Enhanced photocatalytic ammonia oxidation over WO@TiO heterostructures by constructing an interfacial electric field.

WO nanorods and xWO@TiO (WO/TiO mass ratio (x) = 1-5) photocatalysts were synthesized using the hydrothermal and sol-gel methods, respectively. The photocatalytic activities of xWO@TiO for NH oxidation first increased and then decreased with a rise in TiO content. Among them, the heterostructured 3WO@TiO photocatalyst showed the highest NH conversion (58 %) under the simulated sunlight irradiation, which was about two times higher than those of WO and TiO. Furthermore, the smallest amounts of by-products (i.e., NO and NO) were produced over 3WO@TiO. The enhancement in photocatalytic performance (i.e., NH conversion and N selectivity) of 3WO@TiO was mainly attributed to the formed interfacial electric field between WO and TiO, which promoted efficient separation and transfer of photogenerated charge carriers. Based on the results of reactive species trapping and active radical detection, photocatalytic oxidation of NH over 3WO@TiO was governed by the photogenerated holes and superoxide radicals. This work combines two strategies of morphological regulation and interfacial electric field construction to simultaneously improve light utilization and photogenerated charge separation efficiency, which promotes the development of full-spectrum photocatalysts for the removal of ammonia.