Abstract
Achieving the fast oxygen reduction reaction (ORR) kinetics at the cathode of solid oxide fuel cells (SOFCs) is indispensable to enhance the efficiency of SOFCs at intermediate temperatures. Mixed ionic and electronic conducting (MIEC) oxides such as ABO3 perovskites and Ruddlesden-Popper (RP) oxides (A2BO4) have been widely used as promising cathode materials owing to their attractive physicochemical properties. In particular, oxides in forms of thin films and heterostructures have enabled significant enhancement in the ORR activity. Therefore, we aim to give a comprehensive overview on the recent development of thin film cathodes of SOFCs. We discuss important advances in ABO3 and RP oxide thin film cathodes for SOFCs. Our attention is also paid to the influence of oxide heterostructure interfaces on the ORR activity of SOFC cathodes.
Highlights
Solid oxide fuel cells (SOFCs) have shown great promise to contribute to the ultimate aim of environmentally friendly, efficient energy production and conversion [1,2,3,4]
This review aims to provide a synopsis of the major developments and achievements in thin film Mixed ionic and electronic conducting (MIEC) cathodes of SOFCs, which can help facilitate the development of intermediate temperature
The electrical oxygen surface exchange coefficient can be determined using the expression [53,54], kq = R·T/4F2 ·RORR ·Aelectrode ·co where R is the universal gas constant (8.314 J·mol−1 ·K−1 ), T is the absolute temperature, F is the Faraday’s constant (96,500 C·mol−1 ), RORR is the resistance obtained from the low frequency (LF) feature, Aelectrode is the area of the electrode, and co is the lattice oxygen concentration in thin film cathodes
Summary
Solid oxide fuel cells (SOFCs) have shown great promise to contribute to the ultimate aim of environmentally friendly, efficient energy production and conversion [1,2,3,4]. Overcoming the slow kinetics of the oxygen reduction reaction (ORR) at the cathode is essential to fulfill the increasing demand for developing intermediate temperature SOFCs [5]. New cathode materials with faster ORR kinetics are required to facilitate the development of intermediate temperature SOFCs. Cubic perovskite based mixed ionic and electronic conductors (MIECs) such as ABO3 oxides [6,7,8,9]. Compared to LSM113 , these MIECs possess considerably higher oxygen surface exchange kinetics, which enables to extend the electrochemically active region to the entire oxide surface from the electrode/electrolyte interface Readers can be referred to relevant comprehensive reviews of oxygen transport in ABO3 and RP oxide [12,34,35]
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