Effect of Ag and Pd promotion on CH4 selectivity in Fe(100) Fischer–Tröpsch catalysis

Abstract

The current CO₂ utilization market is dominated by enhanced oil recovery and urea manufacturing; yet, the scale of demand falls well short of that deemed necessary to make a significant impact on climate change. CO₂ conversion to fuels, however, is a utilization technology that can theoretically match the scale of projected CO₂ capture. Fischer–Tröpsch (FT) processing is a long-established technology for converting non-petroleum based precursors into transportation fuels and other valuable chemicals. Here, we report the effects of Pd and Ag doping on CH₄ selectivity over Fe(100), a common FT catalyst, as these metals have shown potential in the direct conversion of co-fed CO₂. Adsorption energies for pathway specific C1 and C2 species were weakened in the presence of Ag and Pd by ca. 0.55 eV and 0.35 eV, respectively. Further, while both Ag- and Pd-promoted surfaces show decreased CH₄ production, Ag introduces a prohibitively high coupling barrier; thus, only Pd offered a decrease in CH₄ selectivity (−36%) relative to unmodified Fe(100).