Abstract
A Ba-based glass-ceramic sealant is designed and tested for solid oxide electrolysis cell (SOEC) applications. A suitable SiO2/BaO ratio is chosen in order to obtain BaSi2O5 crystalline phase and subsequently favorable thermo-mechanical properties of the glass-ceramic sealant. The glass is analyzed in terms of thermal, thermo-mechanical, chemical, and electrical behavior. Crofer22APU-sealant-Crofer22APU joined samples are tested for 2000 h at 850 °C in a dual atmosphere test rig having reducing atmosphere of H2:H2O 50/50 (mol%) and under the applied voltage of 1.6 V. In order to simulate the SOEC dynamic working conditions, thermal cycles are performed during the long-term electrical resistivity test. The glass-ceramic shows promising behavior in terms of high density, suitable CTE, and stable electrical resistivity (106–107 Ω cm) under SOEC conditions. The SEM-EDS post mortem analysis confirms excellent chemical and thermo-mechanical compatibility of the glass-ceramic with Crofer22APU.
Highlights
The high temperature solid oxide electrolysis cell (SOEC) technology is considered as one of the most attractive method to produce green hydrogen because of its high efficiency [1,2,3,4,5]
Glass-ceramics are considered to be the most promising sealant candidates owing to their high electrical resistivity, thermal and chemical stability at high working temperature, and due to the possibility to tune their physical and chemical properties by tailoring their composition [9,10,11,12]
Among alkaline earth metal oxides, BaO is the most extensively used modifier as it improves the coefficient of thermal expansion (CTE) and wettability of the glass-ceramic sealant [6,23,24,25,26,27]
Summary
The high temperature solid oxide electrolysis cell (SOEC) technology is considered as one of the most attractive method to produce green hydrogen because of its high efficiency [1,2,3,4,5]. Alkali oxide-based glass-ceramic sealants are usually not very attractive because of their low electrical resistivity and detrimental reaction with Cr at high temperature and under applied voltage [21,22]. Among alkaline earth metal oxides, BaO is the most extensively used modifier as it improves the coefficient of thermal expansion (CTE) and wettability of the glass-ceramic sealant [6,23,24,25,26,27]. BaO-based glasses mostly suffer from the formation of high CTE BaCrO4 phase because of chemical reaction between Ba (from glass) and Cr (from the interconnect). Schilm et al [31] designed different glass compositions from SiO2 -BaO-CaO-Al2 O3 system and their electrical resistivity was measured in dual atmosphere for 300 h under the applied voltage of 0.7 V and 1.3 V. Thermal cycles were applied during resistivity analysis in order to simulate the dynamic SOEC conditions
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