A comparative study of photocatalytic degradation of phenol of TiO2 and ZnO in the presence of manganese dioxides

The effects of the presence of α-MnO2, β-MnO2 and δ-MnO2 on the photocatalytic degradation of phenol by TiO2 and ZnO have been investigated. Experiments were conducted in a batch reactor, at initial pH 6.0 and 25 °C. The results showed that the TiO2-photocatalytic degradation of phenol was inhibited completely in the first 20–60 min in the presence of three crystal types of MnO2 whereas the ZnO-photocatalytic degradation of phenol only declined slightly. UV-vis diffuse reflectance spectroscopy (DRS) and surface photovoltage spectroscopy (SPS) analysis implied that the interaction of MnO2 with TiO2 and ZnO could change the energetic of these two photocatalysts.