Obtaining a catalyst with high activity and thermal stability is essential for high-performance energy conversion devices operating at an elevated temperature. Herein, the design and fabrication of a heterogeneous catalyst with an ultrathin CeO2 overlayer via atomic layer deposition (ALD) on Pt electrodes for low-temperature solid oxide fuel cells (LT-SOFCs) is reported. The cell with a CeO2-overcoated (five ALD cycles) Pt cathode shows lower activation resistance by 50% after a 10 h operation and higher thermal stability by a factor of 2 compared with the cell with a Pt-only cathode, which is known to be the best single catalyst at 450 °C. Eventually, a thin-film SOFC with a highly active and stable CeO2-overcoated cathode based on an anodized aluminum oxide (AAO) substrate demonstrates a high peak power density of 800 mW cm–2 at 500 °C, which is the highest performance ever reported for an AAO-based SOFC at this temperature.

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Solid oxide fuel cells (SOFCs) are promising candidates for next-generation energy conversion devices, and much effort has been made to lower their operating temperature for wider applicability. Recently, atomic layer deposition (ALD), a novel variant of chemical vapor deposition, has demonstrated interesting research opportunities for SOFCs due to its unique features such as conformality and precise thickness/doping controllability. Individual components of SOFCs, namely the electrolyte, electrolyte-electrode interface, and electrode, can be effectively engineered by ALD nanostructures to yield higher performance and better stability. While the particulate or porous structures may benefit the electrode performance by maximizing the surface area, the dense film effectively blocks the chemical or physical shorting even at nanoscale thickness when applied to the electrolyte, which helps to increase the performance at low operating temperature. In this article, recent examples of the application of ALD-processed nanostructures to SOFCs are reviewed, and the quantitative relationship between ALD process, ALD nanostructure and the performance and stability of SOFCs is elucidated. Abbreviations

Designing and fabricating highly active and thermally stable catalysts with minimal noblemetal loading is crucial for solid oxide fuel cells that operate with direct methane fuel. In this study, ultralow-loading Ru catalysts (<10 μg cm −2 ) are fabricated using plasma-enhanced atomic layer deposition (PEALD) on a samaria-doped ceria (SDC) backbone for a methane oxidation electrode. The Ru catalyst with a high surface area and a high triple-phase boundary density shows electrochemical performance superior to that of its sputtered counterpart despite a 95% reduction in noble-metal loading. Furthermore, the PEALD Ru catalyst demonstrates more stable operation at elevated temperatures with less morphological degradation in comparison to the sputtered catalyst and mitigates carbon coking. Such improvements are ascribed to the nature of PEALD, which can make Ru particles conformally on porous SDC with highly dense and intimate interfaces.

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