NaCl-template-based synthesis of TiO2-Pd/Pt hollow nanospheres for H2O2 direct synthesis and CO oxidation

Abstract

TiO₂ hollow nanosphere (HNS) are prepared via NaCl templates in a one-pot approach. The NaCl templates are realized by solvent/anti-solvent strategies and coated with TiO₂via controlled hydrolysis of Ti-alkoxides. The NaCl template can be easily removed by washing with water, and the TiO₂ HNS are finally impregnated with Pd/Pt. Electron microscopy shows TiO₂ HNS with an outer diameter of 140–180 nm, an inner cavity of 80–100 nm, and a wall thickness of 30–40 nm. The TiO₂ HNS exhibit high surface area (up to 370 m² g⁻¹) and pore volume (up to 0.28 cm³ g⁻¹) with well-distributed small Pd/Pt nanoparticles (Pt: 3–4 nm, Pd: 3–7 nm). H₂O₂ direct synthesis (room temperature, liquid phase) and CO oxidation (up to 300 °C, gas phase) are used to probe the catalytic properties and result in a good stability of the HNS structure as well as a promising performance with a H₂O₂ selectivity of 63% and a productivity of 3390 mol kg_Pd⁻¹ h⁻¹ (TiO₂-Pd HNS, 5 wt%) as well as CO oxidation light-out temperatures of 150 °C (TiO₂-Pt HNS, 0.7 wt%).