Solid Oxide Cells for Power-to-X: Advances, Challenges, and Pathways to Carbon-Neutral Fuels and Chemicals

Solid oxide electrolysis cells (SOECs) represent a critical technology for integrating intermittent renewable electricity into the chemical and fuel production sectors, promising higher electrical efficiency than low-temperature alternatives due to superior operating kinetics. While traditionally optimized for H₂ generation, the actual value of high-temperature co-electrolysis lies in synthesizing complex, drop-in fuels and industrial feedstocks-a domain known as Power-to-X (P2X). This review examines the paradigm shift from basic H₂  production to integrated P2X pathways, highlighting recent advancements in materials that specifically enable multi-electron transfer reactions. We detail the electrochemical routes for producing high-value products such as syngas, synthetic methane, methanol, and ammonia, as well as emerging processes like direct CO₂ conversion to hydrocarbons and high-efficiency hydrocarbon upgrading. Crucially, we analyze the current state of electrochemical performance, stability challenges, and provide a techno-economic perspective on the commercial readiness of SOEC stacks, positioning this technology as a foundational pillar for industrial decarbonization.