Tailoring Pt–Sn Coordination Triggered SnO_<i>x</i>-Modified Pt Cluster for Propane Dehydrogenation

Propane dehydrogenation (PDH) over alumina-supported platinum–tin-based catalysts is one of the most promising solutions to address the increasing global demand for propylene in the chemical industry. A trade-off exists between activity and stability in PtSn catalysts, where Sn alloying typically enhances stability but reduces activity, underscoring the need to tailor the Pt–Sn coordination environment to optimize both. Herein, we constructed Sn–Pt–Al, Pt–Sn–Al, and PtSn–Al catalysts with similar metal cluster sizes using facile sequential impregnation and coimpregnation methods. C3H8 conversion and C3H6 selectivity at 600 °C and C3H8-WHSV = 18.9 h–1 are ranked as follows: Sn–Pt–Al (33.8, ∼99.5%) > Pt–Sn–Al > PtSn–Al. The deactivation rate constant (kd-C3H8, 0.017 h–1 for Sn–Pt–Al) and carbon deposition rate were in the reverse order mentioned above. X-ray absorption (XAS), X-ray photoelectron (XPS), CO–DRIFTS, and high-angular annular dark field–scanning transmission electron microscopy–energy dispersive spectroscopy (HAADF–STEM–EDS) characterizations confirmed that Sn–Pt–Al exhibited the lowest Pt–Sn coordination number fraction (13.6%) and highest SnOx fraction (90.0%) in contrast to higher alloying degrees in Pt–Sn–Al and PtSn–Al catalysts. Notably, minimal sintering was observed in Sn–Pt–Al (∼1.5 nm metal clusters) through SnOx postcoating modification during a long-term PDH test. DRIFTS experiments and density functional theory (DFT) calculations suggested that the C–H bond activation of C3H8 on the low CN (Pt–Sn) cluster was more favorable compared with that of the high Pt–Sn CN cluster. Importantly, the fraction of Pt–Sn coordination can be used as a descriptor for the PDH catalytic activity. This study presents a specific structure, i.e., SnOx-modified Pt clusters with tailored Pt–Sn coordination, for overcoming the activity–stability trade-off conventionally found in Pt-based PDH catalysts and thus paves the way for the rational design of PtSn bimetallic catalysts.