(452c) A Design Principle of Molybdenum-Based Metal Nitrides for Lattice Nitrogen-Mediated Ammonia Production

Ammonia (NH₃) plays a crucial role in both agriculture as fertilizers and chemical industry as raw materials. Nowadays, ammonia is also an ideal candidate as a carbon-free energy carrier for the sustainable development of human society. The conventional Haber-Bosch process catalyzed by fused iron catalysts is operated under high temperatures and pressures due to both thermodynamic and kinetic constraints, resulting in substantial energy consumption and global carbon emissions. Chemical looping ammonia synthesis (CLAS) is a promising technology for reducing the high energy consumption of 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. In this work, we propose a multiscale strategy to establish the connection between catalyst intrinsic activity and microscopic electronic structure fingerprints using density functional theory (DFT) 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 the 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 multiscale perspective on catalyst rational design.