锌电极在氢氧化钾溶液中阳极惰化时的表面相变的研究

本文试图进一步从动力学方面证明恒电位下的锌电极在KOH溶液中阳极惰化时,阳极溶解电流随时间而缓慢下降是由于“表面相变”所引起。用恒电位法测取了锌电极在不同浓度的KOH溶液中电流对时间的曲线。实验结果与推导的动力学方程式相符,表明在恒电位惰化条件下,锌电极表面上最初形成的Zn(OH)_2]_(ad)在OH~-参预下徐缓地转变为较不易溶的ZnO]_(ad),因而导致阳极溶解电流的下降。这一表面相变过程可表示如下:

A study of the surface phase change of zinc electrode under anodic passivation in KOH solutions

In previous works we have observed that during the passivation of zinc electrode in KOH solutions under potentiostatic control the anodic dissolution current decreased gradually with time. We ascribed this phenomenon to a change of the properties of the initially formed zinc hydroxide on the zinc surface, i.e. to a "surface phase change" on the electrode. In this work we attempt to further prove this assumption kinetically. We measured the courrent-time curves of the zinc electrode during passiviation under potentiostatic conditions and in KOH solutions of different concentrations. The experimental results are in agreement with the derived kinetic equations, showing that during the anodic passivation of zinc electrode under potentiostatio conditions, the initially formed (Zn(OH)2)ad on the surface was gradually changed, with participation of OH- ions, into the less soluble (ZnO)ad, which caused the decrease of anodic dissolution current. This process of surface phase change is catalysed by the OH- ions, its reaction order with respect to OH- is unity,