Surface structure engineering of PtCu clusters enhances the performance of propane dehydrogenation

Abstract

Highly dispersed Pt-based single-atom alloys have been extensively studied in heterogeneous catalysis, particularly for propane dehydrogenation (PDH). However, Pt-based single-atom alloys still suffer from sintering and coke deposition in high-temperature dehydrogenation reactions. Additionally, the atomic structure of the active sites of Pt-based single-atom alloys for PDH remains elusive, and the solid chemistry occurring on the catalyst surface is still under debate. In this work, we discovered that the coordination environment of the single Pt atom for Pt₁Cu₃₀cluster catalysts, encapsulated with a carbon layer, can be regulated by sequential heat treatment under air and H₂ atmosphere. The Pt₁Cu₃₀ cluster catalyst, with a single Pt atom coordinated by 9 Cu atoms, is similar to the surface structure of Pt₁Cu₃ (111) and exhibits excellent catalytic activity and stability at high temperatures, maintaining propane conversion of 43.5% and propylene selectivity of 98.2%, with a deactivation constant (<em>k_d</em>) of 0.01 h^-1, even after 32 hours of testing at 600 °C. The combination of structural characterizations and temperature programmed analysis reveal that the single Pt atom coordinated by around 9 Cu atoms of the Pt₁Cu₃₀ cluster catalyst, serves as the vital active sites for C-H cleavage of propane and propylene desorption due to their electron-rich and geometrically isolated Pt atom structure. Furthermore, the thin carbon layer coated on the surface of Pt₁Cu₃₀ clusters can effectively reduce the desorption energy of propylene, thereby avoiding further dehydrogenation and improving the propylene yield and catalytic stability.

Topics & Concepts