On the Role of Sn Segregation of Pt-Sn Catalysts for Propane Dehydrogenation

Bimetallic nanoparticle catalysts attract extensive attention for relevant catalysis processes due to their flexible structures, while the structure evolution under specific conditions is ambiguous. This paper describes the structure evolution of Pt-Sn bimetallic nanoparticles for catalytic dehydrogenation, especially Sn segregation for surface recovery of a Pt-Sn alloy. An acid etching-reduction process was adopted to investigate the migration of Sn atoms after surface Sn species loss. By acid etching, Sn atoms at the surface of Pt-Sn alloy nanoparticles were removed, leaving nanoparticles with a Pt-rich shell and an unchanged Pt3Sn alloy core. Excitedly, during the following reduction process, the Pt3Sn alloy surface was recovered due to the migration of Sn atoms from the core to the surface, as confirmed by transmission electron microscopy, quasi in situ X-ray photoelectron spectroscopy, and density functional theory calculations. Subsequent studies on the catalyst performance for propane dehydrogenation (PDH) showed that the recoverable Pt3Sn alloy surface structure contributed to the high efficiency with 92% propene selectivity even after 5 cycles of the acid etching-reduction procedure. The recovery of the Pt-Sn alloy through Sn segregation could enable catalysts to overcome component fluctuations, making an efficient catalytic process.