Morphology and size of Pt on Al2O3: The role of specific metal-support interactions between Pt and Al2O3
2020
Lee, Jaekyoung | Jang, Eun Jeong | Oh, Dong Gun | Szanyi, János | Kwak, Ja Hun
The catalytic performance of supported heterogeneous catalysts is significantly affected by the particle size and morphologies of the active phase. In this work, we studied how metal-support interaction affected the morphology and size of Pt clusters on Al₂O₃. Under oxidizing atmosphere, when the specific interaction between oxidized Pt and Al₂O₃ is dominant, highly dispersed 2D PtO₂ rafts (1 nm) and atomically dispersed Pt atoms formed. At high Pt loadings, when only a fraction of the metal atoms can interact with the alumina support, or on weakly interacting supports (e.g., SiO₂), 3D PtO₂ particles (>2 nm) and large Pt crystallites (>10 nm) formed. Due to the weak interaction with the support, these 3D PtO₂ particles can be reduced at a lower temperature (−40 °C) than 2D PtO₂ rafts (~110 °C) and atomically dispersed Pt (>300 °C). The catalytic behavior for CO oxidation is also affected by the reduction properties of supported Pt catalysts. The activity of Pt/Al₂O₃ stepwise increases with the reduction temperature, which is closely related with the reduction of these three types of oxidized Pt species. In contrast, Pt/SiO₂ didn’t show drastic activity change with the subsequent reduction treatments up to 500 °C because it contains mainly 3D PtO₂ particles. All these results demonstrate that specific metal-support interactions guide the geometric and chemical properties and the corresponding catalytic performances of oxidized Pt in Pt/Al₂O₃ catalysts, underlining the importance of careful catalyst activation for the efficient utilization of metallic Pt in real-world catalytic applications.
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