Constructing efficient Pd/Al2O3 catalyst for reverse water-gas shift via alkali-modification

The intrinsic nature of irreducible oxides (e.g. Al 2 O 3 ) makes it hard to tune the charge state of supported late-transition metals, then difficult to adjust the selectivity of catalysts in CO 2 hydrogenation. Herein, we find that modifying the Pd/Al 2 O 3 catalyst with alkali metals (especially potassium) is efficient to boost the CO formation in CO 2 hydrogenation. In comparison to Pd/Al 2 O 3 , approximately twenty-fold promotion in reverse water–gas shift (RWGS) rate was achieved on K-modified catalysts with proper K/Pd proportions. Combined structural characterizations demonstrate that the enhanced Pd-O interactions through K mediation stabilize the ca. 2 nm sized Pd particles as well as the electron-deficient state of Pd, which are robust enough during long-termed evaluation with undamped performance. In situ spectroscopy unveils a bi-dentate *HCOO associated reaction mechanism taking effect on alkali-modified catalysts, which contributes to ∼ 100 % of CO selectivity and 3318.1 mmol∙g Pd -1 ∙h −1 of CO formation rate at 340°C.