Electrochemical Dissolution: Paths in High-Entropy Alloy Composition Space

The stability of a nanoparticle catalyst during electrochemical reaction is crucial for its application. Despite increasing interest in multi-metallic alloy nanoparticles, such as high-entropy alloys (HEAs), for electrocatalysis and emerging models for their catalytic activity, there is limited work on frameworks that can predict the metastability of these alloys under reaction conditions, including stability against electrochemical surface dissolution. Incorporating electrochemical stability in multi-objective optimization would advance HEAs as a catalyst discovery platform. To address the knowledge gap on electrochemical stability, we propose a methodology for simulating the dissolution of n-element alloy nanoparticles comprised of density functional theory and machine learning regression to calculate the dissolution potentials of the surface atoms. We demonstrate the methodology for the Ag-Au-Cu-Ir-Pd-Pt-Rh-Ru HEA system with the conditions of the oxygen reduction reaction. We investigated trends in stability against dissolution through a compositional grid search for the octo-metallic composition space, uncovering two alloying strategies to increase stability against electrochemical surface dissolution: Alloying with a noble metal or a metal with high relative surface energy. In the simulations, stabilization ensues from forming a protective surface layer, and consequently, the dissolution of persistent alloyed nanoparticles results in core-shell structures. The model enables tracing the evolution of the surface and dissolved composition during electrochemical dissolution, forming paths of dissolution and revealing unretainable surface compositions.