In this work, periodic density functional theory (DFT) calculations were performed to investigate the CO₂ activation mechanism over thermodynamically stable χ-Fe₅C₂ (510) and θ-Fe₃C (031) facets. Four major pathways of CO₂ activation were examined, including the direct dissociation of CO₂ and the H-assisted intermediates of *COOH, *HCOO, and *CO + *OH. Both χ-Fe₅C₂ and θ-Fe₃C have proven to be active for CO₂ direct dissociation (E_a =0.17 eV). As for H assisted CO₂ activation, the one-step formation of *CO + *OH is feasible on χ-Fe₅C₂ (E_a =0.24 eV). Furthermore, θ-Fe₃C favors the *HCOO pathway (E_a =0.20 eV) and *CO + *OH formation (E_a = 0.11 eV), while neither phase favors the formation of *COOH. Both CO₂ direct activation and H-assisted CO₂ activation pathways are of vital importance under high ratio of H/C in CO₂ hydrogenation reaction. This work sheds light on CO₂ activation mechanism over iron carbides, improving the rational design of CO₂ hydrogenation catalysts.

在这项工作中，进行周期性的密度泛函理论（DFT）计算，以调查CO ₂激活机构在热力学上稳定的χ -铁₅ Ç ₂（510）和θ-的Fe ₃ C（031）刻面。检查了CO ₂活化的四个主要途径，包括CO ₂的直接解离和* COOH，* HCOO和* CO + * OH的H辅助中间体。既χ -铁₅ c ^ ₂和θ-的Fe ₃ Ç已被证明为CO活跃₂直接离解（E_一 = 0.17 eV）的。至于H辅助CO ₂活化，* CO + * OH的单步形成是在χ -铁可行₅ Ç ₂（E_一 = 0.24 eV）的。此外，θ-的Fe ₃ Ç利于* HCOO途径（E_一= 0.20 eV）的和* CO + * OH的形成（E_一 = 0.11电子伏特），而既不相有利于* COOH的形成。在CO ₂加氢反应中H / C比例高的情况下，CO ₂直接活化和H辅助CO ₂活化途径都至关重要。这项工作揭示了碳化铁在CO _2上的活化机理，改善了CO ₂加氢催化剂的合理设计。