Abstract
We describe a novel electrochemical cell for X-ray absorption spectroscopy (XAS) experiments during electrical polarization suitable for high-temperature materials such as those used in solid oxide fuel cells. A half-cell LSCF/YSZ was then investigated under cathodic and anodic conditions (850 °C and applied electrical bias ranging from +1 V to −1 V in air). The in situ XAS measurements allowed us to follow the LSCF degradation into simple oxides. The rapid deterioration of LSCF is ascribed to the formation of excess of oxygen vacancies leading to the collapse of the mixed perovskite structure.
Highlights
Solid-oxide fuel cells (SOFC) represent a forefront theme in materials research, since they allow the production of electrical energy from hydrogen or hydrocarbon fuels with very high thermodynamic efficiency
We studied, under operating conditions, the atomic and electronic structure of La0.6 Sr0.4 Co0.8 Fe0.2 O3 (LSCF), which is a technologically relevant electrode material for high-temperature and intermediate-temperature SOFC
This paper presents one of the few structural studies of SOFC electrodes during operation
Summary
Solid-oxide fuel cells (SOFC) represent a forefront theme in materials research, since they allow the production of electrical energy from hydrogen or hydrocarbon fuels with very high thermodynamic efficiency. X-ray absorption spectroscopy allows one to obtain information about the atomic and electronic structure of the samples, so that it is suited for SOFC electrode materials, often constituted by variable valence elements that can modify their oxidation state and the local structure in dependence of reaction environment and applied potential [6,7,8,9]. Regarding this concern, the development of reliable experimental protocols [10] is essential to obtain significant information on SOFC materials [11,12,13,14]. By applying an external voltage bias, ranging from −1 V to +1 V, and employing X-ray absorption spectroscopy at a high temperature, we were able to investigate the different role of iron and cobalt concerning the oxidation state and structural rearrangement, as a function of time, temperature, and electrical polarization in operating conditions
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