抗坏血酸在普鲁士蓝薄膜修饰电极上的电催化氧化

The Electrocatalytic Oxidation of Ascorbic Acid on Prussian Blue Film Modified Electrodes

本文详细研究了普鲁士蓝(PB)薄膜本身电荷传输过程的动力学及PB薄膜催化抗坏血酸(AH_2)电氧化的动力学,用电位阶跃计时电流法和计时电量法,恒电流计时电位法测得PB膜中电荷传输表观扩散系数D_(ct)平均为2.62×10^(-10)cm^2·s^(-1);用RDE法测得AH_2在PB薄膜上催化氧化的速率常数为1.23×10~8cm^3·mol^(-1)·s^(-1),催化反应对AH_2为一级,只发生在PB薄膜与溶液的界面上,整个催化过程受到溶液中的传质、膜内部的电荷传输及膜与溶液界面上交叉反应三种因素单独或联合控制,实际出现四种动力学情况。

The kinetics of prussian blue (PB) film itself during the redox process and of the catalytic oxidation of ascorbic acid (AH_2) on it have been studied in detail. The charge transfer diffusion coefficient D_(ct) in PB film is determined as 2.62×10^(-10)cm^2·s^(-1), using potential-step chronoamperometry, chronocoulometry and constant-current chronopotentialmetry, respectively. The rate constant of the cross-exchange reaction between AH_2 in solution and the active centers in PB film is measured in rotating disk electrode as 1.23×10~8cm^3·mol^(-1)·s^(-2). The catalytic reaction occurs only at the outmost part of the PB film and is first order to the bulk concentration of AH_2. The overall process can be limited by mass transfer in solution, by cross-exchange reaction at the film-solution interface, by charge transfer within the film or by some kind of combination of them, with four kinetic subcases experimentally observed and analyzed.