Tuning the CO₂ Hydrogenation Selectivity of Rhodium Single‐Atom Catalysts on Zirconium Dioxide with Alkali Ions

Abstract

Tuning the coordination environments of metal single atoms (M₁ ) in single-atom catalysts has shown large impacts on catalytic activity and stability but often barely on selectivity in thermocatalysis. Here, we report that simultaneously regulating both Rh₁ atoms and ZrO₂ support with alkali ions (e.g., Na) enables efficient switching of the reaction products from nearly 100 % CH₄ to above 99 % CO in CO₂ hydrogenation in a wide temperature range (240-440 °C) along with a record high activity of 9.4 mol_CO g_Rh ^-1 h^-1 at 300 °C and long-term stability. In situ spectroscopic characterization and theoretical calculations unveil that alkali ions on ZrO₂ change the surface intermediate from formate to carboxy species during CO₂ activation, thus leading to exclusive CO formation. Meanwhile, alkali ions also reinforce the electronic Rh₁ -support interactions, endowing the Rh₁ atoms more electron deficient, which improves the stability against sintering and inhibits deep hydrogenation of CO to CH₄ .