Computational design of catalysts for ammonia synthesis

Ammonia plays a crucial role in agriculture and chemical engineering, and acts as a promising carbon-free transportation fuel. Catalysts design is deemed as a key to solve the restriction of energy-intensive Haber–Bosch process of ammonia production. With the development of computational modeling, computation-aided catalyst design serves as one important driving force for material innovation, saving a lot of experimental efforts based on trial and error. Computational modeling not only provides fundamental mechanistic insights into the reaction with great details regarding adsorbate geometries, electronic structures, and elementary-step energies, but also expedites the material discovery with descriptor-based catalyst design, core of which is the establishment of thermo/kinetic scaling relations. In this review, we present firstly the mechanistic understanding of ammonia synthesis and transition state scaling relations developed on pure transition-metal catalysts. We then summarize catalysts design strategies guided by alloy, size, and magnetic effects with the goal of breaking the limitations set by scaling relations to achieve better catalytic performance. Finally, future opportunities and challenges associated with computation design of optimal catalysts for ammonia synthesis are outlined.