[en] Highlights: • TiO₂ nanofibers synthesized by electrospinning and subsequent calcination. • Crystal phases of TiO₂ nanofibers changed by calcination at different temperatures. • Pt/rutile-TiO₂ showed higher catalytic HCHO oxidation activity than Pt/anatase-TiO₂. • More oxygen vacancies in rutile-phase TiO₂ promote adsorption and activation of O₂. • DFT calculation shows that rutile TiO₂ has stronger adsorption to metallic Pt atoms. - Abstract: Catalytic oxidation at room temperature over well-designed catalysts is an environmentally friendly method for the abatement of indoor formaldehyde (HCHO) pollution. Herein, nanocomposites of platinum (Pt) and titanium dioxide (TiO₂) nanofibers with various phase compositions were prepared by calcining the electrospun TiO₂ precursors at different temperatures and subsequently depositing Pt nanoparticles (NPs) on the TiO₂ through a NaBH₄-reduction process. The phase compositions and structures of Pt/TiO₂ can be easily controlled by varying the calcination temperature. The Pt/TiO₂ nanocomposites showed a phase-dependent activity towards the catalytic HCHO oxidation. Pt/TiO₂ containing pure rutile phase showed enhanced activity with a turnover frequency (TOF) of 16.6 min⁻¹ (for a calcination temperature of 800 °C) as compared to those containing the anatase phase or mixed phases. Density functional theory calculation shows that TiO₂ nanofibers with pure rutile phase have stronger adsorption ability to Pt atoms than anatase phase, which favors the reduction of Pt over rutile phase TiO₂, leading to higher contents of metallic Pt in the nanocomposite. In addition, the Pt/TiO₂ with rutile phase possesses more abundant oxygen vacancies, which is conducive to the activation of adsorbed oxygen. Consequently, the Pt/rutile-TiO₂ nanocomposite exhibited better catalytic activity towards HCHO oxidation at room temperature.