High-temperature Reference Electrodes Used in Molten Fluorides

The thermodynamic and dynamic behaviour of Ni^(2+)|Ni couple in FLINAK melt is investigated by us- ing EMF measurement and micropolarization method.The couple shows the Nernstian reversibility and a large exchange current density(6 mA·cm^(-2)).A single crystal LaF_3 which is a fluoride ion conductor used as a membrane of the Ni^(2+)|Ni couple reference electrode is reliable in FLINAK melts at 973 K.The poten- tial of LaF_3 membrane reference electrode is constant within±2 mV.The boron nitride used as a salt bridge was not good in FLINAK melts.The platinum electrode is studied by using micropolarization.The equilibrium potential of Pt electrode is dependent on the absorption and the electrochemical reaction.The potential is stable for a constant composition at constant temperature.

STUDY OF FEASIBILITY OF USING Ag-AgCl ELECTRODE AS REFERENCE ELECTRODE OF THE ISFET

The preparation,principle and measurement results of the complex ISFET withAg-AgCl reference electrode are presented in this paper.Through experiment and theory weendeavor to show the feasibility of using the Ag-AgCl electrode which is without solution contactas reference electrode and the way of overcoming its instability;it gives a rational explanationfor phenomenon of the ion sensitive field effect transistor which does not conform to Nernstianresponse,when we measured cations of Na+, Ca++,etc.with the Ag-AgCl reference electrode.

Enhanced Electrochemical and Physical Properties of Ag/AgCl Planar Reference Electrodesin Potentiometric Sensors by Graphite Oxide Layer

The most common reference electrode (RE) which is used in electrochemical measurements is the Ag/AgCl electrode. In this study, we present a novel solid-state Ag/AgCl planar electrode that was coated with a thin layer of Graphite Oxide (GO) as a protective layer. The Ag/AgCl planar electrode was fabricated by using the photolithography and lift-off method combined with the Ag[NH3]2Cl complex. The GO was produced by Hummer’s method and was deposited on top of the Ag/AgCl layer by drop-casting method. The layers of the fabricated reference electrode were characterized by micro Raman spectroscopy, Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). The responding time of the planar electrode was short and the signal was more stable in comparison to the plainAg/AgCl electrode. The Open Circuit Potential (OCP) measurement with the fabricated electrode as the RE and the platinum electrode as the working electrode in electrolyte solutions which had various pH values was performed with a linear response in pH ranges from pH 5 to pH 8 and the linear correlation coefficient (R^2 = 0.9899). Moreover, the coating of the GO layers also enhanced the durability of the modified electrode. The results showed that the modified Ag/AgCl electrode with a thin layer GO as the protective layer could be used as plana REs for the potentiometric sensors.

Solid Reference Electrode of Metallurgical Oxygen Sensor

The thermal equilibrium state of the reference electrode was investigated. The results show that the temperature difference between the inside and the outside of zirconia tube was very small and the Seebeck effect can be ignored after the sensor was dipped into liquid steel for more than 2 s. A special sensor was designed to test the relation between the EMF （electromotive force） of sensor and the thermal equilibrium state of the reference elec- trode. Based on these results, it is suggested that the peak in EMF curve was caused by the change of oxygen potential in reference electrode before the thermal equilibrium was reached. If NiO was added by 2 M- 5 M to the Cr/Cr2O3 reference electrode, the peak in EMF curve could be eliminated.

Preparation and Properties of Embeddable Ag/Ag Cl Gelling Reference Electrode for Rebars Corrosion Monitoring in Concrete

Reference electrodes are a key part for corrosion monitoring and measurement of rebars in concrete. A reference electrode that can be buried in concrete is fabricated by using Ag/Ag Cl electrode and methyl cellulose gelling electrolyte. The stability, repeatability and anti-polarization of the reference electrode are investigated; the influences of the inner electrolyte loss, exterior OH- contamination, and temperature on the potential of the reference electrode are also investigated in this paper. The results show that the reference electrode has good stability, repeatability, and antipolarization. The influences of inner electrolyte loss, exterior OH- contamination, and temperature on the potential of the reference electrode are minimal. Therefore, it can be used for corrosion monitoring and measurement of rebars in concrete.

A Reliable Reference Electrode in Molten Carbonate and Its Applications

A Ag|AgCl reference electrode which can be used in molten carbonate media has been described in this paper.It consists of a silver wire immersed in a solution of AgCl(1mol%) in (Li 0.62 ,K 0.38 ) 2CO 3,with a zirconia junction.The main properties of reference electrode,such as reproducibility ,stability and reversibility, were checked.The results have demonstrated that the reference electrode is reliable.With such reference electrode catalysis of various electrode materials to oxygen reduction in molten alkali carbonate media was investigated.It is found that as catalysts for oxygen reduction oxidized nickel niobium alloy is superior to nickel oxide.

Study on the High Conductive Polymer as the Miniaturized Reference Electrode

The polypyrrole is the high conductive polymer which was coated onto indium tin oxide (ITO) glass substrate by electroplated technique to fabricate a miniaturized reference electrode.Besides,the morphology of the ITO glass reference electrode electroplated with pyrrole has been studied through the instrumental analysis utilizing cyclic voltammetry (CV). Furthermore,the sensing characteristics of the reference electrode have been measured by using commercial instrumental amplifier as the readout circuit.Using the high conductive polymer as miniaturized reference electrode has many advantages such as easy fabrication of coating polymer,without any expensive fabricating equipment,easy carry by the miniaturized technique.Hence,it is suitable for the reference electrode production.

Preparation of Ti/MnO_2 Reference Electrode and Its Application in Concrete Structures

A novel Ti/MnO2 reference electrode (TMRE) used for concrete environment was fabricated by the electro-deposition method and encapsulated carefully.The properties of the electrode were characterized by open-circuit potential,potentiodynamic polarization behavior in synthetic concrete pore solutions and electrochemical performance in cement mortar.The experimental results indicate that the TMRE shows good stability with and without the addition of Cl-ions and desirable polarization behavior in synthetic pore solution.Results of tests in cement mortar indicate that the potential of TMRE will be stable after about 7 days.The stability and desirable polarization behavior make it a promising reference electrode for concrete environment.

Electrochemical study of different membrane materials for the fabrication of stable,reproducible and reusable reference electrode

Fabrication of stable,reproducible and reusable reference electrodes for low energy and high-temperature steam splitting is of great interest for hydrogen fuel production without anthropogenic carbon dioxide(CO2)emission.This study has been conducted for the detection of suitable material for the fabrication of novel reference electrode.In the present scenario,this research is designed to fabricate a novel nickel reference electrode by using operating conditions of eutectic molten hydroxide(NaOH-KOH,49-51 mol%)at temperature 300℃in an ion-conducting membrane of alumina and mullite tube.Afterwards,the designed nickel reference electrode has been examined for its reusability and stability by using electrochemical technique and cyclic voltammetry.Five scans of cyclic voltammetry are performed for both membrane fabricated reference electrode.A slight positive shift in oxidation peaks is observed for mullite membrane electrode(64 mV from scan 1 to 5).The stability measurements are noted by changing the scan rate between 50 and 150 mV s−1.Furthermore,the results show that the Ni/Ni(OH)2 reference electrode covered with a mullite membrane is stable and reusable at 300℃temperature without any deterioration.The stability and reusability of prepared nickel reference electrode covered by mullite tube in the eutectic molten hydroxide were up to 9 days to carry out an electrochemical investigation,while for alumina tube reference electrode the stability and reliability were up to 3 days.The internal electrolytic material and ionic conductance can play an important role for future studies with this reference electrode along with optimisation of temperature and scan rate parameters.

Parameter-independent error correction for potential measurements by reference electrode in lithium-ion batteries

The safety monitoring of lithium-ion batteries(LIBs) is of great significance for realizing all-climate and full-lifespan battery management. In-situ measurement of anode potential with implanted reference electrodes(REs) has proven to be effective to monitor and avoid the occurrence of severe side reactions like Li plating to ensure the safe and fast charging. However, the intrinsic measurement errors caused by local blocking effects, which also can be referred to as potential artefacts, are seldom taken into consideration in existing studies, yet they highly dominate the correctness of conclusions inferred from REs. In this study, aiming at exploring the physical origin of the measurement errors and ensure reliable potential monitoring, electrochemical and post-mortem tests are conducted using commercial pouch cells with implanted REs. Corresponding electrochemical model which describes the blocking effects, is established to validate the abnormal absence of lithium plating that predicted by measured anode potentials under various charging rates. Theoretical derivation is further presented to explain the error sources, which can be attributed to increased local liquid potential of the RE position. Most importantly, with the guidance of error analysis, a novel parameter-independent error correction method for RE measurements is proposed for the first time, which is proven to be adequate to estimate the real anode potentials and deduce the critical C-rate of Li plating with extra safety margin. After error correction, the resulting critical C-rates are all within the range of 0.55 ± 0.03 C, which is close to the C-rate of 0.6–0.7 C obtained from experiments. In addition, this error correction method can be performed conveniently with only some simple RE measurements of polarization voltages, totally independent of battery electrochemical and geometric parameters. This study provides highly practical error correction method for RE measurements in real LIBs, substantially facilitating the fast diagnosis and safety evaluation of Li plating during charging of LIBs.

聚多巴胺修饰的Ag/AgCl参比电极的制备及其性能试验

为了适应栽培基质等非均相体系pH值的在线检测,并提供稳定的参考电位,采用磁控溅射沉积银膜、NaClO溶液氯化获得的AgCl层和多巴胺沉积修饰膜,研制了聚多巴胺修饰的Ag/AgCl固体薄膜参比电极,并在沉积时间分别为4、8、12、16 h时,对聚多巴胺修饰的参比电极在磷酸缓冲盐溶液(phosphate buffered saline,PBS)中的稳定性、可逆性和循环伏安特性曲线进行了对比测试.结果表明:参比电极在PBS溶液中电位标准差均约为1.00 mV,在不同pH缓冲溶液中均能够恢复到相对稳定的电位,且偏差小于5.00 mV,具有良好的可逆性;在50次循环伏安试验中电位漂移很小;根据参比电极的氯离子灵敏度为2.00~2.50 mV/pCl,聚多巴胺修饰的参比电极对氯离子浓度不敏感,证实聚多巴胺修饰的参比电极可以用作参比电极;沉积时间为12 h时的参比电极在各项试验中综合性能表现最优,应用试验表明该参比电极更适用于开展栽培基质pH检测.

基于参比电极的析锂电池安全充电控制

电池系统是支撑下一代新型电网的关键,然而不合理的充放电策略会使电池发生析锂副反应,导致电池充放电性能大幅减弱。因此,文中针对三元锂离子电池,基于参比电极揭示了析锂后电池的充电性能变化情况,并对其安全充电电流进行控制。首先,设计不同温度下的充放电循环实验,得到低温循环与高温循环后的电池;其次,通过植入参比电极标定安全充电曲线对比电池的负极电位,发现高温循环后的电池发生了析锂,且平均充电电流相比新电池降低了61.7%;最后,对析锂后的电池建立安全充电荷电状态-温度-电流等高线图,对比新电池等高线图后发现,200 A以上的充电电流区域减少了69.84%。文中提供了一个析锂后电池充电性能衰减的量化指标,需要在实际的锂离子电池全寿命周期管理中予以考虑。

涂敷法制备Ag-AgCl参比电极及其性能

目前制备Ag-AgCl参比电极的方法复杂,电极性能也不稳定。首次用涂敷法制备了Ag-AgCl参比电极:分别以水溶性的丙烯酸乳液和乙烯-聚醋酸乙烯乳液作为粘合剂,将AgCl微粒粘结在Ag电极表面制成Ag-AgCl参比电极。结果表明:2种Ag-AgCl参比电极的稳定性良好,使用寿命较长,均能满足使用要求;其中,以乙烯-聚醋酸乙烯乳液为粘合剂制成的Ag-AgCl电极的温度系数更小、使用寿命更长、稳定性更好。

锂电池用参比电极的设计与应用

参比电极对于解析高安全、高性能锂电池内部物理化学过程具有重要意义。然而在科学研究及产品开发中,可靠参比电极的实际构建和集成仍具有挑战性。本文首先阐明锂电池用参比电极的原理和特性,进而梳理基本设计参数,包括活性材料选择、几何尺寸、制备工艺和检测设置。然后介绍了引入参比电极的三电极体系在锂电池工作/失效机制分析方面的应用实例。最后展望了开发和部署锂电池用参比电极的挑战和发展方向。

基于改进点源扩散模型的电极极差电位研究

本文建立点源扩散模型,研究了电极电位的变化规律,将圆柱体Ag/AgCl电极等效为点源模型,通过Fick定律建立Cl-浓度扩散方程,利用0阶贝塞尔函数得到了浓度与时间、距离的函数关系,通过浓度依赖动力学方程建立浓度、温度与电极电位的表达式,利用数值计算分析了不同浓度、温度、时间对电极电位的影响,并与传统的互补误差函数模型作对比,在点源扩散模型的基础上,将氯离子扩散系数视为变量的同时,引入其对时间、温度的影响。利用数值计算分析了不同浓度、温度、时间对电极电位的影响,结果表明:改进的点源模型所推导的极差电位精度更高。

Electrochemical Performance of High Purity Zinc and Zn-Al-Cd Alloy as Reference Electrodes

The effects of Cl-concentration,temperature,pH,flow velocity,soluble oxygen content of seawater and anodic current on the potential of high purity zinc and Zn-Al-Cd reference electrodes were investigated. The results show that the investigated metal materials are liable to establish stable potential and act as reference electrodes in seawater,diluted seawater and urban tap water. Cl-concentration,temperature,seawater flow velocity and anodic current have an obvious effect on zinc potentials. However,seawater pH has no obvious effect on zinc potentials.

基于原位参比的氧化亚硅--石墨复合负极循环衰减机制

为了研究氧化亚硅和石墨在复合应用时的循环衰减机制,本工作通过在循环过程中增加小电流可逆容量标定,消除了电压极化对衰减行为的影响。通过在软包装电池内部预先埋入参比电极,对比不同循环次数时正极和负极的电化学特征变化,利用负极微分曲线解析氧化亚硅和石墨的去锂化容量演变过程和衰减程度。同时,结合交流阻抗谱(EIS)、扫描电子显微技术(SEM)、元素能谱(EDS)和等离子体发射光谱(ICP)等测试。结果表明,造成电池循环衰减的主要原因是活性锂损失和氧化亚硅衰减,两者造成的容量损失分别为0.45 Ah和0.36 Ah。负极衰减速率明显快于正极,循环600次后,负极中石墨和氧化亚硅的衰减程度分别为2.2%和30.3%。电池在循环过程中产生了新的界面阻抗,所有动力学阻抗参数呈逐渐增大的趋势。拆解电池发现,循环后负极发生了严重的体积膨胀和副反应,导致锂损失在负极并失活,引起界面阻抗的增长和电池容量的衰减。本研究可以无损定量识别氧化亚硅和石墨在循环过程中的衰减程度,为含硅复合负极的工程化应用提供了研究基础。

基于RSM的土壤原位测量参比电极制备优化与评估

农用电化学原位监测Ag/AgCl参比电极存在氯离子泄漏风险,探讨通过新型液态金属纳米纤维复合毡改进柔性参比电极稳定性,利用响应面分析方法(RSM)确定材料制备工艺对参比电极稳定性的影响趋势,获取优化方案并进行可行性验证。试验结果表明,液态金属纳米纤维复合毡制备主影响因素包括纺丝收集距离、纺丝混液质量配比和拉伸次数,影响程度依次降低;收集距离和拉伸次数对参比电极稳定性的耦合作用显著;当制备参数方案为质量比为1∶5、收集距离为19 cm、拉伸次数为1150次时,参比电极稳定性最优,平均相对误差不大于4.4%;自制柔性Ag/AgCl参比电极,将其应用于土柱硝态氮和pH值监测原位测量,16 d的连续监测过程中硝态氮与pH值测试数据与离线商用电极测量值的绝对误差、相对误差和均方根误差分别小于5.55 mg/L、7.2%、1.98 mg/L和0.21、2.8%、0.17,参比电极持续提供稳定参考基准,保障了两工作电极与外检数据间良好的一致性,证明了自制Ag/AgCl参比电极在土壤农化分析中的可行性。

锂离子电池用参比电极的研究进展

参比电极广泛应用于锂离子电池的性能评测中。综述锂离子电池参比电极常用材料,如金属锂、二元锂合金和含锂化合物等,以及常用制作方法,介绍参比电极在锂离子电池老化机理研究、电极电位监测和电极阻抗谱分析等方面的应用,并总结参比电极的形状优化、位置优化等优化手段,对今后的研究方向进行讨论。

实海环境下钢壳混凝土结构局部电位监测与参比电极稳定性研究

目的确定高纯锌、钛以及铂等3种参比电极在不同工况下的稳定性差异,以及不同参比电极针对沉管的最佳使用位置。方法以银/氯化银参比电极的监测电位数据为钢壳的实际电位基准,通过在不同区域设计安装电位传感器,持续监测沉管不同区域的钢壳电位,以及9个多月的波动情况。结果高纯锌参比电极所监测数据的变化趋势与钢壳实际电位数据接近,且环境介质的改变对其监测电位数值的影响不大,电位数据波动小。铂和钛参比电极在钢壳底面海泥/抛石耦合的服役环境下,其监测电位数据稳定,但是二者在海水中监测电位时,对环境介质中的溶解氧浓度、金属离子等氧化性介质较为敏感,极易受到氧化性介质的影响,导致测得的电位偏移剧烈。结论高纯锌参比电极更适合应用于沉管侧面阴极保护电位的长期监测,铂和钛参比电极更适用于钢壳底部保护电位的长期测量。