Decorating TiO2 Nanoparticle Thin Film with SnSx (x < 1): Preparation, Characterization, and Photocatalytic Activity

We report a study on the SnSx (x < 1) decoration of porous TiO2 nanoparticle thin films using the ionic layer adsorption and reaction (ILAR) method. UV-vis absorption measurements revealed a direct bandgap of 1.40–2.10 eV for SnSx (with x = 0.85) and 3.15 eV for TiO2. Degradation of rhodamine B molecules in aqueous solutions shows that coating with a Sn-to-Ti molar ratio of 2% improves the efficiency of the photocatalytic performance of titanium dioxide, but excessive coverage decreases it. We interpret the observed behavior as due to a delicate balance of many competing factors. The formation of intimate interfaces guaranteed by the ILAR growth technique and a nearly optimal alignment of conduction band edges facilitate electron transfer, reducing electron–hole recombination rates. However, the valence hole transfer from TiO2 to SnS reduces the oxidative potential, which is crucial in the degradation mechanism.