(532ag) Elucidating the Reverse Water Gas Shift Reaction Mechanism on Single-Atom Fe1-K/?-Al2O3.

The reverse water gas shift (RWGS) reaction is important for converting CO₂ to CO, which is a valuable chemical precursor. The exothermic methanation side reaction causes poor CO selectivity at low temperatures, thus catalysts with higher selectivity are needed. Atomically dispersed single atom catalysts containing platinum group metals have been shown to selectively catalyze the RWGS reaction,^[1-2] but ideally earth-abundant single atom catalysts would be preferred. Here we study a well-defined single-atom Fe₁ catalyst promoted by K on γ-Al₂O₃ (Fe₁-K/γ-Al₂O₃)to selectively catalyze CO₂ reduction to CO via the RWGS reaction. Our experiments show high selectivity toward CO (100%) at 400 °C and 30 bar. To elucidate the RWGS mechanism on Fe₁-K/γ-Al₂O₃ and the role of the K⁺ promoter we build a representative modelof the Fe₁-K/γ-Al₂O₃ catalyst using density functional theory (DFT) supported by experimental EXAFS. We use DFT and microkinetic modeling to examine two proposed reaction pathways based on different hydrogen dissociation mechanisms on Fe₁-K/γ-Al₂O₃(110). Understanding the reaction mechanism for this earth-abundant Fe₁-K/γ-Al₂O₃ catalyst will help design improved catalysts with higher activity and selectivity for the RWGS reaction.