In Situ exsolved Au nanoparticles from perovskite oxide for efficient epoxidation of styrene

Abstract

A Au-doped SrTiO₃ perovskite oxide catalyst (Sr_0.995Au_0.005TiO_3−δ) has been designed and synthesized based on thermodynamic analysis and density functional theory calculations. During reduction, Au nanoparticles with an average diameter of 2 nm are in situ exsolved and evenly distributed on the surface of a SrTiO₃ substrate. The as-prepared catalyst shows a high conversion of 95.0% and a high selectivity of 96.3% towards styrene epoxidation in CH₃CN using H₂O₂ as the oxidant, and the conversion maintained at 78.2% after five cycles. Noteworthily, such performances surpass those of ex situ deposited Au nanoparticles on SrTiO₃ with the same loading (88.5% initial conversion and 90.1% initial selectivity; 48.1% conversion after five cycles). The enhancement is attributed to the smaller particle size and stronger particle–substrate interaction, as revealed by XPS and TEM characterization. Mechanistic investigation confirms the strong support effect in the in situ exsolution system, where charge is transferred from SrTiO₃ to Au, improving the reactivity and selectivity. The results demonstrate the unique advantages of the in situ exsolution approach, which may further be applied to develop heterogeneous catalysts with stable nanoparticles.