Reversed TiO_<i>x</i> Layer-Induced Strong Metal–Support Interactions on Ni/Ti–SiO₂ Catalysts for Propene Epoxidation with H₂ and O₂

Direct propene epoxidation using H2 and O2 to produce propylene oxide (PO) is considered an environmentally friendly and revolutionary industrial process. With the necessity of finding alternatives to precious Au-based catalysts, there is a critical need for highly active nonprecious metal catalysts in epoxidation reactions. Herein, we successfully constructed different degrees of strong metal–support interaction (SMSI) by reversing TiO2 islands into TiOx layers over Ni nanoparticles in a H2 atmosphere. The resulting nonprecious 1.27%Ni/Ti–SiO2 catalyst with moderate SMSI exhibited a remarkable 90.6% selectivity toward PO with a formation rate of 9.23 gPOh–1gNi–1. Mechanistic investigations revealed that tetrahedral-Ti sites and Ni–TiOx overlayers synergistically catalyze propene epoxidation with H2 and O2. The Ni–TiOx interface provided abundant unsaturated Ti (TiOx) sites, enhancing the adsorption capacity of propene and consequently accelerating subsequent propene epoxidation with in situ synthesized H2O2. This study introduces an original approach for the utilization of nonprecious metal catalysts in gas-phase propene epoxidation, with promising implications for advancing industrial olefin epoxidation processes.