Study by isotopic gases and in situ spectroscopies (DRIFTS, XPS and Raman) of the N2O decomposition mechanism on Rh/CeO2 and Rh/γ-Al2O3 catalysts

The N2O decomposition mechanism on Rh/CeO2 and Rh/γ-Al2O3 catalysts has been studied by pulses of isotopic N2O and O2 together with in situ DRIFT, XP and Raman spectroscopies. The higher catalytic activity of Rh/CeO2 in comparison with Rh/γ-Al2O3 is related to the Rh–CeO2 interaction and to the participation of the CeO2 support in the N2O decomposition mechanism, γ-Al2O3 being an inert carrier. Rhodium on Rh/γ-Al2O3 is reduced to Rh0 under reaction conditions and N2O decomposition over this catalyst mainly occurs via the Eley–Rideal mechanism. On the contrary, the ceria support interacts strongly with rhodium partially stabilizing cationic species of the noble metal during N2O decomposition. In Rh/CeO2, the reduced rhodium sites (by N2O) can be reoxidized afterwards either by N2O or by ceria oxygen, and the vacant sites created on the ceria support are then oxidized by N2O. The active sites for N2O chemisorption and decomposition are not only located on rhodium but also on ceria.