Photocatalytic activity of TiO2 and ZnO in the presence of manganese dioxides

The photocatalytic activity of TiO2 and ZnO in the presence of MnO2, a particulate matter present in natural water and wastewater, has been studied. We found that a trace amount of MnO2 particles deactivated TiO2 photocatalysts, but its effect on the activity of ZnO was negligible. UV–visible diffuse reflectance spectra (DRS) and surface photovoltage spectroscopy (SPS) analysis implied that the interaction of MnO2 with TiO2 and ZnO could change the energetics of these two photocatalysts.