Supported metal catalysts with single-atom promoters via reductive atom trapping

Nanosized cerium oxide (CeO2) has been extensively used as an oxygen storage component in automotive emission control systems. However, the possible involvement of atomically dispersed cerium (Ce) has not been explored. Here, we demonstrate the controllable transformation of CeO2 nanoparticles into isolated Ce1 cations on the surface of gamma-type alumina (γ-Al2O3) via reductive atom trapping, achieving over half-monolayer coverage. Supported single-atom rhodium (Rh1) surrounded by dispersed Ce1 shows superior performance to Rh1 on bare Al2O3 or crystalline CeO2 in catalyzing NO reduction, exhibiting a striking one-order-of-magnitude increase in turnover frequency. Dispersed Ce1 also exhibits greatly enhanced oxygen transfer capability and introduces a modified reaction mechanism that involves adjacent Rh1-Ce1 dual-sites, resulting in a greatly decreased activation barrier (96 vs. 192 kJ/mol). The understanding of reductive atom trapping of Ce1 as well as its structure-property relationships obtained in this work could be implemented in the rational design of Ce1-promoted catalysts for many other applications. Benefiting from the greatly enhanced OSC, activity enhancements are also seen with Ce1-promoted platinum nanoparticles for the oxidation of CO and hydrocarbons. Additionally, dispersing Ce1 on Al2O3 results in modified surface properties, which could be further utilized to explore the field of acid-base catalysis