Abstract
As worldwide proposals and policies aimed at achieving carbon neutrality gain momentum, fuel cells stand out due to their high efficiency and stable energy storage capabilities [1]. Among these, protonic ceramic fuel cells (PCFCs) have received significant attention. This is because they can operate in the intermediate-to-low temperature range (350-700°C) due to the movement of protons with small ionic radius, resulting in lower activation energy for conduction, unlike solid oxide fuel cells (SOFCs) in which oxygen ions move [2]. However, the efficiency of PCFCs is often hindered by the sluggish nature of the oxygen reduction reaction (ORR) at the oxygen electrode. To address this challenge, the development of triple ionic-electronic conductors (TIECs) is necessary for PCFCs [3]. TIECs facilitate the simultaneous transfer of protons (H+), oxygen ions (O2-), and electrons (e-), thereby improving ORR kinetics. One notable aspect of TIECs is their capability to interact not only with triple phase boundaries (TPBs) but also with the surface of the oxygen electrode (double phase boundaries, DPBs), effectively increasing the available area for reactions [4].Over the last few decades, the perovskite structured materials (ABO3) has been widely used in oxygen electrode materials, due to its outstanding catalytic properties and electrochemical durability [5]. In particular, the triple-layered perovskite structure, with an increase in the c-axis direction, contains a significant number of oxygen vacancies per unit cell, ensuring high ion conductivity. Meanwhile, triple-layered perovskite materials have showed superior performance as a TIEC oxygen electrode material with a triple-layered perovskite structure [6]. However, triple-layered perovskite materials have a limitation in that it has a large particle size due to the high synthesis temperature (above 1100°C), resulting in reducing the reaction sites. Therefore, we successfully fabricated nanofibrous perovskite structured oxygen electrode at low calcination temperature (850°C) using electrospinning to enhance reaction sites and morphology [7]. As a result, we achieved exceptional peak power densities and superior durability at low temperatures in PCFC operations due to large effective pore tortuosity and high concentration of TPBs.
Published Version
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