Different Reaction Mechanisms of Ammonia Oxidation Reaction on Pt/Al2O3 and Pt/CeZrO2 with Various Pt States

NH 3 emissions were limited strictly because of the threat for human health and sustainable development. Pt/Al 2 O 3 and Pt/CeZrO 2 were prepared by the impregnation method. Differences in surface chemical states, reduction ability, acid properties, morphological properties, reaction mechanisms, and ammonia oxidation activity were studied. It indicated that Pt species states were affected by different metal–support interactions. The homogeneously dispersed Pt species over Pt/Al 2 O 3 exposed Pt(111) because of weak metal–support interactions; there even existed an obvious interface between Pt and Al 2 O 3 . While obscure even an overlapped interface was observed over Pt/CeZrO 2, resulting in the formation of PtO because of the oxygen migration from CeZrO 2 to Pt species (confirmed by CO-FTIR, the cycled H 2 -TPR and transmission electron microscopy results). It was noteworthy that different reaction mechanisms were induced by different states of Pt species; NH was the key intermediate species for ammonia oxidation reaction over Pt/Al 2 O 3, but two kinds of intermediates, N 2 H 4 and HNO, were observed for Pt/CeZrO 2 . It consequently resulted in the obvious distinction of the NH 3 -SCO catalytic performance; the light-off temperatures of NH 3 over Pt/Al 2 O 3 and Pt/CeZrO 2 were 231 and 275 °C, respectively, while the maximum N 2 selectivity (65%) was obtained over Pt/CeZrO 2, it was obviously better than that over Pt/Al 2 O 3 .