Ce(OH)3包覆Zn-Al-LDHs在Zn-Ni二次电池中的电化学性能

采用共沉淀法制备Ce(OH)3包覆Zn-Al-LDHs,并且将其作为锌镍二次电池的新型负极材料.利用X射线衍射仪(XRD)和扫描电镜(SEM)对Ce(OH)3包覆Zn-Al-LDHs进行形貌和微观结构的表征,结果表明,Ce(OH)3成功包覆在Zn-Al-LDHs表面.通过循环伏安曲线(CV)、Tafel极化曲线、交流阻抗曲线(EIS)和恒电流充电放电测试研究了其作为锌镍电池负极材料的电化学性能,结果表明,Ce(OH)3包覆Zn-Al-LDHs表现出很好的循环可逆性能和抗腐蚀性能,Ce(OH)3包覆Zn-Al-LDHs电极在Zn-Ni二次电池中的循环稳定性和充放电特性得到了明显提高,经过80次循环后,其循环保持率可以达到94.5％.     

添加剂对Ni(OH)2电极充放电性能的影响

Mg、Ca、Sr、Ba、Cd、Zn、Co和La等添加剂以化学共沉积的方式添加到镍电极活性物质Ni(OH)2中，XRD显示Ni(OH)2为β型。恒流充放电和循环伏安实验结果表明：添加剂能提高镍电极的充放电性能，其中Sr、Co和La是比较理想的添加剂。它们能明显提高析氧极化，降低析氧速率，增强电极的可逆性，改善电极的充放电性能。     

掺硼金刚石薄膜的电化学性能

利用循环伏安法,通过对比掺硼金刚石薄膜电极和铂／金刚石电极分别作为工作电极时的循环伏安曲线,分析了两种电极表现出的电化学性能差别,并利用能级理论进行了机理探讨。结果表明掺硼金刚石薄膜电极具有宽的电化学窗口（宽度约为3V）、良好的化学稳定性和极低的背景电流（接近0）,是一种较有潜力的电化学电极材料。     

中性体系中钴对镍电极析氧催化性能的影响

为了研究钴镍电极在中性体系中的电催化性能和催化循环稳定性,在金属钛电极上采用电沉积方法制备了不同钴含量的镍涂层电极,通过X射线衍射技术、扫描电镜技术、恒电流极化曲线和循环伏安等测试技术,探讨了不同钴元素的添加量对镍涂层电极在中性体系中析氧电催化活性和循环稳定性的影响.结果表明,添加适量的钴元素细化了镀层晶粒,增大了电极比表面积,提高了电极的析氧催化活性,其中添加40g/L CoSO_4·5H_2O时涂层的晶粒最细,继续增加钴含量颗粒变大但形状多面,比表面积没有减小,对电极析氧催化性能影响不大;同时钴的添加不利于晶体的结晶,降低了电极表面状态的循环稳定性能.     

深共晶溶剂中电沉积制备Co-Fe-Gd/NF电极及其析氢性能研究

为了制备出在碱性环境中具备高效能的廉价析氢电极催化剂,选择不同的沉积电位在氯化胆碱-尿素(ChCl-urea)中电沉积制备出五种Co-Fe-Gd/NF电极催化剂。通过扫描电镜(SEM)和光谱仪(EDX)对电极表面形貌、元素含量及分布情况进行表征,X射线光电子能谱(XPS)对电极表面化学性质进行表征。结合线性扫描伏安法(LSV)、电化学阻抗技术(EIS)和循环伏安法(CV)电化学测试结果,表明-1.24 V沉积电位下制备的Co-Fe-Gd/NF-3电极具备优异的析氢催化性能,在10 mA·cm^-2时的过电位仅为71 mV,最小的塔菲尔斜率(45 mV·dec^-1)与电荷转移电阻(0.28503Ω·cm^-2)表明其具备更快的析氢反应动力学过程,电化学活性表面积(ECSA)最大为390.5,为析氢过程提供更多的反应活性位点。对电极进行循环伏安耐久性测试与计时电流法(I-t)测试,结果表明Co-Fe-Gd/NF-3电极催化剂在碱性环境中稳定性良好。     

GOD/PPy/GC电极的电化学性能研究

采用电沉积法在玻碳(GC)电极表面合成纳米级聚吡咯(PPy),通过扫描电镜得到PPy的形貌。以PPy为载体,通过吸附法固定葡萄糖氧化酶(GOD),得到GOD/PPy/GC电极。利用循环伏安法对GOD/PPy/GC电极的电化学行为进行分析,结果表明,以PPy为载体可以很好地固定GOD并保持其生物活性。在0.1mol/L磷酸盐缓冲溶液中,无任何电子媒介体存在时,GOD/PPy/GC电极显示了很好的电催化性能。     

CeO_2对Ti/RuO_2(0.5)-Co_3O_4(0.5)电极电催化性能的改进作用

为了改进Ti/RuO_2(0.5)-Co_3O_4(0.5)电极的析氧催化性能,采用热分解法在400℃下制备了稀土Ce改性Ti/RuO_2(0.5)-Co_3_O_4(0.5)氧化物电极,对稀土Ce掺杂量进行了优化.通过开路电压、循环伏安及极化曲线研究了电极在1.0 mol/L KOH溶液中的析氧催化活性.结果表明:稀土Ce掺杂可明显提高电极伏安电荷量、内外活性表面积及电极表面粗糙度,同时能降低析氧反应表观活化能;当其掺杂量为10:4时电极性能最佳,伏安电荷量和表面粗糙度分别高达806 mC/cm~2和3 047.83,析氧反应表观活化能低至15.74 kJ/mol.这主要是稀土Ce具有孔引发剂的作用,可提高活性氧化物晶粒的分散性,使电极活性表面积增加,改善了析氧催化活性.     

聚苯胺纳米纤维在电化学电容器中的应用研究

电化学电容器具有高功率、高容量的性能，引起了人们的广泛关注。本研究采用电化学法，在不锈钢电极上沉积聚苯胺纳米纤维。通过扫描电镜（SEM）观测了电极表面聚苯胺的形态。研究了修饰电极的循环伏安特性，并考察了聚合物膜厚度和循环伏安扫描电位范围对修饰电极比电容的影响．     

不锈钢基PbO2-WC-CeO2复合镀的机理及镀层性能

不锈钢基PbO2-WC-CeO2复合电极克服了传统钛基二氧化铅(DSA)电极基体易钝化、寿命短和成本高等缺点,以往对其电化学性能研究不多。采用复合电沉积方式在不锈钢基体上制备了PbO2-WC-CeO2复合电极,通过循环伏安曲线(CV)考察了复合电极的电沉积过程;通过X射线衍射(XRD)、能谱分析仪考察了复合电极的元素组成;通过扫描电镜(SEM)考察了复合电极的表面形貌变化;通过Tafel曲线、析氧曲线考察了电极掺杂前后的电化学性能变化。结果表明:WC和CeO2固体颗粒的加入使得PbO2电沉积过程发生了择优生长和晶粒细化,电极耐腐蚀性能提高,催化活性和节能性能变佳。     

氯化胆碱-尿素中三元合金膜的制备及耐腐蚀性表征

探究ChCl-urea低共熔溶剂对电沉积合金膜含量的影响,并提升二元镁合金的耐腐蚀性能。在353 K的ChCl-urea低共熔溶剂中,利用恒电位电解法制备了Eu-Mg-Co合金膜对Mg合金组成及耐腐蚀性进行优化。利用循环伏安法研究ChCl-urea以及加入金属元素后熔体的电化学行为。在Pt电极上的循环伏安曲线表明,Co(Ⅱ)+2e→Co(0)是一步不可逆反应,并计算得出Co(Ⅱ)在Pt电极上的传递系数α以及扩散系数D_0~([1])。稀土元素Eu和金属Mg沉积电位较负,难以单独沉积得到单一元素的合金膜,但能在Co(Ⅱ)的作用下诱导共沉积得到多元合金膜。在不同电位和不同组成的镀液中采用恒电位计时电流法进行电沉积,用EDS分析和SEM对合金膜进行分析和表征。对合金膜进行Tafel测试,利用外推法得出合金膜在NaCl溶液中的自腐蚀电流与电位。Co(Ⅱ)在Pt电极上的传递系数α=0.093,扩散系数D_0=1.177×10~(-5) cm~2/s。EDS结果表明在沉积电位-1.18 V,镀液配比为0.04 mol/L CoCl_2+0.04 mol/L MgCl_2+0.03 mol/L Eu(NO_3)_3时合金膜中Eu含量最高,Eu-Mg-Co有良好的耐腐蚀性。结论:得到镀层晶粒细致均匀的Eu-Mg-Co合金膜,加入稀土Eu元素的三元合金膜耐腐蚀性能优于Co-Mg二元合金膜。     

杂多酸修饰多晶铂电极的制备及其电催化性能的研究

为了改善铂基催化剂氧化甲醇的催化活性,首先通过循环伏安扫描制备了硅钨酸、磷钨酸、磷钼酸三种杂多酸修饰铂电极。通过研究铂电极修饰前后在硫酸底液中的循环伏安行为可知,尽管杂多酸具有较大的分子构型,但仍能在铂电极上吸附．另外通过循环伏安曲线研究了杂多酸修饰铂电极对甲醇氧化的电催化作用及抗一氧化碳毒化作用．测试结果表明：铂电极经杂多酸修饰后,能够大大提高其对甲醇氧化反应的催化活性以及抗一氧化碳毒化作用．并且三种杂多酸修饰铂电极中,磷钼酸修饰铂电极的催化活性最高,抗毒化作用最强．     

电极制备方法对球形Ni(OH)2循环伏安特性的影响

用镍粉和氢氧化镍压片制备了不同质量的氢氧化镍圆片电极进行不同扫描速度的循环伏安(CV)实验并和粉未微电极进行比较研究,结果表明：用压片法制得的圆片电极随质量的减小电极可逆性递增。在同一扫描速度下,不同电极的电流密度大致相同。以0．1gNi 0．03gNi(OH)2配比制得的圆片电极表现出较好的准可逆特性。鏊于其良好的质量可计量性,这种电极在CV测试中的重复性和可对比性好于粉未微电极。     

氢氧化镍电极导电剂的研究

研究了镍粉，镍粉和石墨的混合物，石墨以及石墨和乙炔墨的混合物分别作为导电剂以机械混合的方式添加到电极活性物质中对氢氧化镍电极性能的影响，并用循环伏安法和交流阻抗法分析了实验结果。结果表明：在这四种导电剂中，镍粉作导电剂时氢氧化镍电极的性能最好，其次是以石墨或镍粉和石墨的混合物作导电剂的氧化镍电极，当石墨和乙炔黑的混合物作导电剂时氢氧化镍电极的性能最差。这是因为当镍作导电剂时氢氧化镍电极的电化学反应电阻最小，质子扩散最容易，电要的可逆性最好，且氧气析出最困难，而当石墨和乙黑和混合物作导电剂时氢氧化镍电极的电化学反应电阻最大，质子扩菜最困难，电极充电过程和析氧过程几乎同时进行，因而充电效率最低，活性物质的利用率最小，电极性能最差。     

Fast-scan voltammetry of cyclic nitroxide free radicals

Fast-scan cyclic voltammetry at carbon fiber microelectrodes is used to detect the cyclic nitroxide 2,2,6,6-tetramethylpiperidinyl-1-oxy free radical (TEMPO) and three analogs. The electrochemical behavior of the TEMPO analogs at unmodified carbon fiber electrodes is found to differ greatly from their behavior at glassy carbon electrodes. After the electrode is coated with the polymer Nafion, the electrodes exhibit increased sensitivity to TEMPO and 4-amino-TEMPO. Voltammograms of the nitroxides at Nafion-coated electrodes indicate that the oxidized form (oxoammonium ion) and the free radical form have greatly different mobilities through the polymeric coating. Response times to changes in nitroxide concentration vary from subsecond at bare electrodes (all four analogs) and 4-hydroxy-TEMPO at modified electrodes to 1-3 s for TEMPO and 4-amino-TEMPO at modified electrodes. The detection limit for 4-amino-TEMPO is 50 μM at an unmodified electrode and 5 μM at a Nafion-coated carbon fiber electrode. The sensitivity of the Nafion-modified electrode to TEMPO, 4-hydroxy-TEMPO, and 4-amino-TEMPO can be improved by choosing a resting potential at which the oxoammonium ion form of the nitroxide is preconcentrated into the Nafion film. Using fast-scan cyclic voltammetry and the modified carbon fiber electrodes, the reaction of two nitroxide free radicals with ascorbate can be monitored. This work shows that fast-scan voltammetry at microelectrodes is a sensitive method that can be used to follow reactions of cyclic nitroxide free radicals in solution.     

New route for synthesis of electrocatalytic Ni(OH)2 modified electrodes—electrooxidation of borohydride as probe reaction

Immobilization of redox species like Ni(OH)₂ onto the electrode surface is important in the application areas such as super capacitor, electrochromic displays and electrocatalysis. Nickel hexacyanoferrate (NiHCF) modified glassy carbon could be further derivatized with Ni(OH)₂ by electrochemical cycling in alkali. The electrodeposition of Ni(OH)₂ was usually carried out onto the electrode surface from nickel salt at high interfacial pH. This paper reports the preparation of Ni(OH)₂ from insoluble nickel tetracyanonickelate supported on carbon (NTN/C). This insoluble precursor complex was decomposed by two methods. (1) By potential cycling of modified electrode with the above complex in alkali. (2) By thermal decomposition of the precursor complex (NTN/C) to form metallic nickel followed by cycling in alkali. Ni(OH)₂ modified electrodes formed using both methods were characterized by cyclic voltammetry and also by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. Further, electrocatalytic properties of Ni(OH)₂/C modified electrodes formed by the above two methods were studied and compared using borohydride oxidation as probe reaction.     

Synergistic catalytic effect of a composite (CoS/PEDOT:PSS) counter electrode on triiodide reduction in dye-sensitized solar cells

Inorganic/organic nanocomposite counter electrodes comprised of sheetlike CoS nanoparticles dispersed in polystyrenesulfonate-doped poly(3,4-ethylenedioxythiophene (CoS/PEDOT:PSS) offer a synergistic effect on catalytic performance toward the reduction of triiodide for dye-sensitized solar cells (DSSCs), yielding 5.4% power conversion efficiency, which is comparable to that of the conventional platinum counter electrode (6.1%). The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry measurements revealed that the composite counter electrodes exhibited better catalytic activity, fostering rate of triiodide reduction, than that of pristine PEDOT: PSS electrode. The simple preparation of composite (CoS/PEDOT:PSS) electrode at low temperature with improved electrocatalytic properties are feasible to apply in flexible substrates, which is at most urgency for developing novel counter electrodes for lightweight flexible solar cells.     

Detailed analysis of the electron-transfer properties of azurin adsorbed on graphite electrodes using DC and large-amplitude Fourier transformed AC voltammetry

The analysis of dc cyclic voltammograms of surface-confined metalloproteins is complicated by large background currents, significant ohmic iRu drop, and frequency dispersion related to protein and electrode surface inhomogeneity. The use of large-amplitude Fourier transform ac voltammetry for the quantification of the electron-transfer properties of a thin film of redox-active protein azurin adsorbed onto edge-plane, basal-plane, and highly oriented pyrolytic graphite electrode surfaces has been evaluated and compared to results obtained by dc cyclic voltammetry. In principle, it has been established that fourth and higher harmonic sine-wave data are ideally suited for analysis of electron-transfer processes as they are almost completely devoid of background capacitance current contributions. However, uncompensated resistance has a higher impact on these components, as is the case with fast scan rate dc techniques, so strategies to include this term in the simulations have been investigated. Application of recommended strategies for the evaluation of the electron-transfer properties of azurin adsorbed onto three forms of graphite, each having different background or uncompensated resistance values, is described and compared to results obtained by traditionally used forms of cyclic voltammetry. The electron-transfer rate constant, k0', of azurin at a highly oriented pyrolytic graphite electrode surface was approximately 250 s(-1), compared with > or =1000 s(-1) at edge-plane and basal-plane graphite electrodes. The significantly lower k0' value found at the highly oriented pyrolytic graphite electrode was related to the relatively low level of edge-plane defect sites present at the surface of this electrode. However, analysis of high ac harmonics suggests that frequency dispersion is substantial at all electrode surfaces. Such effects in these diffusionless situations are significantly enhanced relative to solution-phase voltammetry, where overlay of diffusion layers minimizes the impact of heterogeneity.     

Neodymium conversion layers formed on zinc powder for improving electrochemical properties of zinc electrodes

Zinc powder, as active material of secondary alkaline zinc electrode, can greatly limit the performance of zinc electrode due to corrosion and dendritic growth of zinc resulting in great capacity-loss and short cycle life of the electrode. This work is devoted to modification study of zinc powder with neodymium conversion films coated directly onto it using ultrasonic immersion method for properties improvement of zinc electrodes. Scanning electron microscopy and other characterization techniques are applied to prove that neodymium conversion layers are distributing on the surface of modified zinc powder. The electrochemical performance of zinc electrodes made of such modified zinc powder is investigated through potentiodynamic polarization, potentiostatic polarization and cyclic voltammetry. The neodymium conversion films are found to have a significant effect on inhibition corrosion capability of zinc electrode in a beneficial way. It is also confirmed that the neodymium conversion coatings can obviously suppress dendritic growth of zinc electrode, which is attributed to the amelioration of deposition state of zinc. Moreover, the results of cyclic voltammetry reveal that surface modification of zinc powder enhances the cycle performance of the electrode mainly because the neodymium conversion films decrease the amounts of ZnO or Zn(OH)₂ dissolved in the electrolyte.     

Mg2Ni alloy for metal hydride electrodes

A study was made of the effects of ball-milling Mg2Ni alloy with nickel powder, and chemically coating it with nickel on the alloy properties. Three types of alloys, nickel mixed, nickel ball-milled and nickel coated Mg2Ni alloy, were used as the active material of metal hydride electrodes. The ball-milling of the alloy with nickel powder results in an amorphous or nanocrystaline phase. Chemical coating of the alloy with nickel was carried out at 25°C. The alloy particles were pulverised by the colliding process during the ball-milling and possibly by a hydrogen decrepitation mechanism during the coating process. Electrochemical measurements show that the electrode fabricated from the nickel mixed Mg2Ni alloy was very difficult to charge and discharge at room temperature, while the characteristics of the electrode prepared by nickel ball-milling or nickel coating were greatly improved because of the changed phase structure and surface behaviour.     

Influence of raw carbon nanotubes diameter for the optimization of the load composition ratio in epoxy amperometric composite sensors

In this work, it is reported the necessity to characterize the raw carbon materials before their application in composite electrodes based on multiwall carbon nanotubes (MWCNTs) dispersed in epoxy resin for the development of improved amperometric sensors. These sensors must contain an optimum MWCNT/epoxy ratio for their best electroanalytical response. The main drawback in MWCNTs composite materials resides in the lack of homogeneity of the different commercial nanotubes largely due to different impurities content, as well as dispersion in their diameter/length ratio and state of aggregation. The optimal composite electrode composition takes into account the high electrode sensitivity, low limit of detection, fast response, and electroanalytical reproducibility. These features depend on carbon nanotube physical properties as the diameter. Three different commercial carbon nanotubes with different diameters were characterized by transmission electron microscopy and the results were significantly different from the ones provided by the manufacturers. Then, the three MWCNTs were used for the MWCNT/epoxy sensors construction. After an accurate electrochemical characterization by cyclic voltammetry and electrochemical impedance spectroscopy, they were employed as working electrodes using ascorbic acid as a reference analyte. Percolation theory was applied in order to verify the electrochemical results. It is demonstrated that the optimum interval load of raw carbon material in the optimized-composite electrodes closely depends on the MWCNTs diameter, needing 5 % in carbon content for the narrowest MWCNTs containing composite electrodes versus 12 % for the widest MWCNTs.