电化学沉积对贮氢电极动力学特性的影响

采用电化学沉积镍的方法对贮氢合金电极进行了表面修饰,并对贮氢电极动力学性能进行研究.结果表明,电极表面电化学沉积镍后,提高了氢在贮氢合金中的扩散系数和交换电流密度,降低了电化学反应阻抗和接触电阻,从而明显降低了放电过程中的极化作用,提高了贮氢电极的倍率放电性能.     

球磨法制备表面包覆CoOOH的氢氧化镍及其电化学性能研究

采用机械球磨法直接在氢氧化镍颗粒表面包覆CoOOH,通过扫描电镜（SEM）和X射线衍射（XRD）研究其表面形貌和结构,结果表明,合成的CoOOH呈条状,均匀聚集在氢氧化镍颗粒表面,同时保持了β-Ni（OH）2的结构.电化学阻抗谱（EIS）和充放电测试表明,与混合加入CoO的镍电极相比,表面包覆CoOOH能有效提高镍电极反应活性,改善其大电流放电性能.     

硫酸铵电解液添加剂对铅酸电池电化学性能的影响

采用循环伏安、线性极化和恒流充放电等电化学方法研究硫酸铵添加剂对铅酸电池正极、负极、板栅合金及电池电化学性能的影响.结果表明,适量(15～20 g/L)硫酸铵用作电解液添加剂的加入可以改善电极性能,增强板栅合金的耐腐蚀性,提高电池放电容量。     

十二烷基硫酸钠对电沉积镍电化学行为的影响

研究十二烷基硫酸钠(SDS)沉积镍电化学行为的影响,采用动电位扫描与交流阻抗法分别测定不同质量浓度的SDS镀液电沉积镍的极化曲线和交流阻抗谱,结果表明:在Watts镀液中添加SDS可使阴极极化降低。Watt镀液中SDS质量浓度为0.1～0.2 g/L时,极化下降较小;SDS质量浓度为0.2 g/L时,电荷传递电阻(Rct)可达到1 029Ω.cm2;SDS质量浓度超过0.3 g/L时,极化下降较大,Rct较小,不易形成致密镀层。SDS作为传统的润湿剂和防针孔剂应控制质量浓度为0.1～0.2 g/L。     

聚吡咯/碳纳米管/棉纱复合柔性超级电容器电极制备

采用浸泡-干燥和化学原位聚合的方法制备了聚吡咯/碳纳米管/棉纱(PPy/MWCNTs/CY)复合电极材料。探究了浸泡次数以及化学原位聚合掺杂剂浓度对电极电化学性能的影响。采用Phenom台式扫描电镜、冷场发射扫描电子显微镜、CHI660E电化学工作站和傅里叶红外光谱仪对电极的表观形貌、物质结构和组成进行了分析。研究结果表明:当MWCNTs浸泡次数为3次,对甲苯磺酸浓度为0.5 mol/L时,电极的比电容最大,为214 F/g(241.3 m F/cm),优于在棉纱上直接原位聚合聚吡咯的比电容。当恒电流充放电电流为3 m A时,PPy/MWCNTs/CY的放电时间大于PPy/CY的放电时间,此外PPy包覆的均匀性得到提高。     

石墨烯/棉针织复合电极的制备及性能

利用液相剥离法制备石墨烯分散液,以纯棉针织物为基底,采用电化学沉积法在不同电沉积时间下制备石墨烯/棉针织复合电极材料。通过扫描电镜(SEM)表征电极的微观结构,并结合循环伏安测试(CV)、恒流充放电测试(GCD)以及电化学阻抗测试(EIS)对电极材料进行电化学性能研究。结果表明,该复合电极材料比电容的大小与石墨烯在织物表面的含量以及分布状态有关,当电沉积时间为90 min时,石墨烯/棉针织复合电极比电容达62.19 F/g,电荷转移电阻为12.08Ω,经过1 000次循环充放电后电容保持率仍然可达89.2%。此外,该电极在弯曲折叠测试中,比电容无明显变化,表现出稳定的电化学性能。     

6σ混料设计优选Li／S一次电池正极组分配比工艺

采用混料实验设计,探讨了Li/S一次电池硫正极各组分的最优配比.响应优化预测结果显示.当m(S):m(SP):m(PVDF)=0.4:0.43:0.17时,电池放电比容量达到454 mAh/g.在此优化比例条件实验验证结果为467 mAh/g.同时,电化学阻抗测试结果显示,最优比例下的阻抗较小.     

造纸助剂与湿部化学讲座（二）造纸湿部化学的基本原理

本文介绍了湿部化学的基本原理,并就湿部化学系统中表面电荷的产生,双电层模型与Zeta-电位,Zeta-电位与细小组分的留着,留着的机理与聚合电解质等内容以及湿部化学的发展趋势进行了述评.     

瓷土悬浮液的动电特性

利用微电泳技术对不同状态下瓷土悬浮液的动电电位进行了测定,以了解其在不同条件下所带电荷情况及其本身的动电特性.实验结果表明,pH值通过改变悬浮液中OH-离子浓度而作用于瓷土Zeta电位,瓷土浓度对Zeta电位影响不大;平均粒径的降低及0～2μm粒子比例的增加明显提高了Zeta电位;分散剂通过形成双电层结构提高了Zeta电位,增强了悬浮液的稳定性,杂粒子的存在及分散剂应用不当同样会降低瓷土悬浮液的Zeta电位.     

zeta电位与纸机网部的助滤、助留作用

一、纸浆体系的zeta电位众所周知,纸浆固体表面均带有电荷(通常是负电荷),带电的表面自然会吸附溶液中的异电离子,在其周围形成由紧密层和扩散层组成的“双电层”结构. 紧密层中的离子与固体表面有较强的吸引力,它们随表面一起运动,组成为一个统一体;在紧密层以外,扩散层中的离子则有较强的热运动,它们对表面的吸引力很弱,在很大程度上其行为不受表面的支配.当固体运动时,紧密层和扩散层之间会产生界面,此界面上的电位被定义为zeta电位。由于紧密层     

Whole cell electrochemistry of electricity-producing microorganisms evidence an adaptation for optimal exocellular electron transport

The mechanism(s) by which electricity-producing microorganisms interact with an electrode is poorly understood. Outer membrane cytochromes and conductive pili are being considered as possible players, but the available information does not concur to a consensus mechanism yet. In this work we demonstrate that Geobacter sulfurreducens cells are able to change the way in which they exchange electrons with an electrode as a response to changes in the applied electrode potential. After several hours of polarization at 0.1 V Ag/AgCl-KCl (saturated), the voltammetric signature of the attached cells showed a single redox pair with a formal redox potential of about -0.08 V as calculated from chronopotentiometric analysis. A similar signal was obtained from cells adapted to 0.4 V. However, new redox couples were detected after conditioning at 0.6 V. A large oxidation process beyond 0.5 V transferring a higher current than that obtained at 0.1 V was found to be associated with two reduction waves at 0.23 and 0.50 V. The apparent equilibrium potential of these new processes was estimated to be at about 0.48 V from programmed current potentiometric results. Importantly, when polarization was lowered again to 0.1 V for 18 additional hours, the signals obtained at 0.6 V were found to greatly diminish in amplitude, whereas those previously found at the lower conditioning potential were recovered. Results clearly show the reversibility of cell adaptation to the electrode potential and pointto the polarization potential as a key variable to optimize energy production from an electricity producing population.     

锂离子电池石墨负极嵌脱锂机理研究

利用循环伏安、交流阻抗等方法考察了石墨电极的嵌脱锂机理.研究结果表明:石墨电极阳极过程的速度控制步骤是锂离子在石墨体相中的扩散步骤,其嵌脱锂过程分别在0.20/0.22 V,0.11/0.14 V,0.08/0.10 V(vs.Li/Li+)处存在3个明显的充放电平台,每个平台为1个两相共存区,可能分别对应3个锂石墨层间化合物的相变过程:LiG2(八阶)LiC36(四阶);LiC36(四阶)LiC12(二阶);LiC12(二阶)LiC6(一阶).     

Synergetic degradation of rhodamine B at a porous ZnWO4 film electrode by combined electro-oxidation and photocatalysis

Synergetic degradation of rhodamine B (RhB) was investigated by combining electro-oxidation and photocatalysis using porous ZnWO4 film at various bias potentials. The applied bias potential below 0.8 V enhanced the photocatalytic degradation of RhB by promoting the separation and transfer of photogenerated holes and electrons. At the potential between 0.8 and 1.0 V, the degradation of RhB was further enhanced, which is induced by direct electro-oxidation and photocatalysis. At the potential greater than 1.3 V, indirect electro-oxidation of RhB occurred with the largest synergetic effect. The synergetic effect can also increase the mineralization degree of the RhB. On the basis of the X-ray photoelectron spectra (XPS) analysis of the surface of the electrode after electrochemical reaction, the electropolymerization occurred which blocked the electrode and slowed the electro-oxidation of RhB. Active species generated via the photocatalytic process can activate the passivated electrode and promote the electro-oxidation of RhB. The O2 electrochemically generated at the anode promoted the photocatalysis by capturing the photogenerated electrons and may induce the formation of H2O2. Thus, more active species could be formed through new reactive routines in the photoelectrocatalytic (PEC) process. RhB degradation was mainlythrough decomposition of the conjugated chromophore structure with slight occurrence of de-ethylation. The stability of the electrode in the PEC process was confirmed based on the XPS and Raman analysis.     

Redox and pH microenvironments within Shewanella oneidensis MR-1 biofilms reveal an electron transfer mechanism

The goal of this research was to quantify the variations in redox potential and pH in Shewanella oneidensis MR-1 biofilms respiring on electrodes. We grew S. oneidensis MR-1 on a graphite electrode, which was used to accept electrons for microbial respiration. We modified well-known redox and pH microelectrodes with a built-in reference electrode so that they could operate near polarized surfaces and quantified the redox potential and pH profiles in these biofilms. In addition, we used a ferri-/ferrocyanide redox system in which electrons were only transferred by mediated electron transfer to explain the observed redox potential profiles in biofilms. We found that regardless of the polarization potential of the biofilm electrode, the redox potential decreased toward the bottom of the biofilm. In a fully redox-mediated control system (ferri-/ferrocyanide redox system), the redox potential increased toward the bottom when the electrode was the electron acceptor. The opposite behavior of redox profiles in biofilms and the redox-controlled system is explained by S. oneidensis MR-1 biofilms not being redox-controlled when they respire on electrodes. The lack of a significant variation in pH implies that there is no proton transfer limitation in S. oneidensis MR-1 biofilms and that redox potential profiles are not caused by pH.     

多壁纳米碳管电极电化学行为的研究

研究了多壁纳米碳管(MWNTs)在碱性电解液中的电化学行为.结果表明:电极集流体结构对其电化学活性有较大影响;循环伏安曲线显示,氢在MWNTs上的电化学反应可逆性随循环次数增加而有一定改善;阴极极化曲线表明了MWNTs不同类型上的氢析出电位有一定差别.认为MWNTs在碱性电解液中氢的电化学反应可逆,氢析出电位与MWNTs类型有关.     

Electrochemical regeneration of activated carbon cloth exhausted with bentazone

The electrochemical regeneration of an activated carbon cloth exhausted with a common herbicide (bentazone) was investigated under different operating conditions. The reversibility of the desorption process was confirmed by monitoring the UV spectra of the solution while cathodic polarization is being applied. Neither nanotextural nor chemical changes are produced in the carbon cloth upon polarization in the absence of the adsorbate. Upon cathodic polarization of a carbon cloth working electrode preloaded with bentazone, negative charges appear on the surface. A partial bentazone desorption results from repulsive electrostatic interactions between the negative charges on the carbon cloth and bentazone. When the electrode potential is below the thermodynamic value for cathodic decomposition of water, hydroxyl ions are liberated. Such ions provoke local pH changes that are responsible of the dissociation of bentazone and carbon surface groups to their anionic form. As a consequence of the pH increase, an almost reversible desorption of bentazone is observed. The effects of several operating parameters on the regeneration efficiency were evaluated. Higher regeneration efficiencies were attained under potentiostatic as compared to galvanostatic conditions, as OH- production strongly depends on the applied potential.     

Photoelectrochemical sensor for the rapid detection of in situ DNA damage induced by enzyme-catalyzed fenton reaction

Photoelectrochemical sensors were developed for the rapid detection of oxidative DNA damage induced by Fe2+ and H2O2 generated in situ by the enzyme glucose oxidase. The sensor is a multilayer film prepared on a tin oxide nanoparticle electrode by layer-by-layer self-assembly and is composed of separate layers of a photoelectrochemical indicator, DNA, and glucose oxidase. The enzyme catalyzes the formation of H2O2 in the presence of glucose, which then reacts with Fe2+ and generates hydroxyl radicals by the Fenton reaction. The radicals attack DNA in the sensor film, mimicking metal toxicity pathways in vivo. The DNA damage is detected by monitoring the change of photocurrent of the indicator. In one sensor configuration, a DNA intercalator, Ru(bpy)2(dppz)2+ (bpy = 2,2'-bipyridine, dppz = dipyrido[3,2-a:2',3'-c]phenazine), was employed as the photoelectrochemical indicator. The damaged DNA on the sensor bound less Ru(bpy)2(dppz)2+ than the intact DNA, resulting in a drop in photocurrent. In another configuration, ruthenium tris(bipyridine) was used as the indicator and was immobilized on the electrode underneath the DNA layer. After oxidative damage, the DNA bases became more accessible to photoelectrochemical oxidation than the intact DNA, producing a rise in photocurrent. Both sensors displayed substantial photocurrent change after incubation in Fe2+/glucose in a time-dependent manner. And the detection limit of the first sensor was less than 50 microM. The results were verified independently by fluorescence and gel electrophoresis experiments. When fully integrated with cell-mimicking components, the photoelectrochemical DNA sensor has the potential to become a rapid, high-throughput, and inexpensive screening tool for chemical genotoxicity.     

Capacitive bioanodes enable renewable energy storage in microbial fuel cells

We developed an integrated system for storage of renewable electricity in a microbial fuel cell (MFC). The system contained a capacitive electrode that was inserted into the anodic compartment of an MFC to form a capacitive bioanode. This capacitive bioanode was compared with a noncapacitive bioanode on the basis of performance and storage capacity. The performance and storage capacity were investigated during polarization curves and charge-discharge experiments. During polarization curves the capacitive electrode reached a maximum current density of 1.02 ± 0.04 A/m(2), whereas the noncapacitive electrode reached a current density output of only 0.79 ± 0.03 A/m(2). During the charge-discharge experiment with 5 min of charging and 20 min of discharging, the capacitive electrode was able to store a total of 22,831 C/m(2), whereas the noncapacitive electrode was only able to store 12,195 C/m(2). Regarding the charge recovery of each electrode, the capacitive electrode was able to recover 52.9% more charge during each charge-discharge experiment compared with the noncapacitive electrode. The capacitive electrode outperformed the noncapacitive electrode throughout each charge-discharge experiment. With a capacitive electrode it is possible to use the MFC simultaneously for production and storage of renewable electricity.     

超低载量贵金属催化氢电极的活性

利用恒流极化方法，求出超低载量贵金属催化氢电极反应的交换电流，并以此来反映其电极活性；同时也选择出氢气体扩散电极催化剂（贵金属）的最佳用量为１．９ｍｇ／ｃｍ￣２．     

Procedure for determining maximum sustainable power generated by microbial fuel cells

Power generated by microbial fuel cells is computed as a product of current passing through an external resistor and voltage drop across this resistor. If the applied resistance is very low, then high instantaneous power generated by the cell is measured, which is not sustainable; the cell cannot deliver that much power for long periods of time. Since using small electrical resistors leads to erroneous assessment of the capabilities of microbial fuel cells, a question arises: what resistor should be used in such measurements? To address this question, we have defined the sustainable power as the steady state of power delivery by a microbial fuel cell under a given set of conditions and the maximum sustainable power as the highest sustainable power that a microbial fuel cell can deliver under a given set of conditions. Selecting the external resistance that is associated with the maximum sustainable power in a microbial fuel cell (MFC) is difficult because the operator has limited influence on the main factors that control power generation: the rate of charge transfer at the current-limiting electrode and the potential established across the fuel cell. The internal electrical resistance of microbial fuel cells varies, and it depends on the operational conditions of the fuel cell. We have designed an empirical procedure to predict the maximum sustainable power that can be generated by a microbial fuel cell operated under a given set of conditions. Following the procedure, we change the external resistors incrementally, in steps of 500 omega every 10, 60, or 180 s and measure the anode potential, the cathode potential, and the cell current. Power generated in the microbial fuel cell that we were using was limited by the anodic current. The anodic potential was used to determine the condition where the maximum sustainable power is obtained. The procedure is simple, microbial fuel cells can be characterized within an hour, and the results of the measurements can serve many purposes, such as: (1) estimating power generation in various MFCs, (2) comparing power generation in MFCs using different electroactive reactants, (3) quantifying the effects of the operational regime on the power generation in MFCs, and finally, (4) the purpose for which the procedure was designed, optimizing the performance of existing MFCs.