Abstract
Solid oxide fuel cell (SOFC) is an advanced electricity generation device with attractive fuel flexibility and conversion efficiency. As its reversed process, solid oxide electrolysis cell (SOEC) can efficiently electrolyze notorious CO2 to valuable chemical product such as CO, by utilizing renewable energy. To achieve long-term operation, the development of catalytically active electrode materials in both SOFC/SOEC modes is highly desirable, yet still challenging. In this research, an A-site deficient perovskite oxide (lanthanum chromite) decorated with in-situ exsolved Ni-Co nano-alloy has been fabricated and applied as a potential fuel electrode for both SOFC/SOEC. The influences of A-site non-stoichiometry and B-site dopant concentration on structural properties and in-situ exsolution process have been elaborately studied from various aspects. Diverse characterizations collectively confirm that the existence of A-site deficiency helps the formation of oxygen vacancies and stimulates the exsolution of B-site cations. In addition, the synergistic effect between the dopants of Co and Ni manipulates the reducibility and promotes carbon deposition resistance of the material. The electrolyte-supported SOFC with self-assembled Ni-Co nano-alloy electrode has shown maximum power densities of 329 mW/cm2 (in H2) and 258 mW/cm2 (in syngas, H2 + CO) at 850 °C, which are 50% better than those of the fuel cell with the exsolved Ni nanoparticles only. Also, the nano-alloy decorated electrode catalyst promotes a 30% increase in SOEC performance for CO2 electrolysis with prominently enhanced resistance against carbon deposition, suggesting the versatile functionality of the materials.
Highlights
The rapid growth of the world’s fossil fuel consumption in recent years has led to some severe environmental concerns such as greenhouse effect (Pérez-Lombard et al, 2008)
The LSC-based perovskite oxides were prepared in this work as a potential electrode material for solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC)
The roles of A-site stoichiometry and B-site dopant concentration on material properties were studied by X-Ray diffraction (XRD), TPR, temperature program oxidation (TPO), TGA, X-ray photoelectron spectroscopy spectra (XPS) and SEM
Summary
The rapid growth of the world’s fossil fuel consumption in recent years has led to some severe environmental concerns such as greenhouse effect (Pérez-Lombard et al, 2008). The application of lanthanum chromite in SOFC is still hindered by its low catalytic activity, mainly due to lack of reactive sites To solve this problem, catalytically active metal nanoparticles were incorporated onto perovskite surface by wet impregnation (infiltration) or chemical deposition (Sfeir et al, 2001). The main conception of in-situ exsolution is to dissolve catalytic transition metals into the perovskite structure (at B sites) during the air preparation process (an oxidizing atmosphere), and force them to partially exsolve out of the lattice in a reducing atmosphere. Such process introduces the array of highly uniform dispersed nanoparticles on the perovskite support. Results show that the LSC-NiCo can be a promising candidate for reversible solid oxide cells
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