La_(0.8)Sr_(0.2)MnO_3/YSZ电极氧电化学还原反应动力学

Kinetics of the Electrochemical Reduction of Oxygen on the La_(0.8)Sr_(0.2)MnO_3/YSZ Electrode

用线性极化、循环伏安、电位阶跃等方法详细研究了La0.8Sr0.2MnO3／YSZ高温电极上进行的氧电化学还原反应．实验结果表明，该反应存在两条路径：低温下氧还原反应主要发生在气相-LSM电极-YSZ电解质接触的三相界面（TPB），速度控制步骤为氧原子在LSM表面的浓差扩散，高温下由于氧空位在LSM表面的形成，氧还原反应区扩展至LSM电极表面，速度控制步骤为氧的电荷转移反应．实验同时发现：氧空位的形成受反应温度、氧分压及阴极电位的影响，氧空位在高温及高氧分压下对反应贡献很大．

Electrochemical reduction of oxygen on the La0.8Sr0.2MnO3/YSZ electrode has been investigated in detail with methods of Low Field Polarization , Cyclic Voltammetry and Potential Step. The results demonstrate that the reduction of oxygen on the LSM+YSZ cathode takes place through two pathways: at low temperatures oxygen reduction takes place at Three Phase Boundary (TPB), in which case the rate determining step is the diffusion of atomic oxygen from the LSM surface to TPB, while at high temperatures the reaction area extends over the whole surface of the LSM electrode and the rate determining step is the charge transfer step. It has also been found that the formation of oxygen vacancy is affected by reaction temperature, oxygen pressure and cathodic potential applied. Oxygen vacancy plays an important role in the electrochemical reduction of oxygen at high temperatures and high oxygen partial pressures.