Experimental study of the visible-light photocatalytic activity of oxygen-deficient TiO sub(2) prepared with Ar/H sub(2) plasma surface treatment

Oxygen-deficient TiO sub(2) (TiO sub(2-x)) has been proposed as a visible-light-responsive photocatalyst. TiO sub(2-x) thin films were prepared by Ar/H sub(2) plasma surface treatment, applying varying levels of microwave input power and processing times. The highest visible light photocatalytic activity was observed when using an input power of 200 W, a plasma processing time of 10 min, and a 1 : 1 Ar : H sub(2) ratio, conditions that generate an electron temperature of 5.7(+ or -1.0)eV and an electron density of 8.5 x 10 super(10)cm super(-3). The maximum formaldehyde (HCHO) removal rate of the TiO sub(2-x) film was 2.6 times higher than that obtained from a TiO sub(2-x)N sub(x) film under the same test conditions.