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 Ni3Mo3N 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.