Crystal face dependence of the decomposition of 2-naphthol in water under dark condition by rutile modified with MnO_x

Abstract

Crystal face dependence of the decomposition activity of MnO_x-modified rutile-type TiO₂ on 2-naphthol in water in the dark was investigated. Clusters of MnO_x were modified onto (110) and (001) surfaces of rutile single crystals using chemisorption calcination cycle (CCC) processing. The major valences of Mn on (110) were Mn(III) and Mn(IV), whereas those on (001) were Mn(II) and Mn(III). Energy calculations for the MnO_x cluster on (110) corresponded to experimentally obtained results. Rutile nanorods with high (110) ratio were prepared using hydrothermal methods. Under the same conditions, MnO_x was impregnated on the surface using CCC processing. Despite smaller specific surface area and surface Mn concentration, the synthesized nanorod powder on 2-naphthol in water in the dark exhibited almost identical decomposition activity to that of a commercial rutile powder. The ratio of Mn(IV) of the nanorod powder was higher than that of the commercial rutile powder. The normalized activity for the nanorod powder was more than twice as much as that for commercial rutile powder. These results imply that the interface design between the base material and MnO_x clusters plays an important role in the decomposition activity of organic substances in the dark.