钌镧氧化物涂层析氯反应动力学比较研究

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龙萍, 许立坤, 崔秀芳, 金国. 钌镧氧化物涂层析氯反应动力学比较研究. 无机材料学报, 2015, 30(5): 493-499
LONG Ping, XU Li-Kun, CUI Xiu-Fang, JIN Guo. Comparative Study on Kinetics of Chlorine Evolution Reaction for Ru-La-O Oxide Coatings. Journal of lnorganic Materials,2015, 30(5): 493-499 复制到剪切板

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钌镧氧化物涂层析氯反应动力学比较研究

龙萍^1,², 许立坤², 崔秀芳¹, 金国¹

1. 哈尔滨工程大学超轻材料与表面技术教育部重点实验室, 哈尔滨 150001

2. 中国船舶重工集团公司第七二五研究所, 海洋腐蚀与防护重点实验室, 青岛 266071

金国, 教授. E-mail: jinguo@hrbeu.edu.cn

作者简介: 龙萍(1963-), 女, 博士. E-mail: longping@hrbeu.edu.cn

基金:国家自然科学基金(51275105, 51375106); 国家重点基础研究发展计划(973)(2011CB013404); 中央高校基本科研业务费(HEUCF20151013)

摘要

通过热分解法制备了Ti/RuO₂和Ti/Ru-La-O氧化物涂层, 利用微分电容和极化曲线等实验方法对涂层Clˉ特性吸附、La对RuO₂涂层析氯反应过程的影响及反应机理进行了研究。结果表明, 在NaCl溶液中, 涂层表面存在Clˉ的特性吸附, 这种特性吸附对析氯反应的动力学产生了影响, 导致Tafel斜率上升, 反应级数下降, 加入La使氧化钌涂层的过电位下降, 交换电流密度增大, 有利于析氯反应的进行。本文对涂层存在的两种可能反应机理进行了比较分析, 认为在中性NaCl溶液中析氯反应是由过程控制的。

关键词: 特性吸附; 钌镧氧化物; 析氯反应; Volmer-Tafel机理; RuO2

中图分类号:TQ174 文献标志码:A 文章编号:1000-324X(2015)05-0493-07

Comparative Study on Kinetics of Chlorine Evolution Reaction for Ru-La-O Oxide Coatings

LONG Ping^1,², XU Li-Kun², CUI Xiu-Fang¹, JIN Guo¹

1. Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001, China

2. State Key Laboratory for Marine Corrosion and Protection, Luoyang Ship Material Research Institute, Qingdao 266071, China

Fund:National Natural Science Foundation of China(51275105, 51375106); 973 Program(2011CB013404); Fundamental Research Funds for the Central Universities(HEUCF20151013)

Abstract

The Ti/RuO₂ and Ti/Ru-La-O oxide coatings were prepared by thermal decomposition of the metal chlorides in the precursor solution. The specific adsorption of Clˉ on coatings, the effect of La on the chlorine evolution reactions (ClER) and the kinetic mechanism were investigated by using differential capacity (DC) and polarization curves (PC). Results show that the coating surface exhibits significantly specific adsorption of Clˉ in NaCl neutral solution, which has an influence on the kinetics of the chlorine evolution process, resulting in an increase of the Tafel slope and a decrease of the reaction order. The addition of lanthanum reduces the overpotential of Ti/RuO₂ coating and enhances the exchange current density, which improves the chlorine evolution reaction of the coatings. Both kinetic mechanisms of recombination and electrochemical desorption of adsorbed intermediate species for the coatings are comparatively studied. It is confirmed that the Chlorine evolution reaction on Ru-La-O oxide coatings in NaCl neutral solution is controlled by the process of.

Keyword: specific adsorption; Ru-La-O oxides; chlorine evolution reaction; Volmer-Tafel mechanism; RuO2

Show Figures

钌基氧化物涂层具有很高的电化学活性, 多年来在氯碱工业、硫酸盐工业以及水电解、超电容、燃料电池等领域都受到极大关注。尽管人们对RuO₂涂层的析氯反应机理做了大量工作^{[1, 2]}, 但所得到的数据却存在较大的分歧, 例如Tafel斜率就有120^[3]、108^[4]、40~50^[5]、40^{[6, 7]}、31~32^[8]、38^[8]和30 mV^[9]等多种结果, 这种差异可能与阳极的制备工艺、表面吸附及氧化物表面状态等因素有关^{[10, 11]}。由于反应机理的确证主要以动力学参数Tafel斜率和氯离子反应级数为依据, 因此到目前为止, 对钌基氧化物涂层析氯反应机理还没有获得一致认识。

已提出的析氯反应机理, 有Volmer-Tafel(再结合)机理^[12]、Volmer-Heyrovsky(放电解析)机理^[5]、Kristalik机理^[13]以及阳极催化活性物参加反应的机理^{[14, 15]}等等, 其中Volmer-Tafel机理及Volmer- Heyrovsky机理被许多研究者证实并用于解释各自的实验现象。Volmer-Tafel机理认为, 在电极表面发生了如下反应:

(1)

(2)

其中º S为表面活性点, Cl* 为吸附氯, 第二步是两个吸附Cl* 再结合释放的过程, 为速度控制步骤(rds)。而对于Volmer-Heyrovsky机理, 第二步发生如下反应

(3)

该步骤是析氯反应的速度控制步骤。这两个机理与表面Cl* 覆盖度有很大的关系。当表面Cl* 覆盖度较高时, 一般发生再结合过程; 而当覆盖度较低时, 一般可能发生放电解析过程^[16]。

在RuO₂氧化物电极中添加其他元素, 可以提高其催化活性, 降低成本^{[17, 18, 19]}。有研究表明, 稀土元素能够有效提高钌基氧化物涂层的催化活性^{[20, 21]}, 其中La对电化学活性的影响最为明显^[22]。但到目前为止, 关于镧对钌基氧化物涂层析氯过程的动力学影响还未见报道。在前期对钌镧氧化物涂层成分、表面结构、双电层界面及电化学活性等研究的基础上^{[23, 24, 25]}, 本工作利用极化曲线、微分电容等实验技术对该体系涂层的析氯反应机理作了进一步研究, 为钌镧基系列氧化物涂层的研究提供实验和理论依据。

1 实验方法

1.1 电极制备

将前驱物氯化钌(RuCI₃• 3H₂O, 上海贺利氏工业技术材料有限公司, 分析纯)和氯化镧(LaCl₃• 7H₂O, 分析纯)分别溶解于异丙醇(CH₃CH(OH)CH₃, 分析纯)和乙醇(CH₃CH₂OH, 分析纯)溶液中, 然后用搅拌器将二者按一定比例(Ru: La=7: 3)混合均匀, 配置成涂液。

将TA2钛基材(100 mm× 100 mm× 1.5 mm), 经轧制、喷砂和碱洗后, 放入10%沸腾的草酸溶液中刻蚀2 h, 然后将其放入装有80℃去离子水的超声波清洗仪中清洗15 min, 烘干。将配制好的涂液均匀涂刷在刻蚀后钛板的两面, 放入烘干箱中120℃烘干10 min, 然后送入箱式电阻炉中450℃烧结10 min, 再进行涂刷、烘干和烧结处理, 反复数遍, 直至总氧化物载量达到约10 g/m², 停止涂刷, 最后在箱式电阻炉中450℃烧结1 h, 退火。

采用日本JSM-6700F场发射扫描电子显微镜(SEM)自带能谱仪(EDS)对涂层进行了成分分析, 分析结果表明, Ru-La-O氧化物涂层中Ru含量为63.93at%, La含量为36.07at%, 与设计成分接近, 如图1所示。

1.2 电化学测试

利用德国IM6电化学工作站进行极化曲线和微分电容测试。采用经典三电极体系, EG& G标准电解池, 工作电极即上述氧化物阳极, 其暴露工作面积为1 cm², 辅助电极为铂片, 参比电极为饱和甘汞电极(SCE), 以饱和KCl鲁金毛细管作盐桥, 极化曲线扫描速度为1 mV/s, 电解质溶液取浓度分别为2、3、4和5 mol/L的NaCl溶液。在电位范围为-1.6~0.8 V, 测试频率为50 mHz, 步宽为5 mV, 间隔20 s下测试微分电容, 电解质溶液取浓度分别为0.001、0.01及0.1 mol/L 的NaCl溶液。

2 结果与讨论

2.1 反应动力学常数

在Volmer-Tafel机理中(反应式(1、2)), 第一步为Clˉ 在电极表面放电反应, 形成化学吸附氯, 在这个过程中S(Ruⁿ⁺→ Ruⁿ⁺¹)被氧化或部分被氧化。第二步为两个吸附氯再结合, 脱离表面释放Cl₂, 在Frumkin 吸附条件下, 其动力学方程为^[16]:

	Figure Option View Download New Window
	图1 Ru-La-O氧化物涂层能谱Fig. 1 EDS spectra of the Ru-La-O oxide coating

(4)

其中k₂为反应(2)速度常数, θ _Cl*为吸附Cl* 的覆盖度, 当反应(1)为准平衡时, 则有:

(5)

其中K₁=k₁/k_-1为反应(1)的平衡常数, 将其代入(4)式中, 则有

(6)

变换方程(6)的形式, 则可得到

(7)

利用方程(7)绘制关系曲线应该是一条直线。图2是将Ti/RuO₂和Ti/Ru-La-O 实验数据代入(7)得到的关系曲线, 从图中可以看到exp(η F/RT)/i₂^1/2与exp(η F/RT)均成很好的线性关系, 这表明两种涂层都可能是通过再结合控制步骤实现析氯反应过程的。通过该曲线可以得到反应的动力学常数k₂和K₁。

	Figure Option View Download New Window
	图2 根据Volmer-Tafel机理的公式(7)测试不同浓度下的关系曲线Fig. 2 Test of Volmer-Tafel mechanism according to Eq.(7) for various NaCl solution from 2 to 5 mol/L

图3为k₂和K₁随溶液Clˉ 浓度变化的曲线, 从图中可以看到, 随着溶液浓度增大, 反应k₂明显增大, 这与表面吸附Cl* 增加有关。而Ti/Ru-La-O的k₂明显大于RuO₂, 表明前者Cl* 的覆盖度高于后者。

2.2 Clˉ 的特性吸附

氧化物涂层的微分电容是在不发生析氯反应的电位区间测量的数据, 曲线对应最小电位值为pzc。由于氧化物涂层表面粗糙多孔, 因此其pzc对应的电容值要比光滑的金属表面电容高很多^[26]。从图4可以看到, 随着溶液浓度的增加, pzc向负偏移, 这表明氯离子显著影响了双电层的结构, 这是因为在单一电解质溶液中阴离子比阳离子更容易靠近电极表面, 因此导致pzc随着氯离子浓度增加而向负方向偏移。巴德等认为, 此电位偏移标志着特性吸附^{[27, 28, 29]}。此外, 我们还注意到随着电位不同, 在最小值两端吸附/解析的电位也不同, 这是由于在电解质表面存在Clˉ 和OHˉ 的竞争性吸附所致^[30]。根据文献[28]表面OH可能经历如下反应:

(8)

随着电位增加, 电容增大并逐渐达到最大值, 这是

	Figure Option View Download New Window
	图3 Volmer-Tafel机理动力学常数K₁和k₂与溶液中氯离子浓度关系图Fig. 3 Values of the kinetic constants K₁ andk₂ for the Volmer- Tafel mechanism as a function of chloride concentration in solution

由于随着表面碱性点的增多, 更有利于Clˉ 的吸附, 即发生如下吸附过程:

(9)

根据实验结果, 随着Clˉ 浓度增加, pzc负移且电容明显增大, 表明特性吸附的存在以及特性吸附对表面氧化层电荷的影响^[29]。与纯RuO₂比较(见图5), Ti/Ru-La-O 的pzc及最大吸附峰显示出更明显的负偏移(见图4(a)), 显然加入La明显增强了Clˉ 的特性吸附作用。Takasu等^[31]研究发现, 在Ru基电极中加入La, 能够在RuO₂表面产生多孔结构, 这必然造成表面活性点数目的增多, 也因此提高了表面碱性点的数目, 从而对表面Clˉ 有更大吸附作用, 这应该是加入La能有效提高Clˉ 特性吸附的主要原因。

	Figure Option View Download New Window
	图4 Ru-La-O 氧化物涂层在(a) 0.001 (b) 0.01和(c) 0.1 mol/L NaCl溶液中的微分电容曲线Fig. 4 Differential capacity curves of Ti/Ru-La-O oxide coatings in (a) 0.001, (b) 0.01, and (c) 0.1 mol/L NaCl solution

	Figure Option View Download New Window
	图5 Ti/RuO₂涂层在0.001 mol/L NaCl 溶液中微分电容曲线Fig. 5 Differential capacity curve of Ti/RuO₂ oxide coatings in 0.001 mol/L NaCl solution

2.3 Tafel斜率和反应级数

在NaCl溶液中分别对RuO₂和Ru-La-O氧化物涂层做极化曲线, 根据该曲线得到析氯反应动力学参数列于表1。从表1可以看到, 加La的氧化物涂层a减小, i₀增大, 过电位η 下降, 表明该电极比纯RuO₂具有更好的电化学性能, 这与我们前期的实验结果相符。Ti/RuO₂和Ti/Ru-La-O的Tafel斜率分别为129和168mV。

图6为在不同浓度NaCl溶液中测得的E-lgi关系曲线, 图中曲线存在近似平行关系, 表明Tafel斜率不随溶液中氯离子浓度发生变化。图7是一定电位下的lgi-lgc关系图, 根据反应级数的定义:

(10)

因此, 利用图7即可求出RuO₂和Ru-La-O 氧化物涂层的反应级数分别为0.53和0.43。

Conway等^[16]认为应该考虑在浓度较高的溶液中吸附物间的相互作用, 对于Volmer-Heyrovsky机理, 若考虑吸附物相互作用的影响, 则其动力学方程应为:

(11)

其中k₃为反应(3)速度常数, β 为对称因子, g为横向相互作用参数, 其Tafel斜率为:

(12)

根据该机理得到的反应级数p为:

(13)

根据(式12)和(式13)式绘制Tafel斜率, 反应级数p与吸附物覆盖度θ 的关系曲线如图8所示, 这里取β =0.5。从图8可以看到, 当覆盖度θ → 0时, b=2RT/ 3F=40 mV, p=2; 当θ → 1时, b=2RT/F=118 mV, p=2-θ 。这表明在所有覆盖度范围内Tafel斜率不会超过118 mV, 反应级数也不会小于1。显然, 根据Volmer- Heyrovsky机理不能解释本实验结果。

如果将吸附Cl在表面氧化膜上再结合作为速度控制步骤, 则在考虑吸附离子相互作用影响的条件下, 其动力学方程改为:

表1 钌镧氧化物涂层析氯反应动力学参数 Table 1 Kinetic parameters of Ti/RuO₂ and Ti/Ru-La-O oxide coatings for chlorine evolution reaction

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	图6 不同浓度下Ti/RuO₂ (a) 和Ti/Ru-La-O (b) 氧化物涂层的E-lgi关系图Fig. 6 Potential-current curves of Ti/RuO₂ (a) and Ti/Ru-La-O (b) oxide coatings for chlorine evolution in various NaCl solutions from 2 to 5 mol/L

	Figure Option View Download New Window
	图7 氧化物涂层Ti/RuO₂(a)和Ti/Ru-La-O (b)的lgi-lgc 关系图Fig. 7 Dependence of the reaction rate for Ti/RuO₂(a) and Ti/Ru-La-O (b) oxide coatings on the Clˉ concentration

(14)

根据该公式得到的Tafel斜率和反应级数分别是:

(15)

	Figure Option View Download New Window
	图8 根据Volmer-Heyrovsky机理的Tafel斜率与覆盖度θ (a)及反应级数p与覆盖度θ (b)在g= -2、0、5时关系曲线Fig. 8 Relation between Tafel slope and coverage θ (a), and reaction order p and θ (b) for Volmer-Heyrovsky mechanism at g= -2, 0, 5

(16)

图9给出Volmer-Tafel下Tafel斜率和反应级数p与吸附物覆盖度θ 的关系曲线。从图中可以看到, 当θ → 0时, b=RT/2F=30mV, p=2; 当θ → 1时, b→∞ , p→ 0。根据我们微分电容实验结果, 由于特性吸附现象的存在导致表面Cl* 覆盖率很高, 在高电流密度时Tafel斜率上升到较高的值, 因此测出的结果大于118 mV, 而反应级数也远低于1, 这一结果与高覆盖度下的Volmer-Tafel机理结论相符, 说明析氯反应是吸附Cl* 在表面再结合生成Cl₂作为反应过程的控制步骤, 且由于La的加入使表面氯的特性吸附增强, 导致Tafel斜率增大和反应级数的下降。此外, 从图9可以看到, 随着Cl* 表面覆盖度的增加, 吸附物间的相互作用也增大, 引起Tafel斜率迅速增加, 这也是钌镧氧化物涂层比纯RuO₂涂层具有更高Tafel斜率的原因。

3 结论

本研究以钌镧氧化物涂层为研究对象, 以Ti/RuO₂涂层作为对比, 通过微分电容和极化曲线等实验技术研究了电极涂层表面的特性吸附、La对析氯反应的影响及析氯反应的机理, 认为在NaCl的中性溶液中, 电极表面存在Clˉ 的特性吸附, 这种特性吸附对析氯反应的动力学产生了影响, 导致Tafel斜率上升, 反应级数下降。加入La使电极的过电位下降, 交换电流密度增大, 这有利于析氯反应的进行。根据实验数据对Volmer-Heyrovsky和Volmer-Tafel机理的比较分析, 可以认为, 发生该氧化物涂层的析氯反应符合Volmer-Tafel机理过程。

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	图9 根据Volmer-Tafel机理的Tafel斜率与覆盖度θ (a)及反应级数p与覆盖度θ (b)在g= -2, 0, 5时关系曲线Fig. 9 Relationship between Tafel slope and coverage θ (a), and reaction order p and θ (b) for Volmer-Tafel mechanism atg= -2, 0, 5

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[9]	JANSSEN L J J, VISSER G J, BARENDRECHT E. Effect of molecular chlorine diffusion on theoretical potential-current density relations for chlorine evolving electrode. Electrochim Acta, 1983, 28(2): 155-163. [本文引用:1] [JCR: 3.777]
[10]	ZHANG S J, DU A L, XU L K, et al. Study on deactivation behavior of metal oxide anode at differernt seawater electrolysis temperature. Rare Metal Mat. Eng. , 2013, 42(12): 2613-2618. [本文引用:1] [JCR: 0.16] [CJCR: 0.827]
[11]	BURKE L D, O'NEILL J F. Some aspects of the chlorine evolution reaction at ruthenium dioxide anodes. J. Electroanal. Chem. , 1979, 101(3): 341-349. [本文引用:1] [JCR: 2.905]
[12]	FAITA G, FIORI G. Anodic discharge of chloride ions on oxide electrodes. J. Appl. Electrochem. , 1972, 2(1): 31-35. [本文引用:1] [JCR: 1.836]
[13]	ERENBURG R G. Mechanism of the chlorine reaction of rutheniu- mtitanium oxide anodes. Soviet Electrochemistry, 1984, 20(12): 1481-1486. [本文引用:1]
[14]	KRISHTALIK L I. Kinetics and mechanism of anodic chlorine and oxygen evolution reactions on transition metal oxide electrodes. Electrochim Acta, 1981, 26(3): 329-337. [本文引用:1] [JCR: 3.777]
[15]	AUGUSTYNSKI J, BALSENC L, HINDEN J. X-Ray photoelectron spectroscopic studies of RuO₂-based film electrodes. J. Electrochem. Soc. , 1978, 125(7): 1093-1097. [本文引用:1] [JCR: 2.588]
[16]	CONWAY B E, NOVAK D M. Chloride ion adsorption effects in the recombination-controlled kinetics of anodic chlorine evolution at Pt electrodes. Journal of the Chemical Society, Faraday Transactions 1, 1979, 75: 2454-2472. [本文引用:3]
[17]	KUSMIEREK E, CHRZECIJANSKA E. Use of the CeO₂-modified Ti\TiO₂-RuO₂ electrodes in oxidation of acid orange 7. Przem. Chem. , 2012, 91(10): 2038-2043. [本文引用:1] [JCR: 0.344]
[18]	GAN W P, LIU J Y, LIU H, et al. Characterization and electrochemical properties of RuO₂ film electrode on the inner-wall of tantalum shell for capacitor. J. Inorg. Mater. , 2010, 25(8): 882-886. [本文引用:1]
[19]	SUN J M, WANG X, WEI Z P, et al. Effects of sintering temperature on Ti/RuO₂-CeO₂ electrodes applied in super-capacitors. J. Chin. Rare Earth Soc. , 2011, 29(6): 718-723. [本文引用:1] [CJCR: 1.263]
[20]	NOWAKOWSKI P, VILLAIN S, AGUIR K, et al. Microstructure and electrical properties of RuO₂-CeO₂ composite thin films. Thin Solid Films, 2010, 518(10): 2801-2807. [本文引用:1] [JCR: 1.604]
[21]	FAN N J, ZHU P X, ZHOU S G, et al. Optimization for preparation technique of Ru-La oxide coating titanium anode by orthogonal design. Hot Working Technology, 2014, 43(12): 160-162. [本文引用:1] [CJCR: 0.494]
[22]	MURAKAMI Y, KONDO T, SHIMODA Y, et al. Effects of rare earth chlorides on the preparation of porous ruthenium oxide electrodes. J. Alloys Compd. , 1996, 239(2): 111-113. [本文引用:1] [JCR: 2.39]
[23]	LONG P, XU L K, LI Q F, et al. Effect of microstructure on electrochemical activity of Ru-La oxide coatings on Ti substrate. Rare Metal Mat. Eng. , 2013, 42(6): 1185-1189. [本文引用:1]
[24]	LONG P, LI Q F, XU L K, et al. Electrochemical impedance spectroscopy (EIS) study of Ru-La oxide coatings in NaCl solution. Acta Chim. Sinica, 2012, 70(10): 1166-1172. [本文引用:1] [JCR: 0.622] [CJCR: 1.175]
[25]	LONG P, XU L K, XUE L L, et al. Voltammetry behavior of Ru-La oxide coatings on Ti substrate in NaCl solution. Rare Metal Mat. Eng. , 2014, 43(5): 1133-1137. [本文引用:1] [JCR: 0.16] [CJCR: 0.827]
[26]	BURROWS I R, DENTON D A, HARRISON J A. Chlorine and oxygen evolution on various compositions of RuO₂\TiO₂ electrodes. Electrochim Acta, 1978, 23(6): 493-500. [本文引用:1] [JCR: 3.777]
[27]	VALETTE G, PARSONS R. Adsorption on well-defined solid surfaces chloride adsorption on a (110face of silver. J. Electroanal. Chem. , 1986, 204(1/2): 291-297. [本文引用:1] [JCR: 2.905]
[28]	DAGHETTI A, LODI G, TRASATTI S. Interfacial properties of oxides used as anodes in the electrochemical technology. Mater. Chem . Phys. , 1983, 8(1): 1-90. [本文引用:1] [JCR: 2.072]
[29]	阿伦·j·巴德美, 拉里·r·福克纳. 电化学方法: 原理和应用. 第二版. 北京: 化学工业出版社, 2005: 571. [本文引用:2]
[30]	NOVAK D M, CONWAY B E. Competitive adsorption and state of charge of halide ions in monolayer oxide film growth processes at Pt anodes. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases , 1981, 77: 2341-2359. [本文引用:1]
[31]	TAKASU Y, ARIKAWA T, YANASE K, et al. Preparation of a novel Pt-RuO₂\Ti electrocatalyst by use of highly porous ruthenium oxide support prepared from RuO₂-La₂O₃/electrode. J. Alloys Compd. , 1997, 261(1/2): 172-175. [本文引用:1] [JCR: 2.39]

2009

0.146

0.0

... 尽管人们对RuO₂涂层的析氯反应机理做了大量工作^[1,2], 但所得到的数据却存在较大的分歧, 例如Tafel斜率就有120^[3]、108^[4]、40~50^[5]、40^[6,7]、31~32^[8]、38^[8]和30 mV^[9]等多种结果, 这种差异可能与阳极的制备工艺、表面吸附及氧化物表面状态等因素有关^[10,11] ...

2014

3.777

0.0

Electrochim Acta. 2014, 120:460-466

Chlorine evolution reaction on RuO₂(110): ab initio atomistic thermodynamics study- pourbaix diagrams.

EXNER K S , ANTON J , JACOB T

Constrained ab initio thermodynamics in the form of a Pourbaix diagram can greatly assist kinetic modeling of a particular electrochemical reaction such as the chlorine evolution reaction (CER) over RuO 2 (110). Pourbaix diagrams reveal stable surface structures, as a function of pH and the potential. The present DFT study indicates that the Pourbaix diagram in the CER potential region above 1.36 V and pH values around zero is dominated by a stable surface structure in which all coordinatively undercoordinated Ru sites (Ru cus ) are capped by on-top oxygen (O ot ). This oxygen saturated RuO 2 (110) surface is considered to serve as the catalytically active phase in the CER, quite in contrast to the heterogeneously catalyzed HCl oxidation (Deacon process), for which the active RuO 2 (110) surface is mainly covered by on-top chlorine. The active sites in the CER are suggested to be Ru cus O ot surface complexes, while in the Deacon process both undercoordinated surface Ru and oxygen sites must be available for the activation of HCl molecules.

1974

3.777

0.0

Electrochim Acta. 1974, 19(6):257-265

The mechanism of the chlorine evolution on different types of graphite anodes during the electrolysis of an acidic NaCl solution.

JANSSEN L J J

The behaviour of the electrode and the formation of chlorine were studied practically for porous graphite used in the industrial electrolysis of an aqueous NaCl solution only. In this investigation this was done for Acheson graphite electrodes and for highly orientated pyrolytic graphite electrodes of which the edge plane or the basal plane served as electrode surface. Voltammograms were determined by continuous scanning with different rates of the potential between a minimum and maximum value. From the experimental results it follows that two different surface compounds, the lp oxygen and the hp oxygen are formed on all the graphite electrodes investigated. In the stationary state lp oxygen is present at low potential and the hp oxygen at high potentials. The formation and the removal of each compound depends on the electrolytic conditions, especially on the maximum potential of the sweep. The conditions of the sweep determine whether these oxides are really present on the electrode surface during the anodic or the cathodic sweep. Chlorine is formed according to the Volmer-Heyrovsky mechanism on all the three types of electrodes. The current density, the transfer coefficient and the activation energy for the edge plane electrode and the Acheson graphite electrode are of the same order of magnitude, while for the basal plane electrode they deviate strongly.

1973

0.0

J. Electrochem. Soc.. 1973, 120(2):231-236

The kinetics of chlorine evolution and reduction on titanium-supported metal oxides especially RuO₂ and IrO₂.

KUHN A T , MORTIMER C J.

Current‐voltage curves were determined on precious metal oxide‐coated titanium electrodes under conditions relevant to the chlor‐alkali industry. Electrodes in which the oxide coating was of a base metal or only partly of a precious metal were also studied. Clear electrocatalytic effects were found, though in general, linear Tafel behavior was not observed. A possible explanation for the lack of linear Tafel plots in terms of a semiconducting oxide coating was suggested.

1977

3.777

0.0

Electrochim Acta. 1977, 22(10):1093-1100

Mechanism of the chlorine evolution on a ruthenium oxide itanium oxide electrode and on a ruthenium electrode.

JANSSEN L J J , STARMANS L M C , VISSER J G

The mechanism of the chlorine evolution on titanium electrodes coated with a layer of ruthenium oxide and titanium oxide under different experimental conditions, and on a ruthenium electrode, both in acidic chloride solution, has been investigated. Potentiodynamic current density—potential curves were recorded as a function of the time anodic pre-polarisation, the composition of the solution and the temperature. Moreover, potential decay curves were determined. Theoretical potential decay curves were deduced for both the Tafel reaction (2 Cl ad →Cl 2 ) and the Heyrovsky reaction (Cl − + Cl ad → Cl 2 + e − ) as a rate determining step in the formation of molecular chlorine. They were compared with those found experimentally. The influence of possible diffusion of atomic chlorine out of the electrode was also taken into consideration. It was found that for all the electrodes investigated, molecular chlorine is formed both at anodic polarisation and on open circuit according to the Volmer—Heyrovsky mechanism, where the Heyrovsky reaction is the rate-determining step. The transfer coefficient is 0.5 for the chlorine evolution at an “ideal” ruthenium oxide titanium oxide electrode and at a ruthenium electrode.

... 已提出的析氯反应机理, 有Volmer-Tafel(再结合)机理^[12]、Volmer-Heyrovsky(放电解析)机理^[5]、Kristalik机理^[13]以及阳极催化活性物参加反应的机理^[14,15]等等, 其中Volmer-Tafel机理及Volmer- Heyrovsky机理被许多研究者证实并用于解释各自的实验现象 ...

1979

3.777

0.0

Electrochim Acta. 1979, 24(5):521-527

Chlorine evolution and reduction on RuO₂\TiO₂ electrodes.

DENTON D A , HARRISON J A , KNOWLES R I.

The Cl 2 evolution reaction has been investigated on RuO 2 /TiO 2 electrodes of various composition in 1 M HCl and 1 M KCl electrolyte by means of stationary and non stationary i-E curves and by ac impedance. A reaction mechanism is suggested. The qualitative features of Cl 2 reduction from saturated solutions in HCl and KCl are discussed.

1987

2.905

0.0

J. Electroanal. Chem.. 1987, 228(1/2):393-406

Mechanism of chlorine evolution on oxide anodes study of pH effects.

CONSONNI V , TRASATTI S , POLLAK F

Chlorine evolution on oxides such as polycrystalline RuO 2 , IrO 2 , Co 3 O 4 , NiCo 2 O 4 , RuO 2 + IrO 2 and the (110) face of RuO 2 single crystals proceeds with the same Tafel slope of 40 mV and the same reaction order of 1 with respect to Cl − . On all oxides but RuO 2 (110) the reaction rate is depressed by the acidity, which results in a reaction order with respect to H + of −1 for IrO 2 , Co 3 O 4 and NiCO 2 O 4 , of 0 for RuO 2 (110) and variable for RuO 2 . Possible reasons for pH effects are discussed, and several plausible reaction mechanisms are examined.

1982

2.588

0.0

J. Electrochem Soc.. 1982, 129(8):1689-1693

Surface structure of ruthenium dioxide electrodes and kinetics of chlorine evolution.

ARDIZZONE S , CARUGATI A , LODI G

The kinetics of chlorine evolution on ruthenium dioxide based films supported on titanium and quartz is investigated as a function of the intimate structure of the catalyst surface. The latter is modified by changing the temperature of pyrolysis of and is characterized by measuring the amount of charge exchanged with the solution when the potential is varied within a range where no electrode reaction takes place. The results allow distinguishing between macro‐ and micro‐roughness of the surface. Chlorine evolution appears to be sensitive to the former but not to the latter.

1983

3.777

0.0

Electrochim Acta. 1983, 28(2):155-163

Effect of molecular chlorine diffusion on theoretical potential-current density relations for chlorine evolving electrode.

JANSSEN L J J , VISSER G J , BARENDRECHT E

The effect of molecular chlorine diffusion upon the theoretical potential-current density relations was calculated for chlorine evolution according to the Volmer—Tafel mechanism as well as the Volmer—Heyrowsky mechanism. It has been found that a minimum Tafel slope of 29.6 mV at 298 K occurs for both mechanisms. This slope occurs for the Volmer—Tafel mechanism when either the Tafel reaction or the chlorine diffusion, away from the electrode surface into the bulk of solution, is the rate-determining step, and for the Volmer—Heyrowsky mechanism when it is the chlorine diffusion that is the rate-determining step. Moreover, it has been established that only a careful use of both the polarization resistance at the reversible potential and the stoichiometric number from this deduced, is allowed to elucidate the mechanism of electrode reactions with adsorbed atomic intermediates.

2013

0.16

0.827

1979

2.905

0.0

1972

1.836

0.0

J. Appl. Electrochem.. 1972, 2(1):31-35

Anodic discharge of chloride ions on oxide electrodes.

FAITA G , FIORI G.

The behaviour of a mixed oxide coating thermally deposited on titanium has been examined with respect to the anodic discharge of chloride ions. The electrochemical properties are similar to those of thermal Pt and Pt-Ir alloy electrodes: chlorine evolution takes place through an electrochemical-chemical mechanism, the 2Cl ads →Cl 2 step being rate determining. Evidence is given about the mechanical and chemical stability of the coating and about the satisfactory reproducibility of the catalytic properties. Moreover, the current efficiency for chlorine evolution appears to be at least 99% at high current densities (up to 16,000 A/m 2 ).

1984

0.0

1981

3.777

0.0

Electrochim Acta. 1981, 26(3):329-337

Kinetics and mechanism of anodic chlorine and oxygen evolution reactions on transition metal oxide electrodes.

KRISHTALIK L I.

A short résumé of the data on kinetics of chlorine reaction at RuO 2 and RuO 2 —TTiO 2 electrodes is given. The three step mechanism of the reaction with the rate determining transfer of the second electron and the formation of the nominally unipositive chlorine as an intermediate is substantiated. The applicability of an analogous mechanism to the oxygen evolution reaction is discussed as well as the possibility of participation in the process of higher oxidation states of ruthenium. Some analogies between anodic processes at RuO 2 and other transition metal oxides (perovskites MNi(Co)O 3 , pyrochlores M 2 Re 2 O 7 , spinels MCo 2 O 4 , MCr 2 O 4 ) were pointed out.

1978

2.588

0.0

J. Electrochem. Soc.. 1978, 125(7):1093-1097

X-Ray photoelectron spectroscopic studies of RuO₂-based film electrodes.

AUGUSTYNSKI J , BALSENC L , HINDEN J.

The nature and relative amounts of the different species present in the surface region of and film electrodes, before and after an anodic polarization in solution, have been determined by means of x‐ray photoelectron spectroscopy. The existence of a surface defect structure of , analogous to that found on powder, has been confirmed for both the and electrodes. Two different chlorine species, identified as chloride ions and adsorbed atomic chlorine, have been shown to be present on the surface of the electrodes used as anodes for the chlorine evolution.

1979

0.0

Journal of the Chemical Society, Faraday Transactions 1. 1979, 75:2454-2472

Chloride ion adsorption effects in the recombination-controlled kinetics of anodic chlorine evolution at Pt electrodes.

CONWAY B E , NOVAK D M.

The role of chloride ion adsorption in the anodic Cl 2 -evolution reaction at Pt electrodes in aqueous chloride solutions is examined for a range of Cl – ion concentrations. A new method of testing the applicability of a recombination-controlled mechanism is given. It enables both the rate constant of the rate-controlling recombination step and the quasi-equilibrium constant of the prior Cl – discharge/Cl ˙ electrosorption step to be evaluated quantitatively as a function of Cl – concentration. It is shown that the Cl 2 -evolution process at Pt is recombination-controlled over a wide-range of Cl – ion concentrations. Despite the approach of the anodic current–potential relation towards limiting-current behaviour, consistent with recombination-controlled kinetics, the limiting current densities are dependent on Cl – ion concentration. It is suggested that this is due to ( a ) effects of specifically adsorbed Cl – ion on the Cl ˙ recombination rate constant and ( b ) changes of state of the Pt anode surface due to competitive effects of Cl – ion adsorption on the extent of surface oxidation of the Pt surface on which the catalytic recombination of discharged Cl ˙ takes place in aqueous medium. These two factors complicate the interpretation of reaction orders in [Cl – ] for the Cl 2 evolution reaction since both specific adsorption effects and the competitive effects in surface oxidation have to be taken into account in relating rates to Cl – ion concentration.

... 而当覆盖度较低时, 一般可能发生放电解析过程^[16] ...

... 第二步为两个吸附氯再结合, 脱离表面释放Cl₂, 在Frumkin 吸附条件下, 其动力学方程为^[16]: ...

... Conway等^[16]认为应该考虑在浓度较高的溶液中吸附物间的相互作用, 对于Volmer-Heyrovsky机理, 若考虑吸附物相互作用的影响, 则其动力学方程应为: ...

2012

0.344

0.0

... 在RuO₂氧化物电极中添加其他元素, 可以提高其催化活性, 降低成本^[17,18,19] ...

2010

0.0

J. Inorg. Mater.. 2010, 25(8):882-886

Characterization and electrochemical properties of RuO₂ film electrode on the inner-wall of tantalum shell for capacitor.

GAN W P , LIU J Y , LIU H

Using the methods of coated and thermal decomposed ruthenium chloride, the RuO 2 thin film was synthesized on the inner-wall surface of tantalum shell. Its morphology and structure were characterized by scanning electron microscope and X-ray diffraction. The electrochemical performances of the RuO 2 thin film electrode were tested by cyclic voltammetry, galvanostatic charging/discharging and electrochemical impedance spectroscope. The results show that the RuO 2 thin film calcinated at 280℃ has amorphous structure and the specific capacitance of the electrode is 212F/g (in 0.5 mol/L H 2 SO 4 electrolyte) with good elec-trochemical performance. When the films are assembled into ST3 type 60 V 330 μF tantalum capacitors, the capaci-tance can still maintain 345μF after celaring and electrical aging. The equivalent series resistance (ESR) is less than 1Ω and the leakage current is less than10μA. Key words： tantalum capacitors,ruthenium dioxide (RuO 2 ),thin film electrode

... 在RuO₂氧化物电极中添加其他元素, 可以提高其催化活性, 降低成本^[17,18,19] ...

2011

0.0

1.263

... 在RuO₂氧化物电极中添加其他元素, 可以提高其催化活性, 降低成本^[17,18,19] ...

2010

1.604

0.0

Thin Solid Films. 2010, 518(10):2801-2807

Microstructure and electrical properties of RuO₂-CeO₂ composite thin films.

NOWAKOWSKI P , VILLAIN S , AGUIR K

RuO 2 –CeO 2 composite thin films are deposited on various Si substrates by a radiofrequency magnetron sputtering technique. Compacted polycrystalline pellets of the nanostructured CeO 2 –RuO 2 composite system are used as standard samples for comparative electrical analyses. All films and composite samples are analyzed by X-ray diffraction and transmission electron microscopy. Electrical measurements of radiofrequency sputtering of thin films are performed as a function of the RuO 2 fraction and of the temperature (between 25 and 400 °C). A nonlinear variation in the electrical conductivity of the RuO 2 –CeO 2 composite thin films as a function of the RuO 2 volume fraction ( Φ ) is observed and discussed. It is interpreted in terms of a power law (in ( Φ − Φ c) m ), where m and Φ c are parameters characteristic of the distribution of the conducting phase in a composite medium.

... 有研究表明, 稀土元素能够有效提高钌基氧化物涂层的催化活性^[20,21], 其中La对电化学活性的影响最为明显^[22] ...

2014

0.0

0.494

... 有研究表明, 稀土元素能够有效提高钌基氧化物涂层的催化活性^[20,21], 其中La对电化学活性的影响最为明显^[22] ...

1996

2.39

0.0

J. Alloys Compd.. 1996, 239(2):111-113

Effects of rare earth chlorides on the preparation of porous ruthenium oxide electrodes.

MURAKAMI Y , KONDO T , SHIMODA Y

RuO 2 - Re 2 O 3 /Ti (Ru: Re 7:3) electrodes prepared from the thermal decomposition of RuCl 3 and Re Cl 3 were much more porous than conventional RuO 2 /Ti electrodes. Porosities of the RuO 2 - Re 2 O 3 /Ti electrodes depended on the ionic radii of the rare earth ions. Rare earth ions added to electrodes to prepare the RuO 2 - Re 2 O 3 /Ti electrodes were completely dissolved in the acid solution. After dissolution of the rare earth ions, the voltammetric charges of the resulting RuO 2 /Ti electrodes were still large. Rare earth chlorides were effective as pore initiators in preparing porous RuO 2 /Ti electrodes, and were recovered after the preparation as catalysts.

... 有研究表明, 稀土元素能够有效提高钌基氧化物涂层的催化活性^[20,21], 其中La对电化学活性的影响最为明显^[22] ...

2013

0.0

... 在前期对钌镧氧化物涂层成分、表面结构、双电层界面及电化学活性等研究的基础上^[23,24,25], 本工作利用极化曲线、微分电容等实验技术对该体系涂层的析氯反应机理作了进一步研究, 为钌镧基系列氧化物涂层的研究提供实验和理论依据 ...

2012

0.622

1.175

Acta Chim. Sinica. 2012, 70(10):1166-1172

Electrochemical impedance spectroscopy (EIS) study of Ru-La oxide coatings in NaCl solution.

LONG P , LI Q F , XU L K

Electrochemical surface structure and electrochemical performance of Ti based Ru-La oxide coatings in 3.5% NaCl solution have been investigated by electrochemical impedance spectroscopy (EIS), together with cyclic voltammetry (CV) and scanning electron microscopy (SEM). The best-fit circuit to EIS data of the coatings in the absence of the chlorine evolution reaction is R s ( R ct Q dl ), and that in the potential range of chlorine evolution reaction is R s (R f Q f )( R ct WQ dl ). The high-frequency region corresponds to the impedance behavior of the coating, and the low-frequency region to that of the interface between outer surface and electrolyte. Results show that the pseudo-capacitances of the oxide film and the double layer increase with increasing La content, reaching a maximum at the nominal La content of 30 mol%. This finding agrees with the CV result, suggesting that the La additive in suitable amount can improve the electrochemical activity of the RuO2 coating. The electric conductivity of the coatings, however, significantly decreases when nominal La content is larger than 30 mol% in the region of the chlorine evolution potential. A character with a Warburg impedance at low-frequency region suggests the relationship to passivation of the coating surface and specific adsorption, resulting in a dramatic decrease of electrocatalytic activity of the coatings at norminal La content of 70 mol%.

2014

0.16

0.827

1978

3.777

0.0

Electrochim Acta. 1978, 23(6):493-500

Chlorine and oxygen evolution on various compositions of RuO₂\TiO₂ electrodes.

BURROWS I R , DENTON D A , HARRISON J A.

The chlorine and oxygen evolution reactions have been investigated on various compositions of Ti supported RuO 2 /TiO 2 anodes. Conclusions have been reached on the structure of the electrode, and its influence on the mechanism of these two reactions, at the different compositions of RuO 2 /TiO 2 .

... 由于氧化物涂层表面粗糙多孔, 因此其pzc对应的电容值要比光滑的金属表面电容高很多^[26] ...

1986

2.905

0.0

J. Electroanal. Chem.. 1986, 204(1/2):291-297

Adsorption on well-defined solid surfaces chloride adsorption on a (110) face of silver.

VALETTE G , PARSONS R.

The adsorption of chloride on a (110) face of silver has been studied using mixed solutions with hexafluorophosphate as base electrolyte. The adsorbed charge of chloride was determined from the differential capacity-potential curves. The components of the inner-layer capacity have been calculated only for the more negative peak potential, because of the inversion of the adsorbed charge as a function of the chloride concentration. The component at constant adsorbed charge confirms the prominent role of the orientation of the water dipoles. On the other hand, it is suggested that the less negative peak potential is due to the chloride adsorption. A pseudohexagonal structure, equivalent to the c (5×2) structure, would correspond to the maximum coverage.

... 巴德等认为, 此电位偏移标志着特性吸附^[27,28,29] ...

1983

2.072

0.0

... 巴德等认为, 此电位偏移标志着特性吸附^[27,28,29] ...

2005

0.0

... 巴德等认为, 此电位偏移标志着特性吸附^[27,28,29] ...

... 浓度增加, pzc负移且电容明显增大, 表明特性吸附的存在以及特性吸附对表面氧化层电荷的影响^[29] ...

1981

0.0

... 的竞争性吸附所致^[30] ...

1997

2.39

0.0

J. Alloys Compd.. 1997, 261(1/2):172-175

Preparation of a novel Pt-RuO₂\Ti electrocatalyst by use of highly porous ruthenium oxide support prepared from RuO₂-La₂O₃/electrode.

TAKASU Y , ARIKAWA T , YANASE K

The applicability of the highly porous ruthenium oxide electrode designed by dissolution of lanthanum from a RuO 2 La 2 O 3 /Ti electrode to the electrocatalyst support of a platinum particle electrode was examined. Both the broadness of the X-ray diffraction peaks and the large exposed surface area of the loaded platinum particles showed that the embedded platinum particles were highly dispersed on the porous ruthenium oxide surface. The dependence of the platinum loading on the electrocatalytic activity of the electrode for hydrogen evolution also showed that platinum can be loaded more than 10 mol% retaining the high dispersion of platinum. Thus, the highly porous ruthenium oxide electrode prepared from RuO 2 La 2 O 3 /Ti electrode was clarified to serve as a novel support for the noble metal particle electrodes.

... Takasu等^[31]研究发现, 在Ru基电极中加入La, 能够在RuO₂表面产生多孔结构, 这必然造成表面活性点数目的增多, 也因此提高了表面碱性点的数目, 从而对表面Cl#cod#x002c9 ...