Ammonia decomposition over iron-based catalyst: Exploring the hidden active phase

• Published in: Applied catalysis. B, Environmental Environmental, 2022-10, Vol.314, p.121475, Article 121475
• Main Authors: Lu, Bin, Li, Ling, Ren, Menghao, Liu, Yu, Zhang, Yanmin, Xu, Xin, Wang, Xuan, Qiu, Hengshan
• Format: Article
• Language: English
• Subjects: Active phase; Ammonia; Ammonia decomposition; Catalysis; Catalysts; Dehydrogenation; Density functional theory; Dielectric barrier discharge; Electronic structure; Iron; Iron catalyst; Iron nitride; Nitrogen; Phase transformation; Phase transitions; Plasma catalysis
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2022.121475

The possible phase transformation of catalysts under reaction conditions brings lots of difficulties in establishing the active phase. Herein, we report a hidden active phase over iron catalyst uniquely for the dehydrogenation of ammonia (NH3). The highest dehydrogenation rate corresponds to an evanescent Fe/Fe4N mixing phase while the nitrogen (N) kept on accumulating and gradually deactivated the catalyst. Density functional theory (DFT) calculations demonstrated that deposition of an N on Fe(100) surface modifies the electronic structure of its surrounding iron atoms, causing a significant reduction of the initial dehydrogenation barrier of NH3. To recover the hidden active phase, ambient-pressure double dielectric barrier discharge (DDBD) plasma was applied to the reaction system in situ to remove the excessive surface N, which yields a pronounced improvement of the catalytic performance. The work demonstrates that hidden active phase in thermal catalysis can be unfolded when the rate-determining step is subdued by applied plasma. [Display omitted] •Hidden active phase uniquely for the dehydrogenation of NH3 uncovered at a Fe/Fe4N mixing phase.•Structure-activity relationship determination through real-time tracking of structure and activity evolution.•Recovery of hidden active phase by applying in situ plasma.