Zinc Promotion of Platinum for Catalytic Light Alkane Dehydrogenation: Insights into Geometric and Electronic Effects

Supported metal nanoparticles are vital as heterogeneous catalysts in the chemical transformation of hydrocarbon resources. The catalytic properties of these materials are governed by the surface electronic structure and valence orbitals at the active metal site and can be selectively tuned with promoters or by alloying. Through an integrated approach using density functional theory (DFT), kinetics, and in situ X-ray spectroscopies, we demonstrate how Zn addition to Pt/SiO₂ forms high symmetry Pt₁Zn₁ nanoparticle alloys with isolated Pt surface sites that enable near 100% C₂H₄ selectivity during ethane dehydrogenation (EDH) with a 6-fold higher turnover rate (TOR) per mole of surface Pt at 600 °C compared to monometallic Pt/SiO₂. Furthermore, we show how DFT calculations accurately reproduce the resonant inelastic X-ray spectroscopic (RIXS) signatures of Pt 5d valence orbitals in the Pt/SiO₂ and PtZn/SiO₂ catalysts that correlate with their kinetic performance during EDH. This technique reveals that Zn modifies the energy of the Pt 5d electrons in PtZn, which directly relates to TOR promotion, while ensemble effects from the incorporation of Zn into the catalyst surface lead to enhanced product selectivity.