Design Principle of Molybdenum-Based Metal Nitrides for Lattice Nitrogen-Mediated Ammonia Production.

Chemical looping ammonia synthesis (CLAS) is a promising technology for reducing the high energy consumption of the conventional ammonia synthesis process. However, the comprehensive understanding of reaction mechanisms and rational design of novel nitrogen carriers has not been achieved due to the high complexity of catalyst structures and the unrevealed relationship between electronic structure and intrinsic activity. Herein, we propose a multistage strategy to establish the connection between catalyst intrinsic activity and microscopic electronic structure fingerprints using density functional theory computational energetics as bridges and apply it to the rational design of metal nitride catalysts for lattice nitrogen-mediated ammonia production. Molybdenum-based nitride catalysts with well-defined structures are employed as prototypes to elucidate the decoupled effects of electronic and geometrical features. The electron-transfer and spin polarization characteristics of the magnetic metals are constructed as descriptors to disclose the atomic-scale causes of intrinsic activity. Based on this design strategy, it is demonstrated that NiMoN catalysts possess the highest lattice nitrogen-mediated ammonia synthesis activity. This work reveals the structure-activity relationship of metal nitrides for CLAS and provides a multistage perspective on catalyst rational design.