Dynamic interplay between water and surface carbonates mediates oxygen exchange kinetics in oxide catalysts

Decorating oxide catalysts with basic oxides decreases surface acidity and lowers the work function, which facilitates electron donation to adsorbed reaction intermediates and thereby enhances oxygen exchange kinetics. However, facilitating electron transfer also renders acid-base-engineered catalysts prone to deactivation by interplay with acidic gas species. The present study investigates the effects of H 2 O and CO 2 on the oxygen exchange kinetics of Ca-decorated SrTi 0.65 Fe 0.35 O 3‑δ . Both surface hydroxylation and surface carbonate formation diminish the oxygen exchange kinetics relative to measurements conducted without intentionally added gas phase impurities, consistent with increased surface acidity and a higher work function of the catalyst. However, when surface carbonates are present before H 2 O exposure, water mediates carbonate decomposition, resulting in an apparent improvement in oxygen exchange kinetics relative to the initial catalyst state. This water-mediated decomposition of surface carbonates proceeds at substantially lower temperatures ( T ~300°C) than thermal carbonate decomposition in dry oxygen. Our findings help reconcile conflicting reports on the beneficial and detrimental effects of water on oxygen exchange by linking them to the surface acid-base properties and resulting electronic structure of oxide catalysts.