Iron-based catalysts have been widely used to synthesize value-added hydrocarbons through CO₂ hydrogenation. Fe carbide, Fe₅C₂, was proposed as the active phase responsible for CC coupling during the chain growth. However, the reaction mechanism over iron-based catalysts is still under debate due to the presence of multiple phases of Fe species. In this work, Fe₅C₂ and K-modified Fe₅C₂ were prepared and used to study the relationship between the Fe phase, catalytic performance and reaction pathways. CH₄ and CO selectivities of 46.1 C-mol% and 2.8 C-mol% were obtained on Fe₅C₂ at a CO₂ conversion of 49.8 %, with the main hydrocarbon products being alkanes. With the addition of the promoter K, the C₂-C₄⁼ selectivity increased to above 38.0 C-mol%, and the selectivity to C₅₊ hydrocarbons increased to 23.9 C-mol% at a similar CO₂ conversion. CH₄ and C₂₊ hydrocarbons formed through the CO₂→CO→hydrocarbons (indirect) route over K-modified Fe₅C₂, whereas the direct hydrogenation route occurred on unmodified Fe₅C₂ in addition to the indirect route of CO₂ to CO to hydrocarbons through Fischer-Tropsch synthesis (FTS) processes. This work offers insights in direct CO₂ hydrogenation over Fe₅C₂ and Fe₃O₄-Fe₅C₂ catalysts, which advances the understanding of the functions of active phases and reaction pathways of CO₂ hydrogenation over iron-based catalysts.

铁基催化剂已被广泛用于通过CO ₂加氢合成增值的碳氢化合物。提出了碳化铁Fe ₅ C ₂作为在链增长过程中引起C C耦合的活性相。然而，由于存在铁物种的多相，在铁基催化剂上的反应机理仍在争论中。在这项工作中，制备了Fe ₅ C ₂和K改性的Fe ₅ C ₂，并用于研究Fe相，催化性能和反应途径之间的关系。在Fe ₅ C ₂上获得46.1 C-mol％和2.8 C-mol％的CH ₄和CO选择性CO ₂转化率为49.8％，主要烃产物为烷烃。通过加入助催化剂K，在相似的CO ₂转化率下，C ₂ -C ₄ ^＝选择性增加到38.0 C-mol％以上，并且对C ₅₊烃的选择性增加到23.9 C-mol％。CH ₄和C ₂₊通过CO形成碳氢化合物₂ →CO→烃超过（间接）途径K-改性的Fe ₅ Ç ₂，而在未修饰的Fe发生直接氢化路线₅ Ç ₂除了CO的间接路线₂通过费托合成（FTS）过程将一氧化碳转化为一氧化碳转化为碳氢化合物。这项工作提供了有关在Fe ₅ C ₂和Fe ₃ O ₄ -Fe ₅ C ₂催化剂上直接进行CO ₂加氢的见解，从而进一步了解了铁基催化剂上活性相的功能和CO ₂加氢的反应途径。