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.

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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