Electrochemical Reduction Mechanism of Fe(VI) at a Porous Pt Black Electrode

Abstract

Recently, ferrate(VI) has been widely investigated as a cathode material in alkaline batteries. The cathodic reduction process of the ferrate electrode is very important in understanding the electrochemical mechanism as well as in utilizing ferrate as a battery material. In this work, the direct electrochemical reduction process of was investigated by linear sweep voltammetry (LSV), with a porous Pt black electrode in a 9 M KOH solution at . The cathodic reaction process of is controlled by the diffusion process in a potential range from 0.20 to 0.53 V (vs Hg/HgO). Moreover, the totally irreversible cathodic reactions of include a rate-controlling step with an electron-transfer number less than 3. Sampled-current voltammetry was also applied to investigate the reaction processes, and the plot exhibits two limited currents. The first one is a weak one-electron limited current, corresponding to the rate-controlling step analyzed by LSV; the other one is a two-electron current. They are both affected by the diffusion of ions. Therefore, the electrochemical reduction mechanism of in 9 M KOH can be inferred as an overall three-electron process with a one-electron transfer as the rate-controlling step, in which the intermediate state of Fe(V) is generated from ferrate(VI).