硫酸溶液中V(IV)/V(V)电对在碳纸电极上的阻抗特性

Electrochemical impedance characteristic of V(IV)/V(V) redox couples on carbon paper electrode in H_2SO_4 solution

用交流阻抗结合循环伏安方法研究了硫酸溶液中V(IV)/V(V)电对在碳纸电极上的阻抗特性。结果表明,碳纸电极在开路电位[0.2V(vs.SCE)]下仅表现为–COH/–C=O电对的氧化还原行为。在极化电位0.7-1.2V下测得的交流阻抗是由于V(IV)/V(V)电对的氧化还原行为引起的。极化电位对V(IV)/V(V)电对的交流阻抗参数影响很大,电荷转移电阻及双电层电容在0.9V的极化电位下出现最小值,而扩散电容在此电位下则有极大值,这种影响规律与通过控制V(IV)和V(V)离子在电解液中的比例能构筑不同开路电位的钒电解液中所得的规律相同。

The electrochemical impedance characteristic of V（IV）/V（V） redox couples on carbon paper electrode in H2SO4 solution was investigated.The results show that the oxidation and reduction behavior of carbon paper electrode in the V（IV）-H2SO4 solution under the open circuit potential [0.2 V（vs.SCE）] is attributed to-COH/-C=O redox couples reaction.The electrochemical impedance measured at 0.7~1.2 V polarization potential ranges is due to V（IV）/V（V） redox couples reaction.There is a great impact about the polarization potential on V（IV）/V（V） redox couples reaction in the electrolyte,both reaction resistance and electric double layer have a minimum while diffusion capacitance has a maximum at 0.9 V polarization potential.The different potential systems can be built through controlling the proportion of V（IV） and V（V） in electrolyte,which can obtain the similar impedance law of imposing a certain polarization potential in V（IV）-H2SO4 solution.