Xiong Danfeng, Chen Yang, Yuan Haiyang, Wang Haifeng
Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis and Center for Computational Chemistry, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, China.
Key Laboratory for Ultrafine Materials of Ministry of Education, Shanghai Engineering Research Center of Hierarchical Nanomaterials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China.
Phys Chem Chem Phys. 2024 Oct 9;26(39):25452-25460. doi: 10.1039/d4cp02388a.
To understand the activity- and selectivity-limiting factors of selective catalytic reduction of NO with NH (NH-SCR) catalyzed by CeO-based oxides, a molecular-level mechanistic exploration was performed on CeO(110) using a first-principles microkinetic study. Herein, the favored reaction pathway for N formation on CeO(110) is unveiled, which includes three key subprocesses. (i) NH adsorbs on the Ce site and dissociates into *NH assisted by O; (ii) *NH preferentially couples with NO adsorbed on O (ONO#), forming *NHNO on the Ce site; (iii) *NHNO undergoes dehydrogenation into *NHNO, which can be easily anchored by O and can then decompose into N. The quantitative microkinetic results show that the transfer of NHNO from Ce to O, rather than the further conversion of NO to N on O, emerges as the N selectivity-determining step on CeO, in which O plays a key role. The number of O is an important factor determining the N selectivity of CeO-based catalysts. The sensitivity analysis reveals that NHNO formation, , *NH + ONO# → *NHNO + O#, is the rate-determining step for NH-SCR on the CeO catalyst; accordingly, enhancing NH adsorption could be an effective strategy to boost the catalytic activity of CeO for NH-SCR. In general, creating O on CeO and introducing components (, WO) with strong NH adsorption would be efficient for designing CeO-based catalysts with superior N selectivity and activity. These results could provide a consolidated theoretical basis for understanding and optimizing CeO-based catalysts for NH-SCR.
为了理解以CeO基氧化物为催化剂的NH₃选择性催化还原NO（NH₃-SCR）反应中活性和选择性的限制因素，采用第一性原理微观动力学研究方法，在CeO₂(110)上进行了分子水平的机理探索。在此，揭示了CeO₂(110)上生成N₂的有利反应途径，该途径包括三个关键子过程。（i）NH₃吸附在Ce位点上，并在O的协助下分解为*NH₂；（ii）NH₂优先与吸附在O上的NO（ONO#）偶联，在Ce位点上形成NH₂NO；（iii）NH₂NO脱氢生成NHNO，NHNO可被O轻松锚定，然后分解为N₂。定量微观动力学结果表明，NH₂NO从Ce向O的转移，而非O上NO进一步转化为N₂，是CeO₂上N₂选择性的决定步骤，其中O起着关键作用。O的数量是决定CeO基催化剂N₂选择性的重要因素。敏感性分析表明，NH₂NO的形成，即NH₂ + ONO# → *NH₂NO + O#，是CeO₂催化剂上NH₃-SCR的速率决定步骤；因此，增强NH₃吸附可能是提高CeO₂对NH₃-SCR催化活性的有效策略。一般来说，在CeO₂上创造O位点并引入具有强NH₃吸附能力的组分（如WO₃），对于设计具有优异N₂选择性和活性的CeO基催化剂将是有效的。这些结果可为理解和优化用于NH₃-SCR的CeO基催化剂提供坚实的理论基础。
