AC Impedance Study of the La 0.8 Sr 0.2 MnO 3/YSZ Electrode
- 1998年第4卷 
用交流阻抗方法研究了Ｌａ０．８Ｓｒ０．２ＭｎＯ３（ＬＳＭ）电极上进行的氧电化学还原反应．实验表明反应速度控制步骤（ｒｄｓ）随反应温度、氧分压及过电位发生显著变化．近平衡下反应的ｒｄｓ为氧的解离吸附过程．强阳极极化下，电解质表面产生大量电子空穴；强阴极极化下，ＬＳＭ电极表面形成大量氧空位，二者的结果均使界面电导增加，电化学反应区扩展．低温强极化及高温强阳极极化下反应的ｒｄｓ为氧的电荷转移过程，高温强阴极极化下为氧的表面扩散过程Electrochemical reaction of oxygen on the La 0.8 Sr 0.2 MnO 3/YSZ electrode has been investigated in detail with AC impedance. The results demonstrated that the rate determining step(rds) of the reaction varies with the temperature, oxygen partial pressure and overpotential applied. At open circuit potential, the rds is the dissociative adsorption of oxygen on the LSM surface. A large number of electron holes are generated at high anodic overpotentials, while oxygen vacancies are formed at high cathodic overpotentials. The formation of the electron holes results in the electronic conduction of the YSZ electrolyte and the extension of the electrochemical active area. While the formation of oxygen vacancies leads to the ionic conduction in the LSM electrode and the extension of the electrochemical active area over the LSM electrode surface. The extension of active area and the increase of the conductivity induce some special phenomena reflected in AC impedance spectra, such as the decrease of both the electrode resistance and the ohmic drop, the increase of the double layer capacitance, and the appearance of the low frequency inductive arc at low temperature. The rds of the reaction at low temperature and high overpotentials is the charge transfer step, while at high temperature the rds of the reaction at high anodic and cathodic overpotential are the charge transfer step and the diffusion of oxygen over LSM surface respectively.