Improved activity of Rh/CeO2–ZrO2 three-way catalyst by high-temperature ageing

The effect of high-temperature ageing on the activity of Rh/CeO2–ZrO2 for the NO–C3H6–O2 reaction was quite different depending on the Ce/Zr molar ratio of CeO2–ZrO2 support. The activity of Rh/CeO2–ZrO2 with a Ce/Zr molar ratio of 74/26 (Rh/CZ-74/26) was significantly enhanced by high-temperature ageing, whereas that of the other Rh/CeO2–ZrO2 was decreased. The promotion of the activity of Rh/CZ-74/26 by high-temperature ageing was considered to be due to the formation and stabilization of active reduced Rh species as well as the change in the surface properties of CeO2–ZrO2 to inhibit the formation of formate species poisoning the catalytically active sites.