Probing Structural Reconstruction of Metal Nanoparticles under Annealing and Water Vapor Conditions: A Theoretical Study
ZM Wang and W An and YG Sun and MS Hybertsen, JOURNAL OF PHYSICAL CHEMISTRY C, 123, 29783-29793 (2019).
Understanding the structural reconstruction of metal nanoparticles (NPs) under working conditions is of particular importance to catalytic processes. Here, using Wulff construction combined with density functional theory (DFT) and molecular dynamics (MD) simulation, we investigated truncated octahedron-based Rh and Ir NPs (3.5, 5.5, and 9.5 nm in size) with different morphology for their structural reconstruction under annealing and water vapor conditions. Our MD results show that the NPs with lower average atomic coordination number ((CN) over bar) of surface atoms have lowered structural transformation inertness and thermal stability, resulting in more severe structural transition especially for smaller-sized NPs and Ir NPs. Under water vapor conditions, the competition between the interfacial tension (<(gamma(int)(hid))over bar>) of (111) and (110) facets plays a major role in driving the shape evolution of Rh and Ir NPs by minimizing the total surface tension. It is revealed that annealing in vacuum/water vapor condition is an irreversible/reversible process on Rh and Ir NPs. We identified that the total adsorbate-metal <(gamma(int)(hkl))over bar> can serve as a key stability parameter for describing the potential energy surface of adsorbate-metal NP system in a variable gaseous environment (P, T).
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