Influence of Cr~(3+) concentration on the electrochemical behavior of the anolyte for vanadium redox flow batteries

• 来源期刊: 科学通报(英文版)
• 学科: 工学
• 年，卷（期）: 2012,（32）
• 页码范围: 4237-4243
• 页数: 7页
• 分类号: TM912
• 语种: 中文

摘要

The composition of electrolyte affects to a great extent the electrochemical performance of vanadium redox flow batteries(VRB).The effects of Cr3+ concentration in the anolyte on the electrode process of V(V)/V(IV) couple have been investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS).It was found that Cr3+ causes no side reactions,but affects the electrochemical performance of V(V)/V(IV) redox reaction,including the reaction activity,the reversibility of electrode reaction,the diffusivity of vanadium ions,the interface film impedance,and the electrode reaction impedance.The experimental results show that Cr3+ within a certain concentration range can improve the reversibility of electrode reaction and the diffusion of vanadium ions.With the Cr3+ concentration increasing from 0 to 0.30 g L-1,the reversibility of V(V)/V(IV) reaction increases,while the diffusion resistance decreases.Correspondingly,the diffusion coefficient of vanadium ions increases from(5.48-6.77) * 10-7 to(6.82-8.44) * 10-7 cm2 s-1,an increase of ~24%.However,the diffusion resistance increases and the diffusion coefficient decreases when Cr3+ concentration is over 0.30 g L-1,while the impedances of the interface,the film as well as the charge transfer increase continuously.As a result,Cr3+ with a certain concentration improves the diffusion and mass transfer process,but the resistances of the film,the interface,and the charge transfer rise.Furthermore,Cr3+ concentration of no more than 0.10 g L-1 has few effect on the electrode reaction process,and that of no more than 0.30 g L-1 is favorable to the diffusion of vanadium ions.