Abstract
The chemical state of precious metals plays an important role in redox reaction. In order to maintain rhodium (Rh) at metallic state, which is recognized as reactive center in three-way catalytic reactions, we synthesized Rh/CeO2–ZrO2 (Rh/CZ) catalyst by liquid phase reduction adsorption with glycerol as reductant (Rh/CZ-g). Detailed characterizations were conducted to investigate the chemical state of Rh species, and the CO-FTIR and XPS results indicated that Rh species mainly existed in metallic state for Rh/CZ-g. Through CO chemisorption and H2-TPR, it’s proved that the liquid phase reduction treatment would weaken the interaction between Rh species and CeO2–ZrO2 support, avoiding the supply of oxygen species from CeO2–ZrO2 to Rh in some degree. Compared with Rh/CeO2–ZrO2 catalyst prepared by incipient wetness impregnation, Rh/CZ-g exactly had superior activity in three-way catalytic process. Combined with in situ DRIFTS, some important intermediate species, such as Rh–CN, Rh-(NO)2, formates and acetates, preferred to adsorb and transform on Rh/CZ-g with larger proportion of metallic Rh, which determined Rh/CZ-g was more favorable for three-way catalytic reactions, even after aged at 950 °C for 5 h. The purpose of this work is to inspire researchers use simple and valid methods to synthesize highly efficient three-way catalysts.
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