铁离子电还原过程的研究

A STUDY ON THE ELECTROCHEMICAL REDUCTION PROCESS OF FERRIC IONS

用电位扫描法和旋转电极技术,研究了铁离子在铂电极和玻碳电极上的还原行为.结果表明该还原反应的可逆性明显地依赖于相伴阴离子的本性,在含SO_4^(2-)、NO_3^-、阴离子的溶液中,反应并非完全可逆,当溶液合Cl^-、CN^-离子时,电极反应是可逆的,而在F^-、C_2O_4^(2-)、Cit^(3-)、CNS^-、P_2O_7^(2-)等离子存在时,反应是不可逆的.实验证明,Fe^(2+)离子还原时,电极表面有吸附膜生成,此膜对H^+的放电析出有催化作用.从旋转电极实验求得1.0mol·dm^(-3)KCl溶液中,Fe^(3+)离子的扩散系数D_(Fe^(3+))=(7.9±0.1)×10^(-6)cm^2·s^(-1),标准速度常数k=(2.5±0.2)×10^(-3)cm·s^(-1).

Electrochemical reduction of ferric ions is studied by using potential sweep method and rotating ring disc electrode techniques. It is shown that the reversibity of the reaction varies obviously depending on the nature of the accompanying anions. The reduction of Fe3+is not totally reversible in solutons containing SO42-, NO3- anions, but in the presence of Cl- and CN- anions it behaves reversibly and becomes irrersible in solutions of F-, C2O42-, Cit3-, CNS- and P2 O72-. It is confirmed that an adsorption film, which has catalystic effect on the evolution of hydrogen, occurs during the reduction process of Fe2+ ions. It is obtained from the rotating disc electrode experiments that the diffusion coefficient of Fe3+ ions in the solution of 1.0 mol·dm-3 KCl is (7.9±0.1)×10-6 cm2·s-1 and the standard rate constant kf= (2.5±0.2)×10-3cm·s-1.