Improving the broadband photocatalytic performance of TiO₂ through a highly efficient optical converter

Developing efficient photocatalysts that respond to near-infrared (NIR) light holds significant scientific importance for improving the utilization of solar energy. In this study, the photocatalyst β-NaLuF₄:Yb³⁺/Tm³⁺@TiO₂ that simultaneously responds to both ultraviolet (UV) and NIR light is successfully synthesized. Instead of the conventional use of β-NaYF₄:Yb³⁺/Tm³⁺, β-NaLuF₄:Yb³⁺/Tm³⁺ upconversion (UC) nanoparticles (NPs) are employed as the NIR-UV light converter to achieve stronger UV UC luminescence. The data indicate that the photocatalytic degradation efficiency and rate of β-NaLuF₄:Yb³⁺/Tm³⁺@TiO₂ synthesized in this work are superior to those of NIR-driven photocatalysts based on β-NaYF₄:Yb³⁺/Tm³⁺ under both NIR and sunlight irradiation. Further analysis of the UC emission spectra and the decay curves of the samples reveals an effective fluorescence resonance energy transfer (FRET) process between β-NaLuF₄:Yb³⁺/Tm³⁺ and TiO₂ after the combination, which makes the NIR-driven photocatalytic reactions happen. All results confirm that the present β-NaLuF₄:Yb³⁺/Tm³⁺@TiO₂ is an exceptionally efficient photocatalyst, owing to its responsiveness to both UV and NIR light.