Robust and reactive solid oxide fuel cell cathode achieved through metal-oxide nanocomposite deposition

Abstract

The solid oxide fuel cell is an eco-friendly energy conversion device with high efficiency that can replace fossil fuel combustion. In order for the solid oxide fuel cell to be widely used, it is essential to lower the driving temperature below 800 °C. However, at such low temperatures, the sluggish reaction rate of the cathode causes a large energy loss. Therefore, it is very important to develop a highly active cathode at low temperatures. La$_{0.6}$Sr$_{0.4}$Co$_{0.2}$Fe$_{0.8}$O$_{3-δ}$ (LSCF) is one of the solid oxide fuel cell (SOFC) cathode materials widely used in industrial area because of its high electrical conductivity and catalytic activity as well as its adequate thermal expansion coefficient and ease of synthesis. However, the rate of oxygen reduction reaction at low temperatures is relatively slow and undesired side reactions such as Sr segregation occur during long-term operation, which limits the industrial use of LSCF electrodes. Therefore, improving catalytic activity and durability of LSCF at lower operating temperatures (<800 °C) can be a shortcut to accelerate the commercialization of SOFCs. In this regard, to address these issues simultaneously, we combining two general techniques: infiltration and atomic layer deposition (ALD) to fabricated highly active and robust LSCF-based cathode. Ag nanocatalyst, which is known to have excellent catalytic activity for oxygen reduction reaction, are decorated on the surface of porous LSCF electrode via wet infiltration, and then covered with a thin oxide layer of ZrO$_2$ via ALD. The analyses of SEM, TEM, XPS and electrochemical impedance spectroscopy reveal that ZrO$_2$ layer prevents the agglomeration of the Ag nanocatalysts and suppressed Sr segregation, significantly improving the LSCF electrode performance and durability, showing a low area-specific resistance of only 0.085 Ωcm$^2$ at 650 °C over 200 hours.