钴(II)离子阴极还原的研究

研究Co~(2+)离子的阴极还原,主要是由于钴的湿法冶金和电镀生产的需要,以及理论研究上的兴趣.研究表明,钴离子的阴极还原过程是复杂的,很大程度上取决于电解液的酸度.Simonova 和Rotinyan 根据pH=2.5-4的实验数据,提出了二电子还原和分步还原平行进行的钴还原机理,用以解释85—150mV 的塔费尔斜率,这实际上反映了酸度对钴还原的影响.Epelboin 和Wiart 根据阴极极化特征和阻抗分析,认为Co~(2+)离子还原时可能

AN INVESTIGATION ON THE CATHODIC REDUCTION OF Co~(2+) IONS

The cathodic reduction of Co~(2+) ions in solutions of pH 4—6 has been inves-tigated by using polarization measurements and ac impedance technique. The reduction behaviour depends to a great extent on the acidity of solution. Based on the mechanism proposed, which is characterized by a stepwise reduction and the inter-mediate formation of an adsorbed monovalent cobalt, (CoOH)_(ads), and with the reaction sequence as a model, an impedance analysis is made of the electrode process. The consistency of the conclution derived from the analysis with experimental electrochemical impedance spectroscopy (EIS) further confirms the reasonableness of the proposed mechanism. The present impedance study also gives evidence that there exists no one-to-one correspondence between a given reaction path (mechanism) and a certain mode of EIS, as ascertained by Cao~[12], and the method of equivalent circuit is limited in studying reaction mechanism.