关键词: 钴(II)离子, 阴极还原, 电化学阻抗谱, 反应机理

Abstract: 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.

Key words: Cobalt(II) ions, Cathodic reduction, Electrochemical impedance spectroscopy, Reaction mechanism