Specific reactivity of 4d and 5d transition metals supported over CeO2 for ammonia oxidation. Issue 21 (21st September 2022)

• Record Type: Journal Article
• Authors: Guo, Yitong; Ma, Lei; Li, Zihao; Liu, Zhisong; Chang, Huazhen; Zhao, Xiaoran; Yan, Naiqiang
• Is Part Of: Catalysis science & technology. Volume 12:Issue 21(2022)
• Page Start: 6507
• Page End: 6517
• Publication Date: 2022-09-21
• Subjects: Catalysis -- Periodicals; 541.395
• DOI: 10.1039/d2cy01380k
• Languages: English
• ISSNs: 2044-4753

Abstract

Abstract : Pt/CeO2 catalysts were most active in selective catalytic oxidation of ammonia, where Pt triggered the activation of surface lattice oxygen, and the dehydrogenation of ammonia assisted by surface lattice oxygen was the rate-determining step. Abstract : Optimizing NH3 oxidation activity and N2 selectivity remains a challenge in selective catalytic oxidation of ammonia (NH3 -SCO). Herein, a series of 4d (Pd, Ag, Rh) and 5d (Pt) transition metal catalysts were synthesized and loaded over a reducible CeO2 support and tested for NH3 -SCO reactions. The catalytic results indicated that Pt/CeO2 catalysts outperformed the other supported metals with superior NH3 oxidation performance and N2 selectivity, which was related to the strong metal–support interaction (SMSI) with electron transfer from Pt metals to CeO2 supports. This could be ascribed to the Pt–O–Ce synergistic effects and the high Ce 3+ concentration over the Pt/CeO2 catalysts. The strong interactions between Pt and CeO2 also improved the reducibility of Pt/CeO2 and promoted the activation of surface lattice oxygen participating in the NH3 -SCO reaction. The rigorous kinetic studies elucidated the elementary steps for the NH3 -SCO reaction, where surface lattice oxygen activated surface adsorbed NH3 to form an amide (–NH2 ) which is regarded as the rate-determining step of NH3 oxidation. In situ DRIFTS also confirmed that surface lattice oxygen as a reactant triggered the formation of reactive intermediates of –NH2, which were consumed to generate N2 and H2 O at low temperatures.