Mechanistic insights of surface OH* modulation on methanol production with CO2 hydrogenation by iron-based catalyst

Abstract

The conversion of CO₂ into high-value-added chemicals via the Fischer-Tropsch Synthesis (FTS) reaction has gathered a lot of attention. The surface oxygenation environment is a significant factor affecting the catalyst performance. In this work, spin-polarized density-functional theory calculations have been used to investigate the adsorption and reactions of CO₂ and H to generate CH₄ and CH₃OH on Fe₅C₂(510) surfaces with varying OH* coverage. On the pure Fe₅C₂(510) surface, CO₂ preferentially dissociates via direct dissociation, and the major C₁ species generated is CH₄. At low OH* coverage, the preferential pathway for CO₂ dissociation changes from direct dissociation to the H-assisted route by the formation of COOH*. The major C₁ product of the reaction in this state is transferred to CH₃OH. In addition, CO₂ hydrogenation reactions are facilitated by the OH* species. At high OH coverage, CO₂ preferentially dissociates through the HCOO* intermediates. However, it appears that the CO₂ hydrogenation reaction activity is suppressed. The results demonstrate that maintaining the surface environment with OH* and H* could be an indispensable measure to obtain the target product in the iron-based CO₂ Fischer-Tropsch Synthesis system.