The purpose of this study is to present an “environmental catalyst” possessing both thermocatalytic activity and visible-light activity for the decomposition of organic pollutants. Molecule-sized MnO x clusters are highly dispersed on the surface of TiO 2 (anatase/rutile = 4/1 w/ w, P-25, Degussa) by the chemisorption-calcination cycle technique using Mn(acac) 3 complex as a precursor (MnO x/TiO 2). The thermo- and photo-catalytic activities of MnO x/TiO 2 were studied for the degradation of 2-naphthol used as a model water pollutant. In contrast to the FeO x/TiO 2 system, MnO x/TiO 2 exhibits high thermocatalytic activity exceeding those of bulk β-？β-MnO 2 and Mn 2O 3. Also, visible-light activity is induced by the surface modification of TiO 2 with MnO x clusters, whereas its UV-light activity decreases.
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