Like synthetic V-doped TiO2, natural semiconducting V-bearing rutile (TiO2) has potential capability for visible-light absorption. The traditional modification for the synthetic V-doped TiO2 was to enhance the sample’s visible-light absorption by increasing the doping concentration. This paper demonstrates that the visible-light absorption of natural rutile with low V doping concentration (1.0 mol%) is significantly enhanced simply through annealing under argon. In the visible-light region of 400–750 nm, the integral absorbance of rutile treated at 1173 K increased by around 63 % compared to untreated rutile. Electronic paramagnetic resonance (EPR) measurements indicated that argon annealing induced a substantial increase of V4+ as an active state of V doping ions for the visible-light absorption. This argon annealing can provide a simple modification method for enhancing the visible-light absorption of V-doped TiO2.

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