含胱氨酸的硫酸溶液中铅及铅-锡合金电氧化时新的电势振荡

New Potential Oscillations during the Electrooxidation of Lead and Lead-Tin Alloy in H_2SO_4 with Cystine

利用循环伏安交叉环判据,发现Pb及Pb-0.23%Sn合金电极在含胱氨酸(Cys)的硫酸溶液中电氧化时,涉及周期性析氧的新的电势振荡.阳极极化时电极表面经PbSO4氧化生成PbO2膜,Cys在覆盖PbO2膜的电极表面上的电氧化过程由扩散传质步骤所控制.振荡可归因于电极表面Cys浓度的周期性变化,即扩散控制下的氧化耗尽与析氧导致的对流恢复.通过比较发现,微量Sn的加入不仅显著地减小了电势振荡出现的下限电流值,还缩短了振荡发生的电流区间.

New potential oscillations with periodic oxygen evolution have been observed during the electrooxidation of lead and lead-tin alloy in H2SO4 with cystine based on the CV criterion. The electrode surface could be oxidized to PbO2 via PbSO4 during the anodic polarization, and mass transfer plays the key role in the oscillations for the electrooxidation of cystine on the PbO2-covered surface. The oscillations can be ascribed to the periodic change of cystine concentration on the surface, namely, the consumption by oxidation under diffusion and the resumption by convection through oxygen evolution. Moreover, it has been found that the oscillations begin at a lower current and occur within a narrower region by doping lead with small proportion of tin.