草酸电还原过程中的铅阴极表面状态变化研究

The Study of the Surface State of the Lead Cathode in the Electrolytic Reduction of Oxalic Acid

在饱和草酸溶液中运用双阶跃计时库仑技术研究草酸电解过程中电极表面吸附过程,以此探讨电极失活问题。研究发现在新鲜铅电极表面表现为产物乙醛酸(R)的吸附,但随着恒电流电解的进行电极表面逐渐地表现为反应物(O)的吸附。反应物的直接吸附不利于电荷转移,电极表面呈现钝化现象,电解电流效率也相应下降.

To study the problem of electrode deactivation a double potential - step chronocoulometric method is applied in the study of adsorption on electrode surface in the progress of oxalic acid electrolysis. It is known that the product glyoxylie acid（R） adsorbed on the fresh electrode surface. While with the galvanostatic electrolysis the reactant oxalic acid（O） adsorbing gradually on the electrode surface is proved. The direct adsorption of reactant goes against the charge transfer, which lead to the passivation of the electrode surface and the decline of the current efficiency. Adding the additive tetrapmpylammoniumhydroxide （TPAH） into the catholyte the fresh electrode surface is adsorbed by O. And the current efficiency with the TPAH is larger than that without the TPAH. With the galvanostatic electrolysis the potential become more and more negative, which result in the additive deadsorbing. It is confirmed that the surface is presented that both O and R are adsorbable, and the current efficiency is decreased correspondingly.