Advances in Ceria‐Based Fuel Electrodes for Solid Oxide Cells: Reaction Mechanisms, Performance, Stability, and Future Directions With Focus on Nickel–Gadolinium‐Doped Ceria

Solid oxide electrochemical cells, including solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs), are highly efficient platforms for converting fuels or renewably generated power into energy and value‐added chemicals at intermediate‐to‐high temperatures (600–900 °C), supporting carbon‐neutral energy systems. The fuel electrode plays a critical role in governing device performance and durability. However, conventional Ni–YSZ (yttria‐stabilized zirconia) cermets often suffer from microstructural degradation, loss of active reaction sites, and carbon deposition when operating with carbon‐containing fuels under prolonged operation. Ni–GDC (gadolinium‐doped ceria) cermets have emerged as a promising alternative due to mixed ionic–electronic conductivity of GDC under reducing conditions, which expands the active reaction zone, enhances electrochemical activity, and improves carbon tolerance. Single‐phase ceria electrodes, such as GDC, have also been explored, particularly for SOECs, offering electrochemical performance comparable to that of Ni‐YSZ with superior long‐term stability. This review critically examines Ni–GDC and ceria‐based electrodes, highlighting mechanistic insights, fabrication strategies, microstructure control, and electrode architecture, while extensively discussing performance, long‐term stability, and degradation behavior, and offering guidance for next‐generation solid oxide cells.