Decomposition of 2-naphthol in water by TiO₂ modified with SnO_x or (Mn, Sn)O_x and MnO_x

Abstract

Titanium dioxide (TiO₂) surface was modified with MnO_x, SnO_x or (Mn_0.8, Sn_0.2)O_x by chemisorption calcination cycle (CCC) processing. Samples modified with SnO_x or (Mn_0.8, Sn_0.2)O_x were also modified with MnO_x by subsequent CCC processing. Then the decomposition activity on 2-naphthol in water was evaluated at 50°C in the dark or under visible light illumination. The modification with MnO_x engendered a decrease in the sample bandgap. Although the samples modified with SnO_x or (Mn_0.8, Sn_0.2)O_x only did not show decomposition activity in the dark, they decomposed 2-naphthol in water by subsequent modification with MnO_x on their surface. The results suggest that the interaction between the base material and modified MnO_x plays an important role on the activity order. Samples modified with SnO_x or (Mn_0.8, Sn_0.2)O_x and MnO_x exhibited decomposition activity both in the dark and under visible light. Although the activity in the dark decreased gradually through repeated use, it recovered by ultraviolet light illumination at room temperature or heating at 300°C in ambient air.