Tuning Iron Carbonization Degree to Regulate CO ₂ Hydrogenation: Mechanisms and Product Selectivity

The deepening energy crisis and environmental challenges driven by rising atmospheric CO2 concentration highlight the urgent need for efficient catalytic technologies to convert CO2 into high-value chemicals. Among various strategies, the catalytic hydrogenation of CO2 to higher hydrocarbons offers a promising and industrially viable pathway. In this work, we combine density functional theory (DFT) with microkinetic modeling (MKM) to systematically examine how the carburization degree of iron carbides controls product selectivity in CO2 hydrogenation. Our results show that CO2 preferentially dissociates into adsorbed CO* on iron carbide (FexC) surfaces, with θ-Fe3C favoring CO formation and η-Fe2C selectively promoting ethanol production. The carburization degree modulates the electronic structure and local coordination of active Fe sites, weakening the adsorption of CO species, which suppresses overhydrogenation and promotes C–C coupling, leading to enhanced C2 selectivity. These findings demonstrate that rational control of carburization enables precise tuning of surface properties and intermediate adsorption, thereby directing reaction pathways toward desired products and significantly improving catalytic efficiency. This work not only deepens the fundamental understanding of the catalytic mechanisms of iron-based catalysts in CO2 hydrogenation but also provides practical theoretical guidance for the design of high-performance catalysts and the development of carbon conversion technologies, holding significant promise for catalytic CO2 utilization and chemical industries powered by renewable energy.