A new computational materials chemistry method quantitatively details the behavior of alloyed nanocatalysts under working conditions. Catalysts can undergo a variety of changes induced by the chemical environment in which they operate. A nanocatalyst’s surface composition depends on the overall composition of the catalyst and its local chemical environment. Scientists showcased the power of their method using a 50:50 palladium-rhodium catalyst in an oxygen environment. Without any oxygen, a palladium shell forms; conversely, with oxygen present rhodium elbows palladium out of the way to emerge from the core and interacts directly with oxygen. The vast number of atom combinations makes these computations extremely challenging; for example, a 55-atom nanoparticle comprised of two elements, like the one modeled here, has 36 quadrillion possible alloy configurations. The team detailed the core-shell behavior across all palladium-rhodium compositions, finding that only core-shell nanoparticles with compositions near 50% rhodium show the core-shell reversal induced by oxygen coverage – which was recently experimentally observed. The goal is to design functional and stable alloyed nanocatalysts, for which providing accurate quantitative predictions under working conditions is crucial.
Configurational Thermodynamics of Alloyed Nanoparticles with Adsorbates