Enhanced photocatalytic ammonia oxidation over WO3@TiO2 heterostructures by constructing an interfacial electric field

WO 3 nanorods and x WO 3 @TiO 2 (WO 3 /TiO 2 mass ratio ( x ) = 1−5) photocatalysts were synthesized using the hydrothermal and sol-gel methods, respectively. The photocatalytic activities of x WO 3 @TiO 2 for NH 3 oxidation first increased and then decreased with a rise in TiO 2 content. Among them, the heterostructured 3WO 3 @TiO 2 photocatalyst showed the highest NH 3 conversion (58 %) under the simulated sunlight irradiation, which was about two times higher than those of WO 3 and TiO 2 . Furthermore, the smallest amounts of by-products (i.e., NO and NO 2 ) were produced over 3WO 3 @TiO 2 . The enhancement in photocatalytic performance (i.e., NH 3 conversion and N 2 selectivity) of 3WO 3 @TiO 2 was mainly attributed to the formed interfacial electric field between WO 3 and TiO 2 , 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 3 over 3WO 3 @TiO 2 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.