不同Br^-浓度下铂电极上镀银层的氧化动力学

THE NUCLEATION STEPS AND KINETICS OF THE ANODIC BEHAVIOR OF POROUS SILVER PLATED ON PLATIUM ELECTRODE IN BROMIDE SOLUTION

本文采用循环伏安法研究了镀银铂电极在溴化钾溶液中的成核过程及氧化动力学,结果表明:AgBr的形成包括三个步骤,首先在银表面某些吸附Br^-的特殊位置上以平面方式成核,然后经过二个三维的成核步骤。在较低浓度的KBr溶液中,AgBr的形成由溶液中的Br^-迁移控制。在较高浓度的溶液中,由于生成的AgBr膜是高度松散的,速度控制步骤转化为在膜孔内Br^-的迁移。随着AgBr的生成以及AgBr的溶解沉积作用,膜孔被堵塞,同时反应速度转化为由AgBr膜中的Ag^+迁移控制。电镜结果也支持了以上结论。

The nucleation process of the AgBr film formed on porous silver which is plated on Pt electrode can be divided into three steps. The first involved the 2-dimensional nucleation of AgBr deposoted at Br- adsorbed locations (perhape certain crystal face, defects, kink's and jogs). The second and third are 3-dimensional nucleation of AgBr, which are characterized by two anodic praks respectively. The kinetics of formation of AgBr film on silver is limited by physical parameters such as ionic diffusion and migration. When the bromide concentration was low, the diffusion of Br- in solution is the limiting step . When the bromide concentration is relatively high, then a layer of AgBr containing holes was formed, and the current is controlled by the diffusion of bromide ions into the lenthening holes of the film. In the meantime, the dissolution and deposition of AgBr occurred, and the holes in the film were filled up. The rate of film growth was then limited by the solid-state electromigration of silver ions through the AgBr film.The morphology of the continuous kinetic oxidation process of the porous silver plated on Pt electrode had been substantiated by comprehensive scanning electron microscope investigations.