Determination of Electrode Oxygen Transport Kinetics Using Electrochemical Impedance Spectroscopy Combined with Three-Dimensional Microstructure Measurement: Application to Nd₂NiO_4+δ

Abstract

Oxygen reduction kinetic parameters -oxygen ion diffusion D δ , molar surface exchange rate O and surface exchange coefficient k -were determined for porous Nd 2 NiO 4+δ solid oxide fuel cell cathodes as a function of temperature and oxygen partial pressure by analyzing electrochemical impedance spectroscopy data using the Adler-Lane-Steele model. Electrode microstructural data used in the model calculations were obtained by three-dimensional focused ion beam-scanning electron microscope tomography. Cathodes were fabricated using Nd 2 NiO 4+δ powder derived from a sol-gel method and were tested as symmetrical cells with LSGM electrolytes. The oxygen surface exchange rate exhibited a power-law dependency with oxygen partial pressure, whereas the oxygen diffusivity values obtained varied only slightly. The present analysis suggests that the O-interstitial diffusion has a bulk transport path, whereas the surface exchange process involves dissociative adsorption on surface sites followed by O-incorporation. For Nd 2 NiO 4+δ at 700 • C and 0.2 atm oxygen pressure, D δ = 5.6 · 10 −8 cm 2 s −1 , O = 2.5 · 10 −8 mol · cm −2 s −1 . The present D δ and O values and their activation energies are slightly different to those previously reported for Nd 2 NiO 4+δ using other measurement methodologies, and lower than typical state-of-the-art Co-rich perovskites. However, the average k δ = 1.0 10 −5 cm · s −1 at 700 • C is comparable to those of fast oxygen exchange rate perovskites.

Mechanisms of Performance Degradation of (La,Sr)(Co,Fe)O3-δSolid Oxide Fuel Cell Cathodes

“…Recently, it has been shown that the oxygen surface exchange rate k and solid-state oxygen diffusion coefficient D * can be estimated for porous MIEC electrodes by using the ALS model 20 combined with electrode microstructural data. 27,28 As shown in Fig. 1, electrode EIS data could be modeled reasonably well by an equivalent circuit consisting of an inductor (L), an ohmic resistance (R) and a modified Gerischer element (GE).…”

“…Based on oxygen nonstoichiometry, the oxygen vacancy fraction, χ v , and the thermodynamic factor, A 0 , were estimated to be 0.035 and 1.85, respectively. 27,32,33 With the above quantities known, and R G and t G determined from the EIS fitting shown in Fig. 1, k and D * are calculated from Eqs.…”

Hierarchical Nickel Clusters Encapsulated in Ultrathin N-doped Graphitic Nanocarbon Hybrids for Effective Hydrogen Evolution Reaction

“…The excellent ECSA for Ni@GC-450 suggests that the annealing temperature has a great influence on the electrocatalytic efficiency resulting from the defects of graphitic nanocarbon shells and electrochemical conductivity. Electrochemical impedance spectroscopy (EIS) is further performed to elucidate the characteristics of the intrinsic interfacial charge transfer and charge transport kinetics at the interface of the electrode and electrolyte. , As the Nyquist plots illustrated in Figure b, the smallest charge-transfer resistance for Ni@GC-450 implicates the best HER kinetics and the fastest Faradaic process resulting from the high electrochemical conductivity created from the fast redox reaction. And, an equivalent circuit diagram (the inset of Figure b) was created to model the underlying HER process.…”

Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

“…For this SrTiO 3 :Fe system their results suggested the presence of O 2 n − in the RDS with one electron transferred; further, if the bulk and surface defect concentrations share the same pO 2 dependence, those authors concluded that formation of O 2 2− by electron transfer or dissociation of O 2 2− is the most likely RDS under the measurement conditions. An important point from their work and that of others [46,47] is that the pO 2 dependence of the reaction rate in equilibrium alone may not be sufficient to identify the fundamental, detailed RDS, since many mechanisms can share the same equilibrium pO 2 dependence.…”