Oxygen Exchange Kinetics over Sr- and Co-Doped LaFeO₃

Abstract

Oxygen exchange constants and oxygen diffusion coefficients were determined by relaxation (TGA-DSC and in situ XRD) and steady-state isotopic transient kinetic analysis (SSITKA) techniques as a function of oxygen partial pressure, temperature, and Co content for La 0.6 Sr 0.4 Co y Fe 1-y O 3-δ (y ) 0.1, 0.2, and 0.3). When y ) 0.2, oxygen exchange constants and oxygen diffusion coefficients appeared to be enhanced once above the temperature at which the unit cell symmetry increased from rhombohedral to cubic. Oxygen partial pressure demonstrated minimal influence upon these properties over the higher range (near ambient) studied, but showed a major impact when results obtained near ambient oxygen partial pressures are compared to those obtained under N 2 . The direction of oxygen transport was also important. Oxygen exchange constants and oxygen diffusion coefficients calculated from oxidation steps were greater than values for the same properties calculated from reduction steps under all conditions examined. Explanations for this behavior are proposed with use of kinetic, transport, and ESR spectroscopy data. While the oxygen exchange constant increased with Co content, the oxygen diffusion coefficient progressed through a maximum for the formations studied. The nonlinear trend for oxygen diffusivity with Co content is explained by an electronic structure change over this compositional range, which aligned with differences in Mo ¨ssbauer spectra.

Defect Engineering, Electronic Structure, and Catalytic Properties of Perovskite Oxide La0.5Sr0.5CoO3−δ

“…The ESR data of the original sample LSCO‐1 coincided with other literature data, showing a hump at about 325 mT . However, after topological reduction and urea pyrolysis, the peak intensity at about 300 mT ( g 2.21) clearly increased and other small peaks developed at other positions ( g 3.08 and 2.10), which were attributed to spin interactions of Co ions and various surface oxygen species …”

Tritium Sequestration in Gen IV NGNP Gas Stream via Proton Conducting Ceramic Pumps

“…2-19(b), typically from 6.41 Ωcm 2 at 500 o C to 0.35 Ωcm 2 at 600 o C. Further analysis shows that the ratio of R p to R t decreases with the increase in the cell operating temperatures, from 85.5 % at 500 o C to 32.6 % at 600 o C, indicating that the cell performance is significantly limited by R p at low temperatures. The large R p value observed in this work implies that electrochemical activity of LSCF catalyst is not sufficient at low temperatures, consistent with previous reports 43 . Therefore, the performances may be improved by using materials with better catalytic performance such as Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) 44 and optimizing the electrode microstructure to decrease the electrode polarization.…”

A Review on Perovskite-Type LaFeO3 Based Electrodes for CO2 Reduction in Solid Oxide Electrolysis Cells: Current Understanding of Structure–Functional Property Relationships

“…These MIEC materials demonstrate high catalytic activity, redox stability, and sulfur tolerance compared to Ni-YSZ. , Furthermore, several MIECs have demonstrated high stability in CO 2 /CO at an elevated temperature. − in which the entire surface is electrochemically active leading to a significant performance improvement, unlike cermet electrodes, due to MIEC–gas interface activity (dual-phase-boundary, DPB). Fluorite-type Ce 0.9 Gd 0.1 O 2−δ , perovskite-type LaFeO 3 , La 0.75 Sr 0.25 Cr 0.5 Mn 0.5 O 3−δ , double perovskite-type Sr 2 MgMoO 6 , and Nd 2 WO 6 oxides are reported as potential electrodes for SOCs. − Among these families of MIECs, doped lanthanum ferrites were recently developed as SOEC cathodes due to their good catalytic activity, electronic conductivity, and oxygen mobility. − Since perovskite-type structure oxides are currently being widely explored, this article is aimed to provide an overview of LaFeO 3 electrodes for SOECs.…”