Optimization of High-Entropy Alloy Catalyst for Ammonia Decomposition and Ammonia Synthesis

The successful synthesis of high-entropy alloy (HEA) nanoparticles, a longsought goal in materials science, opens a new frontier in materials science with applications across catalysis, structural alloys, and energetic materials. Recently, a Co25Mo45Fe10Ni10Cu10 HEA made of earth-abundant elements was shown to have a high catalytic activity for ammonia decomposition, which rivals that of state-of-the-art, but prohibitively expensive, ruthenium catalysts. Using a computational approach based on first-principles calculations in conjunction with data analytics and machine learning, we build a model to rapidly compute the adsorption energy of H, N, and NHx (x = 1, 2, 3) species on CoMoFeNiCu alloy surfaces with varied alloy compositions and atomic arrangements. We show that the 25/45 Co/Mo ratio identified experimentally as the most active composition for ammonia decomposition increases the likelihood that the surface adsorbs nitrogen equivalently to that of ruthenium while at the same time interacting moderately strongly with intermediates. Our study underscores the importance of computational modeling and machine learning to identify and optimize HEA alloys across their near-infinite materials design space.

Automated summary

The successful synthesis of high-entropy alloy (HEA) nanoparticles opens up a new frontier in materials science, particularly in the fields of catalysis, structural alloys, and energetic materials. Using computational modeling, a model was built to rapidly calculate the adsorption energy of H, N, and NHx species on CoMoFeNiCu alloy surfaces, showing that a specific Co/Mo ratio can enhance the ammonia decomposition activity.