First‐Principles Thermodynamics‐Based Stability Trends for Single Atom Alloy Catalysts

ABSTRACT Single‐atom alloy (SAA) catalysts consist of isolated atoms of a catalytically active metal guest (M) dispersed on the surface of a relatively inert host (H) metal alloy. These single atoms create highly efficient active sites that maximize metal utilization. To assess their thermal stability, the goal is to determine the fraction of surface covered by single M atoms. We introduce a first‐principles thermodynamic framework for predicting the stability. Aggregation in the surface and/or bulk region and the overall segregation behavior are key aspects that are considered. M atoms can distribute between surface and bulk regions, and are either dispersed as isolated atoms or can form aggregates such as M‐dimers, trimers, etc. Stability trends for seven different M‐H SAA systems, namely, Pt─Ni, Ru─Ni, Re─Ni, Pt─Cu, Pd─Cu, Bi─Pd, and Ni─Ru, are reported here. Our method is valid at low concentrations of guest atoms, and it accounts for temperature, configurational effects, and the probability of various local M aggregates. An attractive feature of our method is that stability trends can be obtained over a wide range of compositions with approximately 30 DFT calculations per system, without the need for an extensive Monte Carlo‐like configurational sampling approach.