Reaction Mechanisms and Carbon Deposition Behavior in Methane Conversion via Solid Oxide Cells: A Review

Methane is an abundant energy carrier and carbon resource. However, its efficient utilization remains challenging because the strong C-H bonds in methane hinder low-temperature activation, whereas high-temperature conversion often leads to undesired side reactions and reduced product selectivity. Solid oxide cells (SOCs) provide a promising platform for methane conversion by integrating high-temperature electrochemistry, catalytic reactions, and ion transport within a single system, enabling efficient energy and chemical production. This review summarizes recent advances in SOC-based methane conversion through three representative pathways: direct electricity generation in methane-fueled solid oxide fuel cell (SOFC), syngas production via SOC-assisted methane reforming, and value-added C2 hydrocarbon synthesis through methane oxidative coupling in solid oxide electrolysis cell (SOEC). For methane-fueled SOFC, the relationships among fuel-electrode materials, microstructural characteristics, carbon deposition behavior, and electrochemical performance are discussed, together with current strategies for improving carbon resistance and operational stability. In methane reforming and upgrading processes, SOCs can regulate oxygen-ion transport, local reaction environments, and electrode reaction pathways, thereby enhancing methane conversion and product selectivity toward syngas, hydrogen, and C2 hydrocarbons. The roles of electrode design, catalyst development, and operating conditions in determining reaction performance are also highlighted. Finally, the major challenges facing SOC-based methane conversion are critically discussed. Future research directions involving advanced electrode materials, microstructure engineering, and multiscale modeling are proposed to support the development of efficient and durable SOC technologies for methane utilization.