Tungsten Trioxide and Its TiO2 Mixed Composites for the Photocatalytic Degradation of NOx and Bacteria (Escherichia coli) Inactivation

The increased air pollution and its impact on the environment and human health in several countries have caused global concerns. Nitrogen oxides (NO2 and NO) are principally emitted from industrial activities that strongly contribute to poor air quality. Among bacteria emanated from the fecal droppings of livestock, wildlife, and humans, Escherichia coli is the most abundant, and is often associated with the health risk of water. TiO2/WO3 heterostructures represent emerging systems for photocatalytic environmental remediation. However, the results reported in the literature are conflicting, depending on several parameters. In this work, WO3 and a series of TiO2/WO3 composites were properly synthesized by an easy and fast method, abundantly characterized by several techniques, and used for NOx degradation and E. coli inactivation under visible light irradiation. We demonstrated that the photoactivity of TiO2/WO3 composites towards NO2 degradation under visible light is strongly related to the WO3 content. The best performance was obtained by a WO3 load of 20% that guarantees limited e(-)/h(+) recombination. On the contrary, we showed that E. coli could not be degraded under visible irradiation of the TiO2/WO3 composites.