Mechanistic insight into accelerating of light olefin products by surface OH* group on the Fe5C2 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 performance of the catalyst. In this work, spin-polarized density-functional theory calculations have been used to investigate the OH* modulation mechanism on CO2 hydrogenation to generate C1 and C2 species. On the pure Fe5C2(510) surface, CH4 is formed through the hydrogenation of dissociated carbon by CO2 activation. At low OH* coverage, the C–C coupling reactions are dramatically promoted compared to methane formation. In addition, CO2 hydrogenation reactions are facilitated by the OH* species, indicating a high activatity and C2+ selectivity. At high OH* coverage, C2 products preferentially form through the CsH2-CdH2* intermediates, contributing to the high selectivity of light olefin products. The results demonstrate that maintaining the surface environment with OH* could be an indispensable measure to obtain the target product in the iron-based CO2 Fischer-Tropsch synthesis system.