Structural, Interfacial, and Electrochemical Stability of La0.3Ca0.7Fe0.7Cr0.3O3-δ Electrode Material for Application as the Oxygen Electrode in Reversible Solid Oxide Cells

A detailed study aimed at understanding the structural, interfacial, and electrochemical performance stability of La0.3Ca0.7Fe0.7Cr0.3O3-δ (LCFCr) electrode material for application as the oxygen electrode in reversible solid oxide cells (RSOCs) is presented. Specifically, emphasis is placed on the stability of the LCFCr oxygen electrode during oxygen evolution (electrolysis mode), whereby many known electrode materials are known to fail due to delamination. The porous microstructure of the electrode was characterized by nanoscale X-ray microscopy (XRM) to reveal the percentage porosity, pore connectivity, average pore size, and electrochemical surface area, etc. Under polarization in a two-electrode symmetrical-cell configuration, while the working electrode was under anodic polarization, a very stable performance was observed at a cell potential of 0.2 V, although increasing the cell potential to 0.65 V caused significant performance degradation. This degradation was reversible when the cell was run at open circuit for 10 h. High-resolution transmission electron microscopy and wavelength dispersive spectroscopy revealed that the working electrode (LCFCr)/electrolyte (GDC) interface was structurally and chemically stable after hundreds of hours under polarization with no interdiffusion of the various species observed across the interface, hence rendering LCFCr a viable alternative for the oxygen electrode in RSOCs.Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEMitacsMinisterio de Ciencia e InnovaciónMCIN/AEIpu

Structural and dielectric properties of ultra-fast microwave-processed La_0.3Ca_0.7Fe_0.7Cr_0.3O3-delta ceramics

Perovskite La_0.3Ca_0.7Fe_0.7Cr_0.3O_(3-delta) (LCFCr) is a mixed ionic and electronic conductor (MIEC) that can be employed as an electrode material in reversible solid oxide fuel cells (RSOFCs). In this work, an ultra-fast (15 min) one-step microwave (MW)-assisted combustion synthesis route has been developed to obtain phase pure and highly crystalline LCFCr powder. The synthesized powders exhibited a sponge-like microstructure with increased electrochemical reaction sites. Neutron thermodiffraction analysis revealed a structural transition above 500 degrees C from the room temperature (RT) orthorhombic Pnma to a rhombohedral R3c perovskite phase. The oxygen vacancy concentration was found to increase from delta = 0.272(7) at RT to delta = 0.333(5) at 900 degrees C. Furthermore, a 3-dimensional G-type antiferromagnetic structure was detected at RT. MW-sintering of pressed green ceramic pellets was carried out at 950 degrees C for 1 h, using a MW-transparent quartz fiber crucible or alternatively a SiC crucible acting as a MW-absorber. Impedance spectroscopy data on sintered ceramic pellets revealed electronic inhomogeneity as demonstrated by the occurrence of three dielectric relaxation processes associated with two grain boundary (GB)-like contributions and one bulk. The dielectric inhomogeneity encountered may be restricted to the extrinsic GB areas, which may be rather thin. More homogeneous dielectric properties of the GBs were found in the pellet that was sintered in the SiC crucible

Structural, Interfacial, and Electrochemical Stability of La0.3Ca0.7Fe0.7Cr0.3O3-δ Electrode Material for Application as the Oxygen Electrode in Reversible Solid Oxide Cells

A detailed study aimed at understanding the structural, interfacial, and electrochemical performance stability of La0.3Ca0.7Fe0.7Cr0.3O3-δ (LCFCr) electrode material for application as the oxygen electrode in reversible solid oxide cells (RSOCs) is presented. Specifically, emphasis is placed on the stability of the LCFCr oxygen electrode during oxygen evolution (electrolysis mode), whereby many known electrode materials are known to fail due to delamination. The porous microstructure of the electrode was characterized by nanoscale X-ray microscopy (XRM) to reveal the percentage porosity, pore connectivity, average pore size, and electrochemical surface area, etc. Under polarization in a two-electrode symmetrical-cell configuration, while the working electrode was under anodic polarization, a very stable performance was observed at a cell potential of 0.2 V, although increasing the cell potential to 0.65 V caused significant performance degradation. This degradation was reversible when the cell was run at open circuit for 10 h. High-resolution transmission electron microscopy and wavelength dispersive spectroscopy revealed that the working electrode (LCFCr)/electrolyte (GDC) interface was structurally and chemically stable after hundreds of hours under polarization with no interdiffusion of the various species observed across the interface, hence rendering LCFCr a viable alternative for the oxygen electrode in RSOCs

Age and frailty are independently associated with increased COVID-19 mortality and increased care needs in survivors: results of an international multi-centre study

Introduction: Increased mortality has been demonstrated in older adults with coronavirus disease 2019 (COVID-19), but the effect of frailty has been unclear. Methods: This multi-centre cohort study involved patients aged 18 years and older hospitalised with COVID-19, using routinely collected data. We used Cox regression analysis to assess the impact of age, frailty and delirium on the risk of inpatient mortality, adjusting for sex, illness severity, inflammation and co-morbidities. We used ordinal logistic regression analysis to assess the impact of age, Clinical Frailty Scale (CFS) and delirium on risk of increased care requirements on discharge, adjusting for the same variables. Results: Data from 5,711 patients from 55 hospitals in 12 countries were included (median age 74, interquartile range [IQR] 54–83; 55.2% male). The risk of death increased independently with increasing age (>80 versus 18–49: hazard ratio [HR] 3.57, confidence interval [CI] 2.54–5.02), frailty (CFS 8 versus 1–3: HR 3.03, CI 2.29–4.00) inflammation, renal disease, cardiovascular disease and cancer, but not delirium. Age, frailty (CFS 7 versus 1–3: odds ratio 7.00, CI 5.27–9.32), delirium, dementia and mental health diagnoses were all associated with increased risk of higher care needs on discharge. The likelihood of adverse outcomes increased across all grades of CFS from 4 to 9. Conclusion: Age and frailty are independently associated with adverse outcomes in COVID-19. Risk of increased care needs was also increased in survivors of COVID-19 with frailty or older age.</p