Ultradispersed noble metal nanoparticles on 3D hierarchical rutile architectures for efficient low-temperature CO oxidation

• Hierarchical rutile stabilizes ultradispersed noble metal nanoparticles. • Os, Ir, Pt, and Au catalysts achieve efficient low-temperature CO oxidation. • Rutile-supported Au NPs shows the lowest T 90 , while Os one gives the lowest E a . • In situ CO-DRIFTS and DFT reveal distinct CO adsorption on Os, Pt, Ir, and Au sites. • Hierarchical rutile outperforms commercial P25 in stability and catalytic activity. The rational design of nanocatalysts for low-temperature CO oxidation remains a key challenge in environmental remediation. Here, we report the synthesis of ultradispersed Os, Ir, Pt, and Au nanoparticles supported on three-dimensional hierarchical rutile TiO 2 architectures, prepared by deposition-precipitation with urea. The hierarchical rutile framework, composed of interconnected nanorods with combined micro-mesoporosity, enables enhanced metal dispersion, thermal stability, and efficient access to active sites. Comprehensive characterization by SEM-EDS, nitrogen physisorption, H 2 -TPR, FTIR, Raman, XRD, Rietveld refinement, STEM-HAADF, and in situ CO-DRIFTS revealed strong metal-support interactions and excellent dispersion stability even after thermal pretreatments in hydrogen and air. Catalytic tests under kinetic control demonstrated that hierarchical rutile outperforms commercial TiO 2 (P25) as a support, delivering superior low-temperature CO oxidation activity across all noble metals. Among them, the Os-supported catalyst exhibited the lowest apparent activation energy (25.2 KJ/mol) and remarkable resistance to sintering and volatilization, highlighting osmium’s unexpected potential for this reaction. DFT calculations further identified preferred CO adsorption configurations consistent with the experimental DRIFTS spectra, providing molecular-level insight into the observed activity trends.