Influence of chloride ion adsorption on the kinetics and mechanism of Ru(NH3)(6)(3 /2 ) electrode reactions
Influence of chloride ion adsorption on the kinetics and mechanism of Ru(NH3)(6)(3 /2 ) electrode reactions
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氯离子吸附对Ru(NH3)(6)(3 /2 )电极反应动力学和机理的影响
DOI：
10.1016/j.electacta.2019.134863
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发表时间：
2019
影响因子：
6.6
通讯作者：
Cao Fahe
中科院分区：
文献类型：
--
作者：
Meng Yao;Du Minshu;Cao Fahe
在本实验中，我们制备了亚微米到纳米级的金属电极，用于扫描电化学显微镜研究Ru(NH3)63+/2+氧化还原体系的动力学。Ru(NH_3)_6(NO_3)_3的还原速率基本上与电极材料的性质无关，但与氯离子浓度有轻微的依赖关系。我们观察到Ru(NH3)6(NO3)3的“外球”反应物在低氯溶液中的还原速度相对较慢。这一现象似乎与配体桥联机理的预期变化相一致，在该机理中，占主导地位的特定吸附的氯离子之间的静电斥力将对内球阳离子反应物的吸附产生不利影响，从而导致反应速度下降。然而，当支持电解质KCl0.1 M加入到目标溶液中时，由于离子双电层效应，反应速度显著提高。阳离子络合物将与外球反应物一样，受到吸附的氯离子的静电吸引。结果表明，随着氯离子浓度的增加，Ru(NH_3)_3~(3+)还原反应路径由阴离子桥连内球体向外球体转变，最高可达0.1 M。
In the experiment, we prepared metal electrodes with sub-micron to nanometer for the scanning electrochemical microscopy to study the kinetics of Ru(NH3)63+/2+redox system. The rates of reduction of Ru(NH3)6(NO3)3were found essentially independent of the nature of the electrode material, but mildly dependent upon chloride ion concentration. We observed that the ‘outer-sphere’ reactant of Ru(NH3)6(NO3)3reduced at relatively slower rates in low-chloride solutions. This phenomenon appears to be compatible with the expected variations in a ligand-bridged mechanism in which the electrostatic repulsions among the specifically adsorbed chloride anions that dominate would have an adverse influence on the adsorption of inner-sphere cationic reactants and thus cause a decrease in the reaction rate. However, as 0.1 M supporting electrolyte KCl was added into the target solution, a significant increase in the reaction rate was measured as a result of the ionic double-layer effect. Cationic complexes will experience the same electrostatic attraction from adsorbed chloride anions as will outer-sphere reactants. It is suggested that the reaction pathway of Ru(NH3)63+reduction can change from the anion-bridged inner-sphere to the outer-sphere with increasing chloride ion concentration up to 0.1 M.