ZrO2(f)-NiFe2O4惰性阳极在冰晶石熔盐中的腐蚀行为

以NiO和Fe2O3为原料,采用固相烧结法合成了NiFe2O4尖晶石,通过添加ZrO2纤维[ZrO2(f)]制备了ZrO2(f)-NiFe2O4惰性阳极材料. 采用失重法测量了阳极试样在冰晶石熔盐中的静态热腐蚀率和电解腐蚀率,并对腐蚀机理进行了探讨. 结果表明,ZrO2(f)添加量由0增加至4%(w)时,阳极试样的气孔率从4.9%上升到5.8%,导致其静态热腐蚀率由3.8 mg/(cm2×h)增大到4.3 mg/(cm2×h);在电场作用下,氧化物在冰晶石熔盐中的溶解反应受到抑制,含3%(w) ZrO2(f)阳极试样的电解腐蚀率为2.2 mg/(cm2×h),远小于其静态腐蚀率,腐蚀均为物理化学溶解过程;高温下ZrO2(f)在冰晶石熔盐中稳定性良好,可作为铝电解NiFe2O4基惰性阳极的强韧化材料.     

不同金属氧化物阳极上甲基橙的电化学氧化降解

分别以Ti/SnO2+Sb2O3和Ti/SnO2+Sb2O3/PbO2电极为阳极进行甲基橙的电化学氧化,研究了两种金属氧化物阳极上甲基橙氧化降解过程的反应速率、电流效率及COD的变化.结果表明,两种金属氧化物阳极都能有效氧化降解甲基橙,氧化反应符合一级反应动力学规律,在Ti/SnO2+Sb2O3和Ti/SnO2+Sb2O3/PbO2电极上甲基橙氧化降解过程的表观速率常数分别为0.148和2.43×10-2 min-1. 以Ti/SnO2+Sb2O3为阳极电解30 min,甲基橙的浓度从初始时的0.305 mmol/L降至4.89×10-3 mmol/L,甲基橙的转化率达98.4%;在Ti/SnO2+Sb2O3/PbO2电极上,相同电解时间下甲基橙的浓度只降至0.14 mmol/L,转化率为55.0%. 对不同电极上甲基橙电化学氧化过程电流效率的研究表明,Ti/SnO2+Sb2O3电极的电流效率明显高于Ti/SnO2+Sb2O3/PbO2电极. Ti/SnO2+Sb2O3电极的反应速率大、电流效率高主要源于其较高的析氧电位.     

A self‐repairing cermet anode: Preparation and corrosion behavior of (Cu–Ni–Fe)/NiFe2O4 cermet with synergistic action

In this paper, the cermet (Cu–Ni–Fe)/(NiFe₂O₄–10NiO) anodes were prepared through the powder metallurgy method, followed by being evaluated in the bench scale (200 A) electrolysis tests for more than 1000 hour. The results showed that the as‐prepared anodes exhibited excellent corrosion resistance with corrosion rate less than 0.99 cm/a, which satisfied the requirements of the aluminum industry. The analysis results were confirmed by SEM, EDS, and XRD. The results showed that the outstanding corrosion resistance of the anodes relied on a continuous and dense NiFe₂O₄ film formed on the surface of the anode material, which protected the inner structure of anode material during electrolysis. Finally, a model based on the synergistic action between the metal phase and the ceramic phase was built to illustrate the forming mechanism of the NiFe₂O₄ passivating film.     

不同金属氧化物阳极组合降解苯酚过程比较分析

钛基氧化铱电极为代表的活性阳极析氧过电位低,钛基氧化铅电极为代表的非活性电极析氧过电位高。以钢板为阴极,选取了Ti/Ir-RuO_x作为单一阳极类型和Ti/Ir-RuOx_Ti/PbO_2作为双阳极类型,对比处理苯酚模拟废水的效果,从电流密度、pH值、苯酚模拟废水初始浓度和电解质类型4个方面来比较对苯酚处理效果的影响。实验表明,在电流密度为10 mA/cm~2、pH为7、苯酚模拟废水初始浓度为100 mg/L和加入少量NaCl为电解质的条件下,双阳极类型组合对苯酚模拟废水的处理效果要好于单阳极,去除率达到98%。     

碳纤维阳极构造对微生物燃料电池性能的影响

微生物燃料电池（MFCs）阳极性能受生物膜的影响,而生物膜则直接与阳极表面积有关。以不同长度和数量的碳纤维丝作为阳极,研究了阳极构造和表面积对MFC输出功率的影响。当阳极为单根长度为1 cm碳纤维丝时,MFC产生的最大功率密度最高,为10.50 W·m^-2,随着碳纤维丝长度逐渐增加（2～14 cm）,MFC产生的最大功率显著下降。以多根的长度为2 cm碳纤维丝构成阳极时,MFC的功率与根数（1～4 根）呈正比,当采用4根2 cm纤维丝时,MFC的最大功率密度为2.92 W·m^-2,该数值为单根8 cm碳纤维丝的2.78倍。观察碳纤维丝长度方向上的生物膜的分布表明：受碳纤维欧姆电阻的影响,在碳纤维丝电流引出端附近的生物量明显大于碳纤维其他地方,这说明：增加纤维丝长度虽可提高阳极的表面积,但并不能提高阳极的产电性能。     

三维锂金属负极的研究进展

金属锂具有高的理论比容量（3 860 mAh·g^-1）,低的电极电位（-3.04 V与标准氢电极相比）和低的密度（0.53 g·cm^-3）,是最有前途的锂二次电池用的负极材料。但仍存在循环过程中枝晶生长及其导致的低库伦效率、短循环寿命等问题。而3D锂金属负极因具有高比表面积和内部空腔能有效缓解上述问题。特别是纳米技术的发展为3D锂金属负极提供了更高效的形貌与结构。基于金属基和碳基3D锂金属负极对三维锂金属负极的设计及研究进展进行了详细的概述。     

GO/PEDOT复合材料修饰阳极的制备及其在MFC中的应用

微生物燃料电池（MFC）是一种利用微生物将有机物中的化学能直接转化成电能的装置,通过改善阳极特性可以有效提高微生物燃料电池的产电性能。通过恒电流法电沉积制备了氧化石墨烯/聚3,4-乙烯二氧噻吩（GO/PEDOT）复合材料修饰碳毡（CF）阳极。通过循环伏安法和交流阻抗法考察了电极特性。将其应用到微生物燃料电池中,对其产电性能进行评价。结果表明,GO/PEDOT-CF电极具有较大的比表面积和优良的电化学性能;以GO/PEDOT-CF为阳极的微生物燃料电池,产电性能良好,其最大功率密度和最大电流密度达到1.138 W·m^-2和4.714 A·m^-2,分别是未修饰阳极的4.80倍和5.51倍。因此,GO/PEDOT复合材料是一种优良的阳极修饰材料,可有效提高MFC的产电性能。     

Electrowinning of gadolinium metal below 1000°C. An introductory investigation

Gadolinium was recovered as dendrites by electrolysis of Gd₂O₃ dissolved in molten LiF-GdF₃ (65-35 mol%) at 850–900°C. Both inert anodes (noble metals) and graphite anode were used. With a platinum anode, anodic corrosion began at current densities (cd) of about 9 A dm^?2. Below this cd the platinum appears to be passivated, and no platinum was detected in the electrowon gadolinium. Electrolysis with graphite anode resulted in carbon contamination of about 0.14 wt% of the gadolinium metal. The electrowon metal contained 100–500 wt ppm oxygen, depending on the oxide concentration in the electrolyte.     

Cr(III) oxidation with lead dioxide-based anodes

A procedure for preparing PbO₂-based electrodes with a titanium substrate is proposed. A platinum underlayer is first deposited on Ti by metal organic chemical vapor deposition (MOCVD), followed by the electrodeposition of the PbO₂ layer. The prepared Ti/Pt/PbO₂ anodes were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) before being used for oxidation of Cr(III) in sulphuric acid. The current efficiency was determined for that electrodes and the results were compared with those obtained with Pb/PbO₂ and Ebonex^®/PbO₂ electrodes with different pH conditions. The Ti/Pt/PbO₂ were found to have a very good electrochemical behaviour (current efficiency: φ=0.93 for pH 2), and may be used as dimensionally stable anodes for the oxidation of Cr(III).     

NiFe2O4隋性阳极的制备及其电解腐蚀机理

以Fe2O3和NiO为主要原料，添加2％（按质量计）MnO2，采用固相烧结工艺制备了NiFe2O4惰性阳极。用X射线衍射和扫描电子显微镜对材料的组成和微观结构进行了研究，测量了样品在冰晶石熔盐中不同电流密度下的电解腐蚀速率，并对其腐蚀机理作了初步探讨。结果表明：惰性阳极由NiO和NiFe2O4尖晶石两相组成，MnO2作为固溶体在尖晶石晶界处富集。电解腐蚀呈现出物理化学溶解过程，熔盐对试样的电解腐蚀首先要在晶界处发生反应生成更稳定的FeAl2O4相，而FeAl2O4相结构致密，冰晶石熔盐通过该相向NiFe2O4尖晶石晶粒内扩散速度减慢，从而降低了腐蚀速率。     

Ti/SnO2+Sb2O3/PbO2电极在硫酸溶液中Cr3+氧化的电化学性能

对用聚合前驱体溶液通过热分解法制备的Ti/SnO2+Sb2O3/PbO2电极在硫酸溶液中Cr3+电化学氧化的电化学性能进行了研究. 分别测定了以Ti/SnO2+Sb2O3/PbO2和PbO2为阳极，硫酸介质中Cr3+电化学氧化过程的极化曲线、抗腐蚀性以及不同操作电流密度、Cr3+浓度、反应温度、硫酸浓度下的电流效率. 实验结果表明，聚合前驱体溶液通过热分解法制备的Ti/SnO2+Sb2O3/PbO2电极与PbO2电极相比具有更高的电催化活性和抗腐蚀性.     

Nickel ferrite as inert anodes in aluminium electrolysis: Part II Material performance and long-term testing

The behaviour of three different compositions based on nickel ferrite–nickel oxide–copper cermets was investigated as anode materials in laboratory electrolysis tests for 50h in a conventional cryolite-based electrolyte. The corrosion of the anodes was assumed to be mass transfer controlled and the transfer of impurities into the electrolyte and subsequently into the cathodically deposited metal was studied. The results indicate that the materials corroded in a controlled manner. Mass transfer coefficients of species from the anode to the electrolyte were of the order of 10–4ms–1 while the mass transfer coefficients for transfer of the species from the electrolyte into the deposited metal were of the order of 10–6ms–1. Nickel exhibited significantly lower mass transfer coefficients than those of iron and copper. The extrapolated corrosion rates of the anode ranged 1.2–2.0 cm year–1, which is acceptable from an industrial perspective. The contamination of the deposited aluminium with respect to Ni and Cu was, however, too high to meet current specifications for commercial grade metal. Post-electrolysis examination of the anodes showed that a reaction layer of approximately 50m thickness was formed on the anodes. This layer did not contain any metal grains and seemed to prevent preferential corrosion of the metal phase in the underlying cermet.     

钛-二氧化铅阳极电解次磷酸钠制备高纯次磷酸

以六室电解槽为反应槽,分别以石墨电极、钛-二氧化铅电极和钛涂钌电极为阳极,不锈钢为阴极电极,研究了电解法制备成本低、纯度高且环境友好的次磷酸新工艺。结果表明：六室电解槽制得的次磷酸杂质少;与国内外常用石墨和钛涂钌阳极材料相比,钛-二氧化铅电极作为阳极材料在阳极电位、产品浓度及产品室电流效率方面性能优良。钛-二氧化铅电极没有固体沉淀,无其他杂质离子产生,阳极液不必更换,只需定期补充电解消耗的水,属于清洁生产。在最佳电解电流、电解温度、原料浓度和电解时间条件下制得次磷酸产品,经减压富集后其杂质含量能够满足电容器生产的要求。     

The electrodeposition of zinc from acidified zinc sulphate solution

In the electrodeposition of zinc from acidified zinc sulphate solutions the loss in current efficiency (CE) due to evolution of hydrogen at the cathode has often been attributed to the presence of metal impurities, and it has been thought that in a pure solution the CE would be 100%. In this paper it is argued that, whatever the degree of purity achieved, hydrogen must always be produced simultaneously with zinc. At the start of electrolysis the CE is determined solely by the zinc/acid ratio, but when impurities are present the CE falls progressively as electrodeposition proceeds. Further, colloid silica which is always present in plant solutions is not responsible for the CE falling below 100%, nor are the lead anodes that are used in practice. Some effects of manganese, both at the anode and the cathode, are reported. The deleterious influences of cobalt and manganese together are also discussed.     

Electrochemical removal of antibiotics from wastewaters

Electro-oxidation tests with different anodes (Ti/Pt, DSA^® type, graphite and three-dimensional (3D) electrode made of a fixed bed of activated carbon pellets) were performed on aqueous solutions containing the antibiotics Ofloxacin and Lincomycin. The effectiveness of the treatment of wastewater containing pharmaceuticals was assessed, as well as the electro-oxidation mechanism.

The use of high electrode potentials (>2.8 V versus NHE) ensured either significant anodic surface activation or minimization of fouling by in situ generated polymeric material. The use of a membrane-divided cell showed positive aspects in terms of molecule demolition, and average power consumption. The electro-oxidation was found to occur with first order kinetics mainly at anode surface when using Na₂SO₄ at low concentration (0.02N). Under these conditions, Ofloxacin is efficiently oxidized over all tested anodes (e.g. 50 mgcm⁻² A⁻¹ h⁻¹ for the bi-dimensional Ti/Pt electrode), whereas Lincomycin is oxidized with slow overall kinetics mainly due to difficult deprotonation, a step that precedes the primary electron transfer stage of the oxidation process. The three-dimensional electrode would be the most appropriate for continuous industrial-scale process. However, at the used potential, unacceptable corrosion of the carbon based electrode was noticed.     

Effect of CeO2 and graphite powder on the electrochemical performance of Ti/PbO2 anode for zinc electrowinning

In the zinc hydrometallurgy process, the key to reduce the voltage of the corrosion is to reduce the oxygen evolution potential of the anode. In this experiment, the effects of doped CeO₂ and graphite powder (GP) on the electrochemical properties of Ti/PbO₂ were investigated. Ti/PbO₂, Ti/PbO₂-CeO₂, Ti/PbO₂-GP and Ti/PbO₂-CeO₂-GP anode were prepared by direct current (DC) plating. The surface morphology and composition of these different Ti/PbO₂ electrodes before and after polarisation were analysed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion mechanism was analysed by linear sweep voltammetry (LSV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The cell voltage, current efficiency, service life and failure mechanism of Ti/PbO₂ anodes were observed and analysed by simulating electrowinning experiments. The results show that Ti/PbO₂-CeO₂-GP anodes is denser than other electrodes. Ti/PbO₂-CeO₂ (12?g/L)-GP (8?g/L) with the lowest anode potential is 1.5390?V. The potential of the lowest oxygen evolution peak of the Ti/PbO₂-CeO₂ (12?g/L)-GP (8?g/L) electrode is 0.824?V. The Ti/PbO₂-CeO₂-GP anode had a minimum cell voltage of 2.85?V and a current efficiency of 95.8%. The Ti/PbO₂-CeO₂-GP has a minimum corrosion rate of ??0.0320?g·A^?1·h^?1 and a longest anode lifetime of up to 127?h. The best electrode for the surface coating is Ti/PbO₂-CeO₂ (12?g/L)-GP (8?g/L).     

Electrolytic production of NF3 with a LiNiO2 coated nickel sheet anode prepared by atmospheric plasma spraying technique

A nickel sheet coated with LiNiO₂ powder having average particle sizes of 40 and 50 μm in diameter by atmospheric plasma spraying technique was employed as the anode for electrolytic production of NF₃. In electrolysis of a molten NH₄F·2HF at 100 °C and 25 mA cm⁻², the anode gas generated at the LiNiO₂ coated Ni sheet anode was composed of N₂, O₂, NF₃, N₂F₂, N₂F₄, and N₂O, and its composition was almost the same as that at the Ni sheet anode. The current efficiency for the NF₃ formation on the LiNiO₂ coated Ni sheet anode was increased to reach the constant value of ca. 55% during electrolysis for 100 h, and it was almost the same as that on the Ni sheet anode. The anode consumption of the LiNiO₂ coated Ni sheet was small compared with that of the Ni sheet. Also, the oxygen content in the oxidized layer formed on the LiNiO₂ coated Ni sheet anode was high compared with that on the Ni sheet anode, and the surface of the LiNiO₂ coated Ni sheet anode was covered with a compact and adhesive film having some defects. Although the bottom of the hollow was covered with a thinner layer, no pore penetrated through the oxidized layer. Hence, the LiNiO₂ coated Ni sheet anode is favorable for the electrolytic production of NF₃, and the oxidized layer on the LiNiO₂ coated Ni sheet anode has the higher resistance to corrosion, because of the compact and adhesive film containing the higher content of oxygen formed on the anode.     

Copper anode corrosion affects power generation in microbial fuel cells

Non‐corrosive, carbon‐based materials are usually used as anodes in microbial fuel cells (MFCs). In some cases, however, metals have been used that can corrode (e.g. copper) or that are corrosion resistant (e.g. stainless steel, SS). Corrosion could increase current through galvanic (abiotic) current production or by increasing exposed surface area, or decrease current due to generation of toxic products from corrosion. In order to directly examine the effects of using corrodible metal anodes, MFCs with Cu were compared with reactors using SS and carbon cloth anodes. MFCs with Cu anodes initially showed high current generation similar to abiotic controls, but subsequently they produced little power (2 mW m^‐2). Higher power was produced with microbes using SS (12 mW m^‐2) or carbon cloth (880 mW m^‐2) anodes, with no power generated by abiotic controls. These results demonstrate that copper is an unsuitable anode material, due to corrosion and likely copper toxicity to microorganisms. © 2013 Society of Chemical Industry     

Methanol reformate treatment in a PEM fuel cell-reactor

The treatment of methanol reformate, containing up to 2500 ppm CO, by the anode of a PEM fuel cell, operating as a preferential oxidation (PROX) reactor, was investigated in order to examine the possibility of electrochemically promoting the water–gas-shift (WGS) reaction and thus making the gas mixture suitable for anodic oxidation. It was found that the electrochemical promotion effect plays a significant role in a normal fuel cell operation (air at the cathode) but not in a hydrogen pumping operation (H₂ at the cathode). This implies that the role of oxygen crossover in the electropromotion (EP) of the WGS reaction and in the CO oxidation is vital. During fuel cell operation, the increase in the rate of CO consumption over a Pt/C anode is 2.5 times larger than the electrochemical rate, I/2F of CO consumption, while for oxygen bleeding conditions (fuel mixture + 1% O₂ at the anode) the increase is up to five times larger than I/2F, i.e. the Faradaic efficiency is up to 5. This shows that the catalytic properties of the Pt anode are significantly modified by varying catalyst potential and by the extent of O₂ crossover.

The effect of temperature, gas composition, membrane thickness and Pt anode alloying with Cu was studied. It was found that the rate of CO consumption is significantly enhanced by increasing T, p_H2 and increasing O₂ crossover rate. Also the Faradaic efficiency reaches even higher values (up to 9) when using PtCu/C anodes. However, the Faradaic efficiency drops in general below 100% at high current densities and CO conversion levels.     

Electrochemical noise studies of the corrosion behaviour of lead anodes during zinc electrowinning maintenance

Following anodic polarisation of lead anodes with different silver contents (0.5-0.7%) during Zn electrowinning, the discharge and corrosion of lead anode during the decay period at open circuit potential in sulphuric acid bath have been studied by electrochemical noise analysis (ENA) method. Potential and current decay behaviour over 16 h shows 4 and 2 main characteristic regions, respectively. The wavelet transform has been employed to analyse the ENA data. The results of wavelets have demonstrated that energy distribution plot “EDP” was a powerful tool to provide useful information about the dominant process for different discharge and corrosion stages and mechanisms. The discharge is predominant than corrosion for all anodes for the regions I, II and III, and ENA feature of events changes from large timescale to low timescale, diffusion control or exfoliation to metastable pitting and pit growth, respectively. Region IV, only observed for 0.6% and 0.7%Ag, corresponds to general and metastable pitting corrosion under diffusion control. It has been found that anode containing lower silver content have more corrosion products even after 16 h of decay (discharge and attack dominated by pitting corrosion type with the highest corrosion due to the longest period of pitting during the 16 h).