Platinum microelectrodes on gadolinia doped ceria single crystals – bulk properties and electrode kinetics

Abstract

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.

Tailoring the protonic conductivity of porous yttria-stabilized zirconia thin films by surface modification

“…The impedance spectra were evaluated using the software RelaxIS 3. 37 TiO 2 was deposited by ALD on two YSZ thin films using an ALD R200 Standard system from Picosun. Tetrachloride (TiCl 4 ) and water were used as precursors at a substrate temperature of 150 °C.…”

“…1,35 The semicircle at low frequency with a capacitance of about 1 • 10 -7 F corresponds to the electrochemical response of the electrode-electrolyte interface. 37,50 As the scope of this study is to take a closer look on the transport processes of the electrolyte, we did not investigate the electrode processes in detail. The total conductivity was calculated from the total resistance , i.e., the 𝑅 bulk and the grain boundary resistance, according to:…”

Epitaxial Growth and Structural Characterization of Ceria Deposited by Atomic Layer Deposition on High-Surface Porous Yttria-Stabilized Zirconia Thin Films

“…A promising material for modifying the surface of solid electrolytes for electrochemical application is doped ceria. , Because of its ability to change between Ce 3+ and Ce 4+ oxidation states, solid solutions of ceria exhibit a comparably large surface exchange coefficient, good catalytic properties, , as well as a high oxygen storage capacity. , However, the structural properties of the surface layer, such as crystal structure, grain boundary density, impurity segregation, or dopant concentration, play a significant role on the oxygen exchange reaction. For example, the orientation of the ceria thin film on the surface affects not only the catalytic properties but also the reoxidation kinetics of the thin films .…”

Impact of inversion and non-stoichiometry on the transport properties of mixed zinc-cobalt ferrites

“…Then, the activation energy comprises an additional contribution from the defect formation enthalpy. 72 B is present in the samples, and hopping can only arise in the Fe 2+ /Fe 3+ states. The difference between the activation energy of ZnFe 2 O 4 (E A = 0.19 eV) and all Cocontaining samples (E A o 0.1 eV) can again be attributed to the more pronounced ferromagnetic alignment of octahedral sites in the cobalt-containing ferrites.…”