Abstract
The phenomena taking place in Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) as cathodic material in solid oxide fuel cells are investigated by electrochemical impedance spectroscopy. BSCF powders are prepared by solution combustion synthesis. Measurements are collected at different temperatures, under various bias potentials and also recorded after long-term operation. Impedance spectra are thoroughly analyzed by the distribution of relaxation times (DRT) approach and compared to the standard equivalent circuits method. At 700 °C, losses are dominated by ionic conduction and charge transfer at the electrode/electrolyte interface, while oxygen adsorption and bulk diffusion provide a minor contribution to polarization. The performances of pristine materials are remarkable as a very low polarization resistance is measured at 700 °C. After prolonged testing at operative temperature, the BSCF cathodes show increasing total polarization resistance, especially due to progressive limitations in the migration of oxygen ions, caused by secondary phase formation. DRT analysis supports the physical interpretation of phenomena taking place in the material and shows the formation of a new contribution at low frequency which can be ascribed to partial decomposition of BSCF.
Highlights
Solid oxide fuel cells (SOFCs) have been developed for several decades as a power production technology [1]
Regardless of the architecture, the cathode is the major source of energy losses, due to limited activity towards the oxygen reduction reaction (ORR), deriving from intrinsic electrocatalytic properties of active materials as well as from the microstructure [8,9,10]
Results be taken without some criticalisinsight, which is necessary decade some apparent relaxations are present in the distribution function plot of distributed avoid, misinterpretation
Summary
Solid oxide fuel cells (SOFCs) have been developed for several decades as a power production technology [1] Their suitability in “power to gas” or “power to chemicals” processes as efficient energy converters was pointed out in several studies addressing the need to store/convert peak and intermittent energy production from renewable sources [2,3]. For these reasons, scientific and technological development of SOFCs is still highly pursued, aiming to better cell architectures and materials, among other aspects. Regardless of the architecture, the cathode is the major source of energy losses, due to limited activity towards the oxygen reduction reaction (ORR), deriving from intrinsic electrocatalytic properties of active materials as well as from the microstructure [8,9,10].
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