Effect of oxide supports in stabilizing desirable Pt–Ni bimetallic structures for hydrogenation and reforming reactions

Abstract

Previous surface science studies have shown that bimetallic surfaces often show unique activity for reactions involving the consumption and production of hydrogen, such as hydrogenation and reforming reactions, respectively. These two types of reactions require different bimetallic configurations. For example, for the Pt–Ni bimetallic system, the desirable structure is Pt-terminated for hydrogenation while Ni-terminated for reforming. In the current study, 1,3-butadiene hydrogenation and ethanol reforming were used as probe reactions to investigate the effect of oxide supports (γ-Al₂O₃ and TiO₂) on the structural and catalytic properties of Pt–Ni catalysts. The supported catalysts were characterized by transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS). The reactions were carried out in a batch reactor equipped with a Fourier transform infrared (FTIR) spectrometer. For ethanol reforming, Pt–Ni/TiO₂ showed higher activity than Pt–Ni/γ-Al₂O₃, and the Pt–Ni bimetallic catalyst outperformed the monometallic catalysts on TiO₂ but not on γ-Al₂O₃. In contrast, for 1,3-butadiene hydrogenation, Pt–Ni/TiO₂ showed much lower activity than Pt–Ni/γ-Al₂O₃. Density functional theory (DFT) calculations of Pt–Ni nanoparticles on γ-Al₂O₃ and TiO₂ were performed to provide possible explanations for the different modification effects of the two oxide supports.