High-Temperature CO2 Reduction: Operando Analysis and Reaction Dynamics

Abstract High-temperature carbon dioxide (CO2) conversion is emerging as a compelling pathway for climate-relevant CO2 utilization, as it can efficiently produce CO and syngas intermediates for synthetic fuels and chemicals. Among available routes, catalytic reverse water-gas shift (RWGS) and solid oxide electrolysis cells (SOECs) are particularly attractive owing to favorable high-temperature kinetics and the ability of SOECs to supply a substantial fraction of the energy demand as heat, thereby reducing electrical input. However, practical implementation remains constrained by an activity-stability trade-off arising from incomplete mechanistic understanding and the continuous evolution of surface states, defect chemistry, and microstructure under operating conditions. Recognizing dynamic active states and degradation as the central bottlenecks, this review establishes a mechanism-centered framework that integrates thermodynamic-kinetic descriptors, operando/intermediate identification, and degradation/activation pathways to rationalize performance across RWGS and SOEC-based CO2 electrolysis and CO2/H2O co-electrolysis. It elucidates how dissociative/redox and associative mechanisms compete and how oxygen vacancies, interfacial reconstruction, and in situ redox processes govern rate control, selectivity, and durability. State-of-the-art operando characterization and kinetic analyses are highlighted as essential tools for validating reaction pathways and diagnosing failure signatures in catalysts and electrodes. Building on these insights, this review highlights practical design guidelines for redox-stable materials and interfaces. It outlines next steps, including integrating stacks and systems with renewable energy and using data-driven optimization to make high-temperature CO2 conversion more durable and scalable.