铂电极上醋酸-醋酐溶液中Mn(III)/Mn(II)电对研究

平衡电极电势实验确定了25 ℃， 1.5 mol?L－1醋酸钾＋醋酸-醋酐(3:1体积比)溶液中Mn(III)/Mn(II)的条件电极电势为0.719 V（vs SCE）;采用电势扫描和旋转圆盘电极技术研究了醋酸-醋酐溶液中铂电极上Mn(III)/Mn(II)电对的阳极氧化动力学. 结果表明:Mn(II)阳极氧化成Mn(III)的电极反应控制步骤属电荷传递过程, 阳极传递系数β=0.347,交换电流密度i0=5.84×10－6 A?cm－2，阳极标准反应速率常数ka=1.35×10－8 m?s－1, Mn(II)和OAc－的反应级数均为一级.

Studies of Mn(III)/Mn(II) on Platinum Electrode in Acetic Acid-Anhydride Solution

The electrochemical behavior of Mn(III)/Mn(II) on platinum electrode in acetic acid-anhydride was investigated. The results show that the conditional electrode potential of Mn(III)/Mn(II) was 0.719 V(vs SCE) in the solution of 1.5 mol?L－1 KOAc＋HOAc-Ac2O(3:1 volume ratio) at 25 ℃. The results of potential sweep and RDE on platinum electrode show that the rate determing step of the electrode processes for Mn(II) anodic oxidation was a charge-transfer step. The anodic charge-transfer kinetic parameters were determined. The results show that the anodic charge-transfer coefficient is 0.347, the exchange current density i0 is 5.84×10－6 A?cm－2, the conditional charge-transfer rate constant ka is 1.35×10－8 m?s－1 at 25 ℃. The rate was found to be first order with respect to the concentration of both Mn(II) and OAc－.