Regulating local coordination environment of rhodium single atoms in Rh/CeO2 catalysts for N2O decomposition

Rh single atom catalysts (SACs) have been insensitively investigated recently due to the maximum utilization efficiency of Rh, one of the most expensive precious metals. Although great efforts have been made in the development and application of Rh SACs, there are few reports on the precise control of the local coordination environment of Rh single sites on CeO2 and their catalytic performance for N2O decomposition. Herein, Rh/CeO2 catalysts with different Rh–O coordination numbers (CNs) were successfully prepared using different CeO2 supports and a simple incipient wetness impregnation (IWI) method. It is observed that the Rh/CeO2 catalyst with slightly higher CN of Rh–O (Rh/CeO2-H) prepared from CeO2 shows much higher N2O decomposition activity than the catalyst with lower CN of Rh–O (Rh/CeO2-L) obtained from Ce(OH)x. The Rh species within Rh/CeO2-H are found to be more reactive than those within Rh/CeO2-L, which can better facilitate the O2 desorption once formed during N2O decomposition. In addition, more surface oxygen vacancies are present on Rh/CeO2-H than on Rh/CeO2-L, well explaining the superior N2O adsorption and activation capability on the former catalyst. It is concluded that more abundant oxygen vacancies and reactive Rh single atom sites with slightly higher CN of Rh–O and significantly higher reducibility altogether contribute to the superior N2O decomposition activity on the Rh/CeO2-H catalyst.