Computational Screening of Bimetallic Catalysts: Application to Ammonia Decomposition

First-principles calculations and ab initio molecular dynamics (AIMD) are carried out to perform catalyst screening and investigate the structural dynamics of various transition-metal bimetallic surfaces (guest Fe, Co, and Ni; host Pd, Ag, Ir, Pt, and Au) for ammonia decomposition. First, we identify the activities of stepped/edged bimetallic surfaces using a library of surface N atom (N*) binding energies guided from a scaling-based kinetic Monte Carlo model with a focus on N* coverage effect. Second, based on segregation energy calculations and AIMD simulations, the improved thermodynamic and dynamic stability of bimetallic monolayer and stepped/edged surfaces are illustrated by considering N*–metal interactions. Several active Ir(111)-, Pd(111)-, and Pt(111)-based bimetallic surfaces with well-ordered stripes are found to be stable even without N*. For Ag(111)- and Au(111)-based surfaces, their stability depends on guest atoms’ loading and coverage of N*. In particular, we discover that N* can lead to the spontaneous formation of well-ordered Fe stripes on the Ag(111) surface, a lower N*–N* association barrier (1.74 eV) is observed at step/edge sites, and the striped structure can be preserved in 10 ps’ AIMD simulations at 800 K by N* regulation. Our work offers a family of efficient bimetallic catalysts in ammonia decomposition and provides guidance for tailoring bimetallic surfaces with multifunctionality microstructures in terms of adsorbate-induced catalyst dynamics. This approach also sheds light on other structure-sensitive reactions with complex chemistries to design highly active and stable catalysts under reaction conditions.