Physico‐Chemical Properties of Nb/Ti Binary Oxides and their Photo‐Catalytic Activities

A series of binary Nb/Ti ox ides was prepared by co‐precipitation. Their structure and physico‐chemical properties in term of surface area, surface acidity, bandgap energy and life time of the radiation‐excited electron‐hole pair were examined. These properties were correlated to their catalytic activities in photodegradation of oxygenated organic pollutants in water. The organic pollutants under investigation were phenol, cyclohexanol and tetrahydrofuran (THF). The lab‐made titanium oxide and those doped with a small amount of Nb (molar ratio of Nb/(Nb+Ti) less than 20%) showed higher activities in degradation of the organic pollutants. However, the mineralization efficiencies were different for the three oxygenated organic pollutants. Nearly complete mineralization to form CO2 could be achieved in the degradation of phenol. For cyclohexanol, only ca. 50% selectivity of CO2 was obtained over all the catalysts. Similar low efficiency in complete mineralization was observed in the degradation of THF, but higher selectivity (ca. 65–75%) of CO2 could be obtained on the binary oxide with Nb content less than 4 molar %. In contrast, the binary Nb/Ti oxide with equal Nb and Ti molar content gave the poorest catalytic activity. The photocatalytic activity is generally correlated well to the life time of the radiation‐excited electron‐hole pairs. The contribution of surface acidity to the photocatalytic activity was only demonstrated on the niobia‐dominant oxide catalysts to ward THF. The photocatalytic activity was found to have no correlation with the crystal line structure, the bandgap energy, the surface area or the surface hydroxyl density.