(1. 中南大學(xué) 化學(xué)化工學(xué)院， 長沙， 410083;
2. 攀枝花鋼鐵研究院， 成都 610000)
摘 要: 采用循環(huán)伏安、 極化曲線和交流阻抗三種電化學(xué)實驗方法研究了V(Ⅳ)/V(Ⅴ)電對在石墨氈電極上的反應(yīng)機理及其可能的速度控制步驟。 研究結(jié)果表明： V(Ⅳ)/V(Ⅴ)電對在石墨氈電極上的反應(yīng)屬準(zhǔn)可逆過程，且氧化過程包含有后置化學(xué)轉(zhuǎn)化步驟； 理論計算得到了電化學(xué)步驟和后置化學(xué)轉(zhuǎn)化過程分別為控制步驟時的Tafel斜率值為0.12和0.06， 實驗得到的Tafel斜率值為0.124， 表明電極氧化過程受電化學(xué)過程控制； 不同極化電位下的交流阻抗圖譜擬合結(jié)果表明， 電化學(xué)反應(yīng)阻抗值遠(yuǎn)大于其他阻抗值，說明電化學(xué)反應(yīng)可能是電極反應(yīng)的控制步驟， 與實驗得到的極化曲線分析結(jié)果相一致。
關(guān)鍵字: 釩電池； 石墨氈； V(Ⅳ)/V(Ⅴ)； 速度控制步驟
CHANG Zhi-feng2
（1. School of Chemistry and Chemical Engineering,
Central South University, Changsha 410083, China;
2. Steel Institute of Panzhihua, Chengdu 610000, China）
Abstract: The V(Ⅳ)/V(Ⅴ) reaction mechanism was investigated on a graphite felt electrode by means of cyclic voltammetry, polarization curve and impedance spectroscopies. Cyclic voltammetry analysis indicates that V(Ⅳ)/ V(Ⅴ) redox reaction at graphite felt electrode is quasi reversible. A certain chemical reaction step is suspected to follow the electron transfer step of this reaction. The Tafel slope value (0.124) obtained from the polarization curve agrees well with theoretical value (0.12) when the electron transfer step is supposed to be the rate determining step. Impedance spectroscopies at various potentials were studied and simulated by equivalent circuits. The impedance value of the electron transfer step modified is greatly higher than the others, which shows that the electron transfer step is the rate determining step. This further confirms the conclusion obtained by polarization curve test.
Key words: vanadium redox battery; graphite felt; V(Ⅳ)/V(Ⅴ); rate determining step
