Figure 4 shows SEM micrographs and Mn elemental mapping. Mn elemental mapping images show the distribution of manganese on the MnOx/TiO2 samples. The most homogeneous Mn dispersion is observed for Tp/TiO2 (Fig. 4c) sample while the most heterogeneous is observed for b-MnO2/TiO2 sample (Fig. 4a). These observations are consistent with the highest particle size (*6 lm) of b-MnO2 and the lowest one for Tp(*11 nm)