Electrocatalytic oxidation of methanol on carbon-nanotubes/graphite electrode modified with platinum and molybdenum oxide nanoparticles

Electrochemical codeposition and electrocatalytic properties of platinum and molybdenum oxide nanoparticles(Pt-MoOx) on carbon-nanotubes/graphite electrode for methanol oxidation were investigated.The micrograph and elemental composition of the resulting Pt-MoOx/CNTs/graphite electrode were characterized by scanning electron microscopy(SEM)and energy dispersive X-ray spectroscopy(EDS).The results show that the Pt-MoOx particles with the average size of about 50 nm are highly dispersed on the CNTs surface.The Pt-MoOx/CNTs/graphite electrode delivers excellent electrocatalytic properties for methanol oxidation.The highest mass activity(Am)reaches 264.8 A/g at the loading mass of 159.3μg/cm2.This may be attributed to the small particle size and high dispersion of Pt-MoOx catalysts deposited on the CNTs surface.The kinetic analysis from electrochemical impedance spectroscopy(EIS)reveals that the existed MoOx phase can improve the chemisorptive and catalytic properties for methanol oxidation.     

Polypyrrole/thermally sensitive polyelectrolyte composite (I)

Polypyrrole (PPy) was prepared by electrochemical polymerization with the polyelectrolyte (PE) as a dopant. The PEs were copolymers of the water soluble polymers and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS). The water soluble polymers were thermally sensitive poly(N-isopropyl acrylamide), P(NiPAAm) and thermally insensitive poly(acrylamide), P(AAm). The surface of PPy/PE film observed by SEM was smoother than that of PPy film doped with a monoelectrolyte. PPy/PE composites were fairly conductive, whose electrical conductivities measured by the four-probe method were in the range of 10⁻¹ to 10⁻² S/cm. The characteristics of cation and anion exchange during redox processes were investigated by applying potential from −0.8 to 0.5 V vs. an Ag/AgCl reference electrode to the PPy. The effect of temperature on the doping–dedoping behavior and mass change of PPy composites was investigated by potentiodynamic voltammetry and electrochemical quartz crystal microbalance (EQCM). The electrochemical activity of the PPy/PE gradually decreased with increasing temperature. PPy/P(NiPAAm/AMPS) showed much greater mass change with increasing temperature than PPy/P(AAm/AMPS), mainly because of a decrease in the degree of swelling of thermally sensitive moiety. This confirms that PPy/P(NiPAAm/AMPS) possesses temperature-dependent electrochemical activity, which indicates that it can be utilized for many attractive applications. The thermal volume transition temperature of PPy/P(NiPAAm/AMPS) was estimated from the slope change of mass decrease. The transition temperature of the oxidized state of PPy/P(NiPAAm/AMPS) was higher than that of the reduced state.     

Electrolytic silicon/graphite composite from SiO2/graphite porous electrode in molten salts as a negative electrode material for lithium-ion batteries

Nano-silicon(nano-Si)and its composites have been regarded as the most promising negative electrode materials for producing the next-generation Li-ion batteries(LIBs),due to their ultrahigh theoretical capacity.However,the commercial applications of nano Si-based negative electrode materials are constrained by the low cycling stability and high costs.The molten salt electrolysis of SiO₂is proven to be suitable to produce nano-Si with the advantages of in-situ microstructure control possibilities,cheap affordability and scale-up process capability.Therefore,an economical approach for electrolysis,with a SiO₂/graphite porous electrode as cathode,is adopted to produce nano-Si/graphite composite negative electrode materials(SGNM)in this study.The electrolytic product of the optimized porous electrode is taken as the negative electrode materials for LIBs,and it offers a capacity of 733.2 mAh·g^-1and an initial coulombic efficiency of 86.8%in a coin-type cell.Moreover,the capacity of the SGNM retained 74.1%of the initial discharging capacity after 50 cycles at 0.2C,which is significantly higher than that of the simple mixture of silicon and graphite obtained from the formation of silicon carbide(SiC)between nano-Si and graphite particles.Notably,this new approach can be applied to a large-scale production.     

改性J422焊条电弧焊碳钢接头在亚硫酸铵溶液中的耐蚀性

针对亚硫酸铵介质中碳钢焊接接头腐蚀严重的实际,采用向普通碳钢焊条J422药皮中添加镍的方法,以三电极电化学研究方法和金相组织分析法研究了焊缝不同含镍量情况下碳钢焊接接头在亚硫酸铵溶液中的腐蚀行为.结果表明,镍元素的加入使得焊缝组织晶粒细化,针状铁素体减少;同时提高了碳钢焊接接头的自腐蚀电位;焊接接头在亚硫酸铵溶液中的极化率增大,自腐蚀电流减小;其中焊缝Ni元素含量为1.2%的焊接接头腐蚀速率最小.     

V(Ⅳ)/V(Ⅴ)电对在石墨毡电极上的反应机理

采用循环伏安、极化曲线和交流阻抗三种电化学实验方法研究了V(Ⅳ)/V(Ⅴ)电对在石墨毡电极上的反应机理及其可能的速度控制步骤。研究结果表明:V(Ⅳ)/V(Ⅴ)电对在石墨毡电极上的反应属准可逆过程,且氧化过程包含有后置化学转化步骤;理论计算得到了电化学步骤和后置化学转化过程分别为控制步骤时的Tafel斜率值为0.12和0.06,实验得到的Tafel斜率值为0.124,表明电极氧化过程受电化学过程控制;不同极化电位下的交流阻抗图谱拟合结果表明,电化学反应阻抗值远大于其他阻抗值,说明电化学反应可能是电极反应的控制步骤,与实验得到的极化曲线分析结果相一致。     

Ultrafine SnO2 in situ modified graphite felt derived from metal-organic framework as a superior electrode for vanadium redox flow battery

Metal-organic framework(MOF) and its derivatives have low-cost,controllable structure,and good catalytic performance,which are often used in the electrochemical field.In this work,SnO₂ in situ modified graphite felt(SnO₂/GF) is prepared by hydrothermal method then simple thermal treatment using Sn-based MOF(Sn-MOF) as precursor.SnO₂ is uniformly and firmly distributed on the GF surface rather than the common agglomeration and poor bonding of metal oxides on carbo...     

Dye sensitized solar cells (DSSCs) based on modified iron phthalocyanine nanostructured TiO2 electrode and PEDOT:PSS counter electrode

An iron phthalocyanine with tetra-sulphonated substituents (FeTsPc) was used as photosentizer for the development of dye sensitized nanostructured TiO₂ solar cells. The influence of surface modification (TiO₂ film treated with HCl and HNO₃) and thermal annealing of TiO₂ photo-electrode on the performance of dye sensitized solar cell (DSSC) having structure FTO/TiO₂–FeTsPc/electrolyte/PEDOT:PSS (carbon added)/FTO was investigated through the analysis of current–voltage characteristics under illumination and electrochemical impedance spectra (EIS). The improvement in crystallinity of TiO₂, decrease in the internal surface area and adsorbed amount of dye and increase in the lifetime of injected electrons upon thermal annealing of TiO₂ photo-electrode affects the photovoltaic properties of DSSC. The increase in power conversion efficiency of DSSC based on nitric acid treatment for the photo-electrode is mainly attributed to the increase in photocurrent. A comparative photovoltaic investigation of DSSCs using HCl-treated TiO₂ photo-electrode, indicates that the HNO₃-treated photo-electrode retards back electron transfer at the interface with electrolyte and increases the amount of dye.     

Ordering of nitric acid (HNO3) intercalated in graphite

X-ray studies of intercalation compounds of single crystals of natural graphite have enabled us to settle essential features of the in-plane ordering of α-HNO₃-graphite. A low temperature superstructure with $\textcolor{red}{}\text{= 17}\textcolor{red}{}{}_{\mathrm{<mtext>G</mtext>}}\text{,}\textcolor{red}{}\text{= 2}\textcolor{red}{}{}_{\mathrm{<mtext>G</mtext>}}\text{+ 9}\textcolor{red}{}{}_{\mathrm{<mtext>G</mtext>}}$ is found below 210 K. Above this temperature, the structure is incommensurate with the graphite lattice, with $\textcolor{red}{}\text{～- 17}\textcolor{red}{}{}_{\mathrm{<mtext>G</mtext>}}\text{/12}$. In stage 8 sample this structure persists until the disordering temperature at about 250 K, whereas fresh stage 2 samples show an intermediate phase strongly incommensurate and quite different from the low temperature phase. The X-ray pattern from the liquid phase above 250 K shows pronounced hexagonal modulation.     

Electrochemical study on the semiconductor properties and fractal dimension of poly ortho aminophenol modified graphite electrode in contact with different aqueous electrolytes

The fractal dimension of poly ortho aminophenol (POAP) films in the presence of different counter ions was investigated. The POAP films were deposited on graphite electrode by cyclic voltammetry. The deposited films were also characterized by electrochemical impedance spectroscopy (EIS) in wide frequency range. The length scale, the distances between two nearest points that the anions somehow sense (by yardstick of the size of their jump-length), were also derived. The resulting Mott-Schottky plot of the polymer capacitance describes the reduced polymer as a p-type semiconductor with a flat band potential of about 200 mV vs. SCE. The discussion shows that the nature of the anion plays a major role on the electrochemical behavior of the polymer.     

苯甲酸修饰碳纳米管的制备及其负载Co(OH)2的电化学电容性能

以苯甲酸功能化碳纳米管为基底,制备Co(OH)2/苯甲酸化功能化碳纳米管复合材料.苯甲酸官能团在合成过程中发挥了双重作用:既明显改善碳纳米管在去离子水中的分散性,又使得碳纳米管管壁与Co2+表面结合能力大大加强.透射电子显微镜、扫描电子显微镜以及X射线衍射等表征表明,Co(OH)2在碳纳米管上的分散性得到很大改善;电化学实验结果表明,该复合材料拥有优良的电容行为,其比容量在电流密度为5 mA/cm2时达到322.3 F/g,较Co(OH)2/纯化碳纳米管复合材料以及纯Co(OH)2电极高出100 F/g左右.实验结果表明,以苯甲酸功能化碳纳米管为基底可以进一步有效提高Co(OH)2的利用率.     

Application of spherical Ni（OH）2/CNTs composite electrode in asymmetric supercapacitor

1 Introduction Electrochemical capacitors (hereafter ECs) have greater power density than usual batteries and can be deeply discharged without any deleterious effect on life time[1]. Activated carbon(AC) with various modifications is the electrode materia…     

4-methoxy-2,6-bis(3,5-dimethylpyrazoyl)-1,3,5-triazine modified carbon paste electrode for trace Cu(Ⅱ) determination by differential pulse volt-ammetry

A differential pulse voltammetric method was developed for the sensitive and selective determination of Cu(Ⅱ) at 4-methoxy-2,6-bis(3,5-dimethylpyrazoyl)-l,3,5-triazine modified carbon paste electrode in 0.05 mol/L KHC8H4O4 solution (pH = 4.02). The oxidation peak of Cu(Ⅱ) was observed at 0.065 V(vs Ag/AgCl) by scanning the potential in positive direc-tion. The analysis procedure consisted of an open circuit accumulation step in stirred sample solution. It was followed by medium exchange to a clean solution and subsequently an anodic potential scan was affected to obtain the voltammetric peak. The current was proportional to the concentration of the Cu(Ⅱ) ion in a range of 1× 10-7-1×10-4 mol/L for 6 min accumulation; the most of metal ions did not interfere with the determination. The developed method was applied to Cu(Ⅱ) determination in coal-ash sample, the results agreed with that of atomic adsorption spectroscopy(AAS).     

Preparation of self-healing protective films on a zinc electrode treated in a cerium(III) nitrate solution and modified with sodium phosphate and cerium(III) nitrate

Self-healing protective films were prepared on a zinc electrode previously treated in a Ce(NO₃)₃ solution by modification with Na₃PO₄ and Ce(NO₃)₃. The protective and self-healing abilities of the films were examined by polarization measurements and observation of pit formation after the electrode was scratched with a knife-edge crosswise and immersed in oxygenated 0.5 M NaCl at 30 °C for many hours. Mechanisms of the protective and self-healing activities were discussed using X-ray photoelectron spectroscopy and electron-probe microanalysis. The protective and self-healing abilities of the films prepared on the zinc electrode by treatment in the Ce(NO₃)₃ solution and modification with Na₃PO₄ plus Ca(NO₃)₂, Mg(NO₃)₂, Zn(NO₃)₂ or Ce(NO₃)₃ were summarized.     

A study of electroless copper-phosphorus coatings with the addition of silicon carbide (SiC) and graphite (Cg) particles

Copper composite coating with graphite (C_g) and/or silicon carbide (SiC) particles were deposited by electroless plating. The surface morphology of the coatings that were analysed using scanning electron microscopy (SEM) showed that Cu particles were uniformly distributed. The obtained coating thickness was approximately ± 5 μm. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were used to characterise the structure and to study the phase transition of the coatings, respectively. Phases such as Cu, Cu₂O, Cu₃P, Cu₃Si, SiC and C_g were observed from X-ray diffraction patterns and the presence of Cu₂O, Cu₃P and Cu₃Si was confirmed by differential scanning calorimetry (DSC) studies. The results demonstrated that SiC and C_g particles have little influence on the phase transition of the coating. The hardness and wear resistance of Cu-P composite coatings were improved with the incorporation of SiC particles. The friction coefficient of Cu-P composite coatings decreased with the incorporation of C_g particles. Atomic force microscopy (AFM) results of coatings showed that the roughness of the coatings increased with the incorporation of SiC to the Cu-P coatings and decreased with the incorporation of C_g. Cu-P-C_g-SiC composite coatings showed a moderate roughness, hardness between Cu-P-SiC and Cu-P-C_g coatings, had low friction and good anti-wear properties. The anti corrosion resistance of the electroless Cu-P composite coatings on carbon steel were studied in 3.5% NaCl and 1 M HCl solutions by the potentiodynamic polarisation technique. The study revealed that the corrosion resistance increased with the incorporation of SiC particles in the Cu-P and Cu-P-C_g matrix but reduced with the incorporation of graphite.     

Effects of graphite content on the microstructure and wear properties of an AISI 8620 steel surface modified by tungsten inert gas (TIG)

A surface modification process was used to modify the surface properties of a steel material by using the TIG method on AISI 8620 steel with a 135-A constant energy input and the addition of 0.5 g of constant SiC particle and variable C content. SEM and optical microscopy were used to characterize the microstructure of the materials tested. To evaluate the mechanical properties, the microhardness distribution was determined from the surface to the central region. Wear tests were performed under dry friction conditions with WC balls at a 5-N normal load in a ball-on-disk geometry.The results of this study indicated that the surface properties of the material could be modified with the TIG method and by using SiC/C particles and that the newly formed structure could improve the wear characteristics and the hardness of the surface.     

A complete list of the lattices of first-stage epitaxic graphite derivatives XCn (for n ⩽ 24)

A computer has been used to determined all the possible lattices corresponding to a given value of n for the first-stage epitaxic derivatives of graphite XC_n, with n ? 24. The conditions of existence for orthorhombic cells are that n should be divisible by 4, for monoclinic cells that n should be different from 2, 4 or 8, and for hexagonal cells that n = 2(u² + uv + v²) where u, v are positive integers or 0.     

B参杂对NiO/Ni(OH)2电极材料电容性能的影响

通过化学镀再电化学氧化的方法在铜片表面制备出带有微米微坑和微米微球的均一NiO/Ni(OH)₂和B参杂的NiO/Ni(OH)₂(B)两种电极材料,采用扫描电镜(SEM/EDX)、X射线衍射(XRD)、X射线光电子能谱(XPS)和电化学技术对所制备的两种电极材料进行表征和电化学性能测试。SEM、XRD和XPS的测试结果表明, 所制备的两种电极材料由Ni、NiO和Ni(OH)₂组成,并且NiO/Ni(OH)₂(B)中B的参杂量可达14.6wt%。循环伏安测量和恒电流充放电试验表明,两种电极材料均具有较高的电化学活性和可逆性;在1 A/g的充放电电流密度下, 两种NiO/Ni(OH)₂和NiO/Ni(OH)₂(B)电极材料经历10000次充放电循环后分别给出了1380 和1930F/g的比电容, 显示出较高的比电容特性和良好的电化学稳定性;电化学阻抗谱表明NiO/Ni(OH)₂(B)电极材料较NiO/Ni(OH)₂电化学反应电阻降低了约2个数量级;Ragone曲线揭示了所制备的两种电极材料具有较高的功率密度和较低的能量密度。B的参杂使得NiO/Ni(OH)₂(B)电极材料表面氧化物含量增大并且形成微米微球形貌,增大了电极表面积以及与电解液的接触和润湿作用,降低了电极材料表面能带带隙能,从而导致较小的电化学反应电阻和电导率的提高是其显示优异赝电容性能的主要原因。     

Study on hydrogen diffusion behavior in MlNi_(3.75) Co_(0.65) Mn_(0.4) Al_(0.2) alloy electrode by chronoamperometry

1　ＩＮＴＲＯＤＵＣＴＩＯＮＮｉｃｋｅｌ ｍｅｔａｌｈｙｄｒｉｄｅ (Ｎｉ/ＭＨ )ｂａｔｔｅｒｉｅｓｈａｖｅｂｅｅｎｄｅｖｅｌｏｐｅｄｔｏｍｅｅｔｔｈｅｄｅｍａｎｄｓｆｏｒａｐｏｗｅｒｓｏｕｒｃｅｗｉｔｈｈｉｇｈｅｎｅｒｇｙｄｅｎｓｉｔｙ ,ｅｘｃｅｌｌｅｎｔｈｉｇｈ ｒａｔｅｃａｐａｂｉｌｉｔｙ ,ｌｏｎｇｃｙｃｌｅｌｉｆｅａｎｄ ｇｏｏｄｅｎｖｉｒｏｎｍｅｎｔａｌｃｏｍｐａｔｉｂｉｌｉｔｙ[1,2 ] ,ａｎｄｅｘｔｅｎｓｉｖｅｒｅｓｅａｒｃｈｅｓｈａｖｅｂｅｅｎｄｏｎｅｏｎｔｈｅｍ[3～ 5] .Ｔｈｅｐｅｒｆｏｒ…     

The forty years of vermicular graphite cast iron development in China (Part Ⅱ)

2 Manufacturing methods and vermicularisers 2.1 Manufacturing methods From the long period of practical experiences of VGCI production, the following four points are very important for the successful production of VGCI:     

The forty years of vermicular graphite cast iron development in China (Part Ⅲ)

5 Heat treatment of VGCI Research work has shown that the microstructure of VGCI can be modified by heat treatment to give improved properties;martensitic, bainitic, sorbitic and pearlitic structures can be produced by quenching, quenching plus tempering,austempering and normalisation respectively.