Nanosized cerium oxide (CeO2) has been extensively used as the oxygen storage component in automotive emission control systems. However, the possible influence of atomically dispersed Ce in these catalysts has not been recognized. Here, we demonstrate the controllable transformation of ceria nanoparticles into isolated cerium cations on γ-Al2O3 via reductive atom trapping in 10% H2 at 800 °C, achieving over half-monolayer coverage. Dispersed Ce1 ions anchored by surface penta- and octa-coordinated Al sites exhibit outstanding thermal stability in air up to 500 °C, enabling further loading of active metals with well-defined catalyst structures. With this strategy, supported single-atom Rh1 surrounded by dispersed Ce1 is confirmed to exhibit much superior performance to Rh1 on bare Al2O3 or nanocrystalline CeO2 in catalyzing NO reduction by CO, exhibiting a striking one-order-of-magnitude increase in activity. Dispersed Ce1 exhibits greatly enhanced oxygen transfer capability compared to ceria nanoparticles and introduces a modified reaction mechanism that involves an adjacent Rh1-Ce1 motif, resulting in a greatly decreased activation barrier (from 192 to 96 kJ/mol). The reactivity enhancements are also seen with Ce1-promoted Pt nanoparticles for oxidation of CO and hydrocarbons.
Jiang et al. (2026) studied this question.