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.