Effect of metal-oxide interactions on the crystallinity of supported metal nanoparticles

Le résumé fourni par la source

In most applications, transition metal nanoparticles (NPs) are supported on substrates, hindering NP agglomeration and modifying their shape and electronic structure. Interestingly, in experiments supported NPs are most commonly observed with crystalline structures even at small NP sizes, at which non-crystalline icosahedral structures are thought to be more thermodynamically stable. Herein, we characterize how the structures and crystallinities of Ir, Pd, Pt, Cu, Ag, and Au nanoparticles are affected by their interaction with ZnO, which is a common NP support in catalytic and other applications. Surprisingly, 1-3 nm large crystalline NPs forming interface with ZnO through {111} facets are found to be the most energetically stable in the supported state, although non-crystalline icosahedral structures are more stable for unsupported nanoparticles of similar sizes. These findings are rationalized by the strong destabilization of icosahedral NPs upon truncation, necessary to form an extended interface with the support, which undermines the stabilization of icosahedral NPs by the oxide. Thus, the proposed destabilization mechanism is transferrable to other oxides and can explain why transition metal nanoparticles are experimentally observed more frequently with a crystalline structure, although icosahedral metal NPs were thought to be more stable according to previous theoretical studies.

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