Mechanistic Understanding of Hydrocarbon Formation from CO2 Hydrogenation over χ-Fe5C2(111) and the Effect of H2O and Transition Metal Addition

Converting CO 2 into a range of chemicals and fuels is an effective approach to address excessive CO 2 emissions. In this work, density functional theory (DFT) calculations were performed to investigate the reaction mechanism of hydrocarbons formation from CO 2 hydrogenation on the surface of χ-Fe 5 C 2 (111). Optimal energetic pathways, key reaction intermediates (such as CO*, H 2 COH*, and CH 2 *), and rate-liming steps were identified for the production of CH 4 and C 2 H 4 . The calculation results revealed that H 2 O* species formed on the surface of χ-Fe 5 C 2 (111) significantly reduced the barriers of the O–H bond formation step, altering reaction pathways and promoting CO 2 conversion kinetics. Importantly, it was identified that the introduction of a second transition metal, such as Cr, Mn, Pd, or Zn, into χ-Fe 5 C 2 (111) could regulate the surface C/H ratio and product desorption rate, effectively tuning the product selectivity.