, the W/O microemulsion has a good electrical conductivity and K₃Fe(CN)₆ shows good electrochemical performance in it. The results of CV and EIS studies indicate that the electrochemical behavior of Fe(CN)₆ ³⁻/Fe(CN)₆ ⁴⁻ in the W/O microemulsion is different from that in the aqueous solution. This may be due to the unique liquid structure of the W/O microemulsion and the unique mass transfer in the W/O microemulsion. Foundation item: Projects(20673036, J0830415) supported by the National Natural Science Foundation of China; Projects(05JT1026, 2007JT2013) supported by the Science Technology Project of Hunan Province, China     

Carbonized Zn-MOF/PANI的合成及其电容性能研究

通过简单的方法将煅烧过的金属有机框架(MOF)与聚苯胺(PANI)复合,形成了简单的MOF/PANI复合材料.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、傅立叶转换红外线光谱(FTIR)对其进行了表征,并用循环伏安法(CV)对其电化学性能进行了测试.结果证明了MOF/PANI的比容量在电流密度为1 A/g下可高达477 F/g.     

Synthesis and characterization of triclinic structural LiVPO4F as possible 4.2 V cathode materials for lithium ion batteries

A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction （CTR） process. Firstly, V2O5, NH4H2PO4 and acetylene black are reacted under an Ar atmosphere to yield VPO4. The transition-metal reduction is facilitated by the CTR based on C→CO transition. These CTR conditions favor stabilization of the vanadium as V^3＋ as well as leaving residual carbon, which is useful in the subsequent electrode processing. Secondly, VPO4 reacts with ElF to yield LiVPO4F product. The property of the LiVPO4F was investigated by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurement. XRD studies show that LiVPO4F synthesized has triclinic structure（space group p I ）, isostructural with the naturally occurring mineral tavorite, EiFePO4-OH. SEM image exhibits that the particle size is about 2μm together with homogenous distribution. Electrochemical test shows that the initial discharge capacity of LiVPO4F powder is 119 mA·h/g at the rate of 0.2C with an average discharge voltage of 4.2V （vs Ei/Li^＋）, and the capacity retains 89 mA·h/g after 30 cycles.