Crystal-Phase-Mediated Restructuring of Pt on TiO2 with Tunable Reactivity: Redispersion versus Reshaping

Restructuring of supported metal nanoparticles (NPs) (e.g., reshaping and redispersion) is of tremendous interest for the rational design of well-defined catalyst materials, but the underlying mechanism to tune their dynamic behaviors and thus reactivity is still unspecified. Here, we show a crystal-phase-mediated redispersion/reshaping of Pt NPs on TiO2, boosting opposite reactivities in hydrogenation/oxidation reactions. Utilizing a variety of state-of-the-art characterization methods, we unraveled that rutile TiO2 favors the reshaping of Pt NPs into two-dimensional planar geometry, whereas the anatase surface facilitates the redispersion of Pt NPs to single atoms (SAs) upon the same calcination procedure. Environmental transmission electron microscopy and density functional theory calculations were employed to directly visualize the dynamic transformation of Pt NPs and reveal the specific role of TiO2 supports in promoting the stability and diffusion of Pt SAs. As a result, the opposite reactivity was achieved by tuning their distinct restructuring behaviors. Thus, the redispersion of Pt on anatase TiO2 facilitates the selective hydrogenation of phenylacetylene with a high styrene yield of 21.22 × 10–2 s–1, whereas the reshaping on the rutile phase favors the combustion of methane with a turnover frequency as high as 3.11 × 10–2 s–1. Our results therefore open up an effective route for tuning the restructuring behavior of supported metal catalysts and designing catalysts with controlled catalytic structures and reactivities.