High-porosity Pt-CeO2 nanosponges as oxidation catalyst.

Abstract

Pt-CeO₂ nanosponges (1 wt% Pt) with high surface area (113 m² g^-1), high pore volume (0.08 cm³ g^-1) and small-sized Pt nanoparticles (1.8 ± 0.4 nm) are prepared by thermal decomposition of a cerium oxalate precursor and examined for catalytic oxidation of CO, volatile organic compounds (VOCs), and NH₃. The cerium oxalate precursor Ce₂(C₂O₄)₃·10H₂O is prepared by aqueous precipitation from Ce(NO₃)₃·6H₂O and K₂C₂O₄·H₂O and thermally converted to CeO₂ nanosponges by heating in air. Optimal conditions for decomposition in terms of surface area and porosity are observed at 350 °C for 20 min. Finally, the CeO₂ nanosponges are decorated with small-sized Pt nanoparticles, using a wet-chemical impregnation with Pt(ac)₂ in methanol. Electron microscopy with tomography, electron spectroscopy and further methods (TG, XRD, FT-IR, sorption analysis) are used to characterize the catalyst composition and especially the structure and porosity of the Pt-CeO₂ nanosponges as well as the uniform distribution of the Pt nanoparticles. The Pt-CeO₂ nanosponges show good thermal stability (up to 400 °C) and, already as a new, non-optimized catalyst, promising activity for catalytic oxidation of CO, VOCs, NH₃ as indicated by high activities in terms of low and stable light-out and light-off temperatures as well as a high selectivity to N₂ (for NH₃ oxidation) with >80% at 170-250 °C.