High-Performance Solid Oxide Electrochemical Cells with Ultrathin and Dense Double-Doped Ceria Interlayers

Abstract

To mitigate the drastic global climate change, which mainly originated from the indiscriminate use of fossil fuels, various alternative eco-friendly energy conversion technologies have been studied. Among them, solid oxide electrochemical cells (SOCs) are one of the most promising devices with superior power and energy densities and low environmental impact. The current main objective of the SOCs research field is lowering the operating temperature to secure thermal cycling stability and minimize system costs. To achieve a feasible performance for commercial usage at reduced temperatures, it is inevitable to use state-of-the-art cobalt-based oxygen electrode materials. However, cobalt-based materials inherently react with conventional zirconia-based electrolytes at high temperatures forming insulating phases at the interface. Thus, the ceria interlayer is essentially required to prevent unwanted chemical reactions. In this study, we newly developed thin and dense doubly doped ceria interlayers (~250 nm) using a non-vacuum solution deposition process with gelatin. The SOCs with the thin-film ceria interlayers achieved superior electrochemical performance both in the fuel cell (FC) and the electrolysis cell (EC) mode (~3.5W/cm2 and ~2.1A/cm2 at 750°C for the FC and EC modes, respectively) compared to the SOC with a conventional porous and thick interlayer. The mechanistic analyses showed that the thin-film interlayer provides a much shorter route for oxygen ionic conduction and more active sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (ORR) at the interface compared to the porous interlayer. Our results suggest that the thin-film doubly-doped ceria interlayer fabricated using the gelatin-assisted process has a high potential for development of high-performance SOCs.