Tuning the CO Hydrogenation Selectivity of Rhodium Single-Atom Catalysts on Zirconium Dioxide with Alkali Ions.

Tuning the coordination environments of metal single atoms (M ) 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 Rh atoms and ZrO support with alkali ions (e.g., Na) enables efficient switching of the reaction products from nearly 100 % CH to above 99 % CO in CO hydrogenation in a wide temperature range (240-440 °C) along with a record high activity of 9.4 mol  g  h at 300 °C and long-term stability. In situ spectroscopic characterization and theoretical calculations unveil that alkali ions on ZrO change the surface intermediate from formate to carboxy species during CO activation, thus leading to exclusive CO formation. Meanwhile, alkali ions also reinforce the electronic Rh -support interactions, endowing the Rh atoms more electron deficient, which improves the stability against sintering and inhibits deep hydrogenation of CO to CH .