Neumeier Jonas J, Elm Matthias T, Luerßen Bjoern, Janek Jürgen
Institute of Physical Chemistry, Justus-Liebig-University Gießen, Heinrich-Buff-Ring 17, 35392 Gießen, Germany.
Phys Chem Chem Phys. 2018 Mar 28;20(12):8294-8301. doi: 10.1039/c8cp00261d. Epub 2018 Mar 13.
To better understand the electrode kinetics of oxygen reduction and oxidation of gadolinia doped ceria (GDC), the electrochemical properties of platinum electrodes on GDC single crystals and polycrystalline samples were investigated with geometrically well-defined microelectrodes. For comparison measurements were also performed on polycrystalline samples using platinum interdigital electrodes in order to access the effect of the electrode geometry on the electrochemical properties. The transport properties were characterised using impedance spectroscopy, allowing to separate the transport processes of the electrode and the electrolyte. Evaluation of the temperature dependence shows activation energies of 0.77 eV for bulk transport and 1.03 eV for the electrode exchange. Oxygen partial pressure dependent measurements in a reducing atmosphere reveal a strong increase in activation energy due to electronic defect formation. A distinct chemical capacitance is observed in the electrode impedance for all sample types independent of the electrode geometry. While this chemical capacitance is only visible in the electrolyte contribution for the samples measured with interdigital electrodes, for the samples investigated with microelectrodes no chemical capacitance is observed in the electrolyte contribution of the impedance. As the chemical capacitance is related to stoichiometry changes in the electrolyte materials, the results confirm the non-uniform potential distribution occurring at a microelectrode, which results in a vanishing lateral potential gradient and therefore in a negligible stoichiometry gradient inside the electrolyte at a distance from the microelectrode.
为了更好地理解钆掺杂二氧化铈（GDC）的氧还原和氧化的电极动力学，使用几何形状明确的微电极研究了GDC单晶和多晶样品上铂电极的电化学性质。为了比较，还使用铂叉指电极对多晶样品进行了测量，以了解电极几何形状对电化学性质的影响。使用阻抗谱对传输性质进行了表征，从而能够区分电极和电解质的传输过程。对温度依赖性的评估表明，体传输的活化能为0.77 eV，电极交换的活化能为1.03 eV。在还原气氛中进行的与氧分压相关的测量表明，由于电子缺陷的形成，活化能大幅增加。在所有样品类型的电极阻抗中都观察到了明显的化学电容，且与电极几何形状无关。虽然这种化学电容仅在使用叉指电极测量的样品的电解质贡献中可见，但对于使用微电极研究的样品，在阻抗的电解质贡献中未观察到化学电容。由于化学电容与电解质材料中的化学计量变化有关，结果证实了微电极处存在的非均匀电位分布，这导致横向电位梯度消失，因此在距微电极一定距离处的电解质内部化学计量梯度可忽略不计。
